SDL-News: Object-orientation in SDL

Subject: SDL-News: Object-orientation in SDL
From: Glenn Lewis (
Date: Thu Dec 03 1998 - 04:43:27 GMT

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-----From Glenn Lewis <> to sdlnews -----


I am interested in object-orientation in formal methods. I wonder if anyone
can tell me of papers/reports etc assesing the object-oriented features of

I am rather new to SDL (I have only done some introductory reading), but
what I understand of how OO is supported in SDL is below. I would
appreciate any answers/corrections/comments etc and or confirmation that I
have got it right (...I am particularly unsure of the final sentence ...)

Instead of classes SDL speaks of types. The types can be instantiated and
refernces are used, but there is a one-one relation between references and
instances (i.e. you don't have the general references between objects as in
an OO language). SDL supports a form of single inheritance, where it is
possible to replace or redefine components but this is limited, for example
you can only replace a transition that is declared to be virtual (does this
mean that once such a transition is refined, it cannot be further refined?
is it only possible to redefine virtual components of processes?). There is
no way to guarantee that the behaviour of the subtype is consistent with
the behaviour of the supertype, i.e. there is no concept of behavioural
inheritance or subtyping of some other OO languages (has this ever been
addressed or is it just left up to the specifier?).


-----End text from Glenn Lewis <> to sdlnews -----
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