XML Schemas are much more powerful than DTDs.
One of the greatest strength of XML Schemas is the support for data types.
With support for data types:
Another great strength about XML Schemas is that they are written in XML.
Some benefits of that XML Schemas are written in XML:
When sending data from a sender to a receiver, it is essential that both parts have the same "expectations" about the content.
With XML Schemas, the sender can describe the data in a way that the receiver will understand.
A date like: "03-11-2004" will, in some countries, be interpreted as 3.November and in other countries as 11.March.
However, an XML element with a data type like this:
<date type="date">2004-03-11</date>
ensures a mutual understanding of the content, because the XML data type "date" requires the format "YYYY-MM-DD".
XML Schemas are extensible, because they are written in XML.
With an extensible Schema definition you can:
A well-formed XML document is a document that conforms to the XML syntax rules, like:
Even if documents are well-formed they can still contain errors, and those errors can have serious consequences.
Think of the following situation: you order 5 gross of laser printers, instead of 5 laser printers. With XML Schemas, most of these errors can be caught by your validating software.
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