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FIWARE.OpenSpecification.Apps.Registry - FIWARE Forge Wiki

FIWARE.OpenSpecification.Apps.Registry

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Name FIWARE.OpenSpecification.Apps.Registry
Chapter Apps,
Catalogue-Link to Implementation [ N/A]
Owner SAP, Torsten Leidig

Contents

Preface

Within this document you find a self-contained open specification of a FIWARE generic enabler, please consult as well the FIWARE Product Vision, the website on http://www.fiware.org and similar pages in order to understand the complete context of the FIWARE platform.

Copyright

  • Copyright © 2014 by SAP

Legal Notice

Please check the following FI-WARE Open Specification Legal Notice (essential patents license) to understand the rights to use this open specification. As all other FI-WARE members, SAP has chosen one of the two FI-WARE license schemes for open specifications.

To illustrate this open specification license from our SAP perspective:

  • SAP provides the specifications of this Generic Enabler available under IPR rules that allow for a exploitation and sustainable usage both in Open Source as well as proprietary, closed source products to maximize adoption.
  • This Open Specification is exploitable for proprietary 3rd party products and is exploitable for open source 3rd party products, including open source licenses that require patent pledges.
  • If the owner (SAP) of this GE spec holds a patent that is essential to create a conforming implementation of the GE spec (i.e. it is impossible to write a conforming implementation without violating the patent) then a license to that patent is deemed granted to the implementation.

Note: SAP provides the software associated to the Registry - RI as open source under the BSD License. Please check the specific terms and conditions linked to this BSD open source license at https://github.com/service-business-framework/Registry-RI/blob/master/license.txt. You can also obtain the Registry GE software using the FI-WARE Catalogue at http://catalogue.fi-ware.org/enablers/registry-sap-ri

Overview

While the Repository Enabler is used to store complete service descriptions, which are more or less static and change only rarely, the Registry Enabler is used to store information on service instances necessary for run-time execution. Discovering entities and their description in an open distributed system often is achieved via registries, which have a well-known address. The registry serves as a kind of directory and for example can store detailed settings for concrete infrastructure components as well as information about human or computing agents. The information can range from stable to extremely volatile and is needed to make specific settings for and adjustments to other components in the platform. For example, the Registry can be used by the Marketplace in order to register stores, providers, persons, infrastructure components and more. The functionality and purpose of the Registry GE is comparable to the Microsoft Windows Registry [ REG3 ] or the Light-weight Directory Access Protocol LDAP [ REG1 ] or the UDDI Business Registry [ REG4 ]. The main difference is that the Registry GE is fully relying on standard Web protocols and has a simpler data model.

Target usage

The Registry acts as a universal directory of information used for the maintenance, administration, deployment and retrieval of services. Existing (running) service endpoints as well as information to create an actual service instance and endpoint are registered. This GE will be used by potentially all GE in the Apps Chapter in order to build a common database of run-time configuration options and properties. It can also be used by GE of other chapters, such as the Cloud, Security, Data or IoT to announce their instance specific information to the rest of the platform components. In a FI-WARE instance there could be multiple instances of the Registry for different purposes and usage domains, which are accessed uniformly according the Repository RESTful interface specification.

Rationale

The Registry has specific requirements according to scalability and performance. Highly volatile information about runtime aspects are to be handled with quick response times. On the other hand, the number of clients and the amount of data is usually small.

Background

Registries are quite a common pattern in software architectures. With in the internet protocol stack defined by the IETF RFC, LDAP (Light-weight Directory Access Protocol) [ REG1 ] is a common technical realization of the registry functionality. Other examples of registry implementations are UDDI [ REG4 ]and the Windows Registry database [ REG3 ].

Basic Concepts

Register and Deregister Entries

This function is used by resource providers to register and deregister their resources as entries in the Registry. This information can be used by other components in the FI-WARE instance. E.g. the Application Mashup component can use the Registry to find out Marketplaces and their respective endpoint information.

Retrieving Registry Entries

The Retrieving Registry Entries component is responsible for read access of entries. A client service can ask for specific settings and options of the operating environment. The retrieval is either controlled by giving the entry key, which identifies the entry in a unique way. Or the retrieval is based on a filter expression, which is referring to concrete entry values. In this case a list of matching entries is returned. Using a selector expression, the user can limit the number of property values to be returned.

