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Really Simple Asynchronous Web Services

By Eric Newcomer, IONA Technologies
March 25, 2003 12:00 PM ET

Computerworld - The first word in SOAP (Simple Object Access Protocol) is "simple," but the world of Web services has become very complicated. In early 2000 the SOAP specification was published, and it was quickly followed by the SOAP with Attachments; Universal Description, Discovery and Interoperability (UDDI); and Web Services Description Language (WSDL) specifications. These core technologies have been very widely adopted, implemented and endorsed. Then came a plethora of proposals for additional functionality, positioned as extensions to the core technologies, such as WS-Security, WS-Transactions, WS-Routing, BPEL, WS-Coordination, HTTP-R and WS-Reliability.
It's not yet clear exactly what applications Web services are really going to be used for, and therefore it's not really clear whether or not all these additional specifications and technologies are really necessary. Most business applications have fundamental requirements around security and reliability that represent a kind of minimum criterion for adoption. Many, if not all, of the proposed extensions fall into these two major categories. But these basic requirements can actually be met using a very simple approach in which a lot of these complicated extensions aren't necessary.
Most current Web services applications are used in a connection-oriented manner. That is, in order to use the applications over the Internet, a connection is required between the service requester and service provider. But for the mobile traveler, and for the emerging world of wireless networks, always being connected may not be possible or practical.
In the world of high-speed, wireless networking and mobile Internet-enabled devices such as laptops, personal digital assistants (PDA), cellular telephones and automobiles, it is unlikely that a connection will always and constantly be available. A really simple solution works well in this environment, insulating users from worrying about connectivity loss. If a connection is present, the message is immediately transferred. If a connection is not present, the message is queued up for later transfer.
Connections also pose security risks because they represent a hole in the firewall. Many Web sites impose security checks through log-on popups and encrypted protocols to help prevent unwanted access to sensitive or valuable data, and to guard against intrusions. But this is a constant battle, and many viruses and other security breaches often occur despite the best precautions. A simple solution improves the situation through the use of file and directory protection, and by allowing an intermediary data store to be placed outside the firewall, thereby avoiding the need for direct connections.
The most popular transport protocol for Web services, HTTP, doesn't provide the type of message delivery guarantee business applications depend upon. A really simple

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