Inside XML

Annotating Schemas

In DTDs, you can use XML comments to add annotations and provide documentation. In schemas, you might expect that the situation would be a little more complex, and you'd be right. XML schemas define three new elements that you use to add annotations to schemas: <xsd:annotation>, <xsd:documentation>, and <xsd:appInfo>.

Here's how things work: The <xsd:annotation> element is the container element for the <xsd:documentation> and <xsd:appInfo> elements. The <xsd:documentation> element holds text of the kind you'd expect to see in a normal comment—that is, text designed for human readers. As its name implies, the <xsd:appInfo> element, on the other hand, holds annotations suitable for applications that read the document. Such applications ...