Re: [SystemSafety] Modelling and coding guidelines: "Unambiguous Graphical Representation"

From: Mike Ellims < >
Date: Fri, 26 Feb 2016 11:54:36 -0000


>> Except that semantics of MathLab/Simulink is very fragile, e.g. order >> of execution of state machines on a diagram depends on the order they were drawn.

> Yep.

You can get around this issue by explicitly defining the execution order by assigning block priorities, but you have to know to do it.

-----Original Message-----
From: systemsafety
[mailto:systemsafety-bounces_at_xxxxxx Peter Bernard Ladkin
Sent: 26 February 2016 11:35
To: systemsafety_at_xxxxxx Subject: Re: [SystemSafety] Modelling and coding guidelines: "Unambiguous Graphical Representation"

On 2016-02-26 10:33 , David MENTRE wrote:
> Le 26/02/2016 09:43, Peter Bernard Ladkin a écrit :

>> Another reason is the prevelance of MathLab/Simulink in this domain. 
>> Simulink is now an executable specification language. Since there is 
>> one supplier, it is de facto unambiguous (there is just one 
>> simulator, so the single meaning of a Simulink spec is precisely what
that simulator does with the spec).
>
> Some people have even formally defined the semantics of Simulink or a
subset of it:

I think what this says is that some people have interpreted in a formal way what they think Simulink diagrams should ideally mean. Whether they do mean that or not is another question.

It's laudable, but it's a long way from what "formally defined the semantics of Simulink" would mean to practicing engineers. That would further entail that (a) one of those semantics had been independently assessed as adequate, (b) MathWorks had accepted it, and (c) MathWorks had demonstrated that their simulator (the execution engine for Simulink) conformed to the semantics.

> Except that semantics of MathLab/Simulink is very fragile, e.g. order
> of execution of state machines on a diagram depends on the order they were
drawn.

Yep.

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Je suis Charlie Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de

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