About ID matching

XML has the concept of an id attribute whose value is unique throughout a document. For example, only one <alpha id="1"> can exist. However, ids are scoped by element type, so you can have elements <alpha id="1"> and <beta id="1">.

Such an attribute is said to be of type ID. Although you can assign the type ID to any attribute, the most common convention is to use the attribute name id. When ID matching is enabled, Rational® ClearCase® XML Diff Merge assumes that attributes named id or ID are of type ID.

The ability to match elements using id attributes enables XML Diff Merge to achieve powerful matching results. For example, <alpha id="1"> can be matched across versions even if:

For most documents (notably in record-oriented XML applications), ID matching has the following advantages:


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