Network Computingwww.networkcomputing.com

Generally a DTD/schema is generated to support existing applications or development efforts. Those applications are coded in a number of languages, from Java to COBOL to COM. Several DTD/schema editors--including Turbo XML and XML Junction--let you import data structures and documents from languages such as Java and COBOL, as well as via ODBC, LDAP and COM. Developers of XML DTDs and schemata often are not application developers, and the ability to convert code to a matching DTD or schema is valuable.

Importing schemata or DTDs from databases is mandatory. Most data transferred between businesses or customers ends up in a database. Many editors offer ODBC or JDBC to a database and can create a DTD that models a table automatically. While the import of data structures from code is nice, the ability to read database tables and create accurate DTDs and schemata is essential. The process is more accurate than manual transcription and provides assurance that the data received via XML conforming to a DTD or schema will be usable.

Just as XML documents must be validated against a DTD or schema, schemata too should be checked for validity. A number of schema dialects are available: DTD, XDR (External Data Representation), SOX (Schema for Object-Oriented XML), Relax (Regular Language Description for XML) BizTalk and XSD (XML Schema Recommendation). Many editors, such as Stilo Technology's XML-Developer, Turbo XML and XMetal, can validate your DTD or schema against these standards. For more information, see "DTD/ Schema Links," at left.



Some DTD/schema editors also can validate XML documents for conformance to your DTD/schema. If your XML editor doesn't provide this, you must have this feature available elsewhere. Compliance is important to ensure business processes don't break down, so validate!

Technology editor Lori MacVittie has been a software developer and a network administrator. Most recently, she was a member of the technical architecture team for a global transportation and logistics organization. Send your comments on this article to her at lmacvittie@nwc.com.

DTD/Schema Links

Quite a few DTDs and schemata are available. The following are some of the more popular: