Wout Hofman
email: wout.hofman@tno.nl

Towards a federated infrastructure for the global data pipeline

Keywords: seamless interoperability, data pipeline, federated platforms, service, protocol, Physical Internet

Interoperability in logistics is a prerequisite for realizing data pipelines and the Physical Internet. Forecasting data, real time data, and actual positions of shipments, containers, and transport means shared via events have to be harmonized and are expected to improve all types of processes, support synchromodal planning, and improve risk analysis from a compliance and resilience perspective. Technically, several solutions are implemented by organizations and innovations have been validated in so-called Living Labs or demonstrators in various projects. These solutions do not yet provide open systems required for a (global) data pipeline. A federation of solutions is required to construct data pipelines and to support sustainable development of applications on smart devices allowing Small and Medium sized Enterprises to collaborate. This paper proposes a set of platform services and so-called platform protocols to allow interoperability of different platforms for constructing a data pipeline. The proposed services and protocols further extend existing interoperability solutions and services for supply and logistics.

Introduction

Customs authorities require additionally data to their current declaration for risk analysis improvement and introduced the concept of data pipeline for seamless data sharing as a solution [START_REF] Klievink | Enhancing Visibility in International Supply Chains: the Data Pipeline concept[END_REF]. Such a data pipeline consists of a large number of stakeholders like shippers, consignees, forwarders, and carriers, exchanging value according a transaction hierarchy, called logistic chain, in an organizational network (reference). The actual implementation of a data pipeline is by interconnecting legacy systems of the stakeholders and/or support by commercial -and community solutions [START_REF] Hofman | A global IT infrastructure improving container security by data completion[END_REF]. It is not to be expected that one global system will implement the data pipeline, but interoperability between existing systems and solutions needs to be constructed [START_REF] Hofman | A global IT infrastructure improving container security by data completion[END_REF]. As of currently, many interoperability implementations in trade and logistics are based on the message paradigm, but also other mechanisms are explored to address for instance real time data sharing for dynamic planning or resilience [START_REF] Dobler | A Pan-European Ecosystem for Intelligent Cargo and its Impact on Emmission Reduction[END_REF], Service Oriented Architecture (SOA) supported by Enterprise Services Busses (ESBs) [START_REF] Erl | Service Oriented Architecture -concepts, technology and design[END_REF] or Linked Data [START_REF] Heath | Linked Data -evolving the Web into a Global Data Space[END_REF]. For real time data sharing, the current generation of platforms supports an Application Programming Interface (API) registry [START_REF] Hofman | A technical framework for data sharing[END_REF], a particular SOA implementation based on the REST protocol. APIs are still technical specifications that require interpretation to derive semantics.

Seamless data sharing between systems and components of different stakeholders requires universal connectivity [START_REF] Montreuil | Physical Internet Foundations[END_REF]. In this respect, scoping of specifications is also important like taking a bilateral or multilateral interoperability [START_REF] Schonberger | A requirements analysis of Business-to-Business integration[END_REF] or a modeling approach covering organizational chains [START_REF] Huemer | The development process of the UN/Cefact Modeling Methodology[END_REF]. Interconnecting internal business processes resulted in reference models either specifying both processes and data [START_REF] Pedersen | One Common Framework for Information and Communication Systems in Transport and Logistics: Facilitating Interoperability[END_REF] or only data with a messaging choreography [START_REF]WCO Data model -cross border transactions on the fast track[END_REF]. Implementation of these reference models still lead to closed systems, since, organizations make bilateral or community agreements based on these models [START_REF] Hofman | Applying semantic web technology to interoperability in freight logistics[END_REF]. Several sources [START_REF]European Interoperability Framework for European public services[END_REF] [START_REF] Wang | The levels of conceptual interoperability model: applying systems engineering principles to M&S[END_REF] stress the importance of unambiguous semantics as part of interoperability, but do not address the implementation of this semantics in legacy systems or other solutions. It is yet unclear how process aspects need to get addressed in interoperability. Interoperability layering [START_REF] Wang | The levels of conceptual interoperability model: applying systems engineering principles to M&S[END_REF] considers pragmatics without presenting a way to model pragmatics like taking the bilateral or multilateral, chain approach.

A complicating factor is that Small and Medium sized Enterprises (SMEs) cover some 80% of the logistics market [START_REF]Transport in figures[END_REF] performing some 20% of the business. These SMEs have either simple or no IT solutions or systems, but interface manually with systems of their customers, potentially supported by web interfaces. Thus SMEs have to deal with different interfaces to become interoperable with their customers instead of having simple applications running on smart devices with cloud solutions of one or more communities and or providers, since these SMEs operate international and require interfacing with many systems and solutions. This paper proposes a set of platform services that enables an enterprise to connect once to an infrastructure of federated platforms and compose a data pipeline. Standardization of this set of services allows development of applications on smart devices, where these applications can interconnect to any given platform thus creating a sustainable business model for app developers in logistics. Each solution provider in this infrastructure can have its particular implementation of the services, thus satisfying their customer requirements and have sufficient market share. Firstly, requirements to platform services leading to design choices are formulated and secondly the services and the protocol for platform federation are introduced. The research presented by this paper is based on an action design research approach [START_REF] Sein | Action Design Research[END_REF] across several EU funded and Dutch projects addressing interoperability in logistics. Each project has constructed artifacts that do however not meet requirements formulated in [START_REF] Montreuil | Physical Internet Foundations[END_REF] and [START_REF] Chituc | A framework proposal for seamless interoperability in a collaborative networked environment[END_REF].

Design choices

A (federation of) platform(s) has to meet particular user requirements. Since it is fairly complex to assess user requirements for all global data pipelines, those stemming from various European Union (EU) funded projects and literature will be transformed into design choices. An example of a design choice is for instance the support of the messaging paradigm, common to most interoperability implementations between organizations. By making these design choices explicit, discussion on their applicability to meet user requirements is supported. Design choices are on distinction of 'service', 'protocol', and 'interface', bilateral versus multilateral business process modeling, semantics, and data governances supported by privacy-enhanced technologies. This section presents choices based on practice inspired research [START_REF] Sein | Action Design Research[END_REF] and briefly reflects the state of the art in research. It does not pretend to be complete, but identifies some basic research questions. The answers to these questions have to be supported by a federation of platforms; the next section shows the mechanisms to do so. Semantics is core to all choices made.

2.1

Participating in a federated infrastructure Currently, organizations bilateral or multilateral develop interoperability agreements, encompassing both functional and non-functional aspects, like message implementation guidelines and process alignment, based on open standards or with proprietary formats leading to closed solutions [START_REF] Hofman | Applying semantic web technology to interoperability in freight logistics[END_REF]. Each time a business relation with another enterprise needs to be established, investments in agreements has to be done. Seamless interoperability [7] [17] addresses this problem, but does not provide solutions. [START_REF] Huemer | The development process of the UN/Cefact Modeling Methodology[END_REF], [START_REF] Heuvel | Towards Business Transaction Management in Smart Networks[END_REF], and [START_REF] Kotok | ebXML -the new global standard for doing business over the Internet[END_REF] introduce business process modeling either for bilateral or multilateral interoperability as a solution, but [START_REF] Tanenbaum | Computer Networks[END_REF] argues to model only behavior between any two peer entities. There are different ways to specify behavior; [START_REF] Dietz | Enterprise Ontology, Theory and methodology[END_REF] provides transaction templates for bilateral interoperability to construct chains. A generic specification of behavior will not be applicable to all resources, since they all have different goals and capabilities [START_REF] Spohrer | Service Science, Management, Engineering, and Design (SSMED) -An emerging discipline -Outline and References[END_REF]. A generic specification can however serve as a reference framework for specifying these particular goals and capabilities.

This paper proposes to apply the concept of 'resource' offering both real time data and providing or requesting logistic services as specified by an 'Information Profile' of such a resource. In this respect, several issues need to be addressed, namely how to express the external behavior of a resource in terms of interactions and semantics. The concept of transaction templates to express external behavior for business transactions can be applied [START_REF] Dietz | Enterprise Ontology, Theory and methodology[END_REF]; other mechanisms like events might be required to share any logistic state changes like arrival of a vessel and delivery of a container at its destination. Semantics of one's profile can be expressed as an ontology, based on a networked ontology of logistics concepts and services (see for instance ontology.tno.nl for a logistics ontology). Semantics of data and behavior need to have a technical binding to a paradigm like messaging and SOA [START_REF] Erl | Service Oriented Architecture -concepts, technology and design[END_REF] supported by a syntax like XML or JSON. In case any two communicating organizations have different technical bindings, binding negotiation and a data transformation function have to be implemented, either by a data provider, a consumer, or as service of the federation of platforms (see next section). In case Information Profiles of any two communicating organizations are based on an identical -or matched semantic models, an on-the-fly technical binding by a platform can be constructed, as long as the federation of all platforms support that technical binding.

