perfectxml.com
 Basic Search  Advanced Search   
Topics Resources Free Library Software XML News About Us
  You are here: home »» Focus »» Web Services: WSDL, UDDI, DISCO and more Saturday, 23 February 2008
 

Focus » Web Services

Introduction

Tutorials & Articles

WSDL, UDDI, DISCO & more

Web Services & Microsoft

Web Services & IBM

Web Services & Bowstreet

Web Services & SUN ONE

Web Services & Borland NEW!

Web Services Software & Tools

Miscellaneous


Web Services: WSDL, UDDI, DISCO and more

WSDL

Given a Web Service, it would be nice to have a standard way to document what messages the Web Service accepts and generates—that is, to document the Web Service contract. A standard language makes it easy for developers and developer tools to create and interpret contracts. The WSDL (Web Services Description Language) is an XML-based contract language jointly developed by Microsoft and IBM.

The Web Services contract written using WSDL is an XML document that defines the inputs and outputs of a Web Service, including the XML Schemas that should be used to create the input and output documents. Each WSDL document contains both an abstract definition of the service and how the service binds to a particular network implementation and data format bindings.

Over the past years Microsoft and IBM have proposed several contract languages: SDL (Service Description Language), SCL (Service Contract Language), and Network Accessible Services Specification Language (NASSL). All these are superceded by WSDL.

Official W3C definition of Web Services:
WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services). WSDL is extensible to allow description of endpoints and their messages regardless of what message formats or network protocols are used to communicate, however, the only bindings described in this document describe how to use WSDL in conjunction with SOAP 1.1, HTTP GET/POST, and MIME.

More at: http://www.w3.org/TR/wsdl  External link

Some useful articles/tutorials:
  • Introduction to WSDL  External link

    Nice introductory article on WSDL from Yasser Shohoud (Devxpert.com).

  • Web Services Description Language (WSDL) Explained  External link

    Using WSDL, users can automate the generation of proxies for Web services in a truly language- and platform-independent way. (A detailed article on MSDN Web site.)

  • Defining Web services in WSDL: A primer  External link

    In a Web services world, applications basically consist of remote, XML-driven components written in different languages connected via the Web using a standard remote-activation protocol. Service authors need some way to define the data format required to use the service they provide. Similarly, when you look to consume a service in an application model such as this, you need a way to ensure that your client uses the data format expected by the server. This is the niche Web Services Definition Language (WSDL) was meant to fill.

  • Understanding WSDL in a UDDI registry: How to publish and find WSDL service descriptions  External link

    In the first two parts of this series, Peter described how to map WSDL service descriptions to a UDDI registry and provided specific WSDL usage scenarios. In the conclusion, you will learn how to develop two Java applications which publish WSDL service descriptions in a UDDI registry. One application will be used to publish WSDL service interface descriptions, the other to publish WSDL service implementation descriptions.

  • A Quick Introduction to WSDL  External link

    WSDL Introduction from Microsoft SOAP Toolkit 2.0 documentation.

  • Don Box on the Importance of Being WSDL  External link

    A personal appeal to the Web services community to make type-safety a priority by writing WSDL for script-based Web services.

  • WSDL: An Insight Out  External link

    Use WSDL to invoke Web services, or exploit WSDL to expose your service with the same advantages for its users.
    Today programmers talk less about building applications from scratch; instead, they prefer to assemble applications from available third-party services through the Internet. Consider a scenario where you want to access a third-party remote service over the Internet for, say, credit card authorization. To do this, you need to know certain things such as the method signature (input/output parameters, and so forth); the protocol to be used (IIOP, SOAP, and so on); the network address; and the data format (encoding schemes). This is precisely what the Web Services Description Language (WSDL) specification defines in an XML format.
    The official definition of WSDL goes like this: "WSDL is an XML format for describing network services as a set of end points operating on messages containing either document-oriented or procedure-oriented information." By using WSDL as a standard, you can easily invoke remote services; conversely, if you have a remote service, exposing it using WSDL offers the same advantage to its requesters. Let's see how this works by looking at how WSDL fits into the Web services model, generating a WSDL document, and using it for invoking a remote service.

  • All We Want For Christmas is a WSDL Working Group  External link   - a nice article by Martin Gudgin & Timothy Ewald

    Dear Santa Claus,
    We have both been very good this year. We've done our best to promote peace and understanding among web service developers around the world. We have run into some problems, however, with the Web Service Description Language (WSDL).

  • Defining a Web Service for UDDI  External link

    The Web services initiative can be divided into three categories: registering a service, accessing a service, and creating a service. In this article, Peter Vogel walks you though registering your service in UDDI using WSDL.

  • WSDL and the Wild, Wild West  External link

    More than any other recent development, XML has introduced a Wild West atmosphere to Internet technologies. It causes rapid turnover in development trends, inspires people to stake claims on territory without trying to cooperate with others to maximize its usefulness, and it brings about startling successes in all the chaos. Some would say Web services are a perfect example of all three of these traits.

  • The limitations of WSDL and the problems they cause for web services interoperability.  External link

    When you listen to someone explaining Web Services, it's not unusual to hear WSDL compared to the Interface Definition Languages (IDLs) used by classic RPC mechanisms like DCE, ONC, CORBA, and COM. All of these technologies use IDL of one form or another to define contracts between components. In all of these cases, use of an IDL was the key to interoperability across language, process, and vendor boundaries. WSDL is exactly like the IDLs of the past in that a WSDL document describes the portTypes or interfaces a web service implements. However, there is one critical difference between WSDL and the IDLs distributed systems developers know and love: no one wants to use WSDL as a starting point. This is a critical problem that will plague the web service movement until it is solved.

