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<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">Dear Serge,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">I think what you have proposed is fine. It is a more structured way to handle the distinctions between what is extended relative to TGFT itself and that which is not directly within
the purview of the TGFT.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">CSSM Colleagues,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">Does anyone have any further comments on this? I propose that we include review of the latest TGFT updates for the June 12 teleconference.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D">-Erik<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Georgia",serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"> Serge Lacourte <serge.lacourte@scalagent.com>
<br>
<b>Sent:</b> Thursday, May 24, 2018 1:30 AM<br>
<b>To:</b> Ciocirlan Claudia <Claudia.Ciocirlan@cnes.fr>; John Pietras <john.pietras@gst.com>; Barkley, Erik J (3970) <erik.j.barkley@jpl.nasa.gov>; CCSDS SMWG ML (smwg@mailman.ccsds.org) <smwg@mailman.ccsds.org><br>
<b>Subject:</b> Re: updated draft TGFT on CWE<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Dear WG members,<br>
<br>
thank you for adding me to the discussions about TGFT. As Claudia explained, I work on this subject on behalf of CNES.<br>
<br>
I want to comment on the item 2 of the mail of John.<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoListParagraph" style="text-indent:-.25in">2.<span style="font-size:7.0pt">
</span>The standard CCSDS XFDU provides two schema extension mechanisms as part of the<span style="font-family:"Courier New",serif"> environmentInfo</span> element of the
<span style="font-family:"Courier New",serif">packageHeaderType</span>: the<span style="font-family:"Courier New",serif"> xmlData</span> element containing unstructured XML, and the
<span style="font-family:"Courier New",serif">extension</span> element by which the XFDU schema can be extended through the use of an XML type. The TGFT XFDU formally specifies that the
<span style="font-family:"Courier New",serif">extension</span> element is the specified mechanism for extensions to the schema for the base TGFT service, and that such extensions must be done through the
<span style="font-family:"Courier New",serif">TgftXfduExtensionType</span> complex schema type. However, the TGFT XFDU specification does not forbid any user-application-specific use of the (unstructured)
<span style="font-family:"Courier New",serif">xmlData</span> elements. Claudia suggested that the
<span style="font-family:"Courier New",serif">xmlData</span> element be explicitly forbidden to be used in TGFT XFDUs.<br>
<br>
In Gaithersburg, we discussed the difference between what additional metadata might be standard for *<b>all</b>* TGFT XFDUs and metadata that a TGFT-using application might need to add to the XFDU for its own application-specific purposes. Examples of extension
metadata that is common to all TGFT XFDUs are<span style="font-family:"Courier New",serif"> originator</span>,
<span style="font-family:"Courier New",serif">recipient</span>, and <span style="font-family:"Courier New",serif">
creationDate</span>, where <span style="font-family:"Courier New",serif">originator</span> and
<span style="font-family:"Courier New",serif">recipient</span> are included in the
<span style="font-family:"Courier New",serif">TgftXfduExtensionType</span> complex schema type because they apply to the whole XFDU Package, and
<span style="font-family:"Courier New",serif">creationDate</span> is in the <span style="font-family:"Courier New",serif">
TgftContentUnitExtensionType</span> because it applies to each individual Content Unit (i.e., payload data file) within the XFDU Package.<br>
<br>
We agreed that (a) extension metadata that is common to all TGFT XFDUs (and thus part of the TGFT standard itself) must be contained in the
<span style="font-family:"Courier New",serif">TgftXfduExtensionType</span> or <span style="font-family:"Courier New",serif">
TgftContentUnitExtensionType</span> complex schema types, and (b) TGFT-using applications *<b>may</b>* use
<span style="font-family:"Courier New",serif">xmlData</span> elements for adding application-specific metadata that applies to the XFDU Package as a whole. I agreed to review the description of this distinction in the TGFT book and clarify it if necessary.