The concept 'resource' with its 'Information Profile' needs further research and examples stemming from real use cases. These examples are currently developed in EU funded projects like EU FP7 CORE.

2.2

Data governance and privacy enhanced technologies Organizations are hesitant in sharing information due to for instance commercial or liability reasons, e.g. the amount of free capacity of a barge might reduce prices, the location of a truck might increase vulnerability for cargo theft or providing real-time and predicted depth of a waterway might increase liability. There are currently a number of barriers that block the adoption of data sharing amongst resources, e.g. data ownership, privacy, commercial sensitivity, liability, and culture [START_REF] Eckartz | A decision model for data sharing[END_REF]. In this respect, data and events are classified as:

 Open data. Data is publicly available to everyone. Open data is normally considered to be available without any costs, but in some occasions like the Cadastre data, one needs to pay.  Community data. Data is shared within a community according agreed rules.

Like with open data, one might distinguish free -and paid data.  Partner data. Data is shared with a specific partner.  Internal data. Data is only shared within an organization, according internal data policies.

Fig. 1. Decision support instrument for data sharing [23]

Data classification has a lifetime, e.g. it may change over time and/or may be applicable for one or more calls or interactions. For instance, available capacity on a trip may be shared only once in a community at the start of the trip or can be updated during the trip. Communities can also be flexible, e.g. organizations can join and leave a community over time.

The previous figure shows the decision model developed by [START_REF] Eckartz | A decision model for data sharing[END_REF]. It addresses various aspects like data ownership, privacy and commercial sensitivity, and economic aspects, resulting in a data policy supported by interventions. Many of these interventions are supported by privacy-enhanced technologies [START_REF] Lagendijk | Encrypted Signal Processing for Privacy Protection[END_REF] like identification and authentication, access control, filtering, and homomorphic encryption [START_REF] Gentry | A fully homomorphic encryption scheme[END_REF]. One particular technology might support data sharing for one or more decisions, but we have not yet found these for logistics data sharing. For instance, Role Based Access Control expresses access control for internal data, but a more fine grained access control mechanism like Attribute Based Access Control might be required for partner -and community data. Templates for particular roles can be specified to ease the specification of data policies, e.g. a template for a role like a forwarder. These templates are a form of Role Based Access Control that can thus be refined by organizations meeting their particular requirements as they operate in one or more roles. These templates may implement formal restrictions from a liability and financial perspective, e.g. carriers should not receive any data on the content of a container, whilst they are otherwise liable for any damage or loss to the content.

Role -and Attribute Based Access Control can be expressed as an ontology of a set of rules, based on the earlier mentioned networked ontology for logistics. To support global logistics and supply, protocols are required for a federation of identities [START_REF] Pruksasri | Multi-level access control in the data pipeline of the international supply chain system[END_REF]. Further research is required with respect to the relation between privacy-enhanced technologies as interventions for data governance and implementing these technologies in real world cases.

2.3

Service, protocol, and interface The Internet design principles of 'service', 'protocol', and 'interface' [START_REF] Tanenbaum | Computer Networks[END_REF] are applied for specifying a federation of platforms supporting data sharing between organizations. A federated platform is said to offer a 'service' to back office systems of supply and logistic stakeholders, e.g. the ability to exchange messages, validate the message structure and content, and validate the message sequence, whereas a 'protocol' between any two platforms provides the ability to actually share data with for instance messages. The protocol is the set of agreements for sharing data between any two platforms, independent of a local implementation of the service by each of those platforms to their users, which is called 'interface'. The service is the conceptual representation of this protocol to a one or more back office systems and/or end-user. The same service can be implemented by various interfaces, e.g. a file sharing mechanism or an API can serve as an implementation of a service. In fact, 'interface' is the technical binding of a service offered to back office systems of an organization. The technical binding of an interface can differ from that of an agreed binding of the protocol, which requires transformation by a local implementation of the protocol and service by a platform.

Fig. 2. The concepts service, protocol and interface

Introducing these concepts allows conceptually specification of a service and a protocol with different technical bindings, both for the service by its interface and a protocol for interoperability between two local implementations. Complexity reduction of federated platforms is achieved if all participating platforms support the same semantics and technical bindings of the protocol.

Each service -and protocol primitive has a particular structure with control information and a payload, where a semantic model specifies the semantics of the payload. Control information of a service primitive is applied by a local implementation for processing that primitive and constructing a protocol primitive with a negotiated -or on-the-fly technical binding (see before). It allows for instance the transformation between a SOA interface of a service to a message based protocol and vice versa. Communication is already implemented by various protocols and is therefore considered out of scope. Thus, the service and protocol for logistics will be elaborated, whereas a local interface is discussed in the next section considering back office integration.

A federation of platforms

The previous section has introduced a number of research questions and concepts for federated platforms. This section further elaborates the services of a (federation of) platform(s) and its protocol. The services reflect the concept of Information Profile and the support of data governance, all based on networked ontologies.

3.1

Federated platform services A (federation of) platform(s) provides generic services to resources, where these generic services are configured by semantics for a particular application area like supply and logistics. The services can be categorized in two main groups that can be further decomposed (figure 3): operational services consider actual sharing of logistics data utilizing various technical bindings and mechanisms; administrative services consider registration and other types of support services for operating a (federation of) platform(s). The decomposed services can be defined as:  Registration Services. These services support an organization in its registration and connection to a platform (profile specification services) and specify its data policies (data policy specification services).  Real time data sharing services. These support data policy negotiation, both for events and data, search for a particular (composite) service matching a goal (matching services), and sharing the state of supply and logistics chains via events (visibility services). Visibility services can be on particular objects like trucks with their location, speed, etc. in an area (geo-fencing), timeframe (time-fencing) or a combination of both [START_REF] Merrienboer | Using floating truck data to optimise port logistics[END_REF]. Visibility services can only provide the state of an object or also evaluate the state against requirements, which is supported by (complex) event processing [START_REF] Hofman | Control Tower Architecture for Multi-and Synchromodal Logistics with Real Time Data[END_REF]. Matching services can be on search for a (structured set of) profile(s) meeting a customer goal, where a structured set composes a logistics chain or all retrieved profiles exactly meet a customer goal. These matching services can be applied in various ways, e.g. to support synchromodal booking [START_REF] Hofman | Control Tower Architecture for Multi-and Synchromodal Logistics with Real Time Data[END_REF].  Transaction support service: validating the sequencing of interaction according an agreed transaction protocol specified by a choreography. In this particular case, the initiation and processing of transactions is in applications registered at a platform.  Data sharing service: reliable and secure exchange of data and events according a particular technical binding, potentially supported by data transformation. Reliability services consider data resubmission in case the receiving platform or application responds and are not always required. The same is applicable for secure data sharing.  Supporting services. These services support the operation of a federation of platforms providing particular services to platform users. These services not necessarily have a supporting protocol. The following supporting services are foreseen: o Semantic services providing the networked ontologies (see section 2). o Publish/subscribe services providing the ability to subscribe to particular events, where these events provide state information. Publish/subscribe may require policy negotiation services. o Non-repudiation services that provide proof of actual data shared between any two users of a federation of platforms. Non-repudiation services are supported by an audit trail registering all actions in terms of data sharing between any two actors, e.g. sending or receiving particular data with a timestamp, a log containing the actual data that has been shared, and monitoring services providing both access to the audit trail and the log. o

Accounting and billing services supporting paid data according agreed pricing structures. These services utilize the non-repudiation services.

o Certification services providing identification and authentication of platform users.

Fig. 3. Federated platform services

Services are interrelated. Visibility services can for instance use publish/subscribe services and data exchange services for events, transaction support services can utilize data exchange services by messaging and reliability services to assure a reply is received in time. Secure and reliable data exchange is for instance specified by Electronic Business XML with ebMS [START_REF] Kotok | ebXML -the new global standard for doing business over the Internet[END_REF] and implemented by an eFreight access point [START_REF] Angholt | A first security analysis of a Secure Intermodal Goods Transport System[END_REF]. A formal service specification considers the control information and payload [START_REF] Tanenbaum | Computer Networks[END_REF], which yet needs to be performed.

