F Chinesta

Y Chastel

B Tlili

C Nouveau

G Guillemot

Elaboration, characterization of CrN-based coatings

Keywords: Cr-N system, multilayers, thickness, residual stress

Cr, CrN and CrAlN monolayers were synthesized by RF dual magnetron sputtering on AISI4140 steel and silicon substrates at 200°C. Multilayers coatings based on the three mono-layers such as CrN/CrAlN and Cr/CrN/CrAlN were also synthesized only on Si. The physico-chemical and mechanical properties of the layers were determined by AFM, SEM+WDS, stress, roughness and nanoindentation measurements. The influence of the thickness on the mechanical properties of the monolayers stresses has been studied and as a consequence we compared the mono and multilayers stress state.

INTRODUCTION

A variety of multilayer systems such as TiN/CrN [1], TiAlN/CrN [2], TiN/TiAlN [3], etc., have been studied extensively. However, there are very few reports on the multilayer coatings based on CrN and CrAlN [4]. The addition of Al to CrN system permits to work at higher temperatures where the oxidation occurs [5]. CrAlN coatings have been reported to be stable up to a temperature of 900°C depending upon the Al content in the coatings [6]. CrAlN coatings also exhibit higher hardness and a lower friction coefficient compared to CrN coatings [7]. The new ternary film structure brought about significant advances in coating designs, such as the decrease of the grain size and the formation of grain boundaries between the two phases. As a consequence, it is reported that CrAlN films exhibited excellent mechanical properties and oxidation resistance owing to their solid solution structure [8]. Furthermore, it is well known that most properties of these solid solution composite films are influenced by certain factors such as crystalline structure and micro-structure. These factors led to the study of the multilayers coatings of CrN/CrAlN and Cr/CrN/CrAlN, in which the properties of Cr, CrN and CrAlN can be combined. The Cr underlayer is considered as a bonding layer.

In this work, we have investigated the effect of thickness on residual stress and hardness of the monolayers. Moreover, the relationship between mechanical properties and the stress state of the multilayers coatings was also discussed and established.

EXPERIMENTAL PROCESS Deposition

The layers were deposited on mechanical polished steel (AISI 4140) and silicon (100) substrates using an RF dual magnetron sputtering system (NORDIKO type 3500-13, 56 MHz) equipped with two targets of high purity (Cr of 99.995 % and Al of 99.999 %) (Fig. 1).

FIGURE 1. Plasmas operated in the magnetron chamber

Before deposition, the substrates and the targets were etched in pure argon plasma for 10 min. In order to obtain uniform coatings, the substrate was positioned 80mm away from the target. Very high purity nitrogen was introduced into the vacuum chamber as the reactive gas. The residual pressure was 10 -7 mbar. The deposition conditions such as the target bias voltage, the deposition time and the gas mixture are given in Table 1. Where Pc is the highest residual stress where the layers show a peak on the curve "stress vs thickness" and Pt is the lower and stable residual stresses of the films. In the following text, the films will be called PVDi (with i=1, 2, 3, 4, 5 and 6) as mentioned in Table 1.

Experimental

The atomic percentages of N, Cr and Al were determined by Wavelength Dispersive Spectrometry (WDS) microanalysis with a Jeol JSM-5600 Lv Scanning Electron Microscope (SEM). The surface roughness and thickness of the layers were observed and determined by Atomic Force Microscopy (AFM alpha300 A) and a 3D optical profilometer (NT-1100 Veeco Instruments Inc.) respectively. The hardness and the Young's modulus of the layers were determined by nanoindentation (MTS Systems Corporation, XP®) using a Berkovich diamond tip and continuous stiffness option, with a maximum indentation depth of 2000 nm. A theoretical model developed by A. Iost et al. [9] was applied to determine the hardness of the coatings. The residual stresses (σ) were determined by interferometry (method of the Newton's rings) and calculated thanks to the Stoney's equation [10].

RESULTS AND DISCUSSIONS

Coatings thickness, composition and roughness

The Cr, CrN and CrAlN coatings were deposited with different thicknesses in order to determine the influence of the thickness on the residual stress. Taking into account the optimal conditions obtained on monolayer, we developed multilayer coatings of Cr/CrN/CrN and CrAlN/CrAlN. The relative composition, thickness, morphology of the films determined by EDS, WDS and 3D optical profilometer was resumed in Table 2. The N/Cr ratio varied from 0.95 to 1.2 for all the coatings, which reflects their stoichiometry. Furthermore, the Ra and Rq roughness of the films are low, and their variations do not exceed 4/100 on all surfaces. On the other hand the evolution of the thickness versus the deposition time is always linear.

Coating hardness, Young's modulus and residual stress

We were interested to verify the influence of the layers thickness on their hardness, Young's modulus and residual stress. Fig. 2 shows that the evolution of the hardness and Young's modulus is closely related to internal stresses of the layers whatever the layer is. The residual stresses peak close to the interface between the substrate and the monolayers confirm the results obtained by Nouveau et al. [11] and Hanabusa et al. [12] and can be explained by a growth model defined in [11]. The evolution of the Young's modulus is similar with the hardness one versus the layers thickness. All monolayers coatings showed significantly higher hardness as compared to substrate AISI4140 (4.2 GPa). The maximum hardness for Cr, CrN and CrAlN was measured and was 12, 18 and 12.5 GPa respectively. The greatly enhanced mechanical properties of thin films can be explained by solid mixed hardening, complex chemical bonding strengthening, and the novel nanocomposites microstructure that enhances the material strength by a dislocation blocking effect. An explanation of the high hardness of the thin films near the interface with substrate was the local bond strengthening and dislocation motion limited by lattice distortion during germination and growth. According to the amorphous/crystalline nanocomposite design concept, the high hardness of the composite film near the interface was based on the combination of the lack of the dislocation activity in the small nanocrystals and the jamming of grain boundary sliding by the formation of a strong interface between the two phases. The films investigated here had crystallite sizes and amorphous layer thickness similar to the super hard nanocomposites, which were sufficient for formation of nanosized dislocations. At the beginning of the deposition, many nuclei of tiny islands are formed on the substrate surface (Fig. 3a). Since these nuclei are tiny, the stress is considered to be significantly small. As depositing time increases, these tiny nuclei coalesce with each other to form islands (Fig. 3b) and finally change into a solid film on the substrate. After this film formation, compressive stresses developed during the cooling stage will force the atoms through the grain boundaries as well as the film surface. These atomic migrations form hillocks at the grain boundaries on a film surface, bringing stress relaxation in films thicker than 150, 128 and 110 nm for CrAlN, CrN and Cr, respectively. Moreover, this explanation seems useful for hardness; because smaller the grains size is, higher the hardness is. This explains the proportionality between the residual stresses and hardness. Moreover, Fig. 4 shows that residual stresses in multilayers are lower than the monolayers ones. The reduction of the residual stresses in multilayer coatings compared to those of the monolayers is also mainly due to their interface. The interlayers seem to be effective in absorbing residual stresses during film growth. It's obvious that their values strongly depend on the residual stresses of the monolayers. Indeed, the total stress is increase 3.4 times when we compare PVD1 (all the monolayers are at Pt) with PVD6 (all the monolayers are at Pc). The highest stress is obtained for the PVD6 multilayer, where the monolayers presented their stress peak, which reflects this proportionality. Besides, the same results is obtained when we compare PVD4 and PVD5, the stress is also increased 3.5 times. Actually, if we compare the PVD1 and PVD4 or PVD5 and PVD6 multilayers, it's obvious that the underlayer of Cr has a main effect because the Cr bonding or transition layer played a main role on the stress intensity, which proves that the stress level on the coating PVD6 (-1.2 GPa) is higher than that in the PVD5 (-0.7GPa) one for example. We can also note if we compare PVD2 and PVD5 that the stress remains almost the same whatever the CrN stress state (~0.65-0.7GPa). A similar result is obtained when we compare the PVD3 and PVD6 multilayers stress with a Cr underlayer (~1.1-1.2GPa). These results mean that the Cr or CrN underlayers improve the stress of those multilayers only if they are at their Pt point like the sublayers. Otherwise, if the underlayers are at their Pt point and the sublayers at their Pc point, then the increase of the stress is due to the fact that these layers present their highest stress (ex. PVD4 compared to PVD2 or PVD1 compared to PVD3). Finally, these results would help in the choice of multilayers according to their future applications (mechanical, thermal, wear etc…).

CONCLUSIONS

According to the previous results, we can conclude as follows:

(1) The CrAlN, CrN and Cr monolayers presented a residual stress peak that can be related to germination, growth and morphology of the film near the interface film / substrate. (2) The hardness and Young's modulus of the monolayers depend on their residual stresses (3) The residual stresses of multilayer coatings are always lower than the monolayers ones.

