Patent ID: 7363312

Claim:
A computer program product within a computer readable medium for combining first and second attribute sets, each comprising at least one attribute and value pair comprising a named attribute assigned a value that comprises one of a first value and another attribute set in addition to the first and second attribute sets; the computer program product comprising: instructions arranged to control the operation of a computing apparatus running the program product to cause the apparatus to carry out a merge operation to generate a merged attribute set by applying to the first and second attribute sets, as items-to-be-merged, a merge operator by which: where at least one of the items-to-be-merged is a said first value, the value of the merged items is the value of one of the items-to-be-merged; and where both first and second attribute sets, as items-to-be-merged, are attribute sets, the value of the merged items comprises: the attribute and value pairs of attributes that occur in only one of the items-to-be-merged, and attribute and value pairs for attributes occurring in both items-to-be-merged with the value of each such pair being the value resulting from the application of the merge operator to the values of the attribute appearing in each item-to-be-merged, the merge operator being recursively applied as required to merge the attribute values.