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RE: Where are XML types ?

• To: "'Philippe Poulard'" <Philippe.Poulard@s...>,"'XML Developers List'" <xml-dev@l...>
• Subject: RE: Where are XML types ?
• From: "Michael Kay" <mike@s...>
• Date: Thu, 6 Jan 2005 15:15:56 -0000
• In-reply-to: <41DD450A.10607@s...>
• Thread-index: AcTz+N0YnLBVnLRXR62IyxMm4u0xxAACHTpw

> 
> Where are XML types ?
> People know xs:string, xs:int and xs:QName, because they are 
> taken from 
> raw data, but is there high level types for XML items such as 
> xml:element, xml:attribute, or xml:namespace ?
> I have to name (with a QName) objects (that can be XML items) 
> as if they 
> were types.
> I really really don't think that XPath2 offers a reasonable 
> solution with :
> "5 instance of xs:integer"
> ". instance of element()"
> the last one frightened me :(

If you can come up with a better solution, please do.

XML schema defines types for the *contents* of elements and attributes: when
you say that a particular node is an integer, what you really mean is that
the content of the node is an integer. This is probably the confusion that
makes it difficult to get to grips with the XPath type system. There are
actually two overlapping sets of types: the types of the nodes, and the
types of the contents of the nodes. This is why XPath uses different
notations for the two cases: element(), text(), comment() for the nodes, and
xs:integer, my:purchase-order, and so on for their contents. Then it allows
you to combine the two: element(*,my:purchase-order) is an element
containing a purchase order, and attribute(*, xs:integer) is an attribute
containing an integer.

It takes a bit of getting used to, but it works.

Michael Kay
http://www.saxonica.com/ 

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