W3C Schools' XML tutorial makes several good points about the use of elements as opposed to attributes for data storage:
Some of the problems with using attributes are:
* attributes cannot contain multiple values (child elements can)
* attributes are not easily expandable (for future changes)
* attributes cannot describe structures (child elements can)
* attributes are more difficult to manipulate by program code
* attribute values are not easy to test against a Document Type Definition (DTD) - which is used to define the legal elements of an XML document
He/she also notes that using an ID attribute can be useful for differentiating between elements of the same type.
In short, "...metadata (data about data) should be stored as attributes, and that data itself should be stored as elements."
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Some handy links:
DTD (Document Type Definition) tutorialXML Schema tutorialXML validator
