RE: Re: dynamics: comment about MBdyn...

> From: Herman Bruyninckx [mailto:[email protected]]
> Subject: RE: [Orocos] Re: dynamics: comment about MBdyn...
> 
> 
> On Mon, 14 Jul 2003, Tiller, Michael (M.M.) wrote:
> 
> [...]
> > > Well, parsing is not really the big software hurdle... 

I happened to be cleaning out my inbox and upon seeing this statement again,
I realized another "perspective" issue here that might be a source of
confusion.

If you were storing your information in XML, then what you say is exactly
right.  Parsing is not really the big software hurdle.  In fact, with XML
and a couple of other formats, you can find tools that can already parse the
files.  And you are completely correct, this is a small step.

BUT, there is an important caveat that is called out in the article I
referenced before (specifically this section
http://www-106.ibm.com/developerworks/xml/library/x-sbxml.html?dwzone=xml#h2
0077).  The key thing is that "Syntax is not semantics".  Don't get me
wrong, XML is a very nice technology and I use it every chance I get.  But
it only covers the *SYNTAX*.  Modelica is much more than that.  Only a small
part of the specification covers syntax.  For example, "Chapter 2, Modelica
Syntax" is only 7 pages while the whole specification.  In contrast,
"Chapter 3, Modelica Semantics" is 64 pages and the entire specification
(which includes some stuff about standard meta-data and expected solution
methods), covers 107 pages.

One of the big problems I see with XML (and one that, for some reason, I
have a hard time getting across) is that everyone gets all excited saying
"Hey, now we have a common file format...hoorah!".  This is certainly
important, but it is just the first step.  The next step is to answer the
tough question you are faced with when you look at the file...what does this
stuff **mean**?  There is a considerable effort required to define meaning
and that is why I keep bringing up Modelica...because it defines not just
what the files should look like, but what they mean (i.e. their semantics).

> Herman 

--
Mike