  • Supercharging WSDL with RDF  External link

    The Resource Description Framework is the World Wide Web Consortium's official format for defining the metadata of XML objects. Conceptually, it is similar to Web Services Description Language, which is a collection of metadata about XML-based services. This article focuses on building a bridge between the two specifications. It provides an example of what a Web service description might look like as an RDF file. It then goes on to discuss how to take advantage of an RDF visualization tool to generate a graph of the WSDL data. Finally, it presents a portion of a possible RDF Schema for WSDL.

  • WSDL processing with XSLT  External link

    First steps for Web service description processing: Building on earlier articles introducing Web Services Description Language (WSDL) and an RDF application based on WSDL, this article shows ways of using Extensible Stylesheet Language for Transforms (XSLT) to process WSDL in various ways. Familiarity with XSLT and Resource Description Framework (RDF) are required. Resources introducing XSLT are provided.


UDDI & DISCO

Developers will need some way to discover Web Services. The DISCO (Discovery of Web Services) provides a way to discover and retrieve WSDL description of services on remote machines. Using the Discovery Document Format (which is also an XML grammar), one can send a discovery document to a remote server and, if any SOAP enabled services (AKA web service) exist, receive back an WSDL description of the services provided.

In many cases, the developers will not know the URLs where the services can be found. Universal Description, Discovery, and Integration (UDDI) specifies a mechanism for Web Service providers to advertise the existance of their Web Services and for Web Service consumers to locate Web Services of interest.

UDDI is the building block that will enable businesses to quickly, easily and dynamically find and transact business with one another using their preferred applications.

UDDI is designed to provide the searchable directory of businesses and their Web Services. Ariba, IBM, and Microsoft released a draft specification for UDDI version 1.0 on September 6, 2000.

Official W3C definition of Web Services:
WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services). WSDL is extensible to allow description of endpoints and their messages regardless of what message formats or network protocols are used to communicate, however, the only bindings described in this document describe how to use WSDL in conjunction with SOAP 1.1, HTTP GET/POST, and MIME.

Some useful articles/tutorials/resources:
  • UDDI  External link

    Chapter 6 from the book Java Web Services. A good reading to begin learning UDDI.

  • UDDI.org  External link

    UDDI Specifications, White Papers, Technical and General discussion forums, Community, FAQs and more.

  • Why UDDI Will Succeed, Quietly: Two Factors Push Web Services Forward  External link

    On UDDI's six-month birthday, we suggest that two aspects of the growing momentum for web services—one economic, one technical—will help make a success of the standard for registering and discovering web-based services. Bottom line, UDDI will succeed because its technical underpinnings work for the geeks. By Brent Sleeper.

  • Introduction to UDDI  External link

    Nice introductory article on UDDI (Devxpert.com).

  • UDDI Overview  External link

    Introduction to UDDI on "Microsoft for Partners" Web site.

  • UDDI Reference  External link

    UDDI Reference, based on the final version of XML Schema standard, it contains comparison of versions 1 and 2, and both versions contain both abbreviated and expanded schema for the selected element as well as the context it can appear in.

  • uddi.microsoft.com  External link

    Microsoft UDDI Registry

  • Introducing Microsoft UDDI Developer Edition and Microsoft UDDI .NET SDK 1.5 Beta  External link

    The Web services model allows programmable Web service elements to be placed on Web sites where others can access and interact with them. Universal Discovery, Description and Integration (UDDI) supports the discovery and description of Web services allowing a consumer of this information to integrate with them. This article discusses the features and services available in the Microsoft UDDI Developer Edition 1.5 beta and the Microsoft UDDI .NET SDK 1.5 beta.

  • Microsoft's UDDI SDK  External link

    The UDDI SDK for Visual Studio 6 allows developers using COM or ASP to make SOAP calls to UDDI. This version of the Microsoft UDDI SDK contains all the latest updates to both the UDDI SDK for Visual Studio 6 and the UDDI Developer Edition 1.5 (Beta); which includes the UDDI .Net SDK (Beta) for Visual Studio.Net. Also see: http://www.microsoft.com/downloads/release.asp?ReleaseID=30877

  • UDDI - The Weather Report: The Outlook is Mixed  External link

    Over the next few years many tens, possibly hundreds, of thousands of Web Services will be made available across the world. Many of these will find their way onto the UDDI registry, a registry which when it delivers on all of its promises will revolutionize the way we do business with others by allowing us to search in a systematic way for help, contacts and functionality (Web Services) that other companies supply.

  • WSIL: Do we need another Web Services Specification?: Explaining the difference between UDDI  External link

    The Universal Description, Discovery, and Integration (UDDI) specification started out with and still has very noble intentions. The promise of UDDI is simple: to provide a place where service creators can publish their services and service consumers can search for and ultimately integrate with services for consumption. But let's face it; UDDI is not really fulfilling its promise. In fact, preliminary results from independent research and tests conducted by SalCentral (see Resources) makes it pretty obvious that UDDI has yet a long way to go.

  • IBM's UDDI4J  External link

    UDDI4J is a Java class library that provides an API to interact with a UDDI (Universal Description, Discovery and Integration) registry. The UDDI Project is a comprehensive, open industry initiative enabling businesses to (I) discover each other, and (II) define how they interact over the internet and share information in a global registry architecture. UDDI is the building block which will enable businesses to quickly, easily and dynamically find and transact with one another via their preferred applications.

  • ibm.com/services/uddi  External link

    IBM UDDI Registry

  • UDDI: an XML Web Service  External link

  • service.ariba.com  External link

    Ariba's UDDI Business Registry

  • Microsoft UDDI Test Site  External link

  Bookmark this page now!Add this page to your favorites

  Contact Us | E-mail Us | Site Guide | About PerfectXML | Advertise ©2004 perfectxml.com. All rights reserved. | Privacy