Data Model

The basic data elements of the registry are the Registry Entry containing the actual information and the Registry Key to access the data entries in the Registry. A registry entry can be a single atomic piece of data or a structured data such as a record of named properties (name/value pairs). The exact data model and its encoding will be defined in the interface specification. The schema (the exact names of properties and their value encoding) is the matter of the application developer or the community of developers in a respective application domain.

The Registry Key is used for accessing individual entries or a collection of entries is often organized as path into an underlying registry internal organization such as a tree.

Registry Architecture

The Registry is a searchable index of the Repository GE. The following picture shows the schematic architecture of the Repository GE. A protocol handler is responsible for the realization of the RESTful HTTP protocol. Content negotiation is used to deliver the results of the operations in different formats convenient for various client environments. An access control adapter is responsible to check access rights according to the FI-WARE Identity Management & Access Control Enabler. The dispatcher calls different handlers for the registry functions. The registry entries and index is stored in a registry database. The registry handlers can call remote registries if the registry is distributed over multiple servers.

[[

File:registry-architecture.png|thumb|600px|center|Registry architecture (schematic)]]

Main Interactions

The following diagram shows an example sequence how a user or other GEs can register, retrieve, and deregister a registry entry.

Example sequence of Registry operations

Register and Deregister Entries

The Register Entry operation is used to write or update a register information entry into the Registry. Two parameters are essentially needed:

  • key - The Registry Key of the entry to be registered. A key can exhibit an organizational structure such as a tree. The Registry Key is usually given by the client and is chosen according to a published naming scheme.
  • entry - The Register Entry to be registered. The entry is usually a list of name/value pairs.

A registry key is returned.

For the Deregister Entry operation only the Registry Key of the Registry Entry is needed:

  • key - Registry Key of the entry to be de-registered


Retrieving Registry Entries

It must be possible to directly retrieve a Registry Entry using a unique Key using the Get Registry Entry operation. In this case one parameter is sufficient:

  • key - Registry Key of the entry to be retrieved


The Query Registry Entries operation allows the retrieval of Registry Entries matching a filter expression:

  • filter - A filter expression to select entries to be retrieved.


Basic Design Principles

An implementation for the Registry might take different design decisions and technological approaches, depending on the non-functional requirements of the repository. A registry implementation might be highly distributed and scalable if it is used by many parties on a global scale. Also the database schema might be of different complexity depending on the data requirements of the use case. Prominent example technologies which have a distributed nature are LDAP, UDDI, or distributed key/value stores for large amounts of records such as MongoDB, CouchDB, or Cassandra. The Registry specification follows the separation of concerns principle. So it is possible to supplement it with an authentication and authorization system such as OAuth [ REG2 ].

Detailed Open Specifications

  • FIWARE.OpenSpecification.Apps.Registry

Open API Specifications

References

REG1 LDAP protocol specifications(RFCs 4510,4512,4514,4516,4517)
REG2 OAuth2 protocol (http://tools.ietf.org/html/draft-ietf-oauth-v2-30)
REG3 Microsoft Windows Registry (http://msdn.microsoft.com/msdnmag/issues/1100/Registry/)
REG4 UDDI Business Registry (http://en.wikipedia.org/wiki/Universal_Description_Discovery_and_Integration)

Detailed Specifications

Open API Specifications

Other Relevant Specifications

none

Re-utilised Technologies/Specifications

Because the registry can be used to provide central consistent information base of run-time information it might require authentication and authorization in order to safeguard the content. For this reasons it need to be combined with a pluggable authenticaton/authentication provider.

FI-Ware for example offers an Identity GE providing API authorization with bearer tokens of the OAuth2 protocol (http://tools.ietf.org/html/draft-ietf-oauth-v2-30).