3.2

Federation of platforms Like the services, the protocol can also be decomposed. The protocol should support each of the services, but some protocols can support more than one service by a different payload of the protocol primitives [START_REF] Tanenbaum | Computer Networks[END_REF]. The protocol is decomposed as follows:

 Data policy negotiation protocol: negotiate the data that can be shared amongst two organizations.  Matching protocol: sharing goals and (a structured set of) service(s) to support matching services.  Visibility protocol: how to access particular data on the supply chain status, e.g. it basically consists of events either received upon subscription or by a query. Security protocol: selecting a secure protocol with agreed certificates, e.g. https.  Authentication protocol: a protocol for federation between certification authorities to support authentication of an identity [START_REF] Pruksasri | Multi-level access control in the data pipeline of the international supply chain system[END_REF]. One might consider to introduce a protocol for supporting registration services, e.g. to share complete Information Profiles and data policies. Such a protocol would provide complete transparency. In our proposed approach, the data negotiation -, matching -, and binding negotiation protocol support this type of transparency, but does not provide a generic data policy of any registered user.

3.3

Implementation and deployment There are several ways to implement a federation of platforms, e.g. if any two enterprises are connected to the same platform like a Port Community System, data sharing services between them might be implemented via a database and registration is based on administrative services with a proprietary format. Only in case two enterprises connected to different platforms, the protocols will be required. Currently, most of these protocols are message based (see before).

There are two dimensions to the deployment of the Connectivity Infrastructure, namely an business dimension and ICT dimension. Both will be discussed here. The ICT dimension addresses the development of a local implementation, with potentially different components providing different services and supporting particular parts of the protocol. The following options are feasible:

 Open source: the services are provided by an open source software solution that every resource can implement. Like indicated before, eFreight Access Points provide particular functionality, so do iCargo Access Points in supporting virtualization of logistics actuator objects like containers and trucks [START_REF] Dobler | A Pan-European Ecosystem for Intelligent Cargo and its Impact on Emmission Reduction[END_REF].  COTS (Commercial Of The Shelve): the implementation of the protocol with a local interface to its back office systems based on COTS. The software offering the service and supporting the protocol is licensed to a resource or its owner that implements the functionality. The COTS provider is responsible for correct (and complete) implementation of the protocol.  Proprietary: the IT department of an enterprise develops the implementation of the protocol or its implementation is outsourced to an external software developer. The implementation can be based on open source solutions and/or components like available integration brokers. The solution is owned by the enterprise (with the exception of COTS components used for implementation) and the enterprise is responsible for correctness of the protocol implementation. From a business perspective, the service can be implemented in many ways, for instance:

 Resource Deployment: each resource implements and operates the protocol by itself. The services are internal to the resource, but utilizing an ICT solution implementing the services reduces development costs. The iCargo Access Points try to provide this functionality [START_REF] Dobler | A Pan-European Ecosystem for Intelligent Cargo and its Impact on Emmission Reduction[END_REF].  Community Systems: two or more organizations might decide to implement the services themselves with different local interfaces to back office systems and/or end-user functionality. These organizations thus own the community system. Port Community Systems are examples of these types of systems  Cloud Platform: the service and the protocol are provided by a platform of a commercial provider. The latter ones can construct their particular solutions on top of the services. Note that this type of solution is identical to telco or other providers offering services with COTS and/or open source solutions for communication protocols. The services can also be used for open innovation, implying the development of apps for SMEs (see also www.logicon-project.eu). To support open innovation, the services have to be more tailored to a specific target group of end-users, e.g. barge operators are expected to have other services than truck drivers.

A number of services is currently proprietary to a particular solution, e.g. registration of resources at a community system or cloud platform. These deployment solutions do not yet support the protocol, which makes it difficult to find for instance resources in an infrastructure. Furthermore, these deployment solutions have their specific data policies implemented by message implementation guides, which restricts data sharing across these platforms and require all types of transformations between them.

Conclusion and further research

The paper presents a set of services for federation of platform solutions and services supported by a protocol for logistics and supply. By standardizing supply and logistics services and their underlying protocol, the so-called data pipeline for interoperability in trade facilitation will be enabled. The services and protocol enable each individual object or actor to act as a information resource with particular capabilities for data sharing. By examples, we have mapped functionality to existing components like developed for eFreight and iCargo. Dedicated solutions and services can be developed addressing particular interoperability aspects like virtualization of actuators representing physical objects like trucks and containers, thus also contributing to the concept of the Physical Internet [START_REF] Montreuil | Physical Internet Foundations[END_REF]. Standardisation of services of federated platforms also contributes to development of sustainable business models for deployment of apps on smart devices for SMEs. By separating service and protocol, each resource implementing a protocol stack known to the infrastructure will be able to participate, without additional costs and effort for development of bilateral or community guidelines. Each ICT solution -and service provider will also be able to tailor its services to optimally integrate resources in the infrastructure and provide added value like complex event processing and transformations to these resources.

The solutions provided by this paper need to be developed further, including construction of low cost connection to the federation of platforms. We have indicated that lots of existing systems and cloud solutions have a role in implementing the services. Federation of platforms requires additional research into the business models of these platforms, like a sustainable business model of community systems. Not yet, all identified services are fully supported by software solutions.



  Transaction protocol: the agreed choreography of interactions for transaction support services.  Data sharing protocol: sharing data between two communicating systems, where the payload is provided by the aforementioned protocols. The data sharing protocol is decomposed in: o Binding negotiation protocol: to establish the technical binding for sharing data. o Data exchange protocol: the actual sharing of data (and events) according an agreed or selected (on-the-fly) technical binding. o Reliability protocol: resubmission and identification of resubmitted messages, resulting in a receipt acknowledgement, and timers to detect timely replies to support reliability services. o

Acknowledgements

The content of this paper is based on research and development in EU FP7 SEC Cassandra, EU FP7 SEC CORE, EU FP7 INFSO iCargo, EU FP7 INFSO Logicon, several other projects for data sharing in logistics and supply chains, and discussions in various fora like ALICE on the subject of seamless interoperability.


Tijmen Joppe Muller
email: tijmen.muller@tno.nl

Rainer Müller
email: rmueller@isl.org

Katja Zedel
email: zedel@isl.org

Gerwin Zomer
email: gerwin.zomer@tno.nl

Marcus Engler
email: engler@isl.org

Enhancing Awareness on the Benefits of Supply chain Visibility through Serious Gaming

Improving both efficiency and security in international supply chains requires a new approach in data sharing and control measures. Instead of managing supply chain risks individually, supply chain partners need to collaborate in order to exchange cargo information and implement control measures on the level of the entire supply chain. Governmental agencies, having access to this up-to-date and complete information, can implement alternative risk assessment policies, resulting in less disruptive ways of supervising entire trade lanes. However, this paradigm shift requires awareness of these supply chain visibility concepts and increased collaboration between partners in a value chain. In order to disseminate these new concepts and initiate cooperation between key stakeholders, a serious game called 'The Chain Game' was designed, implemented and evaluated.

Supply Chain Visibility

One of the main challenges that international intermodal container logistics faces today is how to balance efficiency and security. Efficiency is one of the key performance indicators businesses are aiming for in order to have competitive advantages. In contrast, governmental agencies, such as customs at border control, have to maintain a high level of security to protect citizens and business partners against unlawful practices. However, increased efficiency and increased security are goals that may oppose each other. For example: in order to reach maximum efficiency, disruptive governmental interventions are undesirable from the business perspective, whereas maximum security is reached by high inspection rates and heavy enforcement measures applied to all incoming and outgoing containers. In current day practice, most organizations in a value chain manage their supply chain risks individually, by applying a combination of the 4Ts: transfer, terminate, tolerate and treat. Risk transfer practices are very mature and widely applied by the more powerful chain actors. The weaker chain actors often cannot transfer such risks and pressure on margins forces them to tolerate certain risks. If risk treatment is being considered, it is often done through internal control measures.

