Web Services Discovery

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Web Services Discovery provides access to software systems over the Internet using standard protocols. In the most basic scenario there is a Web Service Provider that publishes a service and a Web Service Consumer that uses this service. Web Service Discovery is the process of finding suitable web services for a given task. [1]

Contents

Publishing a web service involves creating a software artifact and making it accessible to potential consumers. Web service providers augment a service endpoint interface with an interface description using the Web Services Description Language (WSDL) so that a consumer can use the service.

Universal Description, Discovery, and Integration (UDDI) is an XML-based registry for business internet services. A provider can explicitly register a service with a Web Services Registry such as UDDI or publish additional documents intended to facilitate discovery such as Web Services Inspection Language (WSIL) documents. The service users or consumers can search web services manually or automatically. The implementation of UDDI servers and WSIL engines should provide simple search APIs or web-based GUI to help find Web services.

Web services may also be discovered using multicast mechanisms like WS-Discovery, thus reducing the need for centralized registries in smaller networks.

Universal Description Discovery and Integration

Universal Description, Discovery and Integration (UDDI, pronounced /ˈjʊdiː/ ) is a platform-independent, Extensible Markup Language protocol that includes a (XML-based) registry by which businesses worldwide can list themselves on the Internet, and a mechanism to register and locate web service applications. UDDI is an open industry initiative, sponsored by the Organization for the Advancement of Structured Information Standards (OASIS), for enabling businesses to publish service listings and discover each other, and to define how the services or software applications interact over the Internet.

UDDI was originally proposed as a core Web service standard. [2] It is designed to be interrogated by SOAP messages and to provide access to Web Services Description Language (WSDL) documents describing the protocol bindings and message formats required to interact with the web services listed in its directory.

History of UDDI

UDDI was written in August 2000, at a time when the authors had a vision of a world in which consumers of web services would be linked up with providers through a public or private dynamic brokerage system. In this vision, anyone needing a service, such as credit card authentication, would go to their service broker and select a service supporting the desired SOAP (or other) service interface, and meeting other criteria. In such a world, the publicly operated UDDI node or broker would be critical for everyone. For the consumer, public or open brokers would only return services listed for public discovery by others, while for a service producer, getting a good placement in the brokerage—by relying on metadata of authoritative index categories—would be critical for effective placement.

UDDI was included in the Web Services Interoperability (WS-I) standard as a central pillar of web services infrastructure, and the UDDI specifications supported a publicly accessible Universal Business Registry in which a naming system was built around the UDDI-driven service broker.

UDDI has not been as widely adopted as its designers had hoped. [3] IBM, Microsoft, and SAP announced they were closing their public UDDI nodes in January 2006. [4] The group defining UDDI, the OASIS Universal Description, Discovery, and Integration (UDDI) Specification Technical Committee voted to complete its work in late 2007 and has been closed. [5] In September 2010, Microsoft announced they were removing UDDI services from future versions of the Windows Server operating system. Instead, this capability would be moved to BizTalk Server. [6] In 2013, Microsoft further announced the deprecation of UDDI Services in BizTalk Server. [7] In 2016, Microsoft removed UDDI Services from BizTalk Server. [8]

UDDI systems are most commonly found inside companies, where they are used to dynamically bind client systems to implementations. [9] However, much of the search metadata permitted in UDDI is not used for this relatively simple role.

Structure of UDDI

A UDDI business registration consists of three components:

White Pages

White pages give information about the business supplying the service. This includes the name of the business and a description of the business - potentially in multiple languages. Using this information, it is possible to find a service about which some information is already known (for example, locating a service based on the provider's name). [10]

Contact information for the business is also provided - for example the businesses address and phone number; and other information such as the Dun & Bradstreet.

Yellow Pages

Yellow pages provide a classification of the service or business, based on standard taxonomies. These include the Standard Industrial Classification (SIC), the North American Industry Classification System (NAICS), [10] or the United Nations Standard Products and Services Code (UNSPSC) and geographic taxonomies.

Because a single business may provide a number of services, there may be several Yellow Pages (each describing a service) associated with one White Page (giving general information about the business).

Green Pages

Green pages are used to describe how to access a Web Service, with information on the service bindings. Some of the information is related to the Web Service - such as the address of the service and the parameters, and references to specifications of interfaces. [10] Other information is not related directly to the Web Service - this includes e-mail, FTP, CORBA and telephone details for the service. Because a Web Service may have multiple bindings (as defined in its WSDL description), a service may have multiple Green Pages, as each binding will need to be accessed differently.

UDDI nodes and registry

UDDI nodes are servers which support the UDDI specification and belong to a UDDI registry while UDDI registries are collections of one or more nodes.

SOAP is an XML-based protocol to exchange messages between a requester and a provider of a Web Service. The provider publishes the WSDL to UDDI and the requester can join to it using SOAP.

Federated discovery

The current UDDI search mechanism can only focus on a single search criterion, such as business name, business location, business category, service type by name, business identifier, or discovery URL. In fact, in a business solution, it is very normal to search multiple UDDI registries or WSIL documents and then aggregate the returned result by using filtering and ranking techniques. IBM modularized this federated Web Services Discovery engine in 2001. The released technology from IBM is Business Explorer for Web Services (BE4WS).

See also

Related Research Articles

<span class="mw-page-title-main">SOAP</span> Messaging protocol for web services

SOAP is a messaging protocol specification for exchanging structured information in the implementation of web services in computer networks. It uses XML Information Set for its message format, and relies on application layer protocols, most often Hypertext Transfer Protocol (HTTP), although some legacy systems communicate over Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission.