This decrease is related to the interface between layers, and the variation of the thickness. Besides, the final residual stresses of the multilayers depend on the stress state of the monolayers from whom they are built with. For example, if you want a stressed so a hard coating, you should select one with a Cr underlayer (whatever its stress state) and a sublayer at its Pc stress point. For a lower final stress, we would select no Cr underlayer or all the monolayers at their Pt stress point.

FIGURE 2 .

 2 FIGURE 2. Evolution of the hardness, Young's modulus and residual stresses as a function of the A/ Cr, B/ CrN and C/ CrAlN film thickness

FIGURE 3 .

 3 FIGURE 3. SEM images of a CrAlN layer (a) 50 nm and (b) 1.8µm thick.

FIGURE 4 .

 4 FIGURE 4. Residual stress of multilayer coatings

Table 1 .

 1 Deposition conditions (The target power and the gas pressure are fixed to 4kW and 4µbar respectively)

Coatings Target bias voltage (-V) Deposition time (min) Gas mixture

		Al	Cr		Ar	N2
					(%)	(%)
	Cr	0	-900	3, 5, 7, 8.5,	100	0
				10, 30, 60
	CrN	0	-900	7,10, 12.5,	80	20
				15, 20, 30,60
	CrAlN	-300	-900	7, 10, 15, 20,	//	//
				25, 30, 35,60
	Cr/CrN/CrAlN	-300	-900	99	//	//
	(Pt/Pt/Pt):PVD1
	CrN/CrAlN	//	//	28	//	//
	(Pt/Pc):PVD2
	Cr/CrN/CrAlN	//	//	25.5	//	//
	(Pt/Pc/Pc):PVD3
	CrN/CrAlN	//	//	105.5	//	//
	(Pt/Pt):PVD4
	CrN/CrAlN	//	//	22.5	//	//
	(Pc/Pc):PVD5
	Cr/CrN/CrAlN	//	//	29.5	//	//
	(

Pc/Pc/Pc):PVD6

Table 2 .

 2 The composition of films in atomic proportion

	Coating	N	Al	Cr	N/Cr	Total	Roughness
		Content	Content	Content	ratio	thickness	( µm)
		(at. %)	(at. %)	(at. %)		(nm)	Arithmetic	Roughness
							roughness	average
							(Ra)	quadratic
								(Rq)
	Cr	0	0	100	0	47, 90,	0.1	0.12
						110, 132,	-	-
						150, 412,	0.15	0.14
						860
	CrN	48	0	51	0.95	58, 75,	0.1	0.12
						106, 127,	-	-
						170, 360,	0.14	0.16
						690
	CrAlN	48.2	4	48	1.04	117, 150,	0.1	0.12
						250, 285,	-	-
						416, 550,	0.12	0.13
						582, 980
	PVD1	51.8	4.2	42.9	1,2	1500	0.1	0.14
	PVD2	50.8	4	43.1	1.17	300	0.12	0.16
	PVD3	50.5	4.7	42.5	1.18	300	0.11	0.15
	PVD4	52	5	41.3	1.2	1500	0.13	0.15
	PVD5	49.7	4.9	43.6	1.18	256	0.12	0.16
	PVD6	50.1	4.2	44.5	1.17	356	0.09	0.13


Julien Gaillard

Eitan Altman

Well-argued recommendation: adaptive models based on words in recommender systems

Recommendation systems (RS) take advantage of products and users information in order to propose items to consumers. Collaborative, content-based and a few hybrid RS have been developed in the past. In contrast, we propose a new domain-independent semantic RS. By providing textually well-argued recommendations, we aim to give more responsibility to the end user in his decision. The system includes a new similarity measure keeping up both the accuracy of rating predictions and coverage. We propose an innovative way to apply a fast adaptation scheme at a semantic level, providing recommendations and arguments in phase with the very recent past. We have performed several experiments on films data, providing textually well-argued recommendations.

Introduction

Recommender systems aim at suggesting appropriate items to users from a large catalog of products. Those systems are individually adapted by using a specific profile for each user and item, derived from the analysis of past ratings. The last decade has shown a historical change in the way we consume products. People are getting used to receive recommendations. Nevertheless, after a few bad recommendations, users will not be convinced anymore by the RS. Moreover, if these suggestions come without explanations, why people should trust it? Numbers and figures cannot talk to people. To answer these key issues, we have designed a new semantic recommender sytem (SRS) including at least two innovative features:

• Argumentation: each recommendation relies on and comes along with a textual argumentation, providing the reasons that led to that recommendation.

• Fast adaptation: the system is updated in a continuous way, as each new review is posted.

In doing so, the system will be perceived as less intrusive thanks to well-chosen words and its failures will be smoothed over. It is therefore necessary to design a new generation of RS providing textually well-argued recommendations. This way, the end user will have more elements to make a wellinformed choice. Moreover, the system parameters have to be dynamically and continuously updated, in order to provide recommendations and arguments in phase with the very recent past. To do so, we have adapted the algorithms we described in Gaillard [START_REF] Gaillard | Flash reactivity: adaptive models in recommender systems[END_REF], by including a semantic level, i.e words, terms and phrases as they are naturally expressed in reviews. This paper is structured as follows. In the next section, we present the state of the art in recommendation systems and introduce some of the improvements we have made. Then, we present our approach and define the associated methods in section 3. We describe the evaluation protocol and how we have performed some experiments in section 4. Finally we report results including a comparison to a baseline in section 5.

Related work and choice of a baseline

We present here some methods used in the literature. Collaborative Filtering (CF) systems use logs of users, generally user ratings on items [START_REF] Burke | Hybrid Web Recommender Systems[END_REF]Sarwar et al., 1998). In these systems, the following assumption is made: if user a and user b rate n items similarly, they will rate other items in the same way [START_REF] Deshpande | Item based top-N recommendation algorithms[END_REF]. This technique has many well-known issues such as the "cold start" problem, i.e when new items or users appear, it is impossible to make a recommendation, due to the absence of rating data (Schein et al., 2002). Other limitations of RS are sparsity, scalability, overspecialization and domain-dependency problems.

In Content Based Filtering (CBF) systems, users are supposed to be independent [START_REF] Mehta | Robust collaborative filtering[END_REF]. Hence for a given user, recommendations rely only on items he previously rated.

Some RS incorporate semantic knowledge to improve quality. Generally, they apply a conceptbased approach to enhance the user modeling stage and employ standard vocabularies and ontology resources. For instance, ePaper (scientific-paper recommender), computes the matching between the concepts constituting user interests and the concepts describing an item by using hierarchical relationships of domain concepts [START_REF] Maidel | Evaluation of an ontology-content based filtering method for a personalized newspaper[END_REF]. [START_REF] Codina | Taking Advantage of Semantics in Recommendation Systems[END_REF] propose to take advantage of semantics by using an interest-prediction method based on user ratings and browsing events. However, none of them are actually based on the user opinion as it is expressed in natural language.

Similarity measures

Similarity measures are the keystone of RS (Herlocker et al., 2005). [START_REF] Resnick | Using filtering agents to improve prediction quality in the groupLens research collaborative filtering system[END_REF] was one of the first to introduce the Pearson correlation coefficient to derive a similarity measure between two entities. Other similarity measures such as Jaccard and Cosine have been proposed (Meyer, 2012). Let S u be the set of items rated by u, T i the set of users who have rated item i, r u,i the rating of user u on item i and r x the mean of x (user or item). PEA(i,j) stands for the Pearson similarity between items i and j and is computed as follows:

u∈Ti∩Tj (r u,i -r i )(r u,j -r j ) u∈Ti∩Tj (r u,i -r i ) 2 u∈Ti∩Tj (r u,j -r j ) 2 (1)
In the remainder, the Pearson similarity measure will be used as a baseline. The Manhattan Weighted and

Corrected similarity (MWC), that we introduced in [START_REF] Gaillard | Flash reactivity: adaptive models in recommender systems[END_REF], will be used as a point of comparison as well1 . Again, for none of them, textual content is taken into account.