Research in supply chain dependencies, vulnerabilities and resilience proposes an alternative approach, one that considers the risks from the perspective of the entire supply chain, instead of from each individual fragment of the chain. Risk based control and supervision seems the way forward, targeting high risk consignments and concentrate inspection effort on the targeted categories, whilst applying alternative less disruptive ways of supervision to the rest. This concept of Supply Chain Visibility [START_REF]The CASSANDRA project[END_REF] takes the needs of both governmental agencies and businesses in the chain into account. The basic idea is a data sharing concept that is built on integration of existing data processing systems. This so-called 'Data Pipeline' is used by business companies for end-to-end supply chain visibility, to ensure high data quality and data completeness and efficient connectivity to community systems. Customs and other authorities can connect to the Data Pipeline through a dashboard interface and use selected data for reporting purposes, such as customs declarations. It also allows them to piggy back on the validated and enriched supply chain data and advance the risk analysis and assessment they used to perform on data from declarations. An advantage for all parties is that all available information is up-to-date, since the data itself is fed by the originator of data and only retrieved by authorized users. Time-consuming search for additional information concerning a single transport could be avoided and additional data sources (from container security devices for example) could enrich the data sets without revision of company-wide or governmental data bases.

In theory this Supply Chain Visibility concept can benefit all actors within a supply chain. This approach may not only lower costs for the business partners in the supply chain because of increased data sharing efficiency, but may also have customs recognize that the corresponding trade lane partners are 'in control' of the major risks in their supply chain, resulting in less disruptive interventions from the authorities. However, some required steps need to be taken in practice to operationalize this approach. Most importantly, trade lane partners need to collaborate in implementing both the data sharing concept and additional chain control mechanisms. Examples of control mechanisms on the level of the entire chain are partner screening and coaching, applying technologies for container integrity (e.g. Container Security Devices) and data validation procedures, either through physical checks (e.g. a tallyman checking the packing list information) or by comparing data from different sources (threeway match). A second important step is new policy from the governmental agencies, that allows less disruptive interventions based on a different way of risk analysis.

Creating awareness of the aforementioned concepts and control mechanisms, having key stakeholders in a value chain recognize the benefits of such an approach and initiating collaboration to put these concepts into practice proves to be a difficult and time consuming process. In order to speed up the concept development cycle but also to disseminate the research findings we implemented an alternative approach: a serious game. We believe the characteristics of serious gaming, which allows stakeholders to have concrete experiences with the innovative concepts in interaction with each other, will disseminate the research successfully and will initiate collaboration for future implementation of supply chain visibility.

Serious games have proven to be an excellent medium to explain and teach complex concepts through experiential learning in a wide variety of domains. A wellknown example is strategic war games that have been used in military training for centuries. At least since the mid-19th century the use in the military tactical training of officers has been documented [START_REF] Von Hilgers | Eine Anleitung zur Anleitung. Das taktische Kriegsspiel 1812-1824[END_REF][START_REF] Pias | Computer Spiel Welten[END_REF]. Business simulations, which can be simple board games or massive computer games, are commonly used in management education [START_REF] Keys | The role of management games and simulations in education and research[END_REF][START_REF] Tanner | Using MONOPOLY and Teams-Games-Tournaments in accounting education: A cooperative learning teaching resource[END_REF]]. An almost classic example for this is the Beer Game, which was created in early 1960s at the MIT's Sloan School of Management [START_REF] Forrester | Industrial Dynamics[END_REF] and is still used in management education to have players experience the bullwhip effect. Technological progress has allowed for more complex and realistic simulators, such as flight simulators, nautical simulators, crane simulators or driving simulators.

Simulation games and simulators are commonly used to allow students to experience situations which are too costly, hazardous or unethical to experience in the real world. Simulation games are very useful to understand complex problems through experiential learning: experiencing the effects and dependencies of own behavior is a very strong learning method. Simulation games allow making mistakes in a safe environment and thus learning by trial and error [START_REF] Randel | The effectiveness of games for educational purposes: A review of recent research[END_REF]. This invites players to try new strategies and challenge long-standing patterns of behavior. In "The Chain Game" we use this to guide the players to try more collaboration.

The use of (computer) games in education -either especially designed for education or commercial off-the-shelf (COTS) games -is growing [START_REF] Prensky | Digital game-based learning[END_REF][START_REF] Fletcher | Using computer games and simulations for instruction: A research review[END_REF][START_REF] Charsky | Integrating commercial off-the-shelf video games into school curriculums[END_REF]. The learning theories which can be identified in games include well known theories of learning such as Gagne's "Conditions of Learning theory", Gardner's "Theory of Multiple Intelligences", Skinner's "Operant Conditioning theory", Thorndike's "Laws of Effect", Maslow's "Hierarchy of Needs theory" and Kolb's "Experiential Learning Model". Also incorporated are learning approaches like active learning, experiential learning and situated learning [START_REF] Tang | Introduction to games based learning. Games Based Learning Advancements for Multi-Sensory Human Computer Interfaces: techniques and effective practices[END_REF].

Probably the most compelling point about games is their ability to motivate and engage, far better than other teaching methods. Prensky believes that games "are the most engaging intellectual past-time that we have invented" [START_REF] Prensky | Digital game-based learning[END_REF]. In studies, participants report to have more interest in simulations or games than in classroom instructions. This correlates with the participants investing significantly more time in learning with games [START_REF] Randel | The effectiveness of games for educational purposes: A review of recent research[END_REF], [START_REF] Fletcher | Using computer games and simulations for instruction: A research review[END_REF], [START_REF] Tang | Introduction to games based learning. Games Based Learning Advancements for Multi-Sensory Human Computer Interfaces: techniques and effective practices[END_REF]. For our dissemination we take advantage of the engaging and interest raising nature of games. Buckley and Anderson identified three common characteristics which make games so compelling [START_REF] Buckley | A theoretical model of the effects and consequences of playing video games[END_REF]:

1. Being in control: Players work at their own ability level and speed and repeat material as needed. 2. Feedback and rewards: Games give immediate feedback. Additional most games reward behaviors and actions by the player which are "positive" according to the in-game logic particularly. This increases the frequency of this behavior and teaches a positive attitude towards the content of the game.

3. Challenge and mastery: Games challenge players but remain doable. They keep the balance between too hard and tedium, giving the player feelings of self-efficacy.

Since games are an engaging medium for explaining complex systems, they can be very useful to create awareness for new concepts, such as the data sharing concept of Cassandra, with key stakeholders. Serious gaming allows meaningful interaction with both a relevant representation of the world and between key stakeholders, allowing them to analyze the situation from different perspectives and create a shared understanding of the challenges [START_REF] Janssen | Gaming and simulation for transforming and reengineering government: Towards a research agenda[END_REF]. As such, gaming can play an important role in the transformation process needed to eventually implement these concepts.

The Chain Game

Given the goals we hope to achieve, explaining the complex and abstract concepts of supply chain visibility and initiating collaboration between key stakeholders in supply chains, we believe serious gaming is a very suitable medium -more so than reports or presentation material. In modern supply chain logistics stakeholders face multidimensional problems with complex side effects and non-linear dependencies. A game typically is a simplified world, reducing this complex multidimensional problem to its essentials in order to showcase only the relevant parts. This section describes The Chain Game, the serious game that was designed to transfer the abstract chain visibility and chain control concepts into practical examples and to allow players to experience the effects of the researched innovations, even though the exact effects (in reality) are not yet known.

The starting point for designing The Chain Game is the goals that should be achieved after playing the game. These learning goals were defined as follows:

1. Players understand that collaboration between supply chain partners is needed in order to operationalize the concept of supply chain visibility. Additionally, collaboration will have benefits on the performance of the supply chain, but the investing partners will not necessary receive the gains, so discussion on return-oninvestments is necessary. In general, the performances of businesses within one chain are interdependable. 2. The concept of supply chain visibility and the underlying innovations need to be disseminated. The players (typically key stakeholders in a supply chain) need to understand the broader picture of supply chain visibility, but also understand typical control measures they could implement. 3. Implementation of the supply chain visibility concepts will increase robustness of the entire supply chain as risks are more easily mitigated and governmental agencies will apply less disruptive supervision measures.

These requirements are used to design components such as the world model (cause and effect), physical setting, narrative (i.e. scenario and storyline), aesthetics, but also the game session (i.e. the process of game play). This design is an iterative process in which play-testing is key: by trying out the game, the designers can observe whether the goals are reached and interaction and user experience are what they hoped for. In the sections below, we explain how the design meets the initial requirements.

Benefits of Collaboration

In order to show the effects of collaboration and initiate discussion between key stakeholders, we needed multi-player gameplay. The Chain Game has a fixed amount of five roles, of which each plays part of an international supply chain: two sellers, two freight forwarders and one buyer. The goal within the game is to create highest value for the own company, based on three key performance indicators (KPIs). In order to do so, players can invest in innovations from their limited resources. Innovations are either individual (conform the internal control measures) or collaborative (in which case collaboration obviously is necessary) and will improve specific KPIs of specific companies in the chain.