A web service (WS) is either:

The Organization for the Advancement of Structured Information Standards is a nonprofit consortium that works on the development, convergence, and adoption of projects - both open standards and open source - for Computer security, blockchain, Internet of things (IoT), emergency management, cloud computing, legal data exchange, energy, content technologies, and other areas.

The Web Services Business Process Execution Language (WS-BPEL), commonly known as BPEL, is an OASIS standard executable language for specifying actions within business processes with web services. Processes in BPEL export and import information by using web service interfaces exclusively.

In software engineering, service-oriented architecture (SOA) is an architectural style that focuses on discrete services instead of a monolithic design. SOA is a good choice for system integration. By consequence, it is also applied in the field of software design where services are provided to the other components by application components, through a communication protocol over a network. A service is a discrete unit of functionality that can be accessed remotely and acted upon and updated independently, such as retrieving a credit card statement online. SOA is also intended to be independent of vendors, products and technologies.

Web Services Security is an extension to SOAP to apply security to Web services. It is a member of the Web service specifications and was published by OASIS.

The WS-I Basic Profile, a specification from the Web Services Interoperability industry consortium (WS-I), provides interoperability guidance for core Web Services specifications such as SOAP, WSDL, and UDDI. The profile uses Web Services Description Language (WSDL) to enable the description of services as sets of endpoints operating on messages.

The Web Services Invocation Framework (WSIF) supports a simple and flexible Java API for invoking any Web Services Description Language (WSDL)-described service.

WS-Inspection is a Web service specification for "discovery documents" developed in a joint effort by Microsoft and IBM. WS-Inspection lists groups of web services and their endpoints in an XML format. Currently, other standards are being used for this purpose, such as Microsoft's DISCO. It is expected that WS-Inspection will eventually replace these standards to become the universally accepted discovery standard for Web services.

A web service protocol stack is a protocol stack that is used to define, locate, implement, and make Web services interact with each other. A web service protocol stack typically stacks four protocols:

WebSphere Application Server (WAS) is a software product that performs the role of a web application server. More specifically, it is a software framework and middleware that hosts Java-based web applications. It is the flagship product within IBM's WebSphere software suite. It was initially created by Donald F. Ferguson, who later became CTO of Software for Dell. The first version was launched in 1998. This project was an offshoot from IBM HTTP Server team starting with the Domino Go web server.

Microsoft BizTalk Server is an inter-organizational middleware system (IOMS) that automates business processes through the use of adapters which are tailored to communicate with different software systems used in an enterprise. Created by Microsoft, it provides enterprise application integration, business process automation, business-to-business communication, message broker and business activity monitoring.

WS-Policy is a specification that allows web services to use XML to advertise their policies and for web service consumers to specify their policy requirements.

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Service-oriented communications (SOC) technologies are designed to be easily used in the context of service-oriented architectures. These technologies are generally software based and are built more like a business application than a traditional PBX business communications system. Service-oriented communications systems allow their services to participate in business processes. They make their services available to other business applications within and SOA and allow for reuse of the services. The goal of service-oriented communications is to enable business environments to build communications into their business processes, enabling more streamlined collaboration among people within the business. It typically assumes that certain services are provided in the context of an SOA service provider. This is often in the form of a suite of web services, but may also be attached to other means of sharing the services such as an enterprise system bus (ESB).

The Governance Interoperability Framework (GIF) is an open, standards-based specification and set of technologies that describes and promotes interoperability among components of a service-oriented architecture (SOA). GIF integrates SOA ecosystem technologies to achieve heterogeneous service lifecycle governance and is supported by Hewlett-Packard Company and by GIF partners.

<span class="mw-page-title-main">Web Services Description Language</span> XML-based interface description language

The Web Services Description Language is an XML-based interface description language that is used for describing the functionality offered by a web service. The acronym is also used for any specific WSDL description of a web service, which provides a machine-readable description of how the service can be called, what parameters it expects, and what data structures it returns. Therefore, its purpose is roughly similar to that of a type signature in a programming language.

IBM WebSphere Service Registry and Repository (WSRR) is a service registry for use in a Service-oriented architecture.

References

  1. ↑ Alzaghoul, Esra; Bahsoon, Rami (2014). "Evaluating Technical Debt in Cloud-Based Architectures Using Real Options". 2014 23rd Australian Software Engineering Conference. pp. 1–10. doi:10.1109/ASWEC.2014.27. ISBN   978-1-4799-3149-1. S2CID   14951457.
  2. ↑ "Interoperability". www.w3.org.
  3. ↑ UDDI R.I.P
  4. ↑ "Microsoft, IBM, SAP To Discontinue UDDI Web Services Registry Effort | Microservices Expo". soa.sys-con.com.
  5. ↑ Message announcing closure of Technical Committee
  6. ↑ "Removal of UDDI Services from Server Operating System - Win32 apps". docs.microsoft.com. 27 April 2021.
  7. ↑ "What's New in BizTalk Server 2013 and 2013 R2 - BizTalk Server". docs.microsoft.com. 24 May 2022.
  8. ↑ "What's New in BizTalk Server 2016 - BizTalk Server". docs.microsoft.com. 7 July 2021.
  9. ↑ Alzaghoul, Esra Fawaz Ahmad (December 18, 2015). Value- and debt-aware selection and composition in cloud-based service-oriented architectures using real options (d_ph). University of Birmingham – via etheses.bham.ac.uk.
  10. 1 2 3 Taylor, Ian J. From P2P to Web Services and Grids - Peers in a Client/Server World. Springer, 2005
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