Mathieu Cunche

Mohamed Ali Kaafar

Terence ) Chen

Roksana Boreli

Anirban Mahanti

Why are they hiding ? Study of an Anonymous File Sharing System

This paper characterizes a recently proposed anonymous file sharing system, OneSwarm. This characterisation is based on measurement of several aspects of the OneSwarm system such as the nature of the shared and searched content and the geolocation and number of users. Our findings indicate that, as opposed to common belief, there is no significant difference in downloaded content between this system and the classical BitTorrent ecosystem. We also found that a majority of users appears to be located in countries where anti-piracy laws have been recently adopted and enforced (France, Sweden and U.S). Finally, we evaluate the level of privacy provided by OneSwarm, and show that, although the system has strong overall privacy, a collusion attack could potentially identify content providers.

I. INTRODUCTION

Peer-to-peer (P2P) file sharing continues to be a popular service for many reasons including the large variety of content available on the P2P ecosystem, the ease of accessibility with no sign-up required for downloading content, and good system performance, particularly when downloading popular content. P2P applications such as BitTorrent, however, do little to preserve a user's privacy. The open nature of these applications enables easy monitoring and identification of both content providers and downloaders [START_REF] Isdal | Privacy-preserving P2P data sharing with OneSwarm[END_REF], [START_REF] Siganos | Monitoring the bittorrent monitors: A bird's eye view[END_REF]- [START_REF] Stevens | One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users[END_REF].

In recent years, a number of file sharing solutions offering differing degrees of privacy have been adopted, arguably coinciding with the increased privacy-awareness of Internet users and the tightening, in some countries, of anti-piracy laws [START_REF] Colchester | All eyes on france as officials enforce new antipiracy law[END_REF], [6]. Centralized One-Click Hosting services have emerged as an alternative to P2P file sharing [START_REF] Antoniades | One-click hosting services: a file-sharing hideout[END_REF] and potentially offer greater degree of privacy. Another approach is to augment existing P2P systems with solutions that obfuscate IP addresses, for example, by using standard BitTorrent over an anonymization network such as Tor [START_REF] Dingledine | Tor: The second-generation onion router[END_REF] or I2P 1 . BitTorrent over Tor has been adopted by a large population of users [START_REF] Stevens | One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users[END_REF], but anonymity comes at the cost of system performance [START_REF] Isdal | Privacy-preserving P2P data sharing with OneSwarm[END_REF], [START_REF] Stevens | One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users[END_REF]. More recently, a promising privacy-aware P2P system, OneSwarm, was proposed [START_REF] Isdal | Privacy-preserving P2P data sharing with OneSwarm[END_REF]. OneSwarm includes a number of privacy preserving techniques, and this system is reportedly used by thousands of users [START_REF] Isdal | Privacy-preserving P2P data sharing with OneSwarm[END_REF].

In this paper, we study the usage and the characteristics of the OneSwarm system, including the types of content shared, the geographical location of its users, the size of the system and the anonymity provided by the system. We discuss the possible reasons motivating adoption of OneSwarm, compared to those for using other common P2P alternatives (e.g., BitTorrent over Tor and the standard BitTorrent) which provide varying levels of privacy. We have also developed a mechanism to exploit the OneSwarm client compatibility and the apparent use of BitTorrent for downloading content not currently available in OneSwarm.

Our key observations include the following. We characterize the use of OneSwarm, including the likely geographical locations of users and the type of content shared in the system. There are strong indications that the vast majority of users are located in France (around 50%), Sweden (close to 38%), and the US (under 10%). Our results additionally indicate that the content shared on OneSwarm is similar to that shared using other P2P systems. We argue that the motivations for using file sharing systems can be broadly categorized as sociological (e.g., the potential implications to the person downloading or searching for content, in regards to interest in specific content), legal (e.g., evading infringement notices for downloading copyrighted material), technological (e.g., enabling content download in countries where P2P traffic is filtered out by ISPs), enhanced awareness (e.g., genuine interest in preserving privacy), or a combination thereof. We find strong indicators for the prevalence of the legal/regulatory policy driven adoption, based on the user locations and the timing of OneSwarm introduction compared to regulatory developments in specific countries [START_REF] Colchester | All eyes on france as officials enforce new antipiracy law[END_REF], [6].

The OneSwarm system provides strong overall privacy; however, we identify a potential collusion attack that can compromise privacy. We also discuss a privacy breach introduced by the default behaviour of the OneSwarm client, wherein the client automatically searches for content on the public BitTorrent system if the content is not found within OneSwarm.

This paper is organized as follows. Section 2 provides an overview of OneSwarm. Section 3 describes the measurement methodology. Our results are presented in Section 4. Section 5 identifies a couple of limitations in the OneSwarm design. Section 6 concludes the paper.

II. OVERVIEW OF ONESWARM

OneSwarm uses an overlay network to propagate search messages and establish connections between peers for down-loading content. The connections relate to trust relationships between nodes (e.g., established via manual or automatic exchange of public keys), where trust represents the certainty that the trusted party will not reveal information about activity of nodes (e.g., the origin of the forwarded traffic). To enable new user connections, when trusted connections cannot be established, OneSwarm allows untrusted connections, with limited interaction between the peers.

OneSwarm uses community servers to automatically establish both trusted and untrusted connections. These servers store the identities of the users and allocate connections to new users. Public community servers facilitate introduction of new users; new users are allocated a set of untrusted connections with other subscribers of this server. Currently, there are four public community servers: the default community server hosted by the University of Washington (UW CSE), two French servers, oneswarm-fr (OS-fr) and lavilette, and a Swedish server subcult 2 .

OneSwarm supports two content identification methods: Unique Resource Identification (URI) based, which includes support for the infohash convention used by BitTorrent, and a content name based method. Correspondingly, two types of messages are used to search for content: Hash search and Text search. A Hash search message contains a truncated version of the infohash of the content. A Text search message contains a URI or a human readable string representing a set of keywords. Note that Hash search and Text search containing a URI target unique content, while a Text search containing keywords can target any matching content.

The OneSwarm system requires a connection to be established between the requester and the provider to facilitate content download. OneSwarm uses a flooding algorithm, wherein a search message targeting a specific content is sent by the requester and forwarded by the overlay nodes. Once the message reaches a node that has the targeted content, a response message is sent back following the same path, thus completing the connection establishment.

OneSwarm is backward compatible with the standard Bit-Torrent protocol. The OneSwarm client can handle .torrent files, and the content associated with a torrent can be downloaded either from the OneSwarm network, or from the public BitTorrent ecosystem. When connected to public BitTorrent ecosystem, the OneSwarm node concurrently becomes a content provider on OneSwarm for this content.

III. MEASUREMENT METHODOLOGY

Our measurements consider a combination of OneSwarm and BitTorrent as shown in Figure 1. The OneSwarm part comprises of public and private communities, the former having a number of community servers (CS). For the sake of simplicity, only one CS is shown in Figure 1. Similarly, BitTorrent includes public and private components, and a (large) number of trackers. The nodes which simultaneously reside in both OneSwarm communities, or in both OneSwarm and BitTorrent, are denoted as bridge nodes (B). We monitor OneSwarm messages and three major BitTorrent trackers 3 over a period of one month.

For this study, we developed a customized client derived from the OneSwarm client version 0.6. Our customized client can generate and monitor all OneSwarm message types. Our measurement setup includes connecting two customized clients to all four OneSwarm community servers. The captured OneSwarm messages are used for analysis and characterization of the system. We additionally determined the IP addresses of OneSwarm clients, first from the direct connections allocated to our nodes by the community servers, and second using a method which exploits OneSwarm's backward compatibility with BitTorrent. As a representative data set for public BitTorrent use, we collected content hashes from the Pirate Bay site. Most of our data collection is restricted to nodes that are directly interacting with the public communities. We argue that, in practice, due to bridge nodes (cf. Figure 1) we will observe a mix of traffic from both private and public communities.

A. OneSwarm Monitoring

We monitor all OneSwarm Hash search and Text search request messages and use this data to characterize the activity of the OneSwarm users. We combine this monitoring with additional BitTorrent monitoring to determine the IP addresses of bridge nodes and their geolocation. Cautionary measures were taken to prevent the monitoring nodes from generating artificial traffic or forwarding messages that could modify the overlay topology (e.g., monitoring nodes do not act as bridge nodes between different parts of the network).

During our measurement period, our nodes connected to 190 peers within the 4 public communities. A total of 630 millions 4 OneSwarm search messages have been collected, including 520 million Hash search messages and 110 million Text messages. Of those, 25, 853 were Text search messages in plain text, containing keywords which reflect user interest in specific types of content. To verify the efficiency of our passive traffic monitoring, we perform an experiment to estimate the fraction of messages captured by our monitoring nodes, compared to the total number of messages generated in the system. For this, we introduce six customized nodes and place two nodes in each of the three public communities (excluding the Swedish community server, which was intermittently available). Every 10 seconds, the controlled nodes send a search message and record all incoming traffic. From the captured traffic, we then compute the cross-community connectivity between each pair of our controlled clients, as represented by the fraction of messages received by the node in one community, from among those sent by the node in the second community. The results are reported in Table I. The observed high connectivity values, i.e. 80.8% to 99.4%, enable us to be confident that the placement of monitoring nodes enables capture the majority of the traffic originating from the public part of the Oneswarm system. It is however difficult to estimate the fraction of captured traffic originating from the private part of the network. If the structure of the overlay network is homogeneous over the overall network (public and private part), the fraction of captured traffic from the private parts should be similar to the one of the public part.

