Before Web services, Internet computing and e-commerce were based on the exchange
of information through enterprise application integration (EAI). Developers created
one-time, proprietary solutions for system integration. A new, often makeshift solution
had to be developed each time two companies wanted to interchange data.
The introduction of Extensible Markup Language (XML) was an important step to simplifying
the application integration process. XML enables developers to separate the content
of data exposed over the Web from its presentation. A predefined markup language
like HTML defines a way to describe information in one specific class of documents.
XML, on the other hand, lets you define your own customized markup languages for
different kinds of documents. This means that data can be easily exchanged. More
importantly, XML has been widely accepted as the universal language of choice for
exchanging information over the Web and is a public format (that is, not the proprietary
product of any company). As a result, individuals can develop new standards for
specific functions based on XML or XML-based standards.
Web services let companies bridge communications gaps—between software written in
different programming languages, developed by different vendors or running on different
operating systems. Web services utilize four protocols to perform what they do.
- XML (extensible markup language)
- SOAP (simple object access protocol)
- UDDI (universal description, discovery and integration)
- WSDL (Web services description language)