Rating prediction

Let i be a given item and u a given user. We suppose the pair (u, i) is unique. Indeed, most of social networks do not allow multiple ratings by the same user for one item. In this framework, two rating prediction methods have to be defined: one user oriented and the other item oriented. Sim stands for some similarity function in the following formula.

rating(u, i) = v∈T i Sim(u, v) × r v,i v∈T i |Sim(u, v)| (2)
A symmetrical formula for items rating(i, u) is derived from and combined with (2).

ru,i = β×rating(u, i)+(1-β)×rating(i, u) (3)
3 Methods

In this section, we describe the methods we have used and propose some of the enhancements we have elaborated in our system. In formula (2), Sim can be replaced by several similarity such as Pearson, Cosine or MWC similarity [START_REF] Tan | Introduction to Data Mining[END_REF]. All these methods provide a measurement of the likeness between two objects. We then conclude if two users (or items) are "alike" or not. One has to define what "alike" should mean in this case. If two users rate the same movies with equals ratings, then these similarities will be maximal. However, they may have rated identically but for completely different reasons, making them not alike at all. Moreover, none of these similarity measures can express why two users or items are similar. This is due to the fact that they rely on ratings only.

New similarity based on words

We propose a new similarity method, taking into account words used by users in their past reviews about items. In the remainder, we call it the Word Based Similarity (WBS). Each user x (or item) has a vocabulary set V x and each word w in it is associated with a set of ratings R w,x and an average usage rating r w . In order to balance the contribution of each word, we define a weight function F w , mixing the well-known Inverse Document Frequency IDF (w) with the variance σ2 w . Common words and words w associated with very heterogenous ratings R w,x (i.e a high variance) will have a smaller weight in the similarity. N w is the number of items in which the word w appears. N tot is the total number of items. D is the maximum difference between two ratings. Note that F w has to be updated at each iteration.

F w = -log N w N tot × 1 σ 2 w (4) W BS(x, y) = w∈Vx∩Vy (D -|r w,x -r w,y |)F w D × |V x ∩ V y | w∈Vx∩Vy F w (5)

Adaptation

An adaptive framework proposed in [START_REF] Gaillard | Flash reactivity: adaptive models in recommender systems[END_REF] allows the system to have a dynamic adaptation along time, overcoming most of the drawbacks due to the cold-start. The authors have designed a dynamic process following the principle that every update (u, i) needs to be instantly taken into account by the system. Consequently, we have to update the σ 2 w and IDF(w) at each iteration, for every word. Paying attention to avoid a whole re-estimation of these two variables, we derived an iterative relation for the two of them 2 . We thus reduced the complexity by one degree, keeping our system very wellfitted to dynamic adaptation.

Textual recommendation

The main innovative feature of our proposal is to predict what a user is going to write on an item we recommend. More precisely, we can tell the user why he is expected to like or dislike the recommended item. This is possible thanks to the new similarity measure we have introduced (WBS). Let us consider a user u and an item i. At the intersection of these two pieces of information, we extract a set of matching words that we sort by relevance using F w . Then, by taking into account the ratings associated with each word, we define two sub-sets P w and N w . P w contains what user u is probably going to like in i and N w what u may dislike. Finally, we provide the most relevant arguments contained in both P w and N w , and each of them is given in the context they have been used for item i. As an example, some outputs are shown in section 5.2.

Evaluation criteria

We present here the evaluation protocol we designed. It should be noted that we are not able to make online experiments. Therefore, we can not measure the feedback on our recommendations. However, the cornerstone of recommender system is the accuracy of rating predictions [START_REF] Herlocker | Evaluating collaborative filtering recommender systems[END_REF]. From this point of view, one could argue that the quality of a recommender engine could be assessed by its capacity to predict ratings. It is thus possible to evaluate our system comparing the prediction ru,i for a given pair (u, i), with the actual real rating r u,i . The classical metrics3 [START_REF] Bell | The BellKor 2008 Solution to the Netflix Prize[END_REF] Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) will be used to evaluate our RS. Last but not least, we make the following assumption: if WBS results are as good as MWC's, the words presented by the system to users as arguments are likely to be relevant.

Experiments

This work has been carried out in partnership with the website Vodkaster4 , a Cinema social network. Researchers have used other datasets such as the famous Netflix. Unfortunately, the latter does not include textual reviews. It is therefore strictly impossible to experiment a SRS on such a dataset.

Corpus

The corpus has been extracted from Vodkaster's database. Users post micro-reviews (MR) to express their opinion on a movie and rate it, within a 140 characters Twitter-like length limit. We divided the corpus into three parts, chronologically sorted: training (Tr), development (D) and test (T). Note that in our experiments, the date is taken into account since we also work on dynamic adaptation. the confidence interval, in terms of accuracy, the same perfomances are obtained by MWC and WBS. Both outperform5 PEA and MNA. Our word based approach is thus able to offer the arguments feature without any loss of perfomances with respect to any others RS methods that we know of.

In Table 2, we set a constant coverage (2000 predictions) in order to be able to compare results obtained with different methods. MNA (MWC without adaptation) being better and more easily updated than Pearson (PEA), we have decided to use the adaptive framework only for MWC. Moreover, for Pearson dynamic adaptation, the updating algorithm complexity is increased by one degree. We want to point out that the results are the same for both MWC and WBS methods, within a confidence interval (CI) radius of 1.16%. From a qualitative point of view, these results can be seen as an assessment of our approach based on words.

Example of outputs:

The movie Apocalypse Now is recommended to user Theo6 with a rating prediction equal to 4.3. Why he might like: some brillant moments (0.99), among the major masterpiece (0.91), Vietnam's hell (0.8); dislike: did not understand everything but... (0.71).

The data we have does not contain the information on the reaction of the user to the recommendation. In particular, we do not know if the textual argumentation would have been sufficient for convincing Theo6 to see the film. But we know that after seeing it, he put a good rating (4.5/5) on this movie.

Conclusion and perspectives

We have presented an innovative proposal for designing a domain-independent SRS relying on a word based similarity function (WBS), providing textually well-argued recommendations to users. Moreover, this system has been developed in a dynamic and adaptive framework. This might be the first step really made towards an anthromorphic and evolutive recommender. As future work, we plan to evaluate how the quality is impacted by the time dimension (adaptation delay, cache reset,etc.).

  To keep it simple, the system takes into account what u has written on other items in the past and what other users have written on item i, by using WBS. The idea consists in extracting what elements of i have been liked or disliked by other users, and what u generally likes.

Figure 1 :

 1 Figure 1: Evolution of accuracy as a function of coverage for PEA, MWC and WBS methods on D corpus.

function of Coverage on DEV

					Tr	D		Tr+D	T
			Size	55486 9892 65378 9729
		Nb of Films 8414 3184 9130 3877
		Nb of Users 1627	675		1855	706
				Table 1: Statistics on the corpus
	5.2 Results
	Figure 1 compares four different methods: the
	classical Pearson (PEA) method that does not allow
	quick adaptation, the MWC method with and with-
	out quick adaptation MNA and ours (WBS). Within
	Accuracy	0.86 0.88 0.90 0.92 0.94 0.96	800	1000 MWC WBS MNA Accuracy as a Coverage 1200 1400 PEA	1600	1800	2000

Table 2 :

 2 Results with Pearson (PEA), MWC, MWC without Adaptation (MNA), WBS. CI is the radius confidence interval estimated in % on accuracy (Acc.).

	Corp. Met. RMSE MAE %Acc.	CI
	D	PEA	0.99	0.76	86.41	1.49
	E	MNA	0.93	0.72	90.75	1.26
	V	MWC	0.89	0.69	92.95	1.12
		WBS	0.89	0.70	92.45	1.16
	T	PEA	1.01	0.78	86.02	1.51
	E	MNA	0.98	0.75	90.04	1.30
	S	MWC	0.92	0.71	91.46	1.22
	T	WBS	0.94	0.72	91.15	1.24

Details on MWC can be found in supplementary material.

More details can be found in the supplementary material.

Details on metrics are given in the supplementary material.

www.vodkaster.com

Note that the key point here is the comparison of results obtained with the baseline and with the method we propose. Both of them have been evaluated with the same protocol: RMSE is computed with respect to rating predictions above some empirical threshold as done in[START_REF] Gaillard | Flash reactivity: adaptive models in recommender systems[END_REF].

Acknowledgment

The authors would like to thank Vodkaster for providing the data. This work has been partly supported by the European Commission within the framework of the CONGAS Project (FP7-ICT-2011-8-317672), see www.congas-project.eu. We also would like to thank Agorantic for their support (http://blogs.univ-avignon.fr/sfr-agorantic).


