The Meanings of XML: DTDs, DCDs and Schemas (3/3) - exploring XML
The Meanings of XML: DTDs, DCDs and Schemas
The rule of schemas in B2B
While XML is a handy tool to exchange data between two disparate systems of any kind, the power of industry-wide schemas shines in business-to-business relations (B2B), when the two communicating systems belong to different organizations. And B2B here can mean "your Web Site to mine", not only "your multi-billion company to mine". We are all in many businesses at once, whether we are in business or not...
So for example, rather than defining the next-great way to group and summarize the latest news to spread, why not adopt the RSS standard and make use of the many RSS tools available for it? Sure, you might still have to interface your news store with RSS, but from then on it is a breathe to tap into the existing infrastructure: List your channel at one of the directories and make your always most-up-to-date messages available to an evergrowing set of hosts. And if you want to host RSS at your site, just grab the Perl ChannelManager and the RSSViewerApplet and RSS-enable your site in hours rather than weeks.
Why does it makes sense for me to develop the applet in the first place? Why can these hubs of news syndication exist? Because all of these participants profit from standardization:
- tools writers can create software that apply to greater audiences, beyond the scope of a single, isolated project
- news publishers can distribute their news through many channels at once
- news hubs can aggregate many different sources of information in a homogenous way
Of course now anybody can publish and syndicate news, but is competition not a small prize to pay for the brave new world of interoperable data?
While I used RSS as the standard example for illustrating these types of relationships across the Web it is by no means the only XML application in this area. Some other examples with appeal for use across organization boundaries on the Web include:
- WebDAV and DRP (Web-Based Distributed Authoring and Versioning, HTTP Distribution and Replication Protocol)
This hopefully marks the end of proprietary mechanisms such as Microsoft Frontpage Extensions and Netscape's WebPublisher API, and crutches like FTP for publishing to a Web server. It also enables content replication, also partially, across domains.
- WDDX (Web Distributed Data Exchange)
This is a protocol for transfering arbitrary XML data over HTTP, invented and sponsored by Allaire.
- SOAP (Simple Object Access Protocol)
A Microsoft protocol, also supported by others like RogueWave, for distributed objects across CORBA, DCOM, etc. models.
- CBL (Common Business Language)
This effort defines more complex data types such as phone numbers, addresses all the way to purchase orders etc.
While XML has created an unprecedented success for universal data transfer, its flexibility poses both a boon and a curse: Its universal appeal must first be harnessed with DTDs, so that partners can agree on a common vocabulary for a certain task. Since a single DTD is not enough for most jobs, they have to agree on a whole set of vocabularies. Much of the first wave of electronic commerce, EDI, imploded on incompatible profiles, standards with different substandards and sub-substandards.
Some industry forums try to position themselves as hubs on the Web for finding and exchanging schemas and providing frameworks for certain industries and business processes in an effort to catalyze B2B biz. A later installment will look at RosettaNet, Biztalk, xml.org, CommerceOne's MarketSite and explain their different backgrounds and motivations.
Of course the above list is by no means complete, so if you think of more applications for XML standards or are already making good use of them, I would love to hear from you. In any case the time to start is now, so have a close look at the data around you, and the information you send to and receive from other parties. Can you find a topic not yet covered by a standardized DTD?
Created: Mar. 31, 2000
Revised: Mar. 31, 2000