Interdepence between players is designed in the game model in multiple ways. First off, investing in collaborative innovations will increase chain value more than individual innovations on the long term. However, the collaborative innovations do not necessarily benefit the players that have invested in them: they may benefit one player more than the other, may benefit a player that has not invested at all or may even decrease company value of an investing player. These effects can be reduced by the players themselves, as they are allowed to share their benefits with each other. This game mechanic stimulates investing in collaborative innovations, but also supports discussion on return-on-investment. Additionally, the fact that the players are (collectively) responsible for implementing innovations and they almost immediately see the effects of their actions contributes to the game characteristics 'Being in control' and 'Feedback and Reward' as described by [START_REF] Buckley | A theoretical model of the effects and consequences of playing video games[END_REF].

Second, company value is not only based on the key performance indicators of the own company, but also on the performance of the chain as a whole. But the performance of the chain depends for a large part on the weakest link of that chain. As a result, players need to convince other players to improve certain KPIs, conveying the message that chain partners are highly interdependent.

Disseminating Concepts

The supply chain innovations are made available as actions to the players of the game. This forces the players of The Chain Game to become familiar with the concept of Supply Chain Visibility: they are required to think about the value of the innovations in the context of their working environment and will experience the necessity to cooperate in order to create greater supply chain visibility. The innovations are focused on custom-related interruptions, in line with the research goals of the Cassandra project, and described on an abstract level, in such a way that they have an effect on one or more KPIs of one or more roles. The effects of an innovation are not disclosed until the innovation is implemented, creating the challenge for the players to understand these innovations and estimate their effects if they want to master the game (as described before [START_REF] Buckley | A theoretical model of the effects and consequences of playing video games[END_REF]). As they are trying to implement the best possible innovation for their company, the main goals of the game are achieved: communicating the concept of supply chain visibility, understanding of the underlying innovations and discussion within the supply chain on these innovations.

An example of a supply chain visibility concept is 'Exception Reporting', which is made available as collaborative innovation to the players of The Chain Game (see fig 1). For 'Exception Reporting' three investors are required: both freight forwarders are forced to invest, and a third one (either one of the sellers or the buyer) also needs to contribute to implement this innovation. As described before, the companies that invested in the innovation are not necessarily the companies that receive the (dis)advantages: 'Exception Reporting' not only improves the KPIs for both investing freight forwarders, but also the buyer, whether he invested or not. An important step in clarifying the concepts to the players is explaining the argumentation of the effects, which is done by a game facilitator. In the case of the 'Exception Reporting' innovation, the reason for the impact is described as follows: "Exception Reporting provides the Freight Forwarders with early warnings for expected errors, allowing them to take measures in an early stage. This will give them more control over their business and they will have the ability to reduce the negative consequences, which is also of interest for the Buyer."

Fig. 1. An example of a chain innovation card

A big challenge of designing The Chain Game was that insufficient data is available on the exact effects of these innovative concepts, so it was not possible at this point to create a simulation model that predicts the effects on a detailed level. However, the innovations were already described on an abstract level in the CASSANDRA Project deliverables [START_REF] Zomer | Deliverable D9.1 CASSANDRA Final Report[END_REF]. As the goal of the game is to create awareness about this knowledge, a qualitative model suffices to create this awareness and support discussion about the various concepts. As a result, the effects of each innovation were established by interviewing subject matter experts in a series of workshops to come to the content model of The Chain Game. In total, the effects of 6 individual innovations and 26 collaborative innovations were estimated and implemented this way.

Chain Robustness

One of the promises of increased supply chain visibility is that the supply chain will be less sensitive to incidents that may occur. To communicate this message, incidents occur regularly to test the current state of the supply chain. Incidents typically have a negative effect on one or more KPIs of one or more companies, but implemented innovations may (partly) mitigate these effects. The effects of an incident and the mitigating innovations for each incident have been established by the subject matter experts, similar to the effects of the innovations. An example of an incident is 'Cargo Theft': "Cargo has been stolen from trucks that were on their way from the Seller to the seaport. Trucks are totally emptied by this criminal organization." It has a negative effect on the freight forwarders, the seller and the buyer with the following argumentation: "Both of the Freight Forwarders are held responsible for their lack of security measures for their part of transportation. Their reliability is severely damaged and they have to compensate the costs of the theft and therefore their capability weakens. The Buyer doesn't get its raw product in time, which means that yet again, there will not be enough of his product available for retailers. This hurts the perceived reliability of the Buyer. The Seller is afraid to lose clients and quickly offered to deliver new cargo at cost price." The innovation 'Exception Reporting' discussed before mitigates 25% of these effects.

A second game mechanic that gives players the feedback on the state of their supply chain is the role of Customs. Customs is strongly interested in supply chain visibility, since they profit from additional information in a way that checks on data might be executed in less time. Therefore, the partners in the supply chain may gain advantages in relation to Custom checks if they provide a certain degree of visibility. Ideally, Customs perceives the supply chain as a trusted trade lane, a concept strongly related to supply chain visibility. These dynamics reflect in the game by having Customs to perform a risk assessment on the state of the supply chain at the end of each game round. The risk assessment decides if a physical check of the goods is performed. Such a check has negative effects on the reliability of all stakeholders of the entire supply chain, since goods transported may be delayed for days. However, a number of innovations in the game that are of interest to Customs will have the supply chain proceed towards the certificate of trusted trade lane. Each implementation of one of these innovations decreases the probability of a physical check.

Evaluation

The final version of The Chain Game was disseminated by playing it with two groups of stakeholders: consultants of a large accountancy firm and managers of Dutch Customs. The goal of the play sessions was to both evaluate and disseminate the game with stakeholders. The game was evaluated by a questionnaire; additionally, observations during the reflection phase are also used for the evaluation. A play session consisted of 20 minutes of introduction, 10 game rounds (75 minutes), filling in the questionnaire and 30 minutes of reflection. The goal of the evaluation was to assess whether the game is valuable for creating supply chain visibility awareness and to make an inventory of possible opportunities to apply the game. The questionnaire consisted of 3 questions (see Fig. 2) that needed to be scored on a 5-point Likert scale (1 = totally disagree to 5 = totally agree), and the following open questions:

• What part of The Chain Game should stay the same?

• What part of The Chain Game should be adjusted?

• Which (business) opportunities do you see for this game?

• Any further remarks?

Results

In general it can be concluded that both groups are convinced The Chain Game has value in creating awareness for supply chain visibility. Fig. 2 on the next page shows the results of the three closed questions -the results of question 3 (as shown in Fig. 2) show that both groups are fairly positive about using The Chain Game in their own working environment: the 64% of the consultants are positive (27% negative) and 55% of the Customs group are positive (0% negative). We believe these score may be toned down somewhat by the fact that these groups were not the primary audience for The Chain Game. For example, Customs does not have an active playing role in the game and for consultants the focus on customs-related interruptions covers only a part of their work. On the other hand, socially desirable answers may also have influenced the results, as the questionnaire was hardly anonymous.

The answers to the open questions and the observations of the game facilitators show that both groups are positive about the way of using a game to raise awareness and understanding for complex information. This was also easily observed: players were drawn into the game from the first round on and the game could keep the attention until the final round, for more than an hour. Additionally, the interactivity and direct feedback was praised by both groups, allowing players to quickly gain insight in the effects of certain innovations. Finally, from the group of consultants several people mentioned they were drawn to the digital and visual implementation.

Both groups believed that more time should be reserved for the facilitator to explain the effects of innovations. Sometimes, the effects of innovations or incidents were challenged by a player, but this does not really stand in the way of the goal of the game: creating awareness. Discussion about the effects in real-life situations are a consequence of the fact that the model is an estimate of subject matter experts and not evidence-based. This means innovations sometimes had effects that the players did not expect. This cannot be resolved in the game, as effects need to be undisclosed to force players to think about the meaning of innovations. However, it is necessary for the game facilitator to take sufficient time for the argumentation behind the effects that take place. An expert opinion supports relevant discussion and counters players' frustration. Additionally, some game design choices have resulted in the omission of factors that can be of importance in the real world. For example, the number of players is fixed, in order to keep the game economy as simple as possible (i.e. a player can basically invest only in one innovation each turn). As a result, stakeholders cannot enter or leave a logistics chain, an action that can have big effects in the real world. This pragmatic choice was made to keep the game playable within a few hours.