B. Identifying BitTorrent Bridge Nodes

Our method is based on the hypothesis that a number of OneSwarm clients are acting as BitTorrent bridges. This is supported by the observed behaviour of OneSwarm clients which are connecting to the public BitTorrent system and acting as content importers into OneSwarm.

We use the ability of OneSwarm clients to utilize .torrent files to identify the IP addresses of bridge nodes. We note that OneSwarm clients searching for a content source on OneSwarm in this way will, after an unsuccessful search period (of 90 seconds), automatically connect to the corresponding BitTorrent tracker 5 . The passive monitoring of OneSwarm captures all content search messages. We additionally use the torrent data set from the Pirate Bay site. For each new content instance observed in the Hash search message set, we correlate the truncated infohash (cf. Section II) to the full BitTorrent infohash. We then start monitoring the corresponding BitTorrent tracker for newly connected peers. The tracker is monitored for a period of 5 minutes (heuristic value). Finally, from the set of newly detected BitTorrent peers, we select those using the OneSwarm client (determined by verifying that their BitTorrent client identifier starts with -OS).

To capture the newly connected peers, we first have to capture the full set of peers currently connected to this tracker 5 This is hard coded into the OneSwarm client version 0.6. and then attempt to identify the new peers close to the time of their initial connection. Obtaining both sets of peers in the short time frame available necessitated the use of a number of proxies, as the tracker limits the rate of queries from a specific IP address. To minimize the amount of resources required for monitoring and still ensure the capture of the majority of peers, we limited our measurements to swarms with an advertised size of less than 1000 peers. We additionally note that the generous time frame allocation (5 minutes) enables a high likelihood of capturing bridge nodes, regardless of the delays in the OneSwarm overlay. This time is also required to ensure that the majority of peers, including the newly connected peers, have been collected from the tracker site.

We identified 778 unique OneSwarm users downloading content through BitTorrent. We argue with a high likelihood that these OneSwarm clients used on BitTorrent are also part of OneSwarm, due to the fact that the search for the same content is being detected within a short time frame of the captured BitTorrent activity of these clients.

detect new peers. Indeed the number of random subset required to obtain a particular element increases quickly with the size of the set (interested reader may refer to the coupon collector problem [START_REF] Adler | The coupon subset collection problem[END_REF]).

IV. RESULTS

Our characterization of the OneSwarm system attempts to answer a number of questions: What is the nature of the content that is searched for and downloaded? Where are the users located? What is the size of the system? We then discuss the motivation to use this anonymous file sharing system.

A. Characterizing the Content

We compared content downloaded on OneSwarm with that found on a typical BitTorrent ecosystem and BitTorrent over Tor. For OneSwarm, we consider the torrents that have been downloaded at least once during our passive monitoring (77000 content in total). In the case of the Pirate Bay, we consider the approximately 1.3 million torrents available at the time of data collection. The BitTorrent over Tor data set is composed of torrents collected at the output of six Tor exit nodes as reported in [START_REF] Stevens | Spying the World from your Laptop -Identifying and Profiling Content Providers and Big Downloaders in BitTorrent[END_REF].

Our analysis is based on the meta-information associated to torrents hosted by The Pirate Bay website. More particularly we consider the two level content classification, by 'type' and by 'subtype'. Figure 2 shows the results from our analysis. We observe that the available content in either systems is similar, while noting only a minimal difference for the video, porn, and audio types.

B. Characterizing Keyword Based Search

The OneSwarm system allows users to search for content using keywords in a privacy preserving manner. We have collected a total of 25853 search strings issued on the OneSwarm system. We compare the most popular search strings to similar statistics available on the Pirate Bay web pages6 . Figure 3 shows the relative frequency of the most popular strings for both OneSwarm and Pirate Bay content. Notice that the most popular search string on OneSwarm are different than the corresponding ones of the Pirate Bay. The search string french is the most popular on OneSwarm. In general, in the OneSwarm data set we have observed very few strings related to languages other than French.

Pornography related strings are highly represented on the Pirate Bay. Although these search strings can also be found on OneSwarm, they are in smaller numbers and have smaller relative frequency. It seems that people using the anonymous search engine are not primarily interested in pornographic content, and therefore, not motivated by sociological reasons such as hiding interest in such content.

C. Geolocalisation of Users

We determined the geographic location of OneSwarm users using an IP-to-geolocation database 7 . As mentioned in Section 3, we identified users that were assigned to our monitoring nodes by the community servers (Community server Set) as well as users that were identified by monitoring BitTorrent bridge nodes (BitTorrent Set). There are 190 and 778 unique users (IP addresses) in the Community server Set and the BitTorrent Set, respectively.8 Table II presents results of the country-wise breakdown of OneSwarm user locations; Table III presents the same information for users found in the Community Server Set classified by the identity of the server 9 . Both tables show that an overwhelming majority of the users (among those discovered) are based in France. In the BitTorrent set, Sweden and the US account for the next biggest group of users. We notice that only few Swedish IPs were found on the default community server, and even on the Swedish community server (subcult.org) they represent only 19% of the users. There are two possible explanations for what we observe. Either the BitTorrent backward compatibility feature is prevalently used among OneSwarm's Swedish users, or these users do not rely on community servers to establish new connections in OneSwarm and instead manually exchange public keys. In fact, the OneSwarm official forum10 hosts a thread, dedicated to manual exchange of public keys of Sweden-based users, that includes more than 1200 public keys. This possibly explains the low presence of users from Sweden in our Community server Set, although Sweden is well-represented (28.12% of the collected IPs) in the BitTorrent Set.

The distribution of user per country in Oneswarm largely differs of the one of BitTorrent [START_REF] Zhang | Unrevealing the bittorrent ecosystem[END_REF]. Some countries like Netherlands, Luxembourg, China and Russia are almost absent from Oneswarm, while they are in the most represented countries on BitTorrent. A large fraction of Oneswarm's users are based in France and Sweden, countries that have enacted strong Intellectual Property Rights Protection and Enforcement laws [START_REF] Colchester | All eyes on france as officials enforce new antipiracy law[END_REF], [6] (IPRPE laws). In other words, amongst the highly represented countries in the BitTorrent ecosystem, those with weak or no IPRPE laws have not adopted Oneswarm, while a subset of those with strong IPRPE laws have largely adopted in Oneswarm. The existence of IPRPE laws in a country appears to be a possible reason for Oneswarm adoption, we call this the Copyright law effect. The wide adoption of OneSwarm in those countries can also be explained by social propagation and the existence of community of users. Indeed regional community servers has been deployed in those countries along with forums enabling the creation of a strong community of users. In order to assess the importance of the copyright law effect, it will be interesting to study how OneSwarm use evolves as other countries introduce stringent copyright laws.

D. Characterizing the System Activity

The search messages in OneSwarm can be divided into two categories: keyword-based and URI-based messages. To locate or download a content, either the OneSwarm user sends a Text search message, containing keywords that may target several contents, or the client sends a URI-based search message (Text or Hash search messages) targeting a unique content. Further, once the download is initiated, for performance purposes, the OneSwarm client keeps periodically 11 sending the URI-based search messages in the quest of potential new resources, or to update the list of connected known locations.

To analyze the network activity of OneSwarm, we consider the first category, i.e., the keywords-based search traffic, as an indicator of human activity as very often these messages require human-machine interactions. We then consider the second category of search messages, as an indication of active downloads. Since an active download is generating a search message for the content every 10 minutes, an estimate of the number of active downloads can be computed from the number of search messages observed over a given period of time.

Figure 4 shows our results for system activity. Time-of-day non-stationarity, similar to those observed for in many other network measurements, is observed. The observed traffic is the sum of the traffic of users in different time zones, a fraction of them being continuously connected while others may only be periodically online. According to Akamai statistics 12 , the highest Internet activity in the European regions is observed between 2 PM and 6 PM GMT, which coincides with the time frame of highest activity on OneSwarm. This observation lends further credence to our hypothesis that a large fraction of OneSwarm users are located in Europe.

E. Estimation of the Population Size

By design, OneSwarm prevents observers from either identifying or crawling its users. We estimate the number of OneSwarm users by leveraging the interaction with each of the public community servers. Specifically, when a user subscribes to a community server, the latter returns a list of 20 peers that are the closest to the subscriber 13 . By subscribing multiple times to a community server, using a different randomly generated public key, we can collect different sets of peers. By estimating the relative size of redundancy occurring during multiple subscriptions, a rough estimate of the population size can be obtained. We estimated each of the communities' population size using a Mark-and-Recapture method and the Schumacher-Eschmeyer estimator [START_REF] Schumacher | The estimation of fish populations in lakes and ponds[END_REF] . A total of n samples are collected, each sample i containing C i peers. We note R i the number of peers in capture i that have already been collected in previous samples, and M i the number of distinct peers collected before sample i. The Schumacher-Eschmeyer estimator of the server population is :

N = n i=1 CiM 2 i n i=1 RiMi .
For each community server, we subscribed 20 times, each time with a different identity. The results from our estimation are shown in Table IV. The UW CSE community has the largest population, possibly because it was the first, and the default community server, for the system. Similarly, we estimated the overlap between those communities, and our results show that there were in the order of 3000 users on those community servers.

V. PRIVACY IN ONESWARM

OneSwarm provides a high level of privacy to its users. In this section, we discuss two limitations that can result in a privacy breach.

A. The case of peer identification through BitTorrent

The backward compatibility with BitTorrent can enable identification of OneSwarm users that download content from the public BitTorrent ecosystem (see Section III-B). We notice that the default OneSwarm client behaviour may not be apparent to the users, as there is no visible indication that the client switches from the anonymous to the public mode. Adding a user warning or, preferably, user control of this feature, is a potential for further improvement in OneSwarm.

