To combine the rules with the parts of the document/information set, a method must be choosen to formulate this dependency. E.g. to define that all <short-name> beneath the element <sw-variable> must not be longer than 31 characters we first have to adress these elements in a way that a program can select it:
Therefore the xpath-Recommondation of the w3c offers the right language: //sw-variable/short-name .
These expressions - the adressing of the elements - will be placed in <DCI-XPATH>
But up to now, it is still no possible, to express structural constraints like:
if the document has the maturity level "approved", the signature element is necessary.
Therfore the element <DCI-OCCURENCE> is able to formulate such an expression.
First, the xpath-Statment select the neccessary part of the document. Then, it will be looked, whether other elements have a defined occurence (in the example above - the signature element must occur 1 time.