Dominique Crozat
email: dominique.crozat@univ-montp3.fr

Towards harsh horizons: fear and violence in hyperreality

Since the awful bombings of Guernica, Nanking and Berlin (and we could add Hiroshima, London and Dresden), "we have worked hard to produce a fiction that such destruction will not occur again, in an era of smart bombs, economic sanctions and professional armies. Yet this is nothing more than a convenient fiction, as even smart weapons do damage . . .

nuclear and genetic, no longer at all specular or discursive. It is all of metaphysics that is lost. No more mirror of being and appearances, of the real and its concept. No more imaginary coextensivity: it is genetic miniaturization that is the dimension of simulation. The real is produced from miniaturized cells, from matrices, memory banks and command models -and it can be reproduced an indefinite number of times from these. (Baudrillard, 1981:10-11) The use of these types of hyperreal spaces involves a growing number of tangible spaces which integrate their media exposure as soon as they are produced. Culture becomes media culture (Maigret, 2005;Macé, 2006) in order to build a more suitable reality; tourist spaces (eco-museums) or local fetes create a stand-alone parody of the locality they redefine.

Hyperreal spaces alter the perspective of interaction, question the meaning of societies' inclusion in space and highlight a worrying socio-political process [START_REF] Maigret | L'Hyperprésident[END_REF]. This process of simulation and multiplication of commercially orientated autonomous artefacts generates three levels of violence. Firstly, the broadcasting of brutal scenes by the media: according to a 1995 study, an average of one violent death every 12 minutes was broadcasted on all six French television channels. Secondly, hyperreality acts as a pretext for socio-political regression [START_REF] Miller | Capitalism : an ethnographic approach[END_REF]. Abstract worlds in economic models ignore their real social implications: IMF involvement, relocation of online services to countries with low labour costs, removal of public services in the countryside under the pretext of increased Internet availability, use of information technology to increase control over people… These first two levels are only mentioned here in relation with the third type of violence, consubstantial with the process of hyperrealization: its deep logic favours the disappearance of the world's symbolic dimension (Baudrillard, 1968;[START_REF] Stiegler | De la misère symbolique. 1. L'époque industrielle[END_REF], induces a feeling of de-territorialization, a loss of socialised spatial references and a painful identity crisis. For Eco (1987), Disneyland's fantasy order is the opposite of the rest of the world, supposedly real, when in fact, the whole of America and the world are the hyperreal simulation. This 'perfect crime' (Baudrillard, 1995) is not abstract: in 2004, two English children were mauled to death by bears in a zoo after having climbed into their cage; brought up on cartoons, they only knew about cuddly teddy bears. This ill-being accompanies the hegemony of transparency, it influences the social understanding of spaces and determines their layout: through the installation of CCTV systems, the building of risk-free environments [START_REF] Spring | Behind the Rave: Structure and Agency in a Rave Scene in Bennett[END_REF] or the privatisation of public space [START_REF] Razac | Histoire politique du barbelé[END_REF][START_REF] Rodriguez | Privatopia" versus Ciudad Pública? La materialización del miedo en el espacio urbano[END_REF], political decisions destabilise social relationships and the workings of democracy [START_REF] Davis | City of Quartz. Los Angeles, capitale du futur[END_REF][START_REF] Williams | 45-54) and French (Violence en hyper réel[END_REF]. This paper asks two questions: how is the production of the localised social issues affected by the generalisation of these violent metaphorized spaces? How can the political dimension that has been removed from the major production process of societies' space be reinstalled? We'll start by examining how the manipulation of events gives people a mediatized experience of the world. Then, from tsunami to climate change, from terrorism to criminality or more personal fears borne out of the instrumentalisation of risk, we'll examine how this violence leads people to internalise fear as a major structuring element of our societies [START_REF] Beck | La société du risque. Sur la voie d'une autre modernité[END_REF]: hence, the dream of a world totally secured leads to its distancing in order to build a reactionary world which denies the individual and political representation.

The mediatized experience of the world replaces interaction

«… The hyper real is the concept of […] a simulated […] geography » (Rodaway, 1994:177): its simulations are not flawed copies of the original, nor of aesthetic illusions, "annihilated by technical perfection" (Baudrillard, 1995: 51); clearer and more complete, they are better than the original: Technology builds « a magical world. Consider also the way in which modern technology can be employed in Geographic Information Systems (GIS) technology to personalize an abstract, scientific view of the world, so that it would appear that one can be part of the process of generating spatial relations. (Sack, 1997: 276-22). As the alibi of an authority detached from civic reality, the political decision becomes a technical process that excludes in advance any democratic initiative: by creating a destiny, it condemns voluntary actions.

Africa (Shields, 2003:81), leisure spaces (Rodaway, 1994;[START_REF] Crozat | De la fête aux loisirs : événement, marchandisation et invention des lieux[END_REF], natural parks (Alessandro-d'Amato, 2008), urban outskirts etc, are only perceived through hyperreal reconstructions. Producers of social virtuality (opinion polls, media) look for representative, de facto non-standard individuals (heroic fireman, lucky survivor, leaders...). Media stories of disasters or massacres are reduced to meaningless statistics. In the name of transparency, they ignore complex phenomena or day-to-day banality [START_REF] Aubenas | La fabrication de l'information. Les journalistes et l'idéologie de la communication[END_REF]. This manufacturing of the world changes people's lives in countries like Botswana, where the only source of public information comes from ideologically oriented TV programmes (environmental issues, sustainable development) [START_REF] Perrot | Du vrai-faux au virtuel : mondialisation culturelle et néo-utopie[END_REF]. In Namibia and Uganda, indigenous populations have to radically change their lifestyles (Rossi, 2001:59). The government demands it, pressurised by tour operators who sell environmentally correct holidays. Climate change, the Amazonian rainforest or the 2005 Indonesian tsunami (fig. 1) are instrumentalized in the same way: in 2005, the Mayor of Poussan (in southern France) bought 3000 paper masks in a vain attempt to protect his community against a virus (the human variant of H5N1) which may never come. Thus, the use of hyperreality artificially rebuilds real-life experience and clears away the symbolic. For people, this generates a painful disappropriation of their territory, from body intimacy to the definition of their urbanity.

Death of the symbolic dimension

1 www.senat.fr/noticerap/2007/r07- 117-notice.html This geography of hyperreal spaces gives an intimate existence to the practised world. It is a sensual (Rodaway, 1994), in-corporated [START_REF] Crang | Virtual Geographies: Bodies, Space and Relations[END_REF] or incarnated [START_REF] De Barros | Le virtuel incarné[END_REF] experience of the world for subjects who have become consumers:

In the Body Art and Performance movements of the 60s and 70s, the body was the instrument of a social or political demand, of a suffered emancipation, the physical and conceptual site of tentative explorations of boundaries (pain, nudity, gender, public/private opposition...). Today, the context has changed and the body of art, far from being an inert and indifferent surface, defines itself as a membrane which filters our mutations. Like a mobile interface that reflects relationships (adaptive, osmotic, conflicting...) with the environment.

Basically, what changed isn't the body, but the environment. Mediatized, technologized. The context's mutation implies a shifting of borders: media and technology are no longer restricted to capturing and representing the body, they invade it, modify it, mix with organic tissue, and become carriers of subjectivation and hybridation. We left Foucauld behind and switched to Baudrillard. (Quinz, 2003: 187) Deprived of representation of the subject's unity by genetics, cloning, plastic surgery, digital virtualization devices or networks, the body is no longer central. It becomes a complex inbetween identity, an open and changeable structure, a field of interaction between a plurality of dynamics. With the identical reproduction at will and ad libitum of the same, the question shifts from 'what is real?' to 'am I real?' It is impossible to anticipate the potential uses of one's image once available on networks, as "any image held by the network can be indefinitely reused, manipulated, falsified and reshaped without our knowledge" (Quéaud, 1993: 46). The artist Eduardo Kac displays Alba, his genetically modified fluorescent rabbit, and creates unique pets on demand [START_REF] De Barros | Le virtuel incarné[END_REF]. In The Eighth Day, under a glass dome, mice, fish and genetically modified plants initiate the paradigmatic microcosm of a new world, fed by a robot controlled through the Internet. Video games (The Sims) and reality TV shows have similar ambitions. "Now, the subject mates with exceptionally powerful automatic devices" (Couchot, 1998:12). Destabilised, man is acculturated to "the minimal utopia" (Clarke, 2004:167) of a creation without randomness; in the TV show Okavango, Nicolas Hulot assumes the right to decide between nature and nurture [START_REF] Perrot | Du vrai-faux au virtuel : mondialisation culturelle et néo-utopie[END_REF]. He builds a world around a relevant detail -i.e. its cinematographic quality: populations depend on their screen representation. Unable to distinguish reality from such simulations, viewers absorb them as an experience. This "schizophrenia in which real-life experience is indiscernible from virtual experience, where all boundaries between the realms of reality and fantasy are obsolete" (Jolivat, 1995: 114) leads to 'Les Antilles à Jonzac' (literally The Caribbean in Jonzac, a leisure park in Charente-Maritime, France), or to the countryside on a motorway rest area named Ruralie, near Niort (France). The experience of the world is subjected to media exposure according to the logic of shopping centre developers: why go anywhere else since we sell a more complete reality here? Hyperreality assimilates reality. "Simulation is not an innocent process […]. It reconfigures the entire social areas according to its own methods of confusion and indistinction that prevent any potential burst of reaction, cloud lucidity, and direct people to a soft consensus" (Gauthier, 2002: 233). The project that aims to make "the afterlife of sensitive appearances" (Mandelbrot) visible reaches subjectivity; Alan Tuning wanted to create a wholly utopian order [START_REF] Breton | L'utopie de la communication. Le mythe du village planétaire[END_REF]: the world of the superhuman being that everyone deserves to be. This generalisation swamps all mental and collective individuation devices. This "new phase of individuation loss, linked to a new phase of the history of machines and therefore of technoscience, is also the new phase of a grammatisation process" [START_REF] Stiegler | De la misère symbolique. 1. L'époque industrielle[END_REF]:100, author's italics). In hyperreality, violence rests with the symbolic misery of this dispossession.