B. Indirect collusion attacks

In OneSwarm, a Hash search message is forwarded only if a node does not posses the requested content. This feature can be exploited by a set of colluding nodes, to infer the possession of a content by a targeted node. A direct collusion attack consists of an initiator that sends a Hash search message to the directly connected target node, while a set of observers monitor the traffic coming from the directly connected target. Depending on whether or not the Hash search message has been forwarded to the observers, the colluding nodes are able to infer if the content is shared by the target or not. Introduced by OneSwarm's designers, probabilistic forwarding [START_REF] Isdal | Privacy-preserving P2P data sharing with OneSwarm[END_REF] was supposed to solve this issue by making the attack ineffective unless the attacker controls a large number of nodes directly connected to the target. Prusty et. al. [START_REF] Prusty | Forensic Investigation of the OneSwarm Anonymous Filesharing System[END_REF] recently shown that this countermeasure was not sufficient and that direct collusion attack was practical.

We present an even more powerful variant of the collusion attack, wherein the observers are not directly connected. Note that messages forwarded by a targeted node will propagate through the overlay network and may be detected by monitoring nodes placed anywhere in the overlay network. As shown in Section III-A, a small set of monitoring nodes is sufficient for collection of a significant portion of the traffic generated by a node in the public community (e.g., one monitoring node capture 80% or more of the traffic). By replaying the attack a number of times, and by increasing the number of monitoring nodes, the confidence in the inference can be made arbitrarily close to one. Figure 5 shows the configuration of the attack, where one initiator node is directly connected to the targetet node replay search messages, while monitoring nodes are connected to the F2F network, but not necessarly to the targeted node. The initiator node send search messages to the target node, which in turn will forward them to the rest of the F2F network. Those messages will propagate through the F2F network and eventually reach the monitoring modes.

By design a request message for a content shared by the target will not be forwarded, the false negative probability is therefore equal to zero. A false positive is when the message is forwarded but not received by the monitoring nodes. Meaning that the message has not been propagated to the monitoring nodes. Let M i be the event where the ith search message sent to the target is detected by at least one monitoring node. Then, the false positive probability of a test with n replay is:

P f p = n i=1 (1 -P (M i |content is not shared)) = (1 -α) n
Where α is the probability that a message forwarded by the target is detected by at least one monitoring node. The value of α can be evaluated in the same way the connectivity between community was evaluated in section III-A . Its value depends on the number of monitoring nodes and the topology of the network between the target and the monitoring nodes. In the case of a target node and only one monitoring node, both connected to public communities, we can infer from Table I that α ≥ 80.8%.

We performed an experiment to test the effectiveness of an indirect collusion attack, with one directly connected node, a target node with known content, and only one monitoring node connected to the four public community servers and 100 replays of the search message. We have been able to capture the availability of specific content with a false negative probability of 0% and false positive probability of 2.02%.

VI. CONCLUSION

This paper presents a measurement-driven study of the OneSwarm system, with the goal of understanding the usage of this privacy-aware file sharing systems. We observe that content shared in the system is similar to that shared in other P2P systems and that a vast majority of users are located in few countries (France, Sweden, and US). Even if propagation in social media can explain this adoption, we observe that the highly represented countries have recently adopted anti copyright infringement laws, suggesting that the adoption of OneSwarm has been motivated by legal aspect. We conclude by identifying two limitations that may compromise the privacy of OneSwarm users.

Fig. 1 .

 1 Fig. 1. Overview of the measurement environment, including the public and private OneSwarm, and BitTorrent ecosystems.

Fig. 2 .

 2 Fig. 2. Content 'type' frequency comparison between the torrents found on OneSwarm, BitTorrent over Tor, and the Pirate Bay.

Fig. 3 .

 3 Fig. 3. Relative frequency of string searches.

Fig. 4 .

 4 Fig. 4. System activity and number of active downloads as a function of time (GMT).

Fig. 5 .

 5 Fig. 5. Collusion attack configuration.

TABLE II COUNTRY

 II REPRESENTATION IN ONESWARM.

		BitTorrent Set Community Server Set
	FR	52.94%	69.86%
	SWE	28.12%	5.80%
	US	9.03%	11.16%
	AUS	1.86%	0.44%
	CAN	1.86%	1.11%

TABLE IV ESTIMATION

 IV OF THE COMMUNITY SERVER POPULATION SIZE.

		UW CSE	oneswarm-fr lavilette
	estimated size	2518	666	51
	95 % conf.	(2002;3394)	(553; 780)	(45;59)

I2P Anonymous Network http://www.i2p2.de

Respectivly https://community.oneswarm.org, https://forum.oneswarmfr.net, https://lavilette.dyndns.org:8081, https://kf.subcult.org:8081

The BitTorrent trackers monitored are udp://tracker.openbittorrent.com, udp://tracker.publicbt.com and udp://tracker.istole.it

This high number is explained by the fact that OS clients are periodically generating messages while downloading.

The fonts of tag cloud, available at http://thepiratebay.org/searchcloud, show the popularity of a string relative to the popularity of the most popular string.

http://www.maxmind.com/app/ip-location

Our analysis was performed on-the-fly. We do not store any information such as IP addresses, user identities, or public keys.

Lavilette and subcult community servers were not included in this experiment because of their intermitent availability.

[START_REF] Stevens | Spying the World from your Laptop -Identifying and Profiling Content Providers and Big Downloaders in BitTorrent[END_REF] http://forum.oneswarm.org

Every 10 minutes in the OneSwarm client version 0.6.

http://www.akamai.com/html/technology/nui/retail/charts.html

Distance between subscribers is defined in terms of distances between users' public keys.


Duong Dang

Florent Lamiraux

Jean-Paul Laumond

Experiments on whole-body manipulation and locomotion with footstep real-time optimization

Keywords: locomotion, footsteps, adaptation, reactive, real-time, visual servoing

This paper focuses on the experiments on the HRP-2 humanoid robot using a framework of manipulation and locomotion with real-time footstep adaptation. Two classes of experiments are presented. On the one hand, a grasping task at various height level illustrates a whole-body task in combination with locomotion. On the other, stepping over obstacle experiments illustrate the particularity of humanoid robots. In all presented examples, footsteps are considered as a part of the robot's kinematic chain and are resolved as an optimization problem along with other degrees of freedom of the robot. The environment is perceived by the stereo vision system mounted on the robot which closes the loop with the control through an online footstep adaptation scheme.

I. INTRODUCTION

A. Problem statement and related works T HE high degree of redundancy and legged locomotion are two of the particularities that make the humanoid robotics research field both challenging and exciting. Either with a small size, miniature like robot or with a large size humanoid such as HRP-2, the researcher is provided with a formidable platform that is complex, highly redundant and capable of performing a large set of manipulation tasks. With legs, a humanoid robot can access to an environment specifically built for human, interact with that environment in an interesting way. Some examples are climbing up a stair case, jumping over obstacles, tasks that cannot be done by other type of robots, such as, say a wheeled mobile robot. If numerous works have been carried out in both manipulation and locomotion, the two aspects are usually treated as independent problems. Whole-body tasks are often considered completely separate from the footsteps.

Walking and running locomotion has been studied by a number of research group, [START_REF] Sugihara | Real-time humanoid motion generation through zmp manipulation based on inverted pendulum control[END_REF]- [START_REF] Kagami | A fast dynamically equilibrated walking trajectory generation method of humanoid robot[END_REF], notably with the introduction of the Zero Moment Point (ZMP), the analysis of the cart model and the inverted pendulum.

On manipulation side, task-based methods have been developed since the eighties of the last century for industrial robot and robotic arms, [START_REF] Nakamura | Task-priority based redundancy control of robot manipulators[END_REF], [START_REF] Khatib | A unified approach for motion and force control of robot manipulators: The operational space formulation[END_REF]. These methods have been extended to humanoids in recent years as more and more robots have been made available for research [START_REF] Ott | A humanoid two-arm system for dexterous manipulation[END_REF]- [START_REF] Gienger | Task-oriented whole body motion for humanoid robots[END_REF].

Online generation of footsteps have been studied previously by several research groups [START_REF] Perrin | Fast humanoid robot collision-free footstep planning using swept volume approximations[END_REF]- [START_REF] Kagami | Online 3d vision, motion planning and bipedal locomotion control coupling system of humanoid robot: H7[END_REF]. These online footstep generation methods use search algorithms, which are good at finding a feasible solution without an D. Dang, J-P. Laumond and F. Lamiraux are with CNRS, LAAS, 7, avenue du Colonel Roche, F-31077 Toulouse, France.

nddang@laas.fr emphasis on the optimality of the problem. This might results in unpredictable and "unnatural" footsteps and in practice leads to failure during experiment due to physical limitation of humanoid robots. In addition, whole-body manipulation is not integrated into the stepping decision. Kanoun et al. [START_REF] Kanoun | Planning foot placements for a humanoid robot: A problem of inverse kinematics[END_REF] has the idea of considering footsteps as parts of the robot kinematics and is driven by "whole-body" tasks. The notion of "whole-body" in this case is expanded to the virtual degrees of freedom related to locomotion. Footstep placement is then resolved in an optimization problem, in harmony with the upper-body movement. This way of reasoning about locomotion has been put together into a framework presented in [START_REF] Dang | A framework for manipulation and locomotion with realtime footstep replanning[END_REF] which combines manipulation and locomotion with a reactive footstep adjustment scheme in closed loop with perception. The goals of this framework are:

• Seamlessly integrate locomotion with whole body movement. Footsteps are considered as part of the robot and are dictated by the task applied to the augmented robot. • Build a reactive scheme that helps the robot achieve the task even if the environment is changed during execution.

