Re: SDL-News: Gates and Block Substructure (fwd)

Subject: Re: SDL-News: Gates and Block Substructure (fwd)
From: Jose Marķa Parra Sageras (
Date: Tue Nov 15 2005 - 18:13:17 GMT

First of all, I want to thank Andreas Prinz for his quick answer.

---------- Forwarded message ----------
Date: Tue, 15 Nov 2005 08:25:50 +0100
From: Andreas Prinz <>
To: Jose Marķa Parra Sageras <>
Subject: Re: SDL-news: Gates and Block Substructure

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-----From Andreas Prinz <> to sdlnews -----

Dear Jose Marķa Parra Sageras,
you wrote:
>> I am developing a program (in SDL-92) that requires a substructure
>>inside the
>> definition of a Block Type. I have a doubt about the use of gates in
>> case.
>Please note that in general it is not recommended to use substructure any
>In SDL'2000 this concept is even deleted. It is far better to use the
>object-oriented constructs, e.g. inheritance and redefinition.

I know that with SDL'2000 this matters have been changed but the latest
SDL version supported by the tool I am currently using is SDL-96 so I
have no alternative.

>> In my particular programming context, there is a Block Type definition
>> only contents a block substructure. Inside the substructure there are
>> channels connecting some blocks with the substructure environment. I
>> defined the gates I need in the block type boundary (I cannot do this
>>in the
>> block substructure) and I have specified the name of the appropriate
>>gate in
>> the substructure boundary (as I am supposed to do) in order to connect
>> channel with the block type environment but it does not work.

>The basic idea behind substructure is that you have *two* definitions of
>same thing. This means, you write the first way to do the things using an
>ordinary block type (This one must not be empty!). Then you add a
>definition and put the other alternative in there.
>Please note that the substructure defines a static alternative. This
>means you
>have to decide which version to use when you simulate it.
>I suppose that you start simulation as is, which means your top-level
>is selected (the one with nothing in it). This again means that nothing

I agree with you that one idea behind substructures is that you have two
definitions of the same thing. However another option is a block type
specification containing only a block substructure specification.

>> Is that all correct or it is needed any other element? I have look some
>> but noone tell anything apart from what I am doing.

>So the first thing to do is to make sure that your spec makes sense even
>without the substructure. The substructure is then an alternative to
>this, and
>the spec should make sense when replacing the block type definition by

I see what you mean but taking into account my specs, I need to define a
group of blocks inside a block. I use a block substructure as a way to
achieve this. So I cannot specify anything at the top-level version of the
block type because it is not permmited defining a block in the upper level
block (in SDL-96). I have considered other implementations but there is no
way for them. I need at least three blocks defined inside a block.
Perhaps there are some other posibilities for obtaining my objetives but I
am not considering them.

>Please note that it is a matter of the tool how you select the version
>should be used for simulation. This is not defined within the language
>Best regards,
> Andreas

Andreas Prinz
--End text from Andreas Prinz <> to sdlnews ---
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Yours faithfully,

Jose M. Parra Sageras

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