The relationship with home and places is evolving towards disorientation (Jameson, 2007).

The technical, visual and economical standardisation of landscapes and the compulsive desire for security create an addiction to technical expertise which confuses culture, town planning, marketing, territory management and public policies and which takes away the responsibility of the population (Sennett, 1991) because it reduces the emotional and ethical aspects of places. The hyperspecialisation of spatial functions leads to relational impoverishment (Lopez [START_REF] Levi | Centros comerciales: espacios que navegan entre la realidad y la ficción[END_REF]. The enslavement of desire to consumerist logics [START_REF] Châtelet | Vivre et penser comme des porcs. De l'incitation à l'envie et à l'ennui dans les démocratiesmarchés[END_REF][START_REF] Stiegler | De la misère symbolique. 1. L'époque industrielle[END_REF]Clarke, 2004) produces suburbanites. Once a culture localised in time and space, the place becomes a generic referent in the centrifugal city spaces [START_REF] Baudrillard | Amérique[END_REF], an assembly of standardised elements extracted from different timespaces and infinitely duplicated. Event production replaces symbolic systems [START_REF] Crozat | Les contextes socio-territoriaux de la vie culturelle et de ses événements[END_REF]2005). The consumer/(TV) viewer supersedes the inhabitant/citizen and is no longer seen as an informed individual. This un-realisation of the world through the dehumanisation of the creation process of places generates anxiety, psychasthenia [START_REF] Olalquiaga | Megalopolis : contemporary cultural sensibilities[END_REF]: disturbed in their personal relationship with their surroundings, unable to locate their physical boundaries, subjects mistake those physical parameters for the spaces portrayed. They use differentiated spatial identities, escape into fantasy without escaping the illusion of interaction with the world because the models offered (shopping centres, leisure parks, television, etc.) are valued as a unique reality. However, Olalquiaga notes the emergence of subversive spaces: some groups distort places with the same tools. Signalling 'ironic radicalism' and the return of politics, the reinvention of such elements as the latino culture in Los Angeles [START_REF] Price | Inscribing the border[END_REF], the Superbarrio character in Mexico City, the Chilean festive punk movement, the French band Mano Negra and cyberworld (video games, cyberpunk [START_REF] Bell | An Introduction to Cyberculture[END_REF], electronic art) is a rare revolt [START_REF] Châtelet | Vivre et penser comme des porcs. De l'incitation à l'envie et à l'ennui dans les démocratiesmarchés[END_REF]: for most people, this anxiety-based desire generates sadness [START_REF] Charles | Les temps hypermodernes[END_REF], euphoria and fear (Missonnier/Lisandre, 2003) as well as a need for security, which forms the basis of a reactionary world.

The utopia of creating a secure world by alienating it

The hyperreal world is secured according to two logics: 1) the contextualisation of risk in socio-spatial systems, risk-free environment [START_REF] Spring | Behind the Rave: Structure and Agency in a Rave Scene in Bennett[END_REF] or Privatopia (McKenzie, 1994), and 2) the perfection of design and the totalisation of an orderly world that stifles fantasy; the universe of video games is a gentle and orderly world (Schmoll, 2000:43-44;Shields, 2003:130). The totalitarian utopia of postmetropolitan carceral archipelagos [START_REF] Soja | Postmetropolis[END_REF] is organised around the ideology of transparency: in 2005, the city of Montpellier's budget for 'citizen management' covered the establishment of a Maison de la démocratie (0.3M€) and the expansion of the CCTV surveillance network (1.2M€, i.e. 1.2% of the total investment or 5€ per resident). In the UK, the number of CCTV cameras in public places went from 1 million to 25 million between 1999 and 2007; on average, Londoners are captured 500 times a day on camera, and have no control over the use of the data collected. In Grenoble, the INRIA is working on behaviour analysis software. However, cameras do not prevent terrorist attacks or crime on public roads. Their real aim is to control the population: "The burden of proof is reversed as every citizen is viewed as a potential suspect" 2 . Without any democratic debate, the generalisation of these processes of disciplinary space production reshapes the city [START_REF] Klauser | La vidéosurveillance comme mécanisme de production disciplinaire de l'espace public. Une analyse empirique et théorique : l'exemple de la ville de Genève[END_REF]: the industrial society has developed into a risk society, the society's development stage in which "political utopias have given way to speculation about side effects. Correspondingly, the utopias have turned negative. The structuring of the future is 2 Jean-Pierre Manach (Big Brother Awards/Privacy International), Le Monde, 5 August 2005 taking place indirectly and unrecognizably in research laboratories and executive suites, not in the parliament or in political parties". (Beck, 1992:123) Introducing the "ecology of fear" [START_REF] Davis | City of Quartz. Los Angeles, capitale du futur[END_REF] in French suburbs, a Minister politically close to the Far-Right imposed the constructivist image of violence through the instrumentalisation of statistics; when down in the polls, he incited riots which were amplified through their press coverage. When they died down, he instrumentalised them by declaring a state of emergency -anti-democratic by definition -for two months without preventing the start of new riots on 31 December 2005. Nevertheless, this strategy paid off and his popularity moved up sharply in the polls. Thus, "to talk about violence was to encourage it during the riots of 2005, justifying the initial speech which condemned insecurity" (Maigret, 2008:97). Promoted to the rank of 'Hyper-president' of the Republic, "guided by the absorption of what he believes France represents, and inspired by quantitative studies" (Maigret, 2008:46), he established political hyperrealization through a "narrative offered to the media by a ubiquitous and hyperactive President, in accordance with the art of storytelling", even if it meant "verging on lying" (Maigret, 2008:100). The universe of media representations having absorbed all human activities, any talk on this subject emanates from it and is therefore biased.

Security and consumption impose Rifkin's new order of cultural capitalism (2000): consciences and bodies are controlled by marketing through the mechanisation of everyday life, and the ideology of communication creates "a cyber-civil social peace' [START_REF] Châtelet | Vivre et penser comme des porcs. De l'incitation à l'envie et à l'ennui dans les démocratiesmarchés[END_REF].

The utopian ideal, "transparency of evil" [START_REF] Baudrillard | Simulacres et simulation, réed[END_REF], prescribes a society which is totally readable: this concept, on which strive all totalitarianisms, leads to coding and list building, fluidity and clarity, encryption and seclusion, alienation, homogenisation and commercialism of desire; the new man has no secret. Shopping centres [START_REF] Levi | Centros comerciales: espacios que navegan entre la realidad y la ficción[END_REF], video surveillance systems of gated communities and cerradas [START_REF] Razac | Histoire politique du barbelé[END_REF]Mendes, 1997) and dinner dance evenings in suburban France [START_REF] Crozat | Les contextes socio-territoriaux de la vie culturelle et de ses événements[END_REF] all aspire to a comprehensive definition of the world when faced with the uncertainty of reality: privatopia takes precedence over the public city; we bear witness to a "sinister and homogenous transformation of space. A new type of scheming urbanism is emerging, spread out and hostile to the traditional public space. In such spaces, everything is geared towards absolute control and the idea of true interaction between citizens has disappeared" (Rodriguez, 2005:128).

The building of a reactionary world

Total clarity and control, a reassuring antidote to fear of the unknown -unsafe by definition -, leads to conservatism. Creative imagination is impossible since hyperreality only reproduces what is already represented (Gauthier, 2002): the conventionality of Lara Croft or The Matrix does not usher in another subjectivity (Couchot, 2003). Far from metaphysics, this commercial and technological hyperreal ideology only shows a numbing shopkeeper mentality. This project, which aims at building a reactionary world, works on two levels: political and moral.

