Models are the primary development artifacts in model-driven software engineering making model change management crucial for developers. In our work, we investigate if semantic differencing improves the developers' understandings of differences between model versions. Current research in this field focuses on pure syntactic differences between models which might not reveal the impact of the syntactic change to the real world. Thus, the semantic difference of models is an open field to investigate. We propose differencing operators for model comparison for four different modeling languages (Class Diagrams, Activity Diagrams, Statecharts and Feature Diagrams). This technical report describes the main fundamentals of the semantic differencing operators for the four modeling languages and the results of a pre-study on the usefulness of the differencing operators for software engineers. In the study, we were asking how well aspects such as syntactic differences, semantic differences, a combination of syntactic and semantic differences, and the abstraction as well as the summarization of semantic differences helped to understand the differences between shown models in each of the four modeling languages. The pre-study has shown that a combination of the syntactic and semantic difference is the most suitable alternative to providing intuitive explanations that take semantic differences into consideration. However, a larger study with real-size models is needed for obtaining more meaningful results.