document: The XML typechecking problem When an XML document conforms to a given type -LRB- e.g. a DTD or an XML schema type -RRB- it is called a valid document . Checking if a given XML document is valid is called the validation problem , and is typically performed by a parser -LRB- hence , validating parser -RRB- , more precisely it is performed right after parsing , by the same program module . In practice however , XML documents are often generated dynamically , by some program : checking whether all XML documents generated by the program are valid WRT a given type is called the typechecking problem . While a validation analyzes an XML document , a type checker analyzes a program , and the problem 's difficulty is a function of the language in which that program is expressed . The XML typechecking problem has been investigated recently and the XQuery Working Group adopted some of these techniques for typechecking XQuery . All these techniques , however , have limitations which need to be understood and further explored and investigated . We define the XML typechecking problem , and present current approaches to typechecking , discussing their limitations
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