As mentioned earlier, data fromWindchill PDMLink is in XML format and is transported either as plain XML or as Simple Object Access Protocol (SOAP) Remote Procedure Call (RPC) messages. A SOAP message is an XML document which is a textual representation of data. XML documents with well-defined structures are portable across different platforms and development systems.

The structure of an XML document is defined by an XML schema, typically represented by a Document Type Definition (DTD) or an XML Schema Definition (XSD). XSD language, an XML-based grammar for describing the structure of XML documents, is a recent development.

The purpose of an XSD is to define the legal building blocks of an XML document. It defines the document structure with a list of legal elements. An XSD can be declared in-line in an XML document, or as an external reference. With an XSD, independent groups of people can agree to use a common XSD for interchanging data. An application can use a standard XSD to verify that data received from the outside world is valid.

A schema-aware validating parser can validate an XML document against an XSD schema and report any discrepancies. The schemas contain a list of legal elements, their content, usage, and data types and the relationship with any underlying elements. All XML schemas in Windchill ESI are described by XSD. Child elements, rather than XML attributes, are used exclusively in the XML schema to define Windchill object attributes. Recursive looping in XML data structures is not supported. The Windchill ESI schemas are included in the TIBCO BusinessWorks repository.

Since schemas represent the data structures that are passed from one Windchill ESI component to another, understanding their structure is essential, especially if new data elements need to be added or if other changes in error handling or logging need to be made. Also, understanding schemas is helpful to systems integrators and administrators for troubleshooting purposes when you are deploying or maintaining the system.

The following are key schemas that define the interface between Windchill ESI services and the EAI software components. For more information on schemas, see XML Schemas. For more information on XML, see to the following web site: http://www.w3c.org/XML/Schema