I received the latest installment of my online XML course. This class was on XML Schemas. It mentioned that XML started with just Document Type Definitions (DTDs). However the DTD is specified in a format different than XML. However the newer XML Schema is actually written in XML format.The XML Schema is used to define text data within an XML document. You can define elements of simple type. You can also define elements which have subelements. These are called complex types. There are also built in types which come with XML Schema.
Overall I found this class to be a light treatment of a heavy topic. Perhaps there is more information coming in the next class. Let’s get our bearings here for a moment. XML Schema is used for XML document validation. This validation is performed by the parser. It checks the structure and content of an XML document. In other words it looks at the grammar.
XML Schema itself was approved by the W3C back in 2001. To add to what the class taught, simple types can only have text. They cannot contain attributes. Furthermore, elements from schema must have a namespace qualification. This class glossed over or did not even cover some details such as compositors and facets. I think I mentioned these in an earlier post on my blog. Maybe I will write a separate post to cover them in more detail.