• Resolve the foot placement by optimization so that it preserves the optimality, hence, the high feasibility of the movement. • Integrate with on-robot stereo vision to make the movement the most robust and portable possible. Moreover, combined with a prior motion planning step, the method is less subject to local minima than classical numerical optimization approaches.

B. Contribution

This paper is the follow up of the work introduced in [START_REF] Dang | A framework for manipulation and locomotion with realtime footstep replanning[END_REF]. The laid out framework is demonstrated in a number of new experimental situations (Figure 1). The implementation of stereo-vision on the HRP-2 robot is also improved to achieve tasks such as precise object grasping.

In addition, a new type of experiments is introduced (section III-B) illustrating the real-time footstep adjustment scheme in the typical context of humanoid robots, i.e. stepping over objects.

The representation of footsteps as the robot's extra degrees of freedom can be used to calculate the initial footsteps as well as to adapt these footsteps on the fly during the experiment. The framework is flexible enough to take as input any initial footsteps sequence and adapt them in real-time.

II. APPROACH AND TOOLS

Figure 2 depicts the global architecture of the framework. The planner plays the role of a "visual servo" for footsteps. It optimizes the stepping sequence in real-time and in closed-loop with the vision system. The controller takes as input the information from the visual servo and resolves the prioritized hierarchy of the corresponding primary tasks to send command to the robot in real-time. The perception system includes an automatic calibration process which improves precision and allows the framework to perform precise tasks such as grasping.

A. Perception

The tracking method on the robot is the broadly used CAMShift [START_REF] Bradski | Conputer vision face tracking for use in a perceptual user interface[END_REF] algorithm. The tracked 2D object is then projected into the PCL [START_REF] Rusu | 3D is here: Point Cloud Library (PCL)[END_REF] point cloud. Once outliers have been filtered out, one obtains the 3D-points on the object, hence its estimated position (Figure 3. 4.).

Automatic extrinsic parameter calibration: One major modification of the perception module is a better extrinsic parameter calibration. An automatic process has been developed which involved moving a chessboard fixed to the hand of the robot. During calibration, the robot hand was moved inside the vision field of the robot. (Figure 5) The recorded poses of the chessboard and corresponding joint angles are then recorded. The data is processed and fed to a calibrator using Tsai et. al. algorithm [START_REF] Tsai | A new technique for fully autonomous and efficient 3d robotics hand/eye calibration[END_REF]. This automatic calibration process helped significantly improve the performance of the vision system and allowed the robot to achieve tasks with better precision. The calibration process is available as a ROS package on the paper website.

B. Step deformation by localstepper

In the same spirit the "elastic band" introduced by [START_REF] Khatib | Dynamic path modification for car-like nonholonomic mobile robots[END_REF], [START_REF] Quinlan | Elastic bands: connecting path planning and control[END_REF] which connected path-planning and control for wheeled mobile robots, this framework uses optimization techniques to reactively build and adjust footsteps in real-time, hence provides the control corrections in a timely manner.

The core of localstepper is presented by Kanoun et al. [START_REF] Kanoun | Planning foot placements for a humanoid robot: A problem of inverse kinematics[END_REF]. The main idea here is to consider each footstep as a virtual link with three degrees of freedom (Figure 6). The augmented robot will be then resolved with the prioritized set of task, subjected to various constraints such as self-collision, obstacle avoidance, etc. With the introduction if inequality tasks, the constraints simply become tasks and are added to the prioritized set at the highest priorities. Let J i and e i are the Jacobians and errors corresponding to task i, in an hierarchy of k successive tasks, the resolution of the robot state vector q is summarized as follows Find q * ∈ S k :

S 0 = ℜ n S i = arg min q∈Si-1 1 2 ||J i q -e i || 2
for equality tasks

S i = arg min w, q∈Si-1 1 2 ||w|| 2 s.t. J i q -e i ≤ w
for inequality tasks Fig. 6. Each footstep as a virtual link with 3 degrees of freedom Fig. 7.

Deployment of the augmented robot

At the end of the process, (Figure 7) one obtains from the resulting q

• The footprints (the first 3n terms in q if the robot was to perform n steps). • The final posture (the rest of the terms).

C. StackofTasks

The controller in the framework is the StackOfTask, [START_REF] Mansard | Task sequencing for high-level sensor-based control[END_REF]- [START_REF] Stasse | Real-time (self)-collision avoidance task on a hrp-2 humanoid robot[END_REF]. The role of this controller is to find out, given a prioritized stack of tasks and within the limit of the control cycle, the control law qi .

In the case of a single task, this control law is simply

qi = -λJ + i e i (1)
J + i is the pseudo-inverse of the Jacobian J i . e i is the difference between desired feature s * i (i.e. a position in operational space, a posture, etc. ) and its current value s i :

e i = s i -s * i (2)
The control law on a prioritized set of tasks is written as [START_REF] Siciliano | A general framework for managing multiple tasks in highly redundant robotic systems[END_REF]:

qi = qi-1 + λ i J+ i ( ėi -J i qi-1 ), q1 = λ 1 J+ 1 ė1 (3)
when Ji is the projection of J i in the null space of the augmented Jacobian

J A i = [J 1 , J 2 , . . . J i-1 ] T (4) Ji = J i P A i-1 , P A i = I -(J A i ) + J A i ( 5
)
J+ 1 is simply J + 1 .
One recovers (1) if there is one task in the stack. This formulation guarantees that the task at ith stage does not disturb the previous tasks, i.e. with higher priority.

Goal

D. Pattern generator

The output of the planner, i.e. footprints is fed to a real-time pattern generator presented by Stasse et. al. [START_REF] Stasse | Fast foot prints re-planning and motion generation during walking in physical human-humanoid interaction[END_REF] with the underlying algorithm proposed by Kajita et. al. [START_REF] Kajita | Biped walking pattern generation by using preview control of zero-moment point[END_REF], [START_REF] Kajita | Biped walking pattern generator allowing auxiliary zmp control[END_REF], [START_REF] Morisawa | Pattern generation of biped walking constrained on parametric surface[END_REF]. The role of the pattern generator is to generate trajectories of operational points (feet, center of mass), which can be used directly by the controller, as well as the ZMP's trajectory which is fed to the stabilizer on the robot.

III. EXPERIMENTS

Figure 2 shows the information flow during the experiments. The "Upper body tasks " arrow can be omitted in section III-A and III-B as these experiments involve only footstep placements.

A. Stepping towards a goal

This is the first application of the localstepper concept. Suppose that the robot needs to go to a goal position while avoiding r holes on the ground (Figure 8(a)). To achieve this goal, an initial sequence of n footsteps is added to the robot. In localstepper frameworks, this is translated into 3n additional degrees of freedom added to the robot kinematic chain. (Figure 8(b)). Since the upper body is not subject to a specific task, the optimization problem presented in II-B will simplify and only act on the vector q representing the additional 3n degree of freedom.

arg min q∈R 3n ||X f inal_step -X goal || (6)
subject to q i min ≤ q i ≤ q i max , ∀i ∈ 1, 2 . . . 3n

D ij self _collision > 0, ∀i = j ∈ 1, 2 . . . n (7)
D ij obstacle_step > 0, ∀i ∈ 1, 2 . . . n and j ∈ 1, 2 . . . r (8)
Where X f inal_step and X goal are 3 dimensional vector representing footsteps (x, y, θ).

The resulting footstep (Figure 8(c)) is then executed by the robot. When the goal moves, the footsteps are updated during experiment by resolving the same optimization problem. Since the initial guess of the new optimization problem is the current solution, provided the goal moves at reasonable pace, the optimization process is quick and takes typically tens of milliseconds to compute, more than enough for the control to change the footsteps reactively (the stepping period on the HRP-2 robot is 0.8s.)

B. Stepping over obstacles

In this experiment, the task assigned to the robot is to overcome a long cylindrical bar. The bar is long enough and its unknown characteristics make it impossible for the robot to step on. This example illustrates a main specialty of legged locomotion.

To achieve the assigned task, the robot has to step over the obstacle whose position is estimated by the stereo vision system mounted on the robot. As any stereo system, the precision of the estimated position gets better when the robot gets closer to the tracked object (bar). Moreover, the bar is also intentionally moved by a human during the experiment. As a result, either to take into account the updated perceived position or a real displacement of the object, there is a need of reactive footstep adjustment.

1) Compute initial stepping sequence: As localstepper takes initial footprints and initial robot configuration as inputs, a stepping sequence computed by any method can be fed to localstepper. For instance, the 3D swept volume method as describe in [START_REF] Perrin | Fast humanoid robot collision-free footstep planning using swept volume approximations[END_REF] which allows stepping over obstacles up can be used as the initial sequence.

2) Online deformation: As the perceived position of the obstacle is continuously updated plus the fact that the obstacle might be moved during the experiment; the footsteps have to be recalculated as fast as possible.

Provided that form of the obstacle is unchanged (long cylindrical bar with known diameter), the robot only needs to make sure that the two subsequent steps that cross the bar stay unchanged with respect to the bar. We then recover the same situation described in III-A: stepping towards a moving target.

The footstep adjustment scheme for the stepping over experiment can be written as algorithm 1, when x 0 , y 0 , x are three-dimensional vectors in the footprint coordinate (x, y, θ).

3) Experiment: In the experiment depicted in Figure 9, the bar is marked by a color orange band and detected by the module detailed in II-A.

