From Distributed Systems Architecture: A Middleware Approach

10.2 WEB Services

Web Services have had a short but impressive history. In the late 1990s, Microsoft and a couple of other companies were thinking about an XML-based RPC that could work over HTTP. The term SOAP (Simple Object Access Protocol) was coined in 1998. The IETF published the first versions of SOAP 1.0 in December 1999. With broad support from both the commercial and Open Source community, a new version of SOAP emerged. In July 2001, the IETF published the first working draft of SOAP 1.2.

XML, SOAP, WSDL, and UDDI are the core technologies of Web Services While SOAP is certainly at the very core of Web Services, there have been numerous new technologies that extend the scope of application-level interoperability. Just like SOAP, all these technologies are based on XML. Web Services are comprised of the following key technologies:

XML (eXtensible Markup Language) is a general markup language that can be used in a wide variety of contexts. Virtually all Web Service technologies make use of XML in one way or another.

SOAP (Simple Object Access Protocol) defines application-level interoperability. Its purpose resembles that of CORBA's GIOP/IIOP, except that the data representation is based on XML.

WSDL (Web Service Definition Language) allows the specification of service interfaces. Comparing it with CORBA again, it fulfills a similar function as IDL.

UDDI (Universal Description, Discovery and Integration) serves the role of a mediator. Service providers and service requestors use the UDDI registry to...

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Topics of Interest

10.3 Middleware for Ubiqtitous Computing In this section we want to discuss some issues of middleware for future computing environments known under the term "ubiquitous computing" (ubicomp). We will...

Chapter List Chapter 1: Web Services Overview Chapter 2: Service-Oriented Architecture Chapter 3: Component-Based Service Development Chapter 4: SOAP Chapter 5: WSDL Chapter 6: UDDI Chapter 7:...

WSDL Documents Web Services Description Language (WSDL) is a part of UDDI s initiative to provide business directories and service descriptions for online services. Akin to XML grammar for Web...

Solutions in this chapter: JAX-RPC Summary Mapping Java Data Types Conversion Between Java Classes and WSDL Creating a JAX-RPC Client Creating a JAX-RPC Server Creating a Simple XML-RPC Server...

1.5 Q&A: A time to recap and reflect Q: What are Web services? Q: Are SOAP, WSDL, and UDDI Web services? Q: What is the role of XML in relation to Web services? Q: Why is there a need for Web...