LIMBS: Open Source, Open Standards, and Open Content ... - CiteSeerX

LIMBS: Open Source, Open Standards, and Open Content To Foster Learning Resource Exchanges*

Jean-Noël Colin Sun Microsystems, OXYS [email protected] Abstract LIMBS is an open source brokerage system developed in the framework of the CALIBRATE project. LIMBS relies on open standards and open contents to promote exchanges of learning resources within a federation of e-learning systems. Contrary to the CELEBRATE brokerage system, from which it derives, LIMBS’s role is limited to carrying and routing messages exchanged by the federation members rather than to enforcing semantic interoperability. With LIMBS, semantic interoperability becomes the responsibility of the federation members that rely on “clients” to communicate with the brokerage system and to support the negotiation of common query languages and metadata formats. LIMBS itself adopts a service-oriented architecture so that each service (e.g., resource discovery, digital rights management) can be used separately and combined with any (group) of the others.

1. Introduction E-learning, i.e., the use of information and communication technologies in education, has changed and keeps on changing the way people teach and learn. Nowadays, the use of learning (content) management systems is common in most educational organizations and the number of educational resources available on the web, for free or by subscription, is huge.

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The work presented in this paper is partially supported by the European Commission under the Information Society Technologies (IST) program of the 6th FP for RTD – as part of the CALIBRATE project, contract IST-28025. The authors are solely responsible for the content of this paper. It does not represent the opinion of the European Commission, and the European Commission is not responsible for any use that might be made of data appearing therein.

David Massart European Schoolnet [email protected] When preparing a course or trying to learn more about a given topic, one would like to be able to: 1. Search the pool of existing resources; 2. Assess their usefulness on the basis of search results; 3. Obtain relevant resources and (re)use them transparently regardless of the technical complexity associated with the resources and the technical platforms involved, and 4. Do all this in a way that respects the intellectual property associated with the resources involved. This scenario was addressed by CELEBRATE (a large-scale, €7M Information Society Technologies (IST) demonstration project which ran from June 2002 to November 2004). It developed and successfully demonstrated a federated brokerage architecture for learning resources using asynchronous messaging in a heterogeneous environment. Project deliverables and Final Evaluation Report are available at http://celebrate.eun.org/. During the project, over 1350 learning resources - from both public and private sources - were made available to 500 schools across Europe. However, broad adoption was hampered by two main factors: 1. Content is a key factor to attract users in such a federation. CELEBRATE was a demonstration project; within the available budget, there was only the ambition to develop a critical mass of content to have a credible validation of the approach with schools. At the end of the project, commercial content providers, although interested in a new channel of distribution

(they supplied hundreds of learning objects), did not yet have clear business models to deliver content through the infrastructure. On the other hand potential users, although interested in the samples, found the offer too limited. This led to a chicken and egg situation: not enough users to draw content providers’ attention and not enough content to keep users. 2. CELEBRATE was a complete solution offering protocols that support federated searching [4], semantic interoperability [5], learning resources exchange [3] and digital rights management (DRM) [6,9]. For a system to join the federation, it was necessary to implement all the protocols, even when only a subset of these protocols was actually useful to the system under consideration. For example, the DRM protocols are not needed for systems that provide only free resources. As a consequence, it was still quite a complex task to connect to the federation at the end of the project (up to 3 man/months of work). This paper presents the strategy developed by the later CALIBRATE project which aims to overcome CELEBRATE’s limitations. This strategy consists of encouraging new systems to join the federation by: • Making the integration effort minimal; • Offering as much open content as possible; • Offering a technical solution based on open source software and open standards. The rest of the paper is structured as follows: Section 2 presents how open source software licenses and open content licenses are used to foster adoption. Section 3 describes the technical solutions adopted to create an open, flexible and secure environment based on open standards. Finally, section 4 discusses the proposed solution.

2. Open Content and Open Source In Europe, many Ministries of Education (MoEs) maintain collections of national web-based learning materials for schools. Recently, they have started to store these materials in repositories and to describe them with IEEE 1484.12.1 LOM-based metadata. MoEs have invested and keep on investing public money in these collections and want to promote their use. Therefore, they are interested in moving to the next level: starting to share with others, to capitalize on re-use, as well as to take part in a European-wide initiative to share knowledge resources. The brokerage architecture of CELEBRATE appears to be a good basis to make the collections of the MoEs discoverable. It provides a good balance between trust and autonomy; it is decentralized enough to allow MoEs to manage their collections autonomously, and secure enough to ensure the trust