Thanks to the online optimization scheme, the robot has no problem crossing both a fixed and a mobile bar. Figure 10 describes how the bar is tracked during the movement, Figure 11 depicts the estimated position of the bar. C. Grasping objects [START_REF] Sugihara | Real-time humanoid motion generation through zmp manipulation based on inverted pendulum control[END_REF] Stepping as a side effect of upper-body task: As presented in [START_REF] Kanoun | Planning foot placements for a humanoid robot: A problem of inverse kinematics[END_REF], [START_REF] Dang | A framework for manipulation and locomotion with realtime footstep replanning[END_REF], one important point to be noted here is the fact that stepping is simply the result of the upper-body task, in this case, the grasping task. By considering footsteps parts of the robot's kinematic chain, the resolution of the optimization problem presented in II-B automatically deploys the footsteps. In the same fashion, footstep deformation is also a consequence of the modification of the grasping task (target physically moves or the perceived position changes as the robot approaches the target).

2) Online footstep optimization: It is assumed in this experiment that the grasping target moves but the environment around it stays intact, i.e. the ball is always on the ground or on the table and no new obstacle appears during the experiment. With that assumption, one can "freeze" the posture of the standing robot. The modification of the grasping task will only affect the footsteps. The computation time (Table I) is well below the stepping period (0.8s for HRP-2 in this case) and allows a reactive walking scheme.

3) Walking-grasping transition: In Figure 2, the visual servo has two parts

• localstepper which regenerates posture and footsteps.

• a servo which feeds directly the target into the grasping task. The perception module returns a 3D goal position. The planner only outputs the final posture and desired footsteps. An additional step is needed for the robot to use these pieces of information to generate a movement on the robot.

In order to achieve a feasible, fluid, movement, a posture task is added to the StackOfTasks at the lowest priority. This task does not affect the stability of the system and prepares the robot in the grasping posture even before the last step (Figure 12.).

For the grasping task, a cubic spline is used to make sure that the hand passes by the appropriate way-point to successfully grasp the object. Experiments of grasping with objects at different height and position have been carried out on the robot ( Figure 12 and 13) with the possibility to move the object while the robot is walking. IV. CONCLUSIONS The combination of reactive localstepper, the StackOfTasks and the stereo vision system on the HRP-2 robot forms a powerful toolbox that can be used in a large set of applications.

Footstep deformation by localstepper provides a quick robust footstep planner to adapt arbitrary input stepping sequences to deal with changes in the environment.

One limitation of this footstep adjustment scheme is that it resolves a local problem. If the environment changes drastically, the planner can be stuck in local minima. To amend this limitation, the framework has to be combined with a global step planner.

Fig. 1 .

 1 Fig. 1. Experiments on HRP-2 using the real-time footstep optimization. Videos available at www.homepages.laas.fr/nddang/hm12

Fig. 2 .

 2 Fig. 2. Information flow of the framework. Dotted line means compute only once

Fig. 3 .Fig. 5 .

 35 Fig. 3. 2D tracking Fig. 4. Projection into the point cloud

Fig. 8 .

 8 Fig. 8. Stepping towards a goal with localstepper

Fig. 9 . 2 Fig. 10 .Fig. 11 .Algorithm 1

 9210111 Fig. 9. Stepping over a bar on HRP-2

Fig. 12 .

 12 Fig. 12. Walking and grasping an object at table level on HRP-2

Fig. 13 .

 13 Fig. 13. Walking and grasping an object at ground level on HRP-2

TABLE I CPU

 I TIME FOR FOOTSTEP OPTIMIZATION IN A GRASPING EXPERIMENT


Emmanuel Prados

Pierre-Yves Longaretti

Élise Arnaud

Patrick Criqui

Denis Dupré

Benoit Lefevre

Mathieu Saujot

Peter Sturm

Jean-Yves Courtonne

Julien Alapetite

Denis

Integrated Urban Modelling for Sustainable Policies: Considerations and Difficulties

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

April 2012

The numerous and interrelated pressures exerted by human activity on the environment make the identification of sustainable development pathways arduous. On the one hand urban areas, as focal points of human activity, concentrate most of these pressures in a direct or indirect way. Our civilization has turned worldwide into an urban one, with more than half the human population living in cities, an ever-increasing trend. Furthermore, urban sprawl is a ubiquitous phenomenon showing no sign of slackening yet, even in countries where rural depopulation has long been stabilized. Therefore controlling urban sprawl is a key sustainability issue. These challenges require a panel of policy measures at all institutional levels, but the local decision levels have more and more importance, especially in a "think global/act local" approach. Providing decision-making tools to support local ones in the implementation of this transition is then critical. In particular, it is necessary to evaluate policies in a quantitative way. Data collections and direct analyses can already provide significant insights, but in this context of strongly interrelated phenomena with indirect feedback loops, integrated modeling is a key tool. One of the first questions which then arise is what "kind" of integrated models could help to understand the main blocking points and to identify levers ? What should be the main components of such models and what could be adequate scale ? How to incorporate integrated modeling tools in the whole decision process ? ... Another type of questions is: what are the main limitations and what kinds of technical difficulties one is confronted with when dealing with local scale integrated modeling?

The goal of this presentation is to share our considerations on those questions. Clearly, the problems posed by scale and spatialization are complex but essential. They naturally lead to flux issues of different and complementary types. First this results in material flow analyses as it is done in urban metabolism. It also results in land use and transport modeling as it is done in urban economy. Technical difficulties and challenges are numerous: they go from model calibration and convergence issues to uncertainty management. Model validation and data issues are also a very sensible... To illustrate the discussion, some examples of concrete projects conducted in STEEP research group will be presented.


Eleonora Gentilucci

Military spending : A perspective on the restructuring dynamics of the defense sector

Keywords: military-industrial complex, industry concentration, defense sector, military expenditures, public spending, trade-off effect, financialization, industry restructuring, military-security system complexe militaro-industriel, concentration industrielle, secteur de la défense, dépenses militaires, dépenses publiques, effet d'arbitrage, financiarisation, restructuration industrielle, système militaro-sécuritaire H, H56, L, N4, P

Chercheuse associée au Centre d'économie de la Sorbonne)

This article is articulated in two sections. In the first-one we try to explain the dynamics of military spending and others social expenditures in the period 1988-2010 for the United States. According to empirical data we support the argument that there is a remarkable trade-off in the allocation of public spending, because, often, the increase in military expenditures was to detriment of those for the education, social security and health. In the second section we analyze the transition from the old "military industrial complex" to the new "military security system" in the light of defense industry restructuring. We focus in particular on the role of financialization and industrial concentration of the firms.

2

The economic and financial crisis had profound effects on the global economy. This resulted in a reduction of public expenditure of the states, while military spending continues, to increase. The questions that arise are the following: why this type of expenditure follows a different and contrary route compared to other public expenditures? What are the interactions between this trend in military expenditures and that of arms industry? Furthermore, could we provide a satisfactory answer to these demands, without considering the changes in the economic system as a whole and particularly the financialization of the economy?

From the methodological perspective, two choices are required: one concerning the geographical dimension and the other the temporal dimension.

We chose to conduct our analysis on military spending and on structural changes of the defense sector, limiting ourselves to the particular economic and geostrategic area represented by the United States, because we believe that it constitutes the most representative case and we will explain later the reasons that compel us to support this thesis.

Given the available data for the aggregate object of this work, our analysis covers about two decades, from 1988 until the years 2008-2009. This article supports the argument that the structural changes and dynamics of concentration and financialization of the defense sector are the maximization "of waste and illegal profits"2

We will try to defend this thesis both from a theoretical and empirical point of view, through the data concerning the evolution of military spending and other expenditures, the financialization of defense and the dynamics of concentration of the industry. Theoretical analysis of mutation of the "military-industrial complex" characterized by using the concept of the "military-security system," represents the heart of the issue since it is closely influenced by the so-called vested interests.

in the sense used by Reich, perpetuated by the so-called "vested interests", and this in a area which has always been a source of waste in favor of those individuals who gravitate around the defense industry. Indeed we can easily see in this graph that from 1999 there was a strong recovery in growth of military spending worldwide, driven primarily by North America and particularly by the United States. This trend appears to be in sharp contrast to the long-term forecasts formulated by several researchers and international agencies after the fall of the Berlin Wall, about the so called "peace dividend 5 As already mentioned in the introduction, we must consider the joint evolution of defense spending and defense industry in its context more representative and more structuring in the economic world. Is for this reason that we will study the military of the United State, the country where there are the largest military expenditure in the world, and on the geostrategic level, can also be considered as the leader capitalist country, because of its supremacy both economic and political-military ". Soon, we will find that the reconversion of the military system in civilian activities represented only a tepid mirage face the reality.

6

In fact, U.S. military spending represent 45% of the world total in 2007. Following the commitments to military operations in Afghanistan, military spending in the U.S. increased between 2001 and 2007 by 59% .

7

Since 2007, military spending by the U.S. reached the highest levels since World War II. Certainly it is extremely important to distinguish the evolution of military spending in constant dollars and as the percentage of GDP, as shown by the graphs below. to military spending has increased significantly (3%), much more than health care (1%), while education expenditures have drastically dropped by 3.4 percentage points. The interpretation of this stylized fact suggests the hypothesis that the increase in military spending resulted, at least in part, from an arbitration effect over the other expenses considered. At this stage of our research, the lack of data from the same source for the previous period, prevents us from assessing the trend of these expenditures during the whole period covered by our study. However, this result confirms the findings of an empirical study 12 that we carried out in 2004 13 whose purpose was a diachronical comparative analysis between the ratios defense spending / total public expenditure (Sd) and expenditures for that we called the "Welfare State 14 in the United States there has indeed been a trade-off between the two ratios characterized by an opposite and specular trend of Sw and Sd over time, when the first increases the second falls, and vice versa. At this stage of our work, three results deserve especially to be highlighted in order to tackle, in the next section, the analysis of the restructuring of the armaments sector.

