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Repository - FIWARE Forge Wiki

Repository

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Contents

Target usage

The Repository is a place to store service models, especially USDL descriptions but also other models required by components of the overall delivery framework (e.g. technical models for service composition and mashup). The repository provides a common location for storage (centrally or distributed and replicated), reference and/or safety.

The use of a repository is required in order to appear at the marketplace or other tools referring to a number of central repositories for information relevant for interoperation of the enablers and roles within the FI-Ware platform. The repository contains published descriptions which can be utilized by any component in respect to privacy and authorization constraints imposed by the business models. Usually a repository is under control of an authority and usually is keeping track of versions, authenticity and publication dates.

User roles

  • The Provider creates services and has an original description describing basic service information as well as technical information. He needs to upload and publish service descriptions on the repository in order to make them available to other components of the platform, such as the Shops/Stores, Aggregators, etc.
  • The Aggregator can use for example technical and service-level information for existing in the repository for the purpose creating composite services or mashups from existing services. The Aggregator needs information about the functional and technical interfaces of a service in order to provide an implementation. Service descriptions for the newly created composite service can be uploaded and published to the repository again.
  • The Broker needs all kind of business relevant descriptions of services, such as general descriptions, business partners, service-levels, and pricing, to be presented in the shop/store. Also technical information can be required, on a level to be able to do comparisons between services for the consumer.
  • The Channel Maker needs detailed information about the channel to ensure the proper channel creation or selection. Further a channel may require embedding or wrapping the service so it can be accessed by the user through the specific channel. Various channels and devices such as Web (browser), Android, iOS but also global as well as local social networking and community platforms such as Facebook, LinkedIn, MySpace, Xing, KWICK! might be supported.
  • The Hoster requires information on service-level descriptions, deployment and hosting platform requirements to provide the necessary infrastructure in a reliable and scalable way.
  • The Gateway will use information about technical interfaces to provide data, protocol and process mediation services. The gateway also provides services for mediation towards premise systems outside of the FI-Ware platform.

The repository provides also a shared storage for all metadata related to application components, that is, information related to the description of an application component, its associated business model, the user feedback, technical information and other relevant declarative/descriptive information. To make this possible the USDL model will be used and extended in order to specify the initial meta-information, both technical and business/market related, empowering the acquisition and integration of new application components from external sources.

The repository will allow managing and sharing all application and services ecosystem relevant information for the whole platform. This includes the provision of relevant semantic information to the FI-WARE Data/Context Management in order to be exploitable by the whole FI-WARE platform to improve and enrich the platform‘s recommendation abilities.

There can be many repositories. A repository can be operated by the service provider (his own web presence), the market place owner as well as any other stakeholder.

Users of the repository have to cope with multiple distributed instances based on different implementation technologies. Therefore the API and format specifications need to be defined clearly.

Hence, the developers, domain experts, and users can use different composition tools interacting with one or multiple repositories to create compositions while at the same time taking into account a multitude of different (business) aspects, such as participating parties, ownership and licenses, pricing, service level constraints, and technical implementation.

GE description

A suitable API for reading, filtering, and aggregating service information from the repository as well as maintaining service descriptions will be made available for the interaction of other tools and components with the repository and such allowing a tight integration. Figure 45 shows the interaction of some components and tools with the service repository. One important source for service descriptions in the repository is the USDL Authoring tool. In different versions it allows the various stakeholders to create services descriptions or parts of the description in respect to certain aspects. The Authoring Tool can use the Repository API to retrieve, write and publish service descriptions on the repository built-in into the tool. The USDL Crawler can find service descriptions (in its serialized form such as XML/RDF or RDFa) on the Web and import it into the repository by using the writing functionality of the Repository API. A special Web-based Repository Management application for example can be used to organize and maintain information in the repository.

File:Picture 1
  1. Model Repository for USDL

Other components using the repository are components from the Aggregator, Channel Maker, Broker, Gateway, Provider, and Hoster (see Figure 41).

Functionality

  • The repository allows storing service model descriptions such as expressed by USDL.
  • Searching and filtering allows to access context specific information.
  • Retrieve specific service description elements.
  • Import and export of service descriptions for transport from and into other systems.
  • Organizational management
  • Maintain consistency and constraints within the repository.
  • Provide version management and version tracking.
  • Authorization and access control realized by the FI-Ware framework services.

Critical product attributes

  • Flexible object model for covering various models.
  • Allows for extensions and variants of existing models.
  • Scalability: The repository must be able to store huge amount of models.
  • Optionally distributed architecture.
  • Based on Internet standards
  • Easy on-boarding (e.g. through Web-based access and simple registration)
  • Web-API for integration into other tools/applications

Existing products

There are various approaches for metadata repositories depending on the underlying information model. Most prominent are the relational data model utilized by relational databases, the XML information model and XML databases like eXist, or RDF graph model and RDF repositories like iServe. However, the databases are only the technical foundation for the model repository. One important issue for a repository of service descriptions is to ensure consistency of metadata. Data stored into the repository and referenced by applications and platform components need it to keep the information consistent in order to ensure reliable operation of the platform. Within previous the projects TEXO and Premium Services various implementations of a USDL repository based on an XML serialization of the USDL eCore model were developed and used. Within FI-Ware we will consider Linked Date representations of USDL in order cope with various extensions and variants of USDL. Semantic metadata repository enablers provided by FI-Ware, which can be the basis of a Linked Data version of the model repository.

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