A stream-based mathematical model for distributed information processing   systems - SysLab system model
  In the SysLab project we develop a software engineering method based on a mathematical foundation. The SysLab system model serves as an abstract mathematical model for information systems and their components. It is used to formalize the semantics of all used description techniques such as object diagrams state automata sequence charts or data-flow diagrams. Based on the requirements for such a reference model, we define the system model including its different views and their relationships. 
Cornel Klein, Bernhard Rumpe, Manfred Broy
cs.SE