The first relates to how the U.S. emerged as a leader with regard to military expenditures. Their superiority is shown first by the size of the budget allocated to this expenditure compared to other countries. It suffices to note that during the period studied and in 2009 and 2010, the U.S. has supported nearly half of world military expenditure.

The second, despite the results provided in Figure 3 which shows that the ratio DM / GDP refers to the way in which military expenditures in this country have risen sharply during the period 1988-2008 (see Figure 2). Expectations related to the fall of the Berlin Wall and concerning "peace dividends" were disappointed. In fact, the decrease of military expenditures characterizing the period 1989-1998 was of short duration. At the end of a process of exceptional growth, they have reached levels even higher than that they obtained in 1988. This increase may be explained both by economic, political and military reasons inside the country and attached to the "vested interests" of the so called "military-security system 15 Finally, another key element that emerged from our empirical analysis concerns the distribution of public expenditure of the state between its three main components, i.e. those for health, for military and education. On the basis of the data analysis we can see that, in the interval 2001-2008, military expenditures have experienced a significant growth, whereas at the same time, those for education fell ", and by geopolitical reasons connected with the leading role played by the United States on the international scene. In the following analysis we will place our attention mainly on the first set of reasons by relying on the literature on the "military-industrial complex" and on the "military-security system" to assess the impact of the restructuring of the armaments sector.

significantly. In support of our 2004 study we were able to support the argument that there is a remarkable trade-off in the allocation of public spending, because often the increase in military spending was at the expense of allocations for education, social security and health.

2 The restructuring of the defense sector : from the "militaryindustrial complex" to the "military-security system."

It is with the famous farewell address by President Eisenhower in 1961, we started talking about the "military -industrial complex." The "military-industrial complex" is considered an independent entity, located above the influences that may affect other types of public spending and submit them to some control.

These coalitions of interests are composed of members of the armed forces, the legislative assembly and private enterprises who produce weapons as well as the Department of Defense. In this way decisions on defense and military policy in particular, remain strongly influenced by pressure groups that compose the "military-industrial complex."

As argued by Mills (1956), one of the specific characteristics of the "military-industrial complex" is the link between the elites who have held political, military and economic power.

The military establishment consists of the armed forces, bureaucracy, private arms companies. As stressed by Galbraith 16

To better understand the functioning of the "military-industrial complex", we should highlight certain features, which are quite singular, regulating military expenditures: first it is public spending that cannot be controlled by public opinion as it is a strategic sector in which sensitive information "may" not be revealed. This aspect helps to explain the lack of transparency about feedback on military expenditure. This "secret" character results in a second feature, namely the impossibility of finding a "good measure"

, there was "at stake [, ...,] very tangible financial rewards " especially since these expenses "enriched individuals -corporate managers, scientists, engineers, members of the defense lobbies, workers of armament. " However Galbraith asserts that military power is not only supported by political and democratic decisions, but it also has a very strong self-determining power.17 to quantify the economic and financial efforts made in this sector. This prevents us from making an objective judgment on its weight because the scope is, in the final analysis, the "security" of the nation. It also follows that those who make decisions regarding the security of the nation may always justify the huge effort made in this sector without delivering verifiable data. Moreover information may also be manipulated by sector entrepreneurs and by those who have the power to "share the pie" because military spending is extremely advantageous for the contractors of the Department of Defense. As argued by Melman 18 16 Galbraith, J.K., Economie hétérodoxe, Editions du Seuil, Septembre 2007. rising costs and government grants is ideal for sector companies and managers of the military industry in the Pentagon because it increases their decision-making power. In addition, the most important companies in the military sector contribute significantly to the election campaigns of politicians especially members of the U.S.

Congress. The "waste and illicit profits," as already noted in 1975 by Reich, are inherent to the nature of the sector.

The testimony of former economist of the National Security Agency of the United States, John Perkins19 , emphasizes the strategic role of defense. He argues that there were three phases to force foreign states (in particular developing countries) to implement the economic policies decided by the USA. The first was the persuasion of the heads of governments, " the money in a pocket and a gun in the other", if that one did not lead, then there was a second phase in which CIA 20 agents went into action to overthrow the Government or to assassinate political leaders. Finally, if the goal was not reached, the armed forces went into action. The geo-economic and political vision of defense related to the international role of the United States show us the new form of exploitation of sources of profits where they occur. So here's the concept, according to which militarism is only the armed wing of capitalism is revitalized by a new powerful force, thus restaging of the concept of imperialism 2122 However, today as in the past, to try to understand more fully the challenges facing the sector we must ask a basic question, "Cui prodest"? Indeed it is in Seneca's tragedy, Medea . 23 that we identify the following verses: "Cui prodest scelus, is fecit", that is to say literally: "for whom the crime advances, he has done it" 24 Certainly, today, we can identify the main source of self-determination of military power in the network of relationships and power cemented by the economic-financial component, which links the major players in the defense sector by uniting them in the common goal of optimizing the interests of benchmark lobbies often manifested by profit maximization. Today the concept of "military-security system" was replaced by that of the "military-industrial complex." In order to understand the true nature of this change, we must analyze its two key issues: the security issue and the dynamics of the financialisation of defense, which will be discussed in the next section.

. And so we return to the "vested interests" hiding in the defense sector.

As stated by Serfati (2008 25 We fully share with Serfati the focus on the strategic dimension of the concept of security in the current globalization and the idea of a transition from the model of "military-industrial complex" to that of "military-security system", while emphasizing the continuity of functions that these two modes of regulation play in the reproduction of capitalism, through a combination of historically determined ) one of the most important factors characterizing what he defines as the current military-industrial system, is represented by the transition from the concept of defense to the more general one of security. Indeed, Serfati explains that the concept of security refers to a strategic dimension and is a sort of corollary to the current globalization. 9 institutional forms. The political and ideological goal of a creation of the Department of National Security26

The financialization of the defense sector

was to promote the extension of the concept of "security" beyond the more restrictive connotation of "defense".

In consideration of the fact that the objective of our analysis is to evaluate the defense sector in the economic environment, we cannot ignore one of the phenomena that, with the concentration, have most strongly marked recent economic changes: it is the financialization of the economy. In fact we are witnessing the rise of a strong system, mainly characterized by the "accumulation à dominante financière" 27 Besides, we must focus on the financial component to analyze the changes in the "military-industrial complex" and its transition to the "military-security system." From the 1980s on, but especially in the 1990s, there was a restructuring process of the armaments sector characterized by two main phenomena: the strong dynamics of industry concentration accompanied by the sector financialisation. These two phenomena are closely linked because, increasingly globalized finance penetrates the capital of military industrial groups that are restructuring by increasing their degree of concentration, also thanks to capital provided by institutional investors. Indeed, according to Mampaey (2009) .

28

Restructuring of the armaments industry, is characterized also by a phenomenon closely related to that just described above. In effect, managers of large enterprises, as in the civilian sector of the economy, have on average a percentage of capital of around 5%. This transformation explains why companies are also increasingly subject to the criteria of financial profitability and thus searching for short-term profits. In our opinion, this trend, far from marginalizing, strengthens, in the name of free market, the power of some "vested interests", while opening the door to the logic of financial speculation.

, on average the percentage of capital held by all the institutional investors in the twelve major groups of armament, reached the level of 80% while the average of the Standard & Poor's (S & P ) is 71.5%. Still, "the fifteen largest institutional investors in a group have on average 47.6% stake in this group," but in fact "the capital of major weapons companies is focused on a handful of assets managers, present in the capital of almost all major groups of weapons, and often in a position of the reference shareholders with stakes from 5% to over 15%."

The concentration of the defense sector

One of the processes characterizing the world economy, in the sense of Chesnais, is "the tendency to homogenization, taking the form of strengthening the" world market "as a common area of valorization that puts all companies in competition causing a direct elimination process and a strictly global concentration." 29 Starting from the middle of the 1990s, the defense sector has been marked by an increase in the degree of concentration of military industries. In effect, we have seen an important process of mergers and acquisitions that occurred primarily in the United States. In the table below, we can observe the evolution of the concentration in the sale of weapons and in total sales of the largest companies in the defense sector, in the period 1990-2005. From this observation, the question is whether these trends also affect the field of defense economics. Statistical data provided by SIPRI show that in 2009 seven of the ten largest companies in the defense sector were American. The level of concentration of the sector has grown remarkably in the interval 1990-2000, while between 2000 and 2005, the increase was less important. In fact, this industrial strategy found its starting point around 1993, when the Deputy Secretary to the Department of Defense in the United States, W. Perry, prompted the leaders of the largest companies to merge.

This process has been stopped to some extent in 1998 when the Department of Justice expressed an opinion unfavorable to the acquisition project of Northrop Grumman by Lockheed Martin. However, acquisitions started up again, and using the SIPRI data, we achieved two scatter plots showing the evolution of the concentration of companies through their market share (see Figures 6 and7).

The two graphs below concern the evolution of the concentration of 20 companies of the military from 1990 to 2005. They refer respectively to total sales and sales of arms of the top 20 companies in the armaments sector. We marked the trend line to show more explicitly the increase in the market share held by the enterprises concerned. The market share of weapons held by the top five companies of armaments between 1990 and 2005 increases from 22% to 43%, while the one owned by the top 20 companies from 57% to 74%.

The linear trend line is a good approximation of the evolution of the concentration as shown by the value of the coefficient of determination (R 2 ) which is very significant, approaching unity (see Table 2). 6 and7.