Terms and definitions

This section comprises a summary of terms and definitions introduced during the previous sections. It intends to establish a vocabulary that will be help to carry out discussions internally and with third parties (e.g., Use Case projects in the EU FP7 Future Internet PPP). For a summary of terms and definitions managed at overall FI-WARE level, please refer to FIWARE Global Terms and Definitions

  • Aggregator (Role): A Role that supports domain specialists and third-parties in aggregating services and apps for new and unforeseen opportunities and needs. It does so by providing the dedicated tooling for aggregating services at different levels: UI, service operation, business process or business object levels.
  • Application: Applications in FIWARE are composite services that have a IT supported interaction interface (user interface). In most cases consumers do not buy the application, instead they buy the right to use the application (user license).
  • Broker (Role): The business network’s central point of service access, being used to expose services from providers that are delivered through the Broker’s service delivery functionality. The broker is the central instance for enabling monetization.
  • Business Element: Core element of a business model, such as pricing models, revenue sharing models, promotions, SLAs, etc.
  • Business Framework: Set of concepts and assets responsible for supporting the implementation of innovative business models in a flexible way.
  • Business Model: Strategy and approach that defines how a particular service/application is supposed to generate revenue and profit. Therefore, a Business Model can be implemented as a set of business elements which can be combined and customized in a flexible way and in accordance to business and market requirements and other characteristics.
  • Business Process: Set of related and structured activities producing a specific service or product, thereby achieving one or more business objectives. An operational business process clearly defines the roles and tasks of all involved parties inside an organization to achieve one specific goal.
  • Business Role: Set of responsibilities and tasks that can be assigned to concrete business role owners, such as a human being or a software component.
  • Channel: Resources through which services are accessed by end users. Examples for well-known channels are Web sites/portals, web-based brokers (like iTunes, eBay and Amazon), social networks (like Facebook, LinkedIn and MySpace), mobile channels (Android, iOS) and work centers. The access mode to these channels is governed by technical channels like the Web, mobile devices and voice response, where each of these channels requires its own specific workflow.
  • Channel Maker (Role): Supports parties in creating outlets (the Channels) through which services are consumed, i.e. Web sites, social networks or mobile platforms. The Channel Maker interacts with the Broker for discovery of services during the process of creating or updating channel specifications as well as for storing channel specifications and channeled service constraints in the Broker.
  • Composite Service (composition): Executable composition of business back-end MACs (see MAC definition later in this list). Common composite services are either orchestrated or choreographed. Orchestrated compositions are defined by a centralized control flow managed by a unique process that orchestrates all the interactions (according to the control flow) between the external services that participate in the composition. Choreographed compositions do not have a centralized process, thus the services participating in the composition autonomously coordinate each other according to some specified coordination rules. Backend compositions are executed in dedicated process execution engines. Target users of tools for creating Composites Services are technical users with algorithmic and process management skills.
  • Consumer (Role): Actor who searches for and consumes particular business functionality exposed on the Web as a service/application that satisfies her own needs.
  • Desktop Environment: Multi-channel client platform enabling users to access and use their applications and services.
  • Front-end/Back-end Composition: Front-end compositions define a front-end application as an aggregation of visual mashable application pieces (named as widgets, gadgets, portlets, etc.) and back-end services. Front-end compositions interact with end-users, in the sense that front-end compositions consume data provided by the end-users and provide data to them. Thus the front-end composition (or mashup) will have a direct influence on the application look and feel; every component will add a new user interaction feature. Back-end compositions define a back-end business service (also known as process) as an aggregation of backend services as defined for service composition term, the end-user being oblivious to the composition process. While back-end components represent atomization of business logic and information processing, front-end components represent atomization of information presentation and user interaction.
  • Gateway (Role): The Gateway role enables linking between separate systems and services, allowing them to exchange information in a controlled way despite different technologies and authoritative realms. A Gateway provides interoperability solutions for other applications, including data mapping as well as run-time data store-forward and message translation. Gateway services are advertised through the Broker, allowing providers and aggregators to search for candidate gateway services for interface adaptation to particular message standards. The Mediation is the central generic enabler. Other important functionalities are eventing, dispatching, security, connectors and integration adaptors, configuration, and change propagation.
  • Hoster (Role): Allows the various infrastructure services in cloud environments to be leveraged as part of provisioning an application in a business network. A service can be deployed onto a specific cloud using the Hoster’s interface. This enables service providers to re-host services and applications from their on-premise environments to cloud-based, on-demand environments to attract new users at much lower cost.
  • Marketplace: Part of the business framework providing means for service providers, to publish their service offerings, and means for service consumers, to compare and select a specific service implementation. A marketplace can offer services from different stores and thus different service providers. The actual buying of a specific service is handled by the related service store.
