<div dir="ltr"><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div>We have recently had some discussions on VO-DML in the context<br></div>the the STC2 model, that Mark suggested should be summarized to<br></div>the DM list to entice larger participation.<br><br></div>The current version of the STC2 model is now posted on:<br><a href="https://volute.g-vo.org/svn/trunk/projects/dm/vo-dml/models/STC2/2015-10-30/">https://volute.g-vo.org/svn/trunk/projects/dm/vo-dml/models/STC2/2015-10-30/</a><br></div>As reported yesterday, the following action items have been resolved:<br></div>- Transformations are done in atomic fashion, following the AST style<br></div>- Gerard has a scrippt that will process the XMI file<br></div>The following actions are in progress:<br></div>- Complete the enumerations of standard frames and standard positions<br></div><div> This is trivial and quick<br></div>- Complete the in-model documentation<br></div> Most description boxes in the documentation are still empty<br></div>- Investigate (and experiment with) defining specialized coordinates<br></div> through subsetting. A first attempt is contained in the Specialized<br> package; but it is not clear this is worthwhile.<br></div>The following items are still to be tackled<br></div>- Writing a WD<br> It probably makes more sense to draft that on the basis of completed<br></div> documentation (see above)<br></div>- Collaborating with whoever (if anyone) is working on the Units model<br></div> The issue is the mechanism to restrict units according to context;<br></div> STC2 includes such a mechanism, but this needs to be done in<br></div> consultation<br></div>- Generate a library from the processed model<br></div> The intent is that this be linked to the AST library for transformations<br></div>- Resolve remaining VO-DML issues<br><br><br></div>This last point is the second subject of this message.<br></div>There are two places where the STC2 VO-DML model runs into trouble.<br></div><br>One is a relatively trivial one. I would like to request that the VO-DML<br></div>WD include a section on the syntax of Constraints. It is hard to find<br></div>documentation on this (at least, I find it hard), and adding his would be<br></div>very helpful.<br><br></div>The other concerns the multiplicity of datatype attributes.<span style="font-size:24pt"><span style="color:rgb(15,111,198);font-family:"Wingdings 2";font-size:85%"><br></span></span><font size="2"><span style="font-family:arial,helvetica,sans-serif"><span style="color:black">Attributes
can only have a specific length, specified in the model;<br>i.e., an object cannot
contain a variable array of values.<br>STC2 runs into this in some places where that rule is uncomfortably<br>restrictive; for example:</span></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"><span><span style="color:rgb(0,157,217)"><br></span></span><span style="color:black">- A
polynomial object cannot contain an order and an array of coefficients,<br> its
length determined by the order</span></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"><span><span style="color:rgb(0,157,217)"><br></span></span><span style="color:black">- One
cannot leave the dimensionality of a value (1, 2, or 3) open</span></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"></span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif"><span><span style="color:rgb(0,157,217)"><br></span></span><span style="color:black">- The
coordinate values of an enumerated axis cannot be specified in a vector</span></span></font>
<br><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div>The way to get around this is to turn these items into objects/classes.<br></div><div>But that, in my view, unnecessarily complicates the model further, since<br></div><div>a simple array of data values suffices in these situations.<br></div><div>Dynamic sizing of arrays/vectors of data values at the time of instantiation<br></div><div>is, I think, a must.<br><br><br></div><div>This is a summary of the arguments I have made over the past few days;<br></div><div>I'll leave it to the other participants to voice their opinions.<br></div><div><div><div><div><div><div><div><div><div><div><div><div><br></div><div>Cheers,<br><br></div><div> - Arnold<br></div><div><br></div><div>PS: My access to internet connectivity will be spotty, at best, this coming week.<br></div><div><div><div><div><div><br clear="all"><div><div class="gmail_signature"><div dir="ltr">-------------------------------------------------------------------------------------------------------------<br>Arnold H. Rots Chandra X-ray Science Center<br>Smithsonian Astrophysical Observatory tel: +1 617 496 7701<br>60 Garden Street, MS 67 fax: +1 617 495 7356<br>Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a><br>USA <a href="http://hea-www.harvard.edu/~arots/" target="_blank">http://hea-www.harvard.edu/~arots/</a><br>--------------------------------------------------------------------------------------------------------------<br><br></div></div></div>
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