Somewhat related is the game process: in the play sessions, hardly any reflection on the adopted strategy was possible during the playing of the game because of the fast pace during these sessions. As a result, players were not able to reflect upon the played innovations, the expected and the real effects and the underlying model. This prevented them in creating a broader understanding and forming and adjusting their strategy. Particularly the group of consultants requested one or two reflection phases during the game, in order to improve understanding, which can easily be adjusted by pausing the game after 3 or 4 rounds.

Interestingly, the group of consultants believed the game to be strongly focused on Customs-related innovations, while the group Customs would like a more active role for Customs in the game. The game can be improved for the consultants by adding taxes-and legislation-specific innovations; this is no problem from the perspective of the game design, as long as the effects are sufficiently realistic and in balance with each other. However, it will change the focus of the game, which was primarily aimed at Customs-related interruptions. Making Customs interactive in the game is more difficult to implement, since this would mean adding a new role that is even more asymmetrical to the roles that already exist in the game.

A number of different opportunities were put forward during the play sessions. The group of consultants believed the game can be played with companies to raise awareness about supply chain visibility and on the impact Customs can have on supply chains. Both groups believed the game can provide insight in the interdependence between supply chain partners and the importance of jointly investing in innovations and prevent weak links in the chain. Finally, Customs believed the game can be used as learning tool in management studies related to logistics.

Conclusions

Disseminating the concepts and ideas concerning supply chain visibility is a challenge, as they are abstract and hard to grasp. Additionally, future implementation of these concepts require both support and collaboration of a multitude of stakeholders, hence awareness within this group of stakeholders is essential to effectuate innovations. In order to explain the complex concepts and initiate collaboration between stakeholders, a serious game named The Chain Game was developed. The goal of The Chain Game is to have players experience the effects and advantages of increased supply chain visibility. The serious game focuses on a variety of innovative concepts, which can be implemented by the main actors in a supply chain. Feedback consists of the effects of these innovations on a supply chain level. A qualitative game model was built by a team of game designers and subject matter experts, as little evidence-based data is available as of yet.

The fully digital serious game has been tested by stakeholders in two pilots. Both groups evaluated the game as valuable in raising awareness on the subject of supply chain visibility with stakeholders and believed it can act as a supporting tool in bringing the necessary parties together. Additionally, the game can be used as learning tool in management studies related to logistics. An important observation during the tests is the crucial role of the facilitator as subject-matter expert: he needs to have the time and the knowledge to explain the argumentation behind the presented effects during the game. If this precondition is met, The Chain Game can provide an excellent starting point for further discussion on the future of supply chain visibility.

Fig. 2 .

 2 Fig. 2. Results of the evaluation questionnaire


Marcel Rosenberger
email: marcel.rosenberger@student.unisg.ch

Tobias Lehmkuhl

Reinhard Jung
email: reinhard.jung@unisg.ch

Conceptualising and Exploring User Activities in Social Media

Keywords: social media, user activities, conceptualisation, integration

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

Introduction

Social media have become a noticeable part of society. This development attracts attention of companies that aim to take advantage of the opportunities, such as improvement of the reputation and marketing efficiency, support cost reduction, and product innovation from co-creation [START_REF] Smith | Conference notes -The social media revolution[END_REF][START_REF] Baird | From social media to social customer relationship management[END_REF][START_REF] Cappuccio | Social CRM for SMEs: Current Tools and Strategy[END_REF][START_REF] Fliess | Understanding Patterns of Customer Engagement -How Companies Can Gain a Surplus from a Social Phenomenon[END_REF][START_REF] Jahn | How to transform consumers into fans of your brand[END_REF]. At the same time, consumers benefit from participating companies, e.g. through relationship advantages, interaction and exchange, and influence on business processes. Examples are discounts, special promotions, and the acceleration of the fulfilment of support requests. The many active users perform various actions in social media and create a lot of data therewith. This information overload is a challenge for companies, because the increasing number of content, user profiles, and connections cannot be timely assessed manually [START_REF] Smith | Conference notes -The social media revolution[END_REF]. Information systems (IS) are needed to manage the social media initiatives, providing functions to publish, observe and analyse social media data and integrate it with company data [START_REF] Acker | Social CRM: How companies can link into the social web of consumers[END_REF]. A preliminary step is to identify business-relevant user activities and to process the related data. Examples of user activities are joining groups, placing likeor dislike flags, adding others to the friend list, reading specific texts, watching videos, and changing profile information. These user activities comprise business opportunities in the form of leads (i.e. potential customers), enriched customer profile information, and a better understanding of interests and markets. Fliess & Nesper [START_REF] Fliess | Understanding Patterns of Customer Engagement -How Companies Can Gain a Surplus from a Social Phenomenon[END_REF] state that "activities of customers can be considered as an economic resource". Similarly, Holts [START_REF] Holts | Towards a Taxonomy of Virtual Work[END_REF] highlights that user activities in social media create value and stimulate companies' revenues.

The more social media sites are considered by the company, the higher is the media penetration. Consequently, there is a need to integrate multiple social media sites mutually. However, the social media sites are diverse and facilitate different user activities. Posts, tweets, pins, profiles, groups, and pages, which are posted, tweeted, pinned, modified, added, or viewed, are only a small proportion. There are no common social media data structures, on which the integrations could be built.

Research on user activities in social media is contemporary and there are a number of existing conceptualisations [START_REF] Heinonen | Consumer activity in social media: Managerial approaches to consumers' social media behavior[END_REF][START_REF] Pankong | A combined semantic social network analysis framework to integrate social media data[END_REF][START_REF] Yang | Identifying Implicit and Explicit Relationships Through User Activities in Social Media[END_REF][START_REF] Richthammer | Taxonomy of social network data types[END_REF]. These are valuable to understand the user's motivation of being active and show some features of social media. However, the proposals are inappropriate to guide the implementation of integration software between multiple social media and an enterprise system. For this purpose, the existing conceptualisations are too abstract or they are exemplary and not exhaustive. Especially the related data of the user activities and the technical accessibility had not been researched yet. Our proposed conceptualisation and exploration of user activities closes this gap.

The topic is motivated from practitioners. The research is part of a joint social Customer Relationship Management (CRM) program with scientists and practitioners from companies of the insurance industry. The status quo of the companies shows that social media tools are isolated and not technically integrated into existing CRM systems. Social media monitoring tools are used to capture developments and to extract aggregated metrics, such as number of posts, likes, and age distribution on single sites. Relevant posts can be identified automatically based on tags, keywords, and rules. However, software solutions that recognise business-relevant user activities in multiple social media and invoke adequate business processes automatically are not yet implemented. Profiting business areas are customer service, sales, marketing, human resources, and research and development [START_REF] Cappuccio | Social CRM for SMEs: Current Tools and Strategy[END_REF]. A conceptualisation of user activities is useful for designing general integration solutions. The audience are practitioners and researchers of social media and information systems.

Chapter 2 gives the conceptual background. Chapter 3 connects to existing knowledge and related work. The research methodology is presented in chapter 4. Then, the user activity types in social media are described (chapter 5) and compared with actual features of ten social media sites (chapter 6). The final chapter states implications, limitations, and guides further research.

Related Work

Web 2.0 is an economic, social, and technology concept of the Internet, which enables users to create content and build a network with other users [START_REF] Musser | Web 2.0 Principles and Best Practices[END_REF]. The results from user participation, e.g. posts, friend lists, and profiles, are accessible by other parties of the community. As stated in the definition by Kaplan & Haenlein [9], "social media is a group of Internet-based applications that build on the ideological and technological foundations of web 2.0". We use the term to refer to the sites/platforms that are built on the web 2.0 concept (e.g. Facebook, Google+, and Twitter). The terms "social media site" or "social media sites" are only used when an emphasis on singular or plural is necessary. A basic principle of social media is to connect to others and share information [START_REF] Ang | Is SCRM really a good social media strategy?[END_REF]. Social media and enterprise systems are heterogeneous systems, which can be connected through system integration. According to Hasselbring [START_REF] Hasselbring | Information system integration[END_REF], heterogeneity leads to complexity, which is an issue for the integration task. Küpper et al. [START_REF] Küpper | Features for Social CRM Technology -An Organizational Perspective[END_REF] show results from a market study of 40 vendor solutions for social media tools. The findings indicate that most tools provide features to capture and analyse aggregated social media data. The capturing and analysis of individual data (i.e. single posts, user profiles, etc.) as well as the integration into enterprise systems is sparse. Similarly, other authors state that the integration of social media with enterprise systems is still insufficient [START_REF] Sarner | Magic Quadrant for Social CRM[END_REF][START_REF] Reinhold | How Companies are Implementing Social Customer Relationship Management : Insights From Two Case Studies[END_REF]. In particular, Trainor et al. [START_REF] Trainor | Social media technology usage and customer relationship performance: A capabilities-based examination of social CRM[END_REF] identify a lack of interaction between CRM systems and social media technology. For example, customer data and user data in social media are not interrelated and business-processes are not triggered from incidents in social media automatically.

