Kuryazov, DilshodbekPlödereder, E.Grunske, L.Schneider, E.Ull, D.2017-07-262017-07-262014978-3-88579-626-8Software models evolve over time undergoing various changes and resulting in several versions during their lifetime. Models are differentiated during the evolution process and the differences between subsequent model versions are represented in differences documents for further analysis and manipulations as history information. Software models have rich data structures which differ from the code of software systems. That is why, a representation approach for the model differences has to provide effective handling and management of difference information. Furthermore, the model differences represented in the differences documents have to be easy to access and reuse. This paper introduces the Delta Operations Language (DOL), a meta-model independent and operation-based approach to model difference representations. The approach represents the model differences in terms of DOL and provides several DOL Services to access and reuse the DOL-based differences for further analysis and manipulations. To explain ideas behind the approach, it is applied to UML activity diagrams as a running example.enText/Conference Paper1617-5468