Firstly, security, surveillance and compartmentalization of societies [START_REF] Davis | City of Quartz. Los Angeles, capitale du futur[END_REF] structure this ideal world of social conflict refusal and create new types of discrimination by negating the other: the hyperreal world is compartmentalized for an 'elite' that denies the poor and condemns the homeless to heterotopia (Don Mitchell, 2001:64); the 'underprivileged' of Hong-Kong, the 'economically weak' of Europe, confined to other economic and leisure channels (council housing, working class bars, Lidl or Aldi supermarkets, etc.), are kept apart from the city whilst the richest have access to online shopping (Metton, 1998). Similarly, the social image presented in ecomuseums denies conflict and glamorizes poverty (Cantau, 2003).

The social involvement of GIS implies a selective access of the population involved (D'Alessandro-Scarpari et al., 2008), often due to cultural or economical inequalities. Some (Pickles, 1995;Hoeschele, 2000) insist on the specific nature of the data used, considered 'sensitive' and confidential, derived from an access body restricted to clearly identified populations (members of the security and social support institutions, researchers) whose political and material interests reflect their ability to impose their power and sometimes diverge from those of the populations. The Global Spatial Data and Information User Workshop (GSDIUW) (New York, 2004) points to the growing gap between the increase in the number of uses and the users' understanding and reinvestment abilities: even we, university specialists, are often surprised to discover unsuspected uses. This undulatory world integrates changes in public opinion or interest, and is governed by an ideological system (Williams, 1996:67), meta-account through which the cold and naked reality of social power expresses itself (Foucault, 1975:196). To talk of postmodernity no longer makes sense: the old structurations of power are not being challenged; only their implementation is changing. The 'war' to the poor (Don Mitchell, 2001:57) remains the norm, but the terms of social (Soja, 2001:54) or political conflict are evolving: how can we reintroduce the city and learn to handle the hyperreal society? Indeed, on another level, the project of hyperreal society, morally reactionary, denies the modern, independent and responsible individual: identity dispossession of subjects transformed into consumer zombies and solely defined by their needs (Rodaway, 1995:266), removal of accountability in the handling of images posted on networks, removal of accountability for those who act on those networks. Through their abstract nature and the apparent immunity of anonymity, computer viruses are a type of vandalism that is fostered by hyperreality. More 'inspired' than revolutionary, the prose used by hackers expresses the return of a bogus divinity:

Reality can change before our very eyes, now opened, if we manage to detect in it the hand of a master programmer, of a divine hacker, providing its creatures with the freedom to evolve and to change in accordance with their analysis and their understanding of the 'programme'. […] behind the appearance of things lies something unsuspected, astonishing, wonderful, laying in wait, hiding, immeasurable. Behind the world, or beyond it, lies another world. (Quéaud, 1993:47) This is accompanied by the disappearance of contemporary man fascinated by himself [START_REF] Sloterdijk | Essai d'intoxication volontaire[END_REF], reflecting a will of self-intensification through experimentation that is close to self-annihilation, a culture of self-preservation, growth (cybernetic, body building, aging). This tyranny discredits man through psychotic disembodiment: "absent in his uniqueness, whilst being hyper present as a vehicle for driving the world of image, is he still indispensable?" (Gauthier, 2002:54-55). In the realm of virtual communications, choosing one or several network, blog or chat room identities becomes vital "because users have no certainty as to the proclaimed identities of one another, and therefore as to their reality.

Listening and talking to someone (or, more precisely, reading and writing to them) works on the assumption that, at the other end of the line, lies somebody you have chosen to accept for what they claim they are and whom you expect will accept what you are claiming to be" (Schmoll, 2000:44). It marks the end of the universally objectivable individual's identity which gives him his ability -his capacity as a citizen -to interact with his environment, restricted to the interactive illusion offered by hyperreality without entering the public debate which is left to communication specialists. Reverting to an immanent society, the divine, social or political transcendence becomes a consumption-oriented destiny.

This conservative society discredits the very foundations of the modern project (independence and individual responsibility): those hyperreal structures are political and social projects with an antidemocratic logic; they convey blunt ideological underlying propagandas which have become familiar since the pictures of the bombing of Baghdad during the Iraqi wars (Waks, 1994); already, Rambo 3 chose his enemy. Today, extreme right-wing propaganda spreads Huntington's concepts through the medium of hyperviolence in video games [START_REF] Pilet | Le jeu vidéo comme arme de propagande[END_REF].

A soft violence, consubstantial with hyperreality

The fact that virtual spaces are not limited to the Internet justifies the usage of the term 'hyperreality'. The metaphorical nature of this process of world hyperrealization instils a violence that is merciless because it is soft. As a banal technical development, virtuality is not dangerous in itself; it is the process of hyperrealization it generates that converts it into a seductive and perverse "final solution" (Doel & Clarke, 1999:272). In that sense, Baudrillard's damning statements or Jameson's pessimistic ones should be taken seriously.

The contemporary dictatorship of the simulacrum leads to a loss of space and time references, it suppresses any measurement capable of calibrating senses, it creates closed and poorly interconnected utopian spaces and engenders a feeling of 'delocalization' and confusion amongst individuals: "[…] this latest mutation -postmodern hyperspace -has finally succeeded in transcending the capacities of the individual human body to locate itself, to organize its immediate surroundings perceptually, and cognitively to maps its position in a mappable external world." (Jameson, 1991:44).

The three levels of violence described in the introduction are linked, but the worst form of violence strikes at symbolism and culture. The themscapes (Rodaway, 1994), scenes [START_REF] Bennett | Music scenes: local, translocal, and virtual[END_REF] and other local hyperrealizations undermine the deep-rootedness that [START_REF] Williams | 45-54) and French (Violence en hyper réel[END_REF] considered as an antidote to the sweeping standardization condemned by Jameson. Unlike [START_REF] Santos | La nature de l'espace. Technique et temps, raison et émotion[END_REF] as well, the remediation of the local, capable of introducing the concept of long time in order to interpret global instantaneity, becomes difficult and threatens the identity of individuals: Thus, today's challenge is not about loss of memory […] but about loss of individuation that leads to movements between instances of individuation, of which there have been many throughout the history of mankind, except that the risk of entropy would mean that not only does the instance of individuation move and reorganize itself, but it also collapses, i.e. the individuation as negentropy weakens as a result of the conflict between the psychic, the collective and the mechanical which seems incapable of being resolved.

The question is about the reorganization of ownership through its adjustment to the new informational instrumentality of knowledge. In other words, the risk of growing ignorance, rather than knowledge, would be that of an entropic de-individuation process through lack of proper ownership of the informational hypomnesic structure. (Stiegler, 2005:9; sections highlighted by the author) This violence evolves in three phases: 1-Firstly, media exposure creates widespread confusion with commercial intent. 2-This leads to a loss of spatial and cultural references. 3-Loss of cultural identity and disorientation give rise to an overall sense of suffering which is used to impose a highly reactionary and controlling society.

Between the pain caused by the disappearance of the symbolic dimension of the world and the identity confusion, we are "lost in space" [START_REF] Olalquiaga | Megalopolis : contemporary cultural sensibilities[END_REF]. This pain drives masses of consumers/citizens to search for hyperreal territorial roots rendered deceptive by their artificial nature: there have never been so many rural fetes on the fringes of big cities, and they've never attracted so many people… Some [START_REF] Doel | Virtual worlds: simulation, suppletion, s(ed)uction and simulacra[END_REF] temper this pessimism: the generalization of virtuality gives rise to transient binary readings [START_REF] Bell | An Introduction to Cyberculture[END_REF]. Does simulation create innocent copies tending to reality or a cheap materialization of the refusal of any direct social interaction?

The link with representation is not always severed: « Despite the dominant rhetorics of mimesis, there is the potential within the dimension of simulation to argue for the continuing representational nature of virtual geographies; to emphasise that despite some claims made on their behalf, computer mediated communications do not institute a postsymbolic order" (Crang et al., 1999: 6); accessing new experiences of the world helps individuals to acquire new skills [START_REF] Quéaud | Le virtuel : vertus et vertiges[END_REF][START_REF] Lévy | Qu'est-ce que le virtuel ? Paris[END_REF][START_REF] Giddens | Les conséquences de la modernité[END_REF], re-mediatizes and allows for a better understanding of the world: societies' adaptability to a new technical reality, and the development of specific sociabilities change the conditions of social (Soja, 2001:54) or political [START_REF] Froehling | Internauts and guerrilleros. The Zapatista rebellion in Chiapas, Mexico and its extension into cyberspace[END_REF] conflict.