Atig et al. [START_REF] Atig | Activity profiles in online social media[END_REF] conceive user activity as the time when the user is active in social media. The authors classify users based on activity profiles and thereby do not differentiate between what the users are actually doing when they are active. Heinonen [START_REF] Heinonen | Consumer activity in social media: Managerial approaches to consumers' social media behavior[END_REF] conceptualises consumers' social media activities based on two dimensions: consumer motivation and consumer input. The consumers' motivation to use social media falls into one of three categories: information processing, entertainment activities, and social connection. The consumer input has three main types, which are consumption, participation, and contribution. The author's framework allows classifying users' activities. For example, "creating and managing a social network" is motivated from the need for social connection and requires creating a profile and linking to friends (productive consumer input). The proposed framework is abstract and does not allow deriving the related data of the activities. Pankong et al.'s [START_REF] Pankong | A combined semantic social network analysis framework to integrate social media data[END_REF] ontology for social activities is more concrete. In principle, the ontology is an entity-relationship-model, which shows entities (e.g. users, posts, likes, and topics) and its relationships (e.g. "is a", "has a", and "related to"). Some entities, however, are ambiguous (e.g. reply, retweet, and comment). Besides, the viewing of content is not included in the ontology. The model facilitates a snapshot-view of the social media graph. The circumstances in which the users create the content is not incorporated. This is justifiable considering that the authors focus on existing explicit and implicit relationships of users, similarly to Yang et al. [START_REF] Yang | Identifying Implicit and Explicit Relationships Through User Activities in Social Media[END_REF]. However, the location and time of an activity are also expedient to determine the business-relevance [START_REF] Yu | Empirical Observation of User Activities[END_REF]. Hotho & Chin [START_REF] Woerndl | Logging User Activities and Sensor Data on Mobile Devices[END_REF] analyse the circumstances of user activities. Available sensors of a smartphone are used to conceive the current situation of the user (e.g. installed applications, busy status, missed calls count, position from Graphical Position System (GPS) sensor, remaining battery power, and ringtone volume). Richthammer et al. [START_REF] Richthammer | Taxonomy of social network data types[END_REF] identify 11 online social network (OSN) activities. Examples are "User posts Item/Comment", "User sends messages to Contact/Page", "User is linked to Item/Comment", and "Contact/Page views User's Profile". However, these are only "fundamental user activities on OSNs" and are not complete. For example, the sharing, deletion and modification of content is not considered.

Methods

The literature review follows vom Brocke et al.'s [START_REF] Vom Brocke | Reconstructing the Giant: On the Importance of Rigour in Documenting the Literature Search Process[END_REF] methodology, which comprises three process steps, being (1) definition of review scope, (2) conceptualisation of topic, and (3) literature search. The authors highlight that not only results should be presented, but, to allow replicability, also details about the approach. The scope (1) of the literature review is characterised by six aspects borrowing from Cooper [START_REF] Cooper | Organizing knowledge syntheses: A taxonomy of literature reviews[END_REF] (Table 1). The conceptualisation of the topic (2) includes a "working definition of [the] key variable(s)" [START_REF] Webster | Analyzing the Past to Prepare for the Future: Writing a Literature Review[END_REF]. A keyword search (3) in the databases of AISel, EBSCO, Emerald, IEEE, JSTOR, ProQuest, and Web of Science in the title (TI), topic (TO), abstract (AB), keyword (KW), and full text (TX) fields was applied using the search string: "social media" AND ("user actions" OR "user activities"). The initial list of publications has been filtered by reading the titles and abstracts. Relevant papers were analysed based on the full texts. Table 2 shows the numerical results of the keyword searches.

The development of the user activity types comprised a study of features of large, popular social media. The sample of sites for analysis has been selected on the following criteria: (1) large number of active users per month (> 100 m.); (2) English localisation of the platform; (3) availability of a public API; and (4) permission for commercial use. The initial list of contemplable sites has been compiled of studies and rankings of social media [START_REF] Singh | Global Social Media Usage : Insights Into Reaching Consumers Worldwide[END_REF][START_REF]Leading social networks worldwide as of June 2014, ranked by number of active users[END_REF]. The listed sites have been evaluated against the aforementioned criteria, based on information from press releases, technical notes, terms of use, and responses from enquiries to the providers. Possible user activities have been gathered by analysis of the features and functions. They have been grouped according to the philosophical idea of family resemblance and following an abstractionbased modelling approach [START_REF] Rosch | Family resemblances: Studies in the internal structure of categories[END_REF][START_REF] Bussler | Modeling Methodology. B2B Integration: Concepts and Architecture[END_REF].

User Activity Types in Social Media

The user activity types shown in Fig. 1. represent the actions that users perform in social media. Activities take place in a context, in which the user is situated, defined by time, location, social media site, device, and application. The combination of an object type and an action is termed a user activity type in social media. The complex graph structure of social media is broken down into an activity log, which contains entries of the form: user u invoked action a on object o (on site s with device d in application p from location l at time t).

Social Media Object Types

The idea of family resemblance is adduced to group similar objects. The most prototypical objects constitute an object type. An object type subsumes all objects, which have most functions and structure in common with that object type, and have least commonalities with other object types [START_REF] Rosch | Family resemblances: Studies in the internal structure of categories[END_REF]. Kietzmann et al. [START_REF] Kietzmann | Social media? Get serious! Understanding the functional building blocks of social media[END_REF] present a framework of functional building blocks of social media, which are identity, conversations, sharing, presence, relationships, reputation, and groups. The seven blocks are facets of user experience in social media and give an orientation to gather object types and functions. Table 3

○ • • ◐ ○ ◐ ○ Post-list -is a collection of posts ○ • • ◐ ◐ ○ ◐ Profile -contains descriptive information about an actor • ○ ◐ • ◐ • ○ Profile-list -is a collection of profiles ◐ ◐ ○ ◐ • • • Relationship -connects two objects ○ ◐ ○ ◐ • • ◐
Legend: Object type is …○ not enabling the function, ◐ partly enabling the function, • enabling the function An object type is enabling a function, if it supports the intention behind the concept of the building block. It is partly enabling, if the intended user experience of the functional building block is a side-effect. An object type is not contributing to a functional building block, if it does not enable the function.

The eight object types may have variants that share similar concepts, but have a different terminology or are used to distinguish the same concept that is used in different contexts on the same site. An example is a Comment, which contains multimedia content and has a parent, which may be a Post, Post-list, Comment or another object type. Some sites use a Comment object type to represent answers, like Tumblr, or a job application, like Xing.

The same object type is also used in different variants on the same social media site, such as on Facebook, where both comments and reviews exist. A Comment primarily contributes to the functional building blocks Conversations and Sharing. An Event object type defines a happening, which has relatedness to time. It can be a birthday party, a music festival, a meeting, and so on. Events facilitate to meet people (Presence), build communities (Groups), and relate to each other (Relationships). A Message is multimedia content that is addressed to a specified set of receivers. Posts subsume a main content entry found on all social media sites. They may be termed tweet, job, or pin, and engage interaction by allowing adding Comments and Relationships. A Post-list is a collection of Posts. A Profile is a representation of an entity of the real life, such as a person, company, or a community. A Profile-list is a collection of Profiles with possible variants, such as circle, contact list, and friend list. A Relationship connects two other objects. An example is a bookmark, which can be described as a Relationship between a Profile and a Post. The poke feature in Facebook can be treated as a Relationship between two Profiles.

Actions on Social Media Objects

Table 4 lists actions, which can be invoked on social media objects referring to Hypertext Transfer Protocol (HTTP) methods. HTTP is the underlying, technological protocol of social media sites [START_REF] Gourley | HTTP: The Definitive Guide[END_REF]. Five basic actions on social media objects can be identified. Sharing is something particularly found in social media [START_REF] Kietzmann | Social media? Get serious! Understanding the functional building blocks of social media[END_REF]. The citing of a text phrase or the re-tweet of content on Twitter is an example of the Share-action.

