XSD Schema Summary

XML schemas are a key component in the XML family of technologies. Their use ranges from communicating XML vocabularies and document validation to defining object-relational mappings in SQLXML for Microsoft SQL Server. The .NET Framework recognizes the important role in a number of places and provides the XSD schema definition tool to assist generating XML schemas from a compiled assembly, converting schemas from XDR format to XSD format or deriving a schema from an XML document.

The schema definition tool can speed up the development of XML enabled applications. The .NET Framework provides a number of solutions to process XML documents into objects applications can easily access. Two solutions require custom developed classes to match the data structure of the processed documents: XML serialization and typed DataSets. The tool can automatically generate these custom classes from a schema definition of the data format the classes need to process.

While it may sound compelling to the novice user to create a classes and schemas automatically, we need to be aware that we should view them only as starting point for further refinement. Generated schemas can only reflect the structure of the one document instance from which they were created. We have to complete inferred schemas with more details about multiplicity, data types, constraints and so forth. Generated classes, on the other hand, cannot express all the restrictions found in a schema. Again we have to add somewhere in our application to reflect constraints and relationships the tool could not interpret.

Nevertheless, as long as we remember the tool’s limitations, the XSD tool can save us developing boiler-plate code when we develop an application that has to process complex XML documents.