A repository or digital storage of educative elements is a collection of resources (learning objects) accessible through a communication network. It is not necessary to have a previous knowledge about the collection containing the structure of the resources or only the metadata describing them, together with a reference to locate it (IMS DRI, 2003).
The aim of a repository is to facilitate the reusability of educational resources, providing access to the stored resources to learning management systems (LMS); learning content management system (LCMS); content portals (for an instance: searching systems of digital libraries, World Wide Web searching, etc.); or any application/software developed to access to learning objects.
Digital repositories, in the broadest sense, are used to store any sort of digital material. However, digital repositories for learning objects are much more complex in terms of what to store and how to do it. The purpose of a digital learning object repository is not just to store and distribute learning objects, but to allow them to be shared by different users and, above all, to make it easier to reuse them in different training activities (Figure 13.1). From the users’ point of view, these repositories have the advantage of having access to the content stored in them. To make this possible, the content must be gathered through certain procedures, rules and standards whose implementation is intended to promote the reusability of learning objects. Moreover, the repository itself must follow a series of specifications and standards which enable to browse the content it stores and facilitate interoperability with other repositories.
Most repositories are usually autonomous, that is, they work as portals that can be accessed through a Web-based interface, providing a search mechanism and a list of categories to conduct the search. However, it is becoming increasingly common the possibility of making federated searches in distributed repositories from the original repository.
Some examples of this kind of search can be found in repositories such as those set out in (Table 13.1). In this way, it is possible to access to different repositories from the learning management platform, preview their contents and even download and incorporate them into a course.
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REPOSITORY |
URL |
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Agrega |
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Ariadne |
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EdNA Online |
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EducaNext |
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LORNET |
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MACE |
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Merlot |
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OER Commons |
Therefore, it is now essential that repositories are developed according to standards and specifications that guarantee interoperability with any other repository or search system. In this chapter we present (1) the most important standards and specifications in this area, (2) a service-oriented architecture of a federated repository based on these standards and specifications, and (3) how to develop a federated repository using this SOA architecture. The chapter is structured as follows: Introduction presents the main specifications and standards in the scope of e-learning with an emphasis on those related to construction and management of learning object repositories. Designing a repository with Service Oriented Architecture presents the design of a service-oriented architecture for building a distributed repository of learning objects. Developing a federated repository with SOAP web services details how to develop a federated repository using SOAP Web services while Developing a federated repository with RESTful web services details how to develop a federated repository using RESTful Web services. Finally, Conclusions presents our conclusions.
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