However, those progressive developments fail to conceal some problematic changes. Indeed, it is the power over space and over societies that populate it which is at stake: social and political instrumentalisation of ongoing processes through the development of surveillance and social control systems extends mechanisms that first appeared in the 17 th century (Elias, 1069;Foucault, 1975).

From virtual realities to real virtualities, hyperreality is no longer a copy or a representation. It is an alternative that operates side by side with reality [START_REF] Castells | La société en réseaux[END_REF]. As an Aristotelian perfection of reality (Doel & Clarke, 1999:268), hyperreality offers an illusion of interaction as a substitute for debate. The will to impose total transparency and perfection, and the inability to reach totalization [START_REF] Laurel | Computers as theater[END_REF]Doel & Clarke, 1999:273) threaten the permanence of Derrida's topolitique (1996): the organisation of space and time of mourning, the relationship with the Other etc., are no longer thought out; the very essence of the political is at stake. Our senses are being manipulated in order to produce realistic geographical experiences. Combined with the use of an everlasting present, this suppresses any prospect of reference to culture. Here lies the true violence.

«Dites-moi la vérité : nous sommes encore dans le jeu ?» Last words of French version of eXistenZ, David Cronenberg, 1999

Fig. 1 :

 1 Fig. 1: How to instil fear. With the help of a picture of the Pacific Ocean (La Gazette), the hyperreal tsunami of Montpellier lead to a simulation exercise by the emergency services. In 2007, a parliamentary report 1 (Midi Libre) showed that, on the French Mediterranean coastline, apart from the stretch between Nice and Antibes, the waves wouldn't exceed 60 centimetres ('medium' risk) to one metre ('high' risk), with the potential to occur once a century. La Gazette de Montpellier, 7/01/2005; Midi Libre, 20/01/2007


Benoit Baudry
email: benoit.baudry@inria.frmartin.monperrus@univ-lille1.fr

Martin Monperrus

Cendrine Mony
email: cendrine.mony@univ-rennes1.fr

Franck Chauvel
email: franck.chauvel@sintef.nofranck.fleurey@sintef.no

Franck Fleurey

Siobhàn Clarke
email: siobhan.clarke@scss.tcd.ie

Siobhán Clarke

DIVERSIFY: Ecology-inspired software evolution for diversity emergence

I. INTRODUCTION

Diversity is acknowledged as a crucial element for resilience, sustainability and increased wealth in many domains such as sociology, economy and ecology. In particular, the multiple forms of biodiversity underpin the productivity and stability of ecosystems in the face of perturbations. The relation between biodiversity and resilience of ecosystems has been called the insurance hypothesis [START_REF] Yachi | Biodiversity and ecosystem productivity in a fluctuating environment: the insurance hypothesis[END_REF]: if all species have different responses to changes in the ecosystem, then, the system as a whole is more likely to endure multiple evolutions and perturbations.

With respect to the large body of theoretical and experimental science that emphasizes the need to conserve high levels of diversity in complex systems, the limited amount of diversity in software intensive systems is a major issue [START_REF] Stamp | Risks of monoculture[END_REF], [START_REF] Parnas | Which is riskier: Os diversity or os monopoly? Communications of the ACM[END_REF], [START_REF] Forrest | Building diverse computer systems[END_REF]. This is particularly critical as these systems integrate multiple concerns, are connected to the physical world through multiple sensors, run eternally and are open to other services and to users. Such systems, also called collaborative adaptive systems (CAS), mirror the complexity of other complex systems. One major challenge to building collaborative adaptive systems is that current software engineering techniques require architects to foresee all possible adaptation situations the system will have to face. However, the inherent open and dynamic nature of collaborative adaptive systems makes such a-priori knowledge impossible.

DIVERSIFY explores diversity as essential software design principle. The fundamental intuition is that a pool of software variants will represent a reservoir in which the system can find adaptation solutions. The resulting improved adaptive capacities should enable the system to face situations that were unforeseen at design time, and improve the global resilience of systems under study.

The introduction of diversity for the construction of dependable software systems started in the 1970's when Chen and Avizienis proposed N-version programming [START_REF] Chen | N-version programming: A fault-tolerance approach to reliability of software operation[END_REF], [START_REF] Avizienis | The n-version approach to fault-tolerant software[END_REF] and Randell proposed recovery blocks [START_REF] Randell | System structure for software fault tolerance[END_REF]. Both approaches consider a set of diverse versions of the same software function. Software diversity is also the foundation of many techniques for increasing security. Many randomization techniques aim at diversifying the execution environment on different machines. For example, Lin et al. [START_REF] Lin | Polymorphing software by randomizing data structure layout[END_REF] randomize the data structure layout of a program to generate diverse binaries that are semantically equivalent. Several other pieces of work randomize instruction sets to provide unique execution environments and limit the ability of attackers to inject malicious code [START_REF] Kc | Countering code-injection attacks with instruction-set randomization[END_REF], [START_REF] Barrantes | Randomized instruction set emulation[END_REF].

As long as the software variants are created manually, the number of variants is small and the assumption of failure independence tends to be unsatisfied [START_REF] Knight | An experimental evaluation of the assumption of independence in multiversion programming[END_REF]. Consequently, our objective is to propose techniques that automate the creation of diversity in collaborative adaptive systems through ecological foundations [START_REF] Baudry | Towards ecology-inspired software engineering[END_REF]. DIVERSIFY aims at developing mechanisms that favor the emergence of multiple forms of software diversity in collaborative adaptive systems, through automatic transformation and evolution. The expected outcome is a set of software evolution and maintenance principles that spontaneously sustain diversity in collaborative adaptive systems.

Section II summarizes factual data about the project and section III presents the main objectives and the ecological foundations for software evolution. Section IV discusses the relevance to the CSMR community. Section V summarizes related work and projects.

II. ESSENTIAL FACTS OF DIVERSIFY

• Name and acronym of the project: DIVERSIFY -Ecology-inspired software diversity for distributed adaptation

III. SCIENTIFIC OBJECTIVES AND FOUNDATIONS

DIVERSIFY aims at formalizing and experimenting with new models and for creating and analyzing software diversity in collaborative adaptive systems, based on the ecological concept of biodiversity. The goal is to increase adaptive capacities in the face of unforeseen structural and environmental variations.

DIVERSIFY will converge towards this main objective through the development of the following scientific and technological objectives Objective 1: provide automatic synthesis mechanisms for the emergence of software diversity in collaborative adaptive systems. These forms of diversity will result from the translation of biodiversity models into software concepts.

Objective 2: provide novel distributed, diversity-driven, adaptation mechanisms in collaborative adaptive systems. These spontaneous exploration mechanisms will result from the transfer of ecological specialization and adaptation dynamics to the software domain.

Objective 3: develop software modeling and monitoring techniques to provide accurate and updated models at runtime and support distributed adaptation in collaborative, distributed and heterogeneous adaptive systems.

Objective 4: simulate and provide experimental evidence of the effects of software diversity on the adaptive capacities of a distributed collaborative adaptive system in the domain of large-scale smart cities.

A. Ecology as Foundation

Biodiversity. Ecologists acknowledge that a loss of diversity increases the vulnerability of a system in the face of changes in the environment. However, the diversity-stability debate [START_REF] Mccann | The diversity-stability debate[END_REF] is still challenging because of the number of variables that influence this phenomenon. Two elements inspire DIVERSIFY's research about software diversity:

• Biodiversity types: genetic, specific, functional 1 , species diversity, ecosystem diversity.

• Measuring biodiversity: many metrics exist that depend on the type of diversity and the granularity of observation.

• Measuring the effects of biodiversity: many approaches quantify the effect of diversity on the system's robustness, productivity, or stability. Ecological networks. Food webs, also known as trophic networks, are the most significant model to represent the constituents in an ecosystem. Originally proposed by Lindeman [START_REF] Lindeman | The trophic-dynamic aspect of ecology[END_REF], this holistic model captures the different species present in the ecosystem, as well as trophic (resource providing) flows that relate these species. These webs are organized according to trophic levels, which indicate the level of a given species in a food chain. Each trophic level also corresponds to a family of functionally consistent species. Intra and inter trophic level relationships model prey-predator relations. Ecosystems also host a large number of pairwise species relationships represented as bipartite networks [START_REF] Dormann | Indices, graphs and null models: Analyzing bipartite ecological networks[END_REF]. Examples of bipartite ecological relationships include plantpollinator or host-parasite relationships. Section III-B explains how DIVERSIFY plans to investigate how the structure and dynamics of trophic networks can inspire adaptable software architectures that leverage diversity.

