by Thomas Erl
Whether you use XML for content management, or as a universal data transfer format, there will come a time when you will need to begin authoring custom Schemas or DTDs. Data modelling with XML is much like modelling data for relational databases, and standards used to ensure consistency are just as important to future integration and interoperability requirements.
If you’re just beginning to incorporate XML into your enterprise, there is no better time to think of assigning someone the responsibility of owning and maintaining the format, structure, standards, business rules, and validation rules associated with your XML documents. The XML & Web Services Integration Framework (XWIF), part of the SOA methodology developed by SOA Systems, defines this role and calls it the "XML Data Custodian."
Ownership of XML Vocabularies
The XML Data Custodian will need to create new vocabularies on-demand for XML developers who need to work with corporate data in an XML format, and have to maintain and coordinate these vocabularies. This involves ensuring that XML tags produced for vocabularies correspond correctly to definitions of the same data already residing in databases, and also trying to prevent the creation of any redundant or duplicate meta tags for the same corporate data sets (even if the same corporate data exists in different repositories).
Ownership of DTDs or XML Schemas
Depending on which type of data validation method your organization standardizes on, one person should be in control of how this validation and document structure technology is designed. DTDs and XML Schemas contain DDL-like information that defines the structure of an XML document, the data types allowed, validation rules, and other business rule-like functionality.
Generally, every XML document will need to be linked to a DTD or XML Schema. So, in addition to providing an overall vocabulary, the XML Vocabulary Custodian will need to assist in defining the hierarchical structure of XML documents, as well as the contents of data integrity rules. Again, the additional challenge here is to keep this information synchronized with the data integrity and referential integrity rules already in existence in corporate repositories.
Additional complexities can be anticipated if XML is playing an application interoperability role, where data from multiple data sources is being merged. Here the DTD or XML Schema may need to represent data integrity rules for each repository.
Namespace Domain Administration
Finally, the responsibility of namespace partitioning will likely also be assigned to this role. Namespaces allow for the definition of a domain in which vocabularies are valid. Theoretically, an organization could be partitioned into several namespaces in which independent vocabularies could exist.
- Inside XML Schemas
- SOAP in a Nutshell
- Transforming Data with XSLT
- Understanding DTDs
- Why SAX is Good for DOM
- What You Should Know about XPath
- An XHTML Primer
- XLink - Inside and Out
- Data Access with XQuery
- XSL versus CSS
- Another Introduction to XML
- Unifying Corporate Data & Documents
- Replacing HTML Documents with XML
- Meta-Enable Your Enterprise
- The XML Data Custodian
- Integrating XML into the Enterprise
- The Wireless Enterprise
Foreword by Grady Booch
With contributions from David Chappell, Jason Hogg, Anish Karmarkar, Mark Little, David Orchard, Satadru Roy, Thomas Rischbeck, Arnaud Simon, Clemens Utschig, Dennis Wisnosky, and others.
Governing Shared Services On-Premise & in the Cloud by Stephen Bennett, Thomas Erl, Clive Gee, Anne Thomas Manes, Robert Schneider, Leo Shuster, Andre Tost, Chris Venable
For more information about these books, visit: www.servicetechbooks.com