necessary when dealing with content for sensitive groups like pupils. Copyright law prohibits the use, exchange, and modification of any learning resource without the explicit consent of its copyright owner. Therefore, to authorize the usage of their resources in the federation, participant MoEs agree to release them under Creative Commons (CC) licenses. These contributions of “free” resources make it possible to reach the critical mass of quality content necessary to attract users. Moreover, it creates a virtuous circle, in which new repositories accept to join the federation to enable their own users to benefit from content already available. Therefore they reinforce the federation. The backbone of the federation is a brokerage system, named “Limbs Is My Brokerage System” (LIMBS), to which learning systems (e.g., learning (content) management systems and learning resource repositories) connect thanks to a java library (the “client”) that encapsulates the different networking protocols behind standard application programming interfaces (APIs). LIMBS and its client are released under the Lesser Gnu Public License (LGPL). The decision to open up the code of the brokerage system was motivated by the following considerations: • Foster adoption: An open source brokerage system guarantees the members of the federation that their integration efforts will not be lost. It gives them the possibility to influence the solution that they adopt and enough control over it to ensure its continuation. • Foster development: The involvement of a larger community of developers and public scrutiny of the source code shortens development time and improves the quality of the code and documentation produced. Moreover, the community helps to make sure the developments are in line with users’ requirements. • Promote the federated model outside the elearning community, by encouraging the adoption of LIMBS by other communities (e.g., digital libraries). Among the open source licenses considered to release the code of LIMBS, LGPL was chosen because it allows both commercial systems (such as LearnXact™) and pure open source systems (such as Moodle) to use the client and join the federation.

3. Open Standards for Flexible and Secure Architecture Figure 1 shows the LIMBS brokerage system and the learning systems, connected through the “client” library. Administrative messages (authentication and session management) are handled via synchronous web services calls, while all other application messages are exchanged using the asynchronous Java Messaging

System (JMS) for better scalability and message persistence. The system was originally designed to enforce semantic interoperability and intellectual property rights. The interfaces and message formats were not following any particular standard.

Figure 1: The LIMBS architecture Key goals in CALIBRATE are to: • Simplify LIMBS and make it generic; • Add new content (by connecting the MoEs’ repositories) and new learning environments; • Validate the approach in a pilot involving 100 schools across Europe. This led to an architecture that: • Generalizes LIMBS to support multiple application profiles and different DRM models (e.g., Creative Commons). • Simplifies the integration of new systems in the federation by the adoption of a flexible architecture based on standard interfaces. • Provides a secure overall architecture based on widely adopted open standards.

3.2. Learning Resource Discovery Service The learning resource discovery service is a good example of the new approach. The service is provided by a client module that uses the Simple Query Interface (SQI) to communicate with a learning system. SQI is a standard API to query repositories of learning resources [2,1]. It is characterized by its independence in terms of query language and result format. The methods that compose the API were separated into two groups: the source methods that a system must support to be able to send queries and receive results and the target methods that a system must support to allow another system to send it queries. As depicted on Figure 2, the client module that supports the learning discovery service exposes both the source (SQI(s)) and the target (SQI(t)) groups of SQI methods. To query the federation, a system has to implement a SQI(s) interface that communicates with the SQI(t) interface of the client. Inversely, to connect a repository to the federation, one has to implement a SQI(t) interface that communicates with the SQI(s) interface of its client.

3.1. A Service-Based Architecture LIMBS has been reorganized as a set of independent services (e.g., resource discovery, resource exchange, digital rights management, metadata harvesting), that can be combined arbitrarily. At the client side, each service corresponds to a pluggable module with a simplified (and, when possible, standard) interface. When connecting a new system to the federation, one selects the services needed and integrates the corresponding modules. This makes the integration effort proportional to the number of services being integrated. Since the brokerage system is able to automatically discover the services supported by a client, it is possible to transparently add or remove services to any system connected to the federation.

Figure 2: Federated searching with LIMBS During a federated search, a system uses its SQI client module to send a query to the brokerage system (1). As a result of SQI flexibility, queries may specify any query language and result format. The brokerage system then propagates the query to all the systems of the federation that implement SQI(t) (2a) and (2b). The repositories that support the language of the query and the requested result format process the query and return the results to the brokerage system (3a) and (3b). Finally, the brokerage system forwards the results to the SQI client of the system that originally sent the query (4a) and (4b). Similarly, other services can be added to a system by integrating the corresponding client modules.

3.3. Security Security is a major concern in any large distributed environment such as the one described in this paper. More specifically, it needs to be addressed at different levels [6]: • Authentication • Authorization • Exchange security Many standards and initiatives address these concerns. In line with the overall design of the system, based on open standards and solutions, we adopted a security approach guaranteeing the maximum interoperability for broader adoption. We cover the above security levels in the rest of this section. Any learning system connecting to LIMBS authenticates using username and password, although more sophisticated methods could be easily substituted. Authentication is performed via web service calls, over a SSL/TLS encrypted connection. Upon successful authentication, a session is created and a session token is returned for future reference. All other exchanges are performed using asynchronous JMS messaging, for scalability, security and message persistence reasons. Web Services calls are digitally signed following the OASIS WS- Security standard. Encryption is left to the transport layer. JMS messages are secured using mechanisms derived from the WS-Security standard, modified somewhat to match the constraints of the JMS protocol. This allows us to sign application messages, for integrity and authentication purposes. So far no encryption is implemented because application data are not considered confidential, but, if this was the case, this additional step could be added to the message packing/unpacking chain. A specific contract defines the authorization rules that apply to each learning system connected to LIMBS. More specifically, it specifies an exhaustive list of message types (both requests and responses) it is allowed to send to the broker. The broker enforces contract conformity at any moment.

3.4. Digital Resource Protection An important part of the LIMBS architecture concerns the Intellectual Property (IP) protection of the resources offered through the federation. The only way to attract content is to allow content providers to protect their rights, which implies Digital Rights Management (DRM) mechanisms [6,9]. We use Creative Commons (CC) as one of the ways to describe the rights that apply to the content. With a CC license, the resource author or owner can retain

his/her copyright while allowing people to copy and distribute the resource provided they give the author credit, and only on the conditions specified by the chosen license. The conditions include noncommercial use, no derivative work and "share alike". Each of these CC licenses is unambiguously identified with a URI that is managed as unchanging and persistent by Creative Commons. Thus, this namespace comprises a controlled, enumerated vocabulary of license declarations, open for use by any party for whom their terms and conditions are judged useful. The CC approach was chosen because most resources present in the federation have been developed with the intention of cost-free distribution, but whose creators wish to formally declare various rights. The CC license chosen is either included in the resource metadata or a reference to the actual license is included, allowing unambiguous link resolution. A federated search returns results along with the relevant license, with the user being presented with the restrictions that apply to the use of the resource. As an extension to the current system, we will integrate a more complex licensing scheme, derived from the model described in [7]. This will provide the flexibility and control necessary for the management of the digital rights associated with non-free resources.

4. Validation and Discussion The model proposed in this paper is original and innovative in many ways compared to other initiatives in the domain, like HarvestRoad Hive®, LionShare [10], Ariadne [11], Edutella [12], or ECL [13]: • Content repositories are federated instead of being centralized; this permits more flexibility, scalability, load balancing and resilience; • Communications follow a publish/subscribe model instead of a peer-to-peer scheme; this permits more scalability, resilience, and ease of tracking for reporting purposes; • Digital rights may be defined at various level of granularity, from individual resource to collection of resources; rights are also dynamically managed throughout the federation; • The system is agnostic with regard to both metadata format and query language; this allows for a very open environment, where each system can have its own standards, while still being able to exchange with others; • All components of the model expose standard and open interfaces, for a more open and interoperable environment.

The overall model has been successfully validated during the CELEBRATE project. Since then, it has been accepted and implemented in various contexts to share resources of different kinds. Among these, we may quote the Canadian Space Sciences Data Portal [14] or FIRE (the EUN Federation of Internet Resources for Education: http://fire.eun.org). At the time of writing (April 2006), and although the changes and improvements brought to the original model are still under development, the new approach already seems successful. In Fall 2005, a first prototype of LIMBS was released to which the European Schoolnet learning resource repository was first connected. An Israeli repository joined the federation in November 2005 and a Swedish one in January 2006. From June to September 2006, it is planned to connect 9 repositories belonging to MoEs that are partners in the CALIBRATE project. Moreover, there are ongoing discussions with the Belgian, French and Norwegian MoEs, and several commercial providers to see under what conditions they could join the federation.

5. Conclusion In this paper, we have described a model and its implementation for the federated discovery and exchange of digital resources. This model builds on the lessons learnt from previous large-scale experiences to improve the functionalities, the interoperability, and consequently the adoption of the system. Major development axes are around: the use of open standards for greater interoperability; open sourcing of the brokerage system and client code for broader adoption; and open content to help build a critical mass of users. Further experimentations on the proposed LIMBS model are currently underway, in the framework of large projects funded by the European Commission. Results from these experiments will be used to further improve the model and foster adoption, for the benefit of all participants MoEs, end-users, digital content providers, system and/or technology providers.

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