I have since looked at the relevant sections of the TGFT book and have concluded that it is indeed ambiguous and in need of clarification. As the result:<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.75in;text-indent:-.25in">a)<span style="font-size:7.0pt">
</span>I’ve reworded the text to state that the recommended extension mechanism for adding TGFT-using application-specific metadata that applies to the XFDU Package as a whole is through the addition of another
<span style="font-family:"Courier New",serif">environmentInfo</span> element containing an
<span style="font-family:"Courier New",serif">extension</span> element. <o:p></o:p></p>
<p class="MsoListParagraph" style="mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.75in;text-indent:-.25in">
b)<span style="font-size:7.0pt"> </span>I’ve added a NOTE that says that TGFT-using applications may also use
<span style="font-family:"Courier New",serif">xmlData</span> elements, but any such usage is outside the scope of TGFT and must be documented as part of the specification of the TGFT-using application.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:12.0pt"><span style="font-family:"Georgia",serif;color:#1F497D">eb> That sounds reasonable to me. I'd like to get Claudia's take on your note as obviously this does not explicitly forbid the
use of xmlData element. </span><o:p></o:p></p>
</blockquote>
<p>As far as I understand, the proposed modification explains the specification but does not change it.<o:p></o:p></p>
<p>I will try to explain the purpose of the original remark that led to this discussion.<o:p></o:p></p>
<p>The <span style="font-family:"Courier New",serif">environmentInfo</span> element provides effectively two schema extension mechanisms with the
<span style="font-family:"Courier New",serif">xmlData</span> element and the <span style="font-family:"Courier New",serif">
extension</span> element. More precisely a single <span style="font-family:"Courier New",serif">
environmentInfo</span> element may contain at most 1 <span style="font-family:"Courier New",serif">
extension</span> element and any number of <span style="font-family:"Courier New",serif">
xmlData</span> elements. The key point I want to discuss is the possibility to use both extension mechanisms in the same
<span style="font-family:"Courier New",serif">environmentInfo</span> element.<o:p></o:p></p>
<p>The TGFT specification requires and specializes an <span style="font-family:"Courier New",serif">
environmentInfo</span> element to describe generic TGFT metadata (section 4.2.5.6.1). To do this the "structured" extension mechanism has been chosen, and the specification requires the use of the
<span style="font-family:"Courier New",serif">extension</span> element. I would like to prevent the simultaneous usage of the "unstructured" extension mechanism in that specific
<span style="font-family:"Courier New",serif">environmentInfo</span> element. This could be expressed by the following:<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">4.2.5.6.1 One environmentInfo element shall contain one extension element for the TGFT XFDU extension parameters that are applicable to the XFDU Package as a whole.
<b><u>This element shall not contain any additional </u></b><b><u><span style="font-family:"Courier New",serif">xmlData</span></u></b><b><u> element.</u></b>
<o:p></o:p></p>
</blockquote>
<p class="MsoNormal">Of course this would not prevent any TGFT using service from using the
<span style="font-family:"Courier New",serif">xmlData</span> extension mechanisms, but this should be done in a separate environmentInfo element, not in the one dedicated to the generic TGFT metadata.<o:p></o:p></p>
<p>In order to help visualise the impact of the proposal, here is first what I would like to forbid in TGFT:<o:p></o:p></p>
<p>+ packageHeader<br>
|----+ environmentInfo<br>
|----|----+ extension<br>
|----|----|----+ tgftXfduExtension<br>
|----|----|----|---- originator<br>
|----|----|----|---- recipient<br>
|----|----+ xmlData<br>
|----|----|---- any xml data<o:p></o:p></p>
<p>And here is form that could be used to convey the same content:<o:p></o:p></p>
<p>+ packageHeader<br>
|----+ environmentInfo<br>
|----|----+ extension<br>
|----|----|----+ tgftXfduExtension<br>
|----|----|----|---- originator<br>
|----|----|----|---- recipient<br>
|----+ environmentInfo<br>
|----|----+ xmlData<br>
|----|----|---- any xml data<o:p></o:p></p>
<p>I hope this is more clear.<o:p></o:p></p>
<p>Best regards,<o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>Serge Lacourte<o:p></o:p></pre>
<pre>Directeur general<o:p></o:p></pre>
<pre>ScalAgent Distributed Technologies SA<o:p></o:p></pre>
<pre>tel. +33 4 76 29 79 81<o:p></o:p></pre>
<pre>mobile. +33 6 86 47 41 06<o:p></o:p></pre>
<pre><a href="http://www.scalagent.com">www.scalagent.com</a><o:p></o:p></pre>
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