Hausmann, Jan HendrikKüster, Jochen MalteSauer, StefanEvans, AndyFrance, Robert B.Moreira, Ana M. D.Rumpe, Bernhard2020-01-072020-01-0720013-88579-335-0https://dl.gi.de/handle/20.500.12116/30851Although UML sequence diagrams are widely used in practical software development, there is still a great demand for improvements. Their use both within and outside the standard interpretation of the UML specification is not seldom confused bacause different interpretations for sequence diagrams exist without menas to distinguish between them. Furthermore, alternative sequence diagram notations with more syntactical features and different semantics still have a big influence and are readily used (explicitl as well as implicitly (alongside UML's sequence diagrams. Without necessary clarification, the meaning of sequence diagrams remains vague. Hence they are not suited for providing a common understanding of inter-object behaviour which is a prerequisite for their deployment within rigorous software development processes. Additionally, model quliaty assurance by consistency checking and validation is not well supported. In this paper, we survey, structure, and classify syntactic and semantic alternatives that appear in sequence diagrams in practice. We thereby identify scope of interpretation, level of abstraction, composition and refinement, ordering, time, and represented function as the essential semantic dimensions of sequence diagrams. The spanned semantic space is suited as a basis for discussing and proposing extensions of UML sequence diagrams to precisely determine the semantic interpretation of modeled sequence diagrams.enUML sequence diagramssemantic spacesemantic variation pointssemantic dimensionsextensionssyntactic transformationsText/Conference Paper1617-5468