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<p class="MsoNormal"><span style="font-family:Calibri">Mark and all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">I think the R2 ruling proposal is interesting. By simply making arraysize=”1” illegal, we would:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:Calibri">Eliminate the complications of explaining that option in the spec or of interpreting it in clients.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:Calibri">Possibly be doing what was meant by the original spec anyway (“The arraysize attribute exists when the corresponding table cell contains more than one…”).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">As you say, it has the downside of not supporting 1-element arrays. I admit to feeling a certain appeal in the consistency and completeness of offering 1-element arrays (just as those are available in programming
languages), but I can’t think of a specific need, so I won’t push hard either way.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">I do think it’s important that with either R1 or R2, clients should not have to change. The erratum is just another input to consider when deciding their implementation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">As a side note, I agree that STIL/TOPCAT does do the sensible thing.
</span><span style="font-family:"Apple Color Emoji"">☺</span><span style="font-family:Calibri"> For astropy however, it’s worth noting that although it treats arraysize=”1” cases as “arrays”, those arrays offer flexibility within the astropy/numpy framework
that ends up treating the value as a scalar when one is needed.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">As a simple example, this output:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">One value is an array, the other is a scalar.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">f1 value = [1] (arraysize="1")<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">f2 value = 1 (scalar)<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">The array value is treated as a scalar when needed.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">f1val + f2val == 2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">Is generated by this code:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">from astropy.table import Table<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">import math<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">import io<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">vot = """<?xml version="1.0"?><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><VOTABLE version="1.3" xmlns="http://www.ivoa.net/xml/VOTable/v1.3"><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <RESOURCE><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <TABLE name="trap"><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <FIELD datatype="short" name="f1" arraysize="1"/><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <FIELD datatype="short" name="f2"/><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <DATA><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <TABLEDATA><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <TR><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <TD>1</TD><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> <TD>1</TD><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> </TR><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> </TABLEDATA><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> </DATA><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> </TABLE><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> </RESOURCE><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"></VOTABLE><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">"""<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">t = Table.read(io.BytesIO(bytes(vot, 'utf-8')))<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">for row in t:<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> f1val = row['f1']<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> f2val = row['f2']<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier">
<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> print('One value is an array, the other is a scalar.')<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> print('f1 value = {} (arraysize="1")'.format(f1val))<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> print('f2 value = {} (scalar)'.format(f2val))<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> print('\nThe array value is treated as a scalar when needed.')<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> if (f1val + f2val == 2):<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:10.0pt;font-family:Courier"> print('f1val + f2val == 2')<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Courier"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">I expect that the main problems come up in cases where it’s not clear a scalar is expected, such as re-serialization for sharing with other consumers.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri">Tom<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Calibri"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-family:Calibri;color:black">From:
</span></b><span style="font-family:Calibri;color:black"><apps-bounces@ivoa.net> on behalf of Mark Taylor <m.b.taylor@bristol.ac.uk><br>
<b>Date: </b>Thursday, February 15, 2018 at 5:36 AM<br>
<b>To: </b>Applications WG <apps@ivoa.net><br>
<b>Subject: </b>Re: Proposed erratum to clarify arraysize="1"<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Tom, Markus, others,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">On Mon, 12 Feb 2018, Tom Donaldson wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<blockquote style="border:none;border-left:solid #B5C4DF 4.5pt;padding:0in 0in 0in 4.0pt;margin-left:3.75pt;margin-right:0in" id="MAC_OUTLOOK_ATTRIBUTION_BLOCKQUOTE">
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<p class="MsoNormal" style="margin-left:.5in">Since this is an erratum, I was thinking in terms of putting the wording<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">there that we would have put in the original if we had realized the lack<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">of clarity. In that frame of mind, the use of “must” makes sense.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">That is what the spec should have said. (I do see this as a clarification<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">rather than a change. Section 4.1 does already say, “The arraysize<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">attribute exists when the corresponding table cell contains more than<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">one…”. )<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Yes well that does make me think. That spec text which you quote<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">implies, though it does not explicitly state, that the use of<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">arraysize="1" is simply incorrect.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Given that, behaviour on encountering that construction is unspecified,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">so VOTable consumers should either refuse to process such elements<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">(not very helpful) or if not, should do the most sensible thing.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">As the erratum points out, "it is not likely that the provider meant<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">for the values to be interpreted as an array.", so what current<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">client software ought to do is to treat arraysize="1" as a scalar.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">The Erratum currently says:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> "Clients that interpret arraysize="1" exclusively as a single scalar<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> value should consider interpreting those values as arrays of size 1,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> since that's what compliant services intend."<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">But, as I (and the Erratum) have said above, it's also most likely<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">the *opposite* of what pre-Erratum services intend.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">[Attentive readers will have spotted that in my argument above<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">I'm characteristing STIL/TOPCAT behaviour as "doing the sensible<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">thing", and Astropy as ... well, not that. (If anybody familiar<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">with other VOTable software can report what that does in such<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">circumstances, it would be interesting to hear.) Obviously, I'm not<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">a disinterested observer in this, so if anybody wants to shoot this<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">down, please fire away.]<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">So I'm still not convinced that this erratum looks like a clarification<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">rather than a new decision about what VOTable ought to have said<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">in the first place. So much for the legal philosophy.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">But in practical terms, the Erratum is saying:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> R1:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> - if arraysize="1" is present, it means a 1-element array<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> - don't write arraysize="1" unless you mean a 1-element array<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Given that ruling:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 1a) VOTable producers should reconsider whether they really mean<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> arraysize="1"<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 1b) VOTable validators should present a warning for arraysize="1"<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> that producers may or may not need to do something about<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 1c) Astropy-like clients can carry on unchanged<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 1d) STIL-like clients should go from treating arraysize="1" as a scalar<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> to treating it like an array (but may wish to exercise flexibility)<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">As I've said in an earlier message, I'm not going to make the change (1d)<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">any time soon, at least in the default configuration of TOPCAT/STILTS,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">because it's likely to break stuff.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">An alternative possibility would be:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> R2:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> - arraysize="1" is illegal<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> - don't write arraysize="1", ever<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">(note this does not correspond to any of the options in Markus's<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">final "What do we do?" slide from<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><a href="http://wiki.ivoa.net/internal/IVOA/InterOpOct2017Apps/arraysize-slides.pdf">http://wiki.ivoa.net/internal/IVOA/InterOpOct2017Apps/arraysize-slides.pdf</a>)<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Given that ruling:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 2a) VOTable producers should stop writing arraysize="1"<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 2b) VOTable validators should present an unambiguous error message<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> for arraysize="1"<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> 2c) Astropy-like and STIL-like clients can carry on unchanged<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Thus (2c) clients can continue to implement unspecified but plausible<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">behaviour for arraysize="1", but behavioural differences will<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">disappear as (2a) services stop emitting ambiguous VOTables.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">I am therefore wondering if the Erratum should say R2 rather than R1.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">The prescription is simpler, and the implementation is less disruptive.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">The downside of R2 is that there is then no way to specify a<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">1-element array. Question: is that a problem? Does anybody<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">actually need to communicate 1-element arrays as distinct from scalars?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">As I pointed out earlier in this thread, FITS BINTABLE has got away<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">with that situation since its invention.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Mark<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">--<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Mark Taylor Astronomical Programmer Physics, Bristol University, UK<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><a href="mailto:m.b.taylor@bris.ac.uk">m.b.taylor@bris.ac.uk</a> +44-117-9288776 <a href="http://www.star.bris.ac.uk/~mbt/">http://www.star.bris.ac.uk/~mbt/</a><o:p></o:p></p>
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