Phenotypic plasticity. Plasticity is the ability of individuals of a given species to modify their characteristics in response to changes in their environment [START_REF] De Kroons | Morphological plasticity in clonal plants: the foraging concept reconsidered[END_REF]. Particular growth forms in plants result for each individual in a network of ramets (shoots) connected by modified horizontal stems through which information can be shared. Plasticity is found in this network because ramets that uptake resources are able to specialize in heterogeneous environmental conditions to improve their efficiency in resource harvesting. Local specialization supports increased fitness at the clonal network level, while foraging ability allows spatial dispersion in more favorable patches. DIVERSIFY investigates plasticity mechanisms to design software adaptation processes in response to heterogeneous and variable environments.

B. Evolution Rules for Diversified Software

In the first period of the project, the consortium is focusing on bi-partite relationships in ecosystems to tackle monoculture in client-server software architectures. This monoculture, as mentioned by M. Stamp [START_REF] Stamp | Risks of monoculture[END_REF], characterizes the fact that most server backends run on the same technology. For example, many web servers run on the same operating system, which represents a major potential threat: if attackers find an exploit in the system, they can crash all servers running on this system. This is called the BOBE (blow-one blow-everything) effect in cyber-security.

We model the monoculture of client-server architectures with a bi-partite graph illustrated in figure 1. In this graph, the top layer represents client machines, which are connected to server machines (represented in the bottom layer of the graph). The important point here is that all server machines are the same. Such a network is globally functional: all clients are provided services by server machines, i.e., there is a link between each client and a server. However, the network as a whole is also weak: an attack that can destroy one of the servers can destroy all of them, denying service to all clients. Fig. 1: Software monoculture in client-server relationships Ecological systems include a large number of bi-partite relationships, such as prey-predator or plant-pollinator [START_REF] Dormann | Indices, graphs and null models: Analyzing bipartite ecological networks[END_REF]. These relationships are also modeled as bi-partite graphs in which nodes represent species and edges represent a specific kind of relationship. For example, figure 2 represents bees and flowers species, as well as the pollinating relationships. Ecological bi-partite networks are very robust to perturbations because of the large diversity of species and the functional redundancy of species in the network. In many cases, if a flower species disappears, most bee species that relied on it for pollen can find pollen in one or two other species. The diversity of flower species increases the chances that the extinction of a particular species species will not lead to the extinction of the others, while the functional redundancy increases the chances that bees can find similar pollens in other flowers. Fig. 2: Example of bi-partite mutualistic relationship DIVERSIFY leverages ecological results about species diversity in bi-partite relationships to increase diversity in clientserver systems. One essential result from ecology is that species diversity and redundancy has emerged through species evolution [START_REF] Melián | Frequency-dependent selection predicts patterns of radiations and biodiversity[END_REF], [START_REF] Gavrilets | Adaptive radiation: contrasting theory with data[END_REF]. DIVERSIFY thus aims at defining software evolution rules, which can lead to the emergence of software diversity in client-server networks. This is illustrated in figure 3. There are different kinds of servers that have emerged through software evolution (e.g., through addition/removal of kernel packages) and client machines are possibly connected to more than one server that can provide the required service. The figure also illustrates that we target a network with more diversity but also with more machines. More servers will provide robustness through redundancy, but it will also increase the cost of the network. The set of software evolution rules, should thus consider a trade-off between the robustness of the network and its global cost.

We adapt state-of-the-art ecological metrics to assess the benefit of diversity of software bi-partite relationships. First, we adapt biodiversity metrics to quantify the evolution of diversity among servers. Shannon entropy is a a classical metric to quantify the diversity of species inside one level of the graph, while several indices exist to measure the diversity of relations [START_REF] Dormann | Indices, graphs and null models: Analyzing bipartite ecological networks[END_REF]. To demonstrate a beneficial effect of diversity on robustness, we adapt the robustness metric of Dunne et al. [START_REF] Dunne | Network structure and biodiversity loss in food webs: robustness increases with connectance[END_REF]. This metric for bipartite ecological relations evaluates the ability of one level to survive extinction sequences of the other level. Our experiments will evaluate robustness according to different server extinction sequences, e.g., BOBE attack or random crash. Fig. 3: Emerging software diversity in servers IV. RELEVANCE TO THE CSMR COMMUNITY Software evolution is a major area of research in the CSMR 2 community. This is the essential relationship between the DI-VERSIFY project and CSMR. The project aims at identifying software evolution mechanisms that can drive the emergence of software diversity. Examples of software diversity that we aim at providing through evolution include: performance diversity (some maintenance tasks aim at fixing performance issues, but this might also insert new bugs, thus it is worth keeping several versions on different machines), functional diversity (upgrades in the system might include new features, but it might be safe to keep several instances of the old version running while assessing the quality and stability of the new feature [START_REF] Hosek | Safe software updates via multi-version execution[END_REF]) and technology diversity (e.g., when a database fails on one server, it is possible to change the DB management system on this machine only, but not on all others, leveraging market diversity [START_REF] Barman | Impact of it monoculture on behavioral end host intrusion detection[END_REF]).

V. RELATED WORK DIVERSIFY is related to two main areas of software engineering: software diversity and component-based adaptation.

Software diversity has previously been investigated for fault tolerance [START_REF] Chen | N-version programming: A fault-tolerance approach to reliability of software operation[END_REF], [START_REF] Randell | System structure for software fault tolerance[END_REF] and cyber security [START_REF] Kc | Countering code-injection attacks with instruction-set randomization[END_REF], [START_REF] Lin | Polymorphing software by randomizing data structure layout[END_REF]. The most recent work focuses on automatic synthesis of software diversity to maximize its potential impact on resilience. R. Feldt [START_REF] Feldt | Generating diverse software versions with genetic programming: an experimental study[END_REF] used genetic programming to automatically synthesize variants of an aircraft controller in order to achieve failure diversity. M. Rinard and colleagues [START_REF] Sidiroglou-Douskos | Managing performance vs. accuracy trade-offs with loop perforation[END_REF], [START_REF] Rinard | Obtaining and reasoning about good enough software[END_REF] have developed unsound program transformations that support the runtime production of diversity and handle changes in quality of service. Forrest and colleagues have explored genetic programming for automatic bug fixing [START_REF] Le Goues | Genprog: A generic method for automatic software repair[END_REF] and neutral mutation [START_REF] Schulte | Software mutational robustness[END_REF]. Recently, Mendez et al. [START_REF] Mendez | Empirical Evidence of Large-Scale Diversity in API Usage of Object-Oriented Software[END_REF] have observed natural diversity in object-oriented API usage.

Software architecture aims at reducing complexity through abstraction and separation of concerns by providing a common understanding of component, connector and configuration [START_REF] Medvidovic | A classification and comparison framework for software architecture description languages[END_REF], [START_REF] Van Ommering | The koala component model for consumer electronics software[END_REF]. Several works have shown the benefits of this design style for dealing with adaptive systems [START_REF] Oreizy | Runtime software adaptation: framework, approaches, and styles[END_REF]. However, these models partially failed to gain wide adoption. There are two likely reasons: (1) the models were not accompanied by actual system level facilities for dynamic evolution (too many constraints exist on component implementation for example) and ( 2) the type of dynamism they supported was in some ways overly constrained. Recently, several component-based platforms try to overcome these limitations to provide abstractions and system level support for rich adaptation primitives.

There are related EU funded projects. CONNECT (Emergent CONNECTor for Eternal software intensive Networked Systems) is a FET-IP that aims at dropping interoperability barriers by synthesizing on the fly the connectors via which networked systems communicate. DIVERSIFY explores the positive side of dynamic interoperability abilities by using them to create diversified systems. DIVA (Dynamic Variability in complex, Adaptive systems) was a FP7-STREP that explored how to build self-adaptive systems on top of an adaptation model using models@runtime. DiVA resulted in models for large-scale, distributed software adaptation [START_REF] Morin | Taming dynamically adaptive systems using models and aspects[END_REF]. DIVERSIFY will build on the results of DiVA to exploit emergent diversity.

The SMScom project (ERC Grant) aimed at developing a consistent and integrated set of methods and tools for the design, validation, and operation of self-managing situational software. The term situational indicates that software is built to address a particular situation, problem, or challenge, and behaves according to the evolving situation in which it operates. The emergence of software diversity, tackled by DIVERSIFY, is a specific kind of situational evolution.

i.e., space competitor, nitrogen fixer, etc.