I'm with Rob.  Any (good) XML parser automatically counts the number of
subelements of a particular type and returns that number when requested
(e.g. getLength() in Xerces-C used by Janus) or allows you to iterate
through the list without (e.g. "for i in vars:" in various XML modules
in Python).  The dimensions attribute would only add redundancy that
isn't helpful if it is correct and causes errors if it is wrong (or
maybe just confusion: if "dimensions" is 3 and there are only two <dim>
elements, should the third dimension be assumed to be length 1?).

I do agree that <dim> and not dim1, etc. is the way to go.

An alternative that makes it look a little closer (in style) to how
<breakpointRefs>/<bpRef> is used in <griddedTableDef> would be

<variableDef name="myDataMatrixr_m" varID="myDataMatrix" units="m">

Although I don't know if that really adds anything useful.

Again, the parser will easily know the number of <dim> elements, so it
will easily figure out whether it is a scalar or a vector/array.  Note
that the parser already has to count such things in the
<breakpointRefs>/<bpRef> system.

Of course the real fun of the vector/array will be the mux/demux,
subreferencing, and MathML connections.  Examples:

1) Can an initialValue of an array be one or more previously defined
variables? (scalars, vectors or arrays)

2) Can elements of an array be referenced by scalar variables?

   array:  eulerAngle_d(3)
   scalars: rollEulerAngle_d, pitchEulerAngle_d, yawEulerAngle_d

3) Just for fun: 0-based (C) or 1-based (Fortran) indices?

Dennis J. Linse, Aerospace Engineer
Science Applications International Corporation
+1-703-294-4449  <mailto:[EMAIL PROTECTED]> 
-----Original Message-----
[mailto:[EMAIL PROTECTED] On Behalf Of Bruce Jackson
Sent: Thursday, March 13, 2008 8:17 AM
To: Curtin, Robert (Contractor)
Cc: Aerospace Sim Standard discussion group
Subject: Re: arrayDef & draft simstd comments 


I need to find some time to review your wonderfully rich suggestions  
in depth, but I had a rationale for adding a "dimensions" attribute:  
without it, a parser will have to count the number of <dim> elements  
to determine how many dimensions are required. Plus, it serves as a  
check to make sure the two counts match.

Also, I am trying to avoid names like dim1, dim2, dim3, etc... This  
implies a parser would be limited in how many dimensions it is  
required to look for (up to dim199?).

Good catch on the naming for the initialValue - it does need to be  
consistent with the current element definition. And it may be a good  
idea to reuse variableDef in place of a new arrayDef element. In this  
case, the presence of a "dimensions" attribute (with a value other  
than 1) would clue the parser that the variable is not scalar.

I'm passing the comments about coordinate frames along to Bruce  
Hildreth for his consideration, and I expect we'll be getting back to  
you; I think you have some very valid points from the perspective of  
an implementer.

Thanks again, and enjoy your Fall (as we are enjoying Spring),

-- Bruce

On Mar 12, 2008, at 6:40 PM, Curtin, Robert (Contractor) wrote:

> Hi Bruce,
> You suggestion looks good. The "dimensions" attribute would be
> unnecessary, as it's defined by the number of <dim> elements, in the
> same way that a gridded table's dimensional size is specified by the
> number of <independentVarRef> (and also <bpRef>) elements.
> I'd keep <initialValue> singular to avoid confusion. I'd also carry
> across the optional "axisSystem" attribute, for use with arrays that
> define cartesian vectors/tensors. In fact, could we do all this using
> the existing <variableDef> element, by adding the appropriate
> subelements & rules?
> Cheers, Rob
> Rob Curtin
> QinetiQ Consulting
> on contract to Air Vehicles Division,
> Defence Science & Technology Organisation
> Tel: +61 (0)3 9626 7730
> -----Original Message-----
> From: Bruce Jackson [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, 12 March 2008 11:20 PM
> To: Brian, Geoff
> Cc: Aerospace Sim Standard discussion group
> Subject: Re: Matrix and Vector definitions for DaveML
> Geoff,
> This is a needed improvement to DAVE-ML.
> My first thought is the arrayDef attribute should be something like
> 'dimensions="3"' and then a (set) of subelements that define the  
> actual
> dimensions:
>    <arrayDef name="myDataMatrixr_m" varID="myDataMatrix" units="m"
> dimensions="3">
>      <dim>2</dim>
>      <dim>6</dim>
>      <dim>3</dim>
>      <description>My Data Matrix is a 2x6x3 matrix; the last dimension
> changes most rapidly</description>
>      <initialValues>
>         111 112 113  <!-- the actual order is important, not the  
> way the
> data is formatted -->
>         121 122 123
>         131 132 133
>         141 142 143
>         151 152 153
>         161 162 163
>         <!-- second plane shows another valid way of listing a 6x3
> matrix -->
>         211 212 213 221 222 223 231 232 233 241 242 243 251 252
>           253     261   262       263  <!-- whitespace is unimportant
> -->
>      </initialValues>
>    </arrayDef>

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