Slide 3 of 14
Notes:
There was a significant update to SDL in 1992 by the addition of type
constructs for an object oriented version of SDL. It is perhaps natural
that much of input for this version came from Norway (the home of
Simula) through Birger Møller-Pedersen and Øystein Haugen (then at NCC,
Oslo). It took time for tools and users to catch-up with this
innovation, so the changes in 1996 were minor and were made by an
addendum to the 1992 standard.
1992 saw the introduction of MSC as a separate standard.
Previously they had been an auxiliary notation used with SDL. Ekkart
Rudolph of Siemens proposed MSC as a standard in 1989 and became
rapporteur for the work. Major 1996 additions were “road map” HMSCs and
in-line expressions.
As noted above, SDL (or SDL-like) notations have been in use
in the telecommunications industry throughout the life of SDL as a
standard. Things changed significantly around 1984, as the first tools
were being introduced. Tools forced both users and the designers of SDL
to be more formal. This required more work, but the benefits were the
identification of errors and the ability to animate models, so that
“what if” questions could be answered.
Uptake of tools was initially slow even within the industry,
because using the graphical tools was slow and expensive. Since 1984
computer graphics has become common, prices have fallen and speed has
risen significantly. The situation today is that SDL tools have high
functionality, and a proven track record. The SDL tool market expanded
significantly in the 1996-2000 period.
The market has also changed, because it has become practical
to use SDL for generating implementations (more or less) directly. SDL
tools can generate programming languages (usually C/C++) directly from
SDL and these can be linked with a run time system to make products.
The generated C++ is treated as an intermediate language in much the
same way as compilers treat assembly language. Of course, SDL can still
be used in an abstract way with informal text, so that SDL is a
broad-spectrum language that can be used from requirements capture to
implementation.
These latest trends have pushed SDL-2000 in two directions:
linking with object modelling (in particular UML), and improving its
use for implementation. Examples of modelling changes are the
introduction of interfaces and the unified agent concept for blocks,
processes and services. Examples if the changes for implementation are
a major revision of the data model, exception handling, and the
introduction of textual algorithms to be used on diagrams.
MSC-2000 was updated to include a general data mechanism, time intervals, more object orientation and method calls.