It is clear that the increase in the concentration of the market was very strong. This is especially horizontal concentration, but also vertical concentration. In fact, the disengagement of the groups that produce mainly for the civilian activities from armaments production (especially the sub-armament systems) has determined the acquisition of these activities by the major groups of armaments, namely the prime contractors 30 . This fact has led to increase the market power that Mampaey and Serfati (2004) This leads us to conclude that the defense sector continues an original development dynamic. In fact, its entirely unique evolution brings us to characterize it as a complex system of interrelations between several actors, bearing special and convergent interests.

Increasing the concentration determines a two sided phenomenon: on the one hand, there is an increased dependence on the arms industry compared to the military component of their business, and therefore compared to the decisions of the DoD as well as compared to the strategic choices made by those responsible for international security policy.

On the other hand, the number of companies which are "prime contractors" decreases more and more, as well as the number of enterprises which are suppliers of armament sub-systems. Therefore, the DoD is in a situation where competition among companies falls sharply. This raises questions and doubts about the quality and performance of the systems proposed by the "prime contractors" that, following their vertical integration, can control most of the market, thanks to their "relational power", reinforced moreover by the new financial component. Thus, as we have just seen, in the analysis of factors leading to this high concentration we do not forget the role of financialization in the dynamics of mergers and acquisitions that changed the world economy.

General conclusions

From the analysis in this contribution, it is possible to identify two main sets of conclusions that articulate in a logical order, both theory and history, as well as empirical evidence and theoretical conceptualization.

1. The first set concerns the identification of three key stylized facts, often unnoticed in the economic literature on this topic, namely:

13

-After a period of sharp decline between 1989 and 1998, military spending has begun to grow, reaching levels higher than those recorded in 1988;

-At the sectoral level, the financial component of the economy has affected this sector through the provision of capital from institutional investors as well as through the acquisition, by the managers, of a part of the company's capital (around 5%);

-Finally, the exceptional dynamics of industrial concentration that characterized the industry and which sees the top twenty companies owning more than 80% of the market.

2. The second set of conclusions concerns the theoretical interpretation of the meaning and the issues of these stylized facts. It refers to three main considerations that can contribute to explain the thesis, proposed by Serfati of the passage, from the "Military-Industrial Complex" to the "Militarysecurity system".

a. First, the dynamics of military spending is the driving factor of sector restructuring. This latter can be regarded as the product of the response of the arms industry and of the old "military industrial complex" to the effects of the budgetary cuts to military spending, which followed the fall of the Berlin Wall. It should be understood as the result of a period of severe crisis for interest-bearing (more or less hidden) of the defense sector, a crisis triggered by cutting military spending in favor of the so called "peace dividend". Expectations for this latter were ephemeral and deceptive: after nine years, the restructuring of the defense sector by means of concentration and financialisation, has laid the groundwork for what is called the "military-security system". In this context, many subcontractors, who produced arms subsystems for prime contractors have disappeared; companies that had a dual33 b. Second, the joint effect of the dynamics of financialization and concentration is associated with an industrial strategy more short-term oriented. However, submission to the logic of the short-term financial speculation of a sector strategic by definition such as the defense, can, in our view, accentuate trends to waste and to the pursuit of illegal profits, which have always characterized this sector. In this sense, the old "military industrial complex" changes and becomes systemic. Here we have one of the key factors in the genesis of what Serfati called the "military-security system".

production, have withdrawn completely from the defense sector, and many of them have been acquired (vertical acquisition) by the prime contractors that have diminished following a process of horizontal mergers and acquisitions. With the exception of some particular cases, the authority to regulate competition was rather tolerant, as evidenced by the concentration data. In parallel, we are witnessing a radical change in the shareholding structure of the defense industries: institutional investors are "reverted" in this sector to achieve much higher shareholdings than in the rest of the industry. Moreover, the managers have had access to participation in the capital firms. c. Finally, these changes in the structure of the "military-industrial complex" have also enabled the most powerful "vested interests" to win the internal war triggered by budgetary cuts to the sector. They have also changed its nature and turned it into a "military-security system." The power output of the system is enhanced, while allowing to endogenize and strengthen some of the largest lobbies of power among the oldest "vested interests". Vested interests and the economy in all its aspects, including the financial dimension, support each other taking advantage of the oligopolistic market gained, in a more or less hidden way. The links between interest-bearing were tightened systemically, while the influence and the power of finance on the DoD, on the military and on the politicians increased.

The transition to the "military-security system," resulting from the logic of sector restructuring, was also reinforced by the more extensive assertion of the security concept that has replaced that of defense.

The monster of whom Eisenhower spoke in his farewell address to the nation appeared to have been mortally wounded by the disarmament race that followed the end of the Cold War. However, soon we realized that the military industrial complex, like the Phoenix is always reborn from its ashes. It has reappeared, transformed, more powerful and less vulnerable than ever before: the power of the lobbies around him , increasingly enhanced.

1Figure 1 .

 1 Figure 1. The evolution of world military expenditure in millions of constant US dollars at 2009 prices. Source: SIPRI

Figure 2 ..Figure 4

 24 Figure 2. Military expenditure in the U.S. in millions of dollars constant at 2009 prices. Source: SIPRI

Figure 5

 5 Figure 5 Changes in defense spending and spending for the welfare state on the total public expenditure.

Figure 6 -Figure 7 -

 67 Figure 6 -The concentration of total sales of Defence. Source: SIPRI

Concentration Ratios: Changes in Concentration Ratios (% of combined total of SIPRI Top 100 Companies, 1990-2005)

			Arms Sales			Total sales
	Company	1990 1995 2000	2005 1990 1995 2000	2005
	selection
	5 Largest	22	28	41	43	33	34	43	45
	Companies
	10 Largest	37	42	57	62	51	52	61	62
	Companies
	15 Largest	48	53	65	69	61	64	71	73
	Companies
	20 Largest	57	61	70	74	69	72	79	81
	Companies

Table 1 : The change over time of concentration ratios of the defense sector. Source SIPRI.

 1

Table 2 : Values of R 2 calculated for the trend lines of Figures

 2

			Value of R 2
		5 Largest	10 Largest	15 Largest	20 Largest
		Companies	Companies	Companies	Companies
	R 2 total sales	0,898	0,8733	0,9607	0,9556
	R 2 arms sales	0,9346	0,9529	0,9607	0,973

Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

  call "relational power 31 " because of the characteristics of the armaments sector. As evidenced by Mampaey, "the scheme of vertical concentration [...] does not match the dominant strategic model, only if we consider that the technological process of production of weapons is, in its entirety, a specific trade."32

[START_REF] Reich | Se le spese militari siano necessarie all'economia degli Stati Uniti[END_REF] "Se le spese militari siano necessarie all'economia degli Stati Uniti", Massimo D'Antonio (ed.) La crisi post-keynesiana, Universale Scientifica Boringhieri, Turin.

SIPRI : Stockholm International Peace Research Institute.

The interruption of the two lines in the graph in 1991 is due to a lack of data for the period concerned. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

This notion was introduced for the first time by[START_REF] Knight | The Peace Dividend: Military Spending Cuts and Economic Growth[END_REF], who by using a Solow-type model of growth showed that the increase in military spending produced a negative effect on growth. The quantification of benefits derived from the reduction of these costs has been called the "peace dividend"..

Similar methodological considerations are developed by[START_REF] Mampaey | Gouvernement d'entreprise, finance et technologie dans les groupes de production d'armements aux Etats-Unis : une lecture institutionnaliste[END_REF].

Source : Sipri Yearbook 2008. http://www.sipri.org/yearbook/2008/05/05. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

Star Wars (or Strategic Defense Initiative) was a project launched in 1983, during the Cold War, by the U.S. president, Ronald Reagan.(1988). However it is essential to also take into account data on U.S. military spending in constant dollars in 2009. It is then possible to note that despite the downward trend that followed the fall of the Berlin Wall during the decade 1989-1998, we are Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

Source : SIPRI. " (SW). On the basis of the data obtained for the period 1975-2001, we demonstrated (see graph below) that

Source : SIPRI.

It should nevertheless be noted that the data provided by the World Bank is not exhaustive. It does not provide complete data for the period 2001-2008. http://databank.worldbank.org/ddp/home.do?Step=3&id=4

The weak point is represented by the lack of homogeneity of the data used in both analyzes and therefore, although the results are indicative, we can not to bring a correct and consistent comparison of the two results.

Gentilucci, E., Spese militari e sviluppo economico, Thesis for a degree in business administration, University of Urbino "Carlo Bo", Urbino,[START_REF] Gentilucci | Spese militari e sviluppo economico, Thesis for a degree in economics and business, University of Urbino "Carlo Bo[END_REF]

This ratio is given by the following formula: (Education Expenditure + Expenditure on Health + Expenditure on Social Security) / Total public expenditure. Data source: Government Financial Statistics Yearbook of the International Monetary Fund. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

We will return later on this concept which can be considered like the evolution of the "military-industrial complex." Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

The Pentagon's management accepted the growing historical cost as methodology of cost determination in the defense sector. The Air Force Systems Command in 1965 offers a guide for assessment of costs based on historical cost data to determine future ones. See Fitzgerald(1972).

