Component Technologies of Web Services

Consider a scenario in which you need to locate a particular pharmacy store in your area. You would not go out on the road and ask every person you met the way to the store. You might, instead, refer the Web site of the pharmacy on the Internet. If you knew the pharmacy's Web site, you would look it up directly and find the location through the store locator link. If not, you would go to a search engine and type out the name of the pharmacy in the language that the search engine was meant to recognize. After getting the location, you would find the directions to the store, and then go to the store.

The structure of Web Services is also very similar. Web Services provide for each of these previously described activities.

If you carefully look at the preceding example, you will see that there is a requestor or a consumer—that is you. There is also a service, the pharmacy store. The central database of information is the Internet, through which you find the location of the pharmacy. In the example, when you fire a search in the search engine, your request is wrapped in a structure, whose language is predetermined and localized, and then passed onto the server running the search engine.

In Web Services, SOAP, UDDI, and WSDL represent the roles mentioned in these steps.

SOAP (Simple Object Access Protocol) is the method by which you can send messages across different modules. This is similar to how you communicate with the search engine that contains an index with the Web sites registered in the index associated with the keywords.

UDDI (Universal Description, Discovery, and Integration) is the global look up base for locating the services. In the example mentioned earlier, this is analogous to the index service for the search engine, in which all the Web sites register themselves associated with their keywords. It maintains a record of all the pharmacy store locations throughout the country.

WSDL (Web Services Definition Language) is the method through which different services are described in the UDDI. This maps to the actual search engine in our example.