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October 10, 2003

Web Services: It's About Connections

What do Web services really mean for your organization? The most important effect will be a blurring of internal and external services, spurring a need for new architecture. Thanks to competition, the result will be higher-quality software carried by connected services

by Douglas K. Barry

Web services and service-oriented architectures are all about connections and what we send across them. Simple object access protocol (SOAP) is the basic means for those connections. Other specifications are also part of the connections: Web services definition language (WSDL), security protocols, workflow, encryption, and orchestration. Most of what you read in the industry press deals with the connections: but that is only part of the picture. The other part has to do with XML — specifically the XML vocabularies that will be used in the messages sent across those connections.

More often than not, you can look to the past to find a pattern that will allow you to predict the future. I had an epiphany of this sort about the future of software systems architecture when recently upgrading my audio-video (AV) system. The past, in this case, is the evolution of AV systems.

My AV system has components that have been purchased over the years. I wanted to add a DVD player to my system. The system has the usual cable box, receiver, VCR, CD player, speakers, and TV set. One of the oldest components is the receiver; the DVD had connections that the receiver could not handle, such as s-video and optical connections. It did, however, have the common RCA connections.¹ I used those to connect all my components. In one case, using the RCA connections was an upgrade.

Not long ago, we had monolithic hi-fi or stereo systems. Then, the industry settled on the various components in a stereo system, and later video was added. What does this have to do with software systems architecture? Well, it's all in the connections. Web services have provided an infrastructure for creating connections not unlike those we have with AV systems. Just like AV systems, we will be able to assemble components in all sorts of ways because of those connections.

Connections and Standards

The technology of Web services is, by most accounts, the connection technology of the future. Nevertheless, other existing connections that are in use right now won't go away. These include the Electronic Data Interchange (EDI) standards, CORBA, and DCOM to name a few. Again, much like AV system connections, you can mix and match these connections and upgrade when it makes sense.

Connections such as Web services are part of the inevitable evolution of interconnectedness. Consider how you can now exchange email among disparate products. Although at one time you could not do that, we now take it for granted. This email exchange is possible because of standards. Some day, connections like Web services will also be taken for granted because of standards.

Despite controversy over the standards used for Web services, I am quite confident the standards for the connections will be worked out in the short term. As an industry, we have solved many of these problems before. Distributed transactions aren't new. Security issues aren't new. The same goes for encryption and many other needed specifications. Standards for the connections are not the concern. Not to trivialize the process, but those standards are relatively easy to work out.

What we need to work on are the XML vocabularies. You need a common language if you are going to communicate. Every industry group has its own vocabulary for its activity. Various industry groups have been developing the XML version of their respective vocabularies in order to take advantage of the XML messaging capability of Web services. This is XML used in the messages defined by WSDL and sent using SOAP. (To see the various XML vocabularies, go to www.service-architecture.com/xml/articles/xml_vocabularies.html.)

The standard XML vocabularies will probably be much more difficult to develop than the connection standards. If Web services are to be effective among multiple organizations, such vocabularies are critical. So, if you want to see Web services become effective in your industry, get involved in developing the appropriate XML vocabularies.