Melman, S., Guerra S.p.A. L'economia militare e il declino degli Stati Uniti, Città Aperta Edizioni s.r.l., Troina, 2006. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

See Report, "Effetto valanga" Michele Buono interview with John Hopkins, 30 October

 20 Central Intelligence Agency was founded in 1947 in the United States by the National Security Act.21 For a deepening into the links between militarism and imperialism, see: Serfati, C., Impérialisme et militarisme : actualité du XXI e siècle, Editions Page deux. Collection « Cahiers libres »,Losanna, 2004. 22 See[START_REF] Hobson | Imperialism", italian translation, L'imperialismo[END_REF].23 Seneca, L.A., Medea, Translations of Alfonso Traina, facing Latin text. Preface to the text, introduction and notes by Giuseppe GilbertoBiondi, pp. 165, Fabbri Editore, Milan, 2000. 24 Our translation.25 Serfati, C., Une économie politique de la sécurité, Karthal, Paris, 2008. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

To deepen the role played by the Homeland Security Department, see L. Mampaey and C. Serfati, "Les groupes de l'armement et les marchés financiers : vers une convention « Guerre sans limites?", La finance mondialisée. Racines sociales et politiques, configuration, conséquences, edited by FrançoisChesnais, La Découverte, Paris, 2004.

See on this subject: F.[START_REF] Chesnais | La théorie du régime d'accumulation financiarisée : contenu, portée et interrogations[END_REF] op.cit. and C. Serfati, "Puissance du capital financier : les limites endogènes du capitalisme mondialisé", in G. Duménil and D. Lévy, Le Triangle infernal, op.cit. and "La domination du capital financier" in Appel des économistes pour sortir de la pensée unique, Les pièges de la finance mondiale, book edited by F.Chesnais and D. Plihon, Editions La Découverte et Syros, Paris, 2000.

[START_REF] Mampaey | Gouvernement d'entreprise, finance et technologie dans les groupes de production d'armements aux Etats-Unis : une lecture institutionnaliste[END_REF], pp. 249-251. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

Chesnais, F. « La théorie du régime d'accumulation financiarisée : contenu, portée et interrogations. », Forum de la Régulation, Paris, 11-12 October 2001, Revised and amplified for distribution, March 29, 2002. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

The "prime contractors", that is to say the main contractors of DoD (Department of Defense).

"Pouvoir relationnel".

[START_REF] Mampaey | Gouvernement d'entreprise, finance et technologie dans les groupes de production d'armements aux Etats-Unis : une lecture institutionnaliste[END_REF], p. 239. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

That is to say, in the two branches of the economy: civil and military. Documents de Travail du Centre d'Economie de la Sorbonne -2012.60

Documents de Travail du Centre d'Economie de la Sorbonne -2012.60


Michel Morel
email: michel.morel@dcn.fr

Marie-Pierre Gleizes

Aldo Napoli
email: aldo.napoli@cindy.ensmp.fr

Anne Littaye
email: anne.littaye@ylahe.net

Valerie Bazin
email: valerie.bazin@onera.fr

Bernard Alhadef
email: balhadef@sofresud.com

Christian Scapel

Bruno Leroy
email: bruno.leroy@equipement.gouv.fr

Jacques Lebrevelec

Daniel Dejardin
email: daniel.dejardin@equipement.gouv.fr

ScanMaris: an Adaptive and Integrative Approach for Wide Maritime Zone Surveillance

Introduction

The ScanMaris project is an innovative software workshop conceived to develop and evaluate solutions of prevention and monitoring of wide maritime zones. These solutions rely on tools of tactical picture's exploitation, known as enriched for resulting from the continuous treatment of important volumes of heterogeneous data gathered in real time (sensors) and remote time (intelligence). The ScanMaris solutions enable supervising the permanent evolutions of the dense vessel traffic in order to follow the flows of transported goods (bulk, containers, energy, chemical, fishery product, passenger, etc.) according to various routes (corridor, motorway of the sea, coastal traffic, etc.) and to detect the criminal traffics (narcotics, smuggling, illegal immigration, illegal resource fishing, etc). This paper focuses on the technologies involved in the project with their major results. Nevertheless, there is no global analysis of the workshop at this stage, because ScanMaris will be recently funded by the French National Research Agency ANR, and its duration is of 24 months.

The ScanMaris monitoring system

A ship (pleasure, fishing, freight, etc.) can be considered as an agent searching to satisfy a goal coming from a seaport to another. Thus, the maritime transport is a multi-agent system hiding some illicit activities among a great amount of legal behaviors. To detect these criminal activities, the ScanMaris workshop integrates several modules:

• • • •
Database of ship situations (location, speed, and direction).

• • • •

Database about environmental conditions: freight, destination, certifications, flag, etc; as well as meteorological information.

• • • •

Learning methods to predict a ship itinerary.

• • • •

Inference rules to detect abnormal behaviors.

• • • •

Man-machine interfaces.

The spatio-temporal knowledge representation is based on the recognition of ships from their legal information, their real-time location and environmental situation. All the detected agents are classified and linked with the referenced ships. All these previous information enable to create a virtual map where each ship moves in real-time according to the supposed trajectory it has at time t. In this map, each ship moves from time t to (t+1t) in marking each location step by placing a marker. By analogy with the animal kingdom, these markers are called pheromones. A ship is able to perceive the deposited pheromones in its neighborhood and interacts with the corresponding ships, leading to its Behavior Vector values adjustments. This system architecture for monitoring will be detailed in this section.

Information Sources and Sensors

A maritime surveillance and control system has to be able to collect and fusion heterogeneous data provided by various sensors (radars, IR or classical cameras, AIS receivers, satellite and aircraft imageries, etc.) and external data sources (TF2000, LLOYDS, EQUASIS, TROCS, SATI, etc.). The fusion of all this huge information set has, as far as we know, never been applied for civil wide maritime zone permanent surveillance. An efficient system will have to overcome the difficulties inherent to data fusion and the combination of inputs from different sources, in different places and at different times.

A High Frequency Surface Wave Radar (prototype has been developed by ONERA on DGA funding) is integrated in the project. For a HFSW radar, the sea surface guides electromagnetic waves, such qualified as surface waves. Ships or low flying objects send back through the radar a portion of the incident surface wave as a backscattered surface wave which can be detected. The radar system can measure temporal and spatial properties of objects simultaneously over thousands of square kilometers. Performances of a HFSW radar are related to its design and the geographic place where the sensor is located. The illuminated area on the sea is called a radar cell and its size is a function of the array length and of the observed range. The range resolution is obtained by a ratio between the wavelength and the size of the array. The more the array is spread, the more precise the target localization will be.

The overall cost-efficiency of a HFSW radar installation is therefore very interesting. Raytheon (USA), Daromont (Australia) operate and sell HFSW radars but they are very reticent when it comes to giving pertinent data about true performances. China is already developing its own radar. ONERA deployed during the first quarter 2007 a long range HF radar in the Bay of Biscay (4). We develop in this section some results on recognition based on this sensor by the ONERA partner. In the frame of ScanMaris this HFSW will be completed with an AIS receptor and eventually with conventional coastal radar.

Reasoning Mechanisms on Behaviors

The classical approach to detect illicit behaviors is to use Predictive Analysis. Predictive analysis encompasses a variety of techniques from statistics and data mining that process current and historical data in order to make "predictions" about future events. Such predictions rarely take the form of absolute statements, and are more likely to be expressed as values that correspond to the odds of a particular event or behavior taking place in the future.

Concerning maritime traffic, we use inference rules (5) to detect illicit behaviors. Unfortunately, because a great amount of contextual rules could be used at a time, but only few ships are suspicious, we complement this approach by an adaptive agent technology which is quoted by DARPA (2) as being relevant for Predictive Analysis for Naval Deployment Activity. This is coherent with the choice of AMAS technology [START_REF] Bernon | Engineering Adaptive Multi-Agent Systems: The ADELFE Methodology[END_REF] where each agent reaches (or tends to) its individual goals (the destination port of a ship, for example) while the whole system reaches an overall adequate functionality. This adequacy should be optimal or pareto-optimal as predicted by the AMAS theory, but it still remains a conjecture in a general case. Benefits can be expressed in terms of efficiency, distribution (minimizing shared knowledge, maximizing privacy), openness and flexibility (adding/removing agents or knowledge) and robustness (minimizing problemdependent parameters). This means that the system has the capability, through the agents composing it, to adapt to global or local changes, at runtime, and to provide nearby solutions between changes, even when there is no evaluation function to guide the convergence such as for predicting suspicious maritime activities.

We present results of these two mechanisms in the full paper.

Related Works

Conclusions

The ScanMaris key features will be new sensor capabilities, more efficient and less expensive, allowing to cover wider areas; improved data fusion algorithms, allowing a quicker and better information; innovative behavior analysis methods, allowing automated facilities for detection of illicit traffics; customization options, for total compliance with relevant legal and organizational constraints and maximum adaptability.

  ScanMaris enabling the treatment of a huge amount of information in order to detect abnormal behavior. From our knowledge, PANDA (Predictive Analysis for Naval Deployment Activity) is the only project having approached aims of the DARPA from U.S.A.

	European States should have a coherent and
	common vision in order to prevent illicit activities (3).
	In this context, the creation of the European Security
	Board (ESB) has been proposed by the European
	Security Research Advisory Board (ESRAB) and the
	FRONTEX. The Presidency conclusions of the
	Brussels European Council in 2006 called "for
	enhanced efforts on maritime operational cooperation
	with a view to developing adequate surveillance
	capacities at the sea borders".
	The available Vessel Traffic Management Services
	and the maritime C4ISR systems do not incorporate
	all the functionalities proposed in

European Communities, Towards a future Maritime Policy for the Union: A European vision for the oceans and seas, Green Paper SEC(2006) 689.

Fabbro O V.; Combes P.-F.; Guillet N., Apparent radar cross section of a large target illuminated by a surface wave above the sea, Progress in Electromagnetics Research Volume

50, 2005. 5 Wybo J.L, Colardelle C., Poulossier M.P., Cauchois D., 2002, A methodology for sharing experiences in incident management, International Journal of Risk Assessment, Vol 3, n°2/3/4.