One of the greatest strength of XML Schema is the support for data types.

With support for data types:

• It is easier to describe allowable document contents


• It is easier to validate the correctness of the data
• It is easier to work with data from the database
• It is easier to define data facet (restrictions on data)
• It is easier to define data pattern (data format)
• It is easier to convert the data between different data types

Another great strength about XML Schema is that they are written in XML.

Some benefits of that XML Schemas are written in XML:

• You don't have to learn new language
• You can use your XML editor to edit your Schema file
• You can use your XML parser to parse your Schema file
• You can manipulate your Schema with XML DOM
• You can transform your Schema with XSLT format

When sending data from sender to the receiver, it is essential that both parts have the same "expectations" about the content.

With XML Schema, the sender can describe the data in a way that the receiver will understand.

A date like: "04-11-2004" will, in some countries, be interpreted as type 4.November and in other countries as type 11.March.

However, an XML element with the data type like this:

<date type="date">2004-04-11</date>

ensures a mutual understanding of the content, because the XML data type "date" require the format "YYYY-MM-DD"

XML Schemas are always extensible, because they are written in XML.

With an extensible Schema definition you can:

• Reuse your Schema in other Schemas also
• Create your own data type derived from the standard type
• Reference multiple schemas in the same documents

A well-formed XML document is a document that conforms to the XML syntax rules like:

• it must begin with XML declaration
• it must have an unique root element
• start-tags must have matching with end-tags
• elements are also case sensitive
• all elements should be closed
• all elements should be properly nested
• all attribute values should be quoted
• entities should be used for special characters

Even if documents are well-formed they can still contain error, and those error can have serious consequences.

Think of the following situation: you order 5 gross of laser printer, instead of 5 laser printers. With XML Schema, most of these errors can be caught by your validating software.