Bulldozer00's Blog

The Systems Modeling Language, SysML, is both an extension and a subset of the UML. SysML defines a “frame” that serves as the context for a given diagram’s content. As the diagram below shows, each frame contains a header compartment that houses 4 text elements which characterize the diagram. The two items in brackets are optional.

While learning the SysML, I was often confused as to the order of the header items and their meanings. My first thought when I saw the frame header was; “why are there so many freakin’ header entries; why not just one or two?”. I still get confused, but after studying a bunch of sample diagrams from  System Engineering With SysML/UML: Modeling, Analysis, Design and A Practical Guide to SysMLThe Systems Modeling Language, I think that I have almost figured it out.

With the aid of the two previously mentioned references, I constructed the table below. There are 9 enumerated SysML diagrams, so understanding what the “diagram kind” header field means is trivial.  It’s the optional “model element” header item that continues to confuse me. As you can see from the table, the types of “model element(s)” that can appear within the first 6 diagrams are fixed and finite. However, the last three are open ended.

The problem for me is determining what the set of all “model element types” is. Is it a finite set of enumerations like the “diagram kind” header entry, or is it free form and ad-hoc? Does anyone know what the answer is?