Patent ID: 7437662

Claim:
A method of representing versions of data entities, the method comprising the computer-implemented steps of: performing a determination of a delta between a first data entity that conforms to an extensible mark-up language and a second data entity that conforms to the extensible mark-up language; generating based on said determination a body of instructions that prescribes operations for transforming said first data entity into said second data entity; wherein said body of instructions represents the delta between said first data entity and said second data entity; wherein the body of instructions conforms to an extensible style language transformation language; wherein the delta reflects one or more changes that have been made to said first data entity to obtain said second data entity; creating an unmaterialized version of said second data entity, wherein creating the unmaterialized version comprises persistently storing said body of instructions in association with said first data entity; wherein creating the unmaterialized version of said second data entity does not comprise persistently storing a copy of said second data entity; wherein the unmaterialized version of said second data entity is a version for which there is no copy that is necessarily persistently stored, and wherein the unmaterialized version of said second data entity is associated with a delta representation that represents the delta between the unmaterialized version and another version; wherein the unmaterialized version of said second data entity incorporates the one or more changes through said body of instructions that represents the delta; wherein said body of instructions, when applied to said first data entity, generates the copy of the unmaterialized version of said second data entity.