Action Description HTTP Methods

View

View is triggered when content of an object is loaded and displayed on the user's screen (e.g.: a video is played).

GET

Create

The Create-action occurs when something new is added opposed to the Update-action when a change to an existing object is done by a user.

POST

Update The Update-action results in a modified, existing social media object.

PUT/ MOVE Delete

When an object is removed on social media an event with action Delete is raised.

DELETE

Share

The Share-action occurs when existing content, usually originated from another user, is put into a different context or is exposed to additional users on the same platform. It is a copy of an already existing entity.

COPY

Empirical Exploration

Table 5 shows the results of the empirical exploration of the user activities in ten social media. The APIs of large social media define access options to functions and data using webservices. They include formats and provide methods to publish posts, resolve connections between users, and retrieve comments, for example. Dark underlined numbers signify that the user activity type can be monitored in the specified social media using the provided API. Dark numbers that are not underlined mean that the type exists on the site, but the APIs of the site do not provide access to monitor it. For example, in Facebook a user can view a post. However, this activity cannot be monitored using the public API of Facebook in the recent version of the Graph API V2.1 [START_REF]Facebook: Graph API Reference[END_REF]. On the other hand, it cannot be ruled out that access is included in upcoming versions. Furthermore, using the APIs is not the only access approach to social media data. Instead of using the API, the View-action of own and shared posts can be recognised by linking a Facebook post with external content from a corporate website, where the company can evaluate page requests (by observing the HTTP/1.1 GET-method). Six user activity types are theoretical constructs, which do not occur in the analysed social media. These are Message/Update, Message/Delete, Message/Share, Profilelist/Share, Relationship/Update, and Relationship/Share. Firstly, a Message is private, because it cannot be shared. Secondly, a Message, once sent, cannot be fetched back, removed, or edited. A Profile-list cannot be shared by others. Access privileges of the Profile-lists are maintained by the owners only. A Relationship does either exist or does not exist. It cannot be modified; but it can be deleted.

The majority (70%) of user activity types that exist on a social media site, can also be monitored using the API and thus can be integrated with enterprise systems using a public, recommended access approach. The View-actions are usually not provided; only Google+ has custom activities, which can be triggered by developers in case an entity is read. On most social media Post/Create is observable by subscription to Postlists. The Update-, and Delete-actions could be identified by periodic polling, whereby known objects are checked regularly to notice if they are still existent or modified. Comment, Post, Profile, and Relationship exist in all analysed social media. Thus, these are essential object types. Facebook (83%), Google+ (80%), and Xing (80%) feature the most complete set of user activity types. The APIs of Google+, LinkedIn, and YouTube provide the most complete set of access options, covering 95%, 80%, and 79% of applicable user activities of each site.

Discussion and Conclusions

The user activity types define user activities in social media. They specify what users do in social media when they create or consume content. Hence, the user activity types advance from existing definitions of user activities that conceive user activity as the time when the user is active in social media [START_REF] Atig | Activity profiles in online social media[END_REF]. A user activity type is a crossover of a social media object type and an action and takes place in a specific user's context. The object types reveal the underlying structure and data, which large social media sites share. The actions are operations that users perform with an object type. The user-context describes the situation in which the user resides while invoking an action on an object.

The results are useful to design and develop integration software that facilitates to process user activities of multiple different social media sites. Middleware-based solutions require similar structuring of information. The presented user activity types support that purpose, because they allow to consolidate the different user activities of different, large social media sites. There are technical restrictions limiting the feasibility to capture "everything", because some user activity types cannot be captured using the APIs. Moreover, as also highlighted by other authors, users' permission and privacy need to be considered [START_REF] Woodcock | The evolving data architecture of social customer relationship management[END_REF]. It must be a major concern of all business-oriented social media initiatives, because of the risk to destroy relationships to customers in case of an accident. An example is unintended data exposure to unauthorised parties. As a result, not every user activity that can be monitored technically should also be tracked.

The user activity types originate from the abstraction of individual features collected from a study of ten social media sites. They have an empirical basis and rely on publicly available data. The issue, caused by the underlying induction of the abstraction, is that the user activity types are only certainly valid for the analysed social media, and are not necessarily generalisable to all available sites.

Further research is encouraged to concretise the user activity types in terms of a canonical data schema, which defines data types and attributes. Based on the detailed level, (business-specific) rules can be proposed for filtering user activities. Monitoring of user activities in social media leads to a reactive system [START_REF] Sarkar | High-Level System Modeling[END_REF]. A fully integrated IS, however, should comprise functions to interact, requiring both directions of a communication. This is not contrary to the research results, but is a possible extension.

Fig. 1 .

 1 Fig. 1. User activity types in social media: a combination of context, object type and action Five actions can be applied to eight object types. All user-generated content results from the Create-, Update-, or Share-action. The content is displayed on the screens of the users' devices via the View-action. The Delete-action removes content. The variety of features across different social media that facilitate the creation, modification and viewing of content is reducible to 8x5 user activity types.

Table 1 .

 1 Taxonomy of the conducted literature review (borrowing from[START_REF] Cooper | Organizing knowledge syntheses: A taxonomy of literature reviews[END_REF])

	Characteristic	Categories
	(a) focus	research outcomes research methods theories	applications
	(b) goal	integration	criticism		central issues
	(c) organisation historical	conceptual		methodological
	(d) perspective neutral representation	espousal of position
	(e) audience	specialised schol-	general scholars practitioners general pub-
		ars				lic
	(f) coverage	exhaustive	exhaustive and	representa-	central/piv-
			selective		tive	otal

The focus (a) is on existing research results concerning user activities in social media. The goal (b) is to connect to existing knowledge on a conceptual level (c). The perspective (d) can be characterised as neutral representation, because the position is unbiased. Practitioners and researchers of social media are the target audience (e). The results are representative (f) for the IS community, because prominent data sources have been queried.

Table 2 .

 2 Numerical results of the keyword searches

	Data source	Search fields	Publications
			Total	Relevant
	AISeL	TI, AB	11	2
	EBSCO	TI, AB, KW, TX	22	5
	Emerald	TI, AB, KW	30	1
	IEEE	TI, AB, KW	4	1
	JSTOR	TI, AB, KW, TX	9	1
	ProQuest	TI, AB, KW	4	1
	Web of Science TI, TO	4	1
	Total 1			10

  identifies social media object types by analysing its structure and functions[START_REF] Faulkner | Technological Objects, Social Positions, and the Transformational Model of Social Activity[END_REF].

		User / Context	Object type	Action
				Comment
	Comment	Relationship Profile-list Profile Post-list Event Message Post -contains content (e.g. text, video, audio time, location, site, device, ap-plication and image) -refers to another object	View Create Update Delete Share ○ • • ◐ ○ ◐ ○
	Event Message	User -contains descriptive information about Poke a happening -has a relatedness to time Like -contains content (e.g. text, video, audio and image) -has a sender and recipient (list)	○ ○ ○ • • ◐ • ○ • • ◐ ○ ○ ○
		Event	Guest list	Circle	Video	Photo

Post

contains content (e.g. text, video, audio and image)

Table 4 .

 4 Actions on social media objects

Table 5 .

 5 Empirical exploration of user activities in social media

	Action	View	Create Update Delete	Share
	Object type
	Comment Answer, Recommendation, Job Application, Review	 	 	 	 	 
	Event					
	Meeting, Happening					
	Message					
	Chat, Fanpost, Gift					
	Post Job, Life event, Pin, Project, Question, Status, Tweet	 	 	 	 	 
	Post-list Blog, Board, Page, Photo al-bum, Wall	 	 	 	 	 
	Profile					
	Community, Company, User					
	Profile-list
	Circle, Contact list, Friend list, Group, Guest list, Part-	 	 	 	 	 
	ner list
	Relationship
	Bookmark, Favourite, Fol-low, Invitation, Join, Like,	 	 	 	 	 
	Poke, Rating
	Legend: 1-Facebook, 2-Flickr, 3-Google+, 4-LinkedIn, 5-Meetup, 6-Pinterest, 7-Tumblr,
	8-Twitter, 9-Xing, 10-YouTube
	Event type is … ○ not existent on the social media site, • existent on the social media
	site, • existent on the social media site, and can be accessed using the API

The total number is not equal to the column sum, because duplicates have been counted only once.