  • Mashup: Executable composition of front-end MACs. There are several kinds of mashups, depending on the technique of composition (spatial rearrangement, wiring, piping, etc.) and the MACs used. They are called application mashups when applications are composed to build new applications and services/data mash-ups if services are composed to generate new services. While composite service is a common term in backend services implementing business processes, the term ‘mashup’ is widely adopted when referring to Web resources (data, services and applications). Front-end compositions heavily depend on the available device environment (including the chosen presentation channels). Target users of mashup platforms are typically users without technical or programming expertise.
  • Mashable Application Component (MAC): Functional entity able to be consumed executed or combined. Usually this applies to components that will offer not only their main behaviour but also the necessary functionality to allow further compositions with other components. It is envisioned that MACs will offer access, through applications and/or services, to any available FIWARE resource or functionality, including gadgets, services, data sources, content, and things. Alternatively, it can be denoted as ‘service component’ or ‘application component’.
  • Monetization: Process or activity to provide a product (in this context: a service) in exchange for money. The Provider publishes certain functionality and makes it available through the Broker. The service access by the Consumer is being accounted, according to the underlying business model, and the resulting revenue is shared across the involved service providers.
  • Premise (Role): On-Premise operators provide in-house or on-site solutions, which are used within a company (such as ERP) or are offered to business partners under specific terms and conditions. These systems and services are to be regarded as external and legacy to the FIWARE platform, because they do not conform to the architecture and API specifications of FIWARE. They will only be accessible to FIWARE services and applications through the Gateway.
  • Prosumer: A user role able to produce, share and consume their own products and modify/adapt products made by others.
  • Provider (Role): Actor who publishes and offers (provides) certain business functionality on the Web through a service/application endpoint. This role also takes care of maintaining this business functionality.
  • Registry and Repository: Generic enablers that able to store models and configuration information along with all the necessary meta-information to enable searching, social search, recommendation and browsing, so end users as well as services are able to easily find what they need.
  • Revenue Settlement: Process of transferring the actual charges for specific service consumption from the consumer to the service provider.
  • Revenue Sharing: Process of splitting the charges of particular service consumption between the parties providing the specific service (composition) according to a specified revenue sharing model.
  • Service: We use the term service in a very general sense. A service is a means of delivering value to customers by facilitating outcomes customers want to achieve without the ownership of specific costs and risks. Services could be supported by IT. In this case we say that the interaction with the service provider is through a technical interface (for instance a mobile app user interface or a Web service). Applications could be seen as such IT supported Services that often are also composite services.
  • Service Composition: in SOA domain, a service composition is an added value service created by aggregation of existing third party services, according to some predefined work and data flow. Aggregated services provide specialized business functionality, on which the service composition functionality has been split down.
  • Service Delivery Framework: Service Delivery Framework (or Service Delivery Platform (SDP)) refers to a set of components that provide service delivery functionality (such as service creation, session control & protocols) for a type of service. In the context of FIWARE, it is defined as a set of functional building blocks and tools to (1) manage the lifecycle of software services, (2) creating new services by creating service compositions and mashups, (3) providing means for publishing services through different channels on different platforms, (4) offering marketplaces and stores for monetizing available services and (5) sharing the service revenues between the involved service providers.
  • Service Level Agreement (SLA): A service level agreement is a legally binding and formally defined service contract, between a service provider and a service consumer, specifying the contracted qualitative aspects of a specific service (e.g. performance, security, privacy, availability or redundancy). In other words, SLAs not only specify that the provider will just deliver some service, but that this service will also be delivered on time, at a given price, and with money back if the pledge is broken.
  • Store: Part of the Business Framework, offering a set of services that are published to a selected set of marketplaces. The store thereby holds the service portfolio of a specific service provider. In case a specific service is purchased on a service marketplace, the service store handles the actual buying of a specific service (as a financial business transaction).
  • Unified Service Description Language (USDL): USDL is a platform-neutral language for describing services, covering a variety of service types, such as purely human services, transactional services, informational services, software components, digital media, platform services and infrastructure services. The core set of language modules offers the specification of functional and technical service properties, legal and financial aspects, service levels, interaction information and corresponding participants. USDL is offering extension points for the derivation of domain-specific service description languages by extending or changing the available language modules.
  • Registry Key: A unique identifier for accessing entries in the Registry. The Registry is often given as a hierarchical naming schema or path.
  • Registry Entry: Data that is stored for a specific Registry Key. This data is usually a record of key, value pairs defining a property and its value.
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