Generating a Schema from an XML Document

xsd can be used to generate a best-guess schema from any XML document. It will make certain assumptions about the structure of your document, based on the data found in the example you provide. For example, it will always set minOccurs to 1 and maxOccurs to unbounded for each element. It will also always use the xs:sequence compositor for lists of elements, even if your example XML document has elements in various orders. This can present the odd situation of the sample document used to generate the XSD failing validation with the XSD generated from it. Finally, the type attribute of each xs:element and xs:attribute element defaults to xs:string.

For these reasons, you should never take the generated XSD for granted. Always edit it to make sure it will fit your real requirements.

Using the purchase order document from Chapter 2, you can generate an XSD with the following command line:

xsd po1456.xml

You can go ahead and use XSD to generate the source code. I’ve already done so, and tweaked the generated code to ensure that this XSD validates the PO correctly. These edits are highlighted in Example 8-1. I intentionally introduced a couple of mistakes in my edits. I’ve done this to point out how XmlSchema validates an XSD, and I’ll explain that more in a moment.

Example 8-1. Generated XSD for purchase orders
<?xml version="1.0" encoding="utf-8"?> <xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"> ...

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