<div dir="ltr"><div>A time stamp is a specification on a particular time instance instance within a given space-time frame<br></div>This can be represented as a Julian Date or Modified Julian Date (in which case its primitive is a real) or as a datetime primitive which is to be implemented as a calendar-based string.<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="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>
<br><div class="gmail_quote">On Tue, Apr 18, 2017 at 11:53 AM, Gerard Lemson <span dir="ltr"><<a href="mailto:gerard.lemson@gmail.com" target="_blank">gerard.lemson@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Arnold<div><br></div><div><br></div><div><br></div><div><br><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Tue, Apr 18, 2017 at 11:33 AM, Arnold Rots <span dir="ltr"><<a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Oh, and proleptic Gregorian. See section 3 of the WCS paper.<br></div><div class="gmail_extra"><br clear="all"><div><div class="m_3105801468246703495gmail-m_-7040136663337435096gmail_signature"><div dir="ltr">------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>-------------------<br>Arnold H. Rots <wbr> Chandra X-ray Science Center<br>Smithsonian Astrophysical Observatory tel: <a href="tel:(617)%20496-7701" value="+16174967701" target="_blank">+1 617 496 7701</a><br>60 Garden Street, MS 67 fax: <a href="tel:(617)%20495-7356" value="+16174957356" target="_blank">+1 617 495 7356</a><br>Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a><br>USA <wbr> <a href="http://hea-www.harvard.edu/~arots/" target="_blank">http://hea-www.harvard.edu/~ar<wbr>ots/</a><br>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>--------------------<br><br></div></div></div>
<br><div class="gmail_quote">On Tue, Apr 18, 2017 at 11:27 AM, Arnold Rots <span dir="ltr"><<a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><div><div>The datetime string (subset of ISO-8601, as defined in FITS WCS paper VI) is specified as:<br><br></div>[+|-C]CCYY-MM-DD[Thh:mm:ss[.s.<wbr>..]]<br><br></div>'T' is a literal, the other letters stand for single digits with obvious meaning.<br><br></div> - Arnold<br><div><div><br><br></div></div></div><div class="gmail_extra"><br clear="all"></div></blockquote></div></div></blockquote><div><br></div></span><div><div>This still seems to be a definition in terms of a serialization that in the VO-DML base types I would like to avoid.</div><div>Just like we do not want to be bothered by how an ivoa:real is represented (ASCII-decimal, IEEE standard floating point, whatever).</div><div><br></div><div>I don't know what the best description of this serialization-independent concept would be.</div><div>Would something like "the 0 component of some observer's four vector identifying an event in 4-d space-time" be correct?</div><div><br></div><div>Cheers</div><span class="HOEnZb"><font color="#888888"><div>Gerard</div></font></span></div><div><div class="h5"><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="gmail_extra"><div><div class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065gmail_signature"><div dir="ltr">------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>-------------------<br>Arnold H. Rots <wbr> Chandra X-ray Science Center<br>Smithsonian Astrophysical Observatory tel: <a href="tel:(617)%20496-7701" value="+16174967701" target="_blank">+1 617 496 7701</a><br>60 Garden Street, MS 67 fax: <a href="tel:(617)%20495-7356" value="+16174957356" target="_blank">+1 617 495 7356</a><br>Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a><br>USA <wbr> <a href="http://hea-www.harvard.edu/~arots/" target="_blank">http://hea-www.harvard.edu/~ar<wbr>ots/</a><br>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>--------------------<br><br></div></div></div><div><div class="m_3105801468246703495gmail-m_-7040136663337435096h5">
<br><div class="gmail_quote">On Tue, Apr 18, 2017 at 11:07 AM, Gerard Lemson <span dir="ltr"><<a href="mailto:gerard.lemson@gmail.com" target="_blank">gerard.lemson@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi Mark<br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 17, 2017 at 11:51 AM, CresitelloDittmar, Mark <span dir="ltr"><<a href="mailto:mdittmar@cfa.harvard.edu" target="_blank">mdittmar@cfa.harvard.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote"><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><div dir="ltr"><div class="gmail_extra"><p class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-m_5555787170495511556gmail-MsoPlainText">...</p><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><span style="color:black"></span></div></div></blockquote><span>I don't think this needs to be complicated, so let's put these on the back burner.<br></span></div><div class="gmail_quote"><div><br></div></div></div></div></blockquote><div>Thanks! </div><span><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div></div><br>>> * Quantity and datetime would not have a
common ancestor, so we could<span></span><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span> not define
a TimeStamp<span></span><br>>> which would allow time represented as a
RealQuantity OR datetime.<span></span><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><div class="gmail_extra">>> <a href="https://volute.g-vo.org/svn/trunk/projects/dm/STC-2.0/doc/diagrams/alt/temporal%20domain%20diagram.png" target="_blank"><span style="color:windowtext;text-decoration-line:none">https://volute.g-vo.org/<wbr>svn/trunk/projects/dm/STC-<span></span></span></a><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><a href="https://volute.g-vo.org/svn/trunk/projects/dm/STC-2.0/doc/diagrams/alt/temporal%20domain%20diagram.png" target="_blank"><span style="color:windowtext;text-decoration-line:none"> 2.0/doc/diagrams/alt/temporal%<wbr>20domain%20diagram.png</span></a><span></span><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><br>>> <span></span><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><span style="color:black"> </span><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-m_8131231324588115954gmail-"></span><br><br>>So are you saying you'd like a DatetimeQuantity? With only a "datetime unit" being sufficient?<br>>I had hoped 'ivoa:datetime' would be sufficient and the precise representation would be left to the mapping.<br><br></div>This sounds like you are suggesting that 'ivoa:datetime' should suffice for all uses.<br></div> MJDREF = 50814.02 / [d] zero point for times - MJD<br><div class="gmail_quote"> TSTART = 84244214.<a href="tel:(754)%20697-9934" value="+17546979934" target="_blank">7546979934</a> / [s] Observation start time<br> DATE-OBS= "2000-09-02T01:10:14" / Date and time of observation start<br><br></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">I want all of these to be a TimeStamp type (abstract).<br></div><div class="gmail_extra"> * datetime = has vodml/html description: "Represents a moment in time using a date+timestamp."<br>which covers 'DATE-OBS', the other 2 are satisfied by RealQuantity.<br><br></div><div class="gmail_extra">But.. since RealQuantity and datetime do not have a common ancestor, I cannot define TimeStamp without either an anyType or a DateQuantity.<span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-HOEnZb"><font color="#888888"><br></font></span></div><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-HOEnZb"><font color="#888888"><div class="gmail_quote"><br></div></font></span></div></div></blockquote><div><br></div></span><div>Yes, that is correct, but I see now (I think) what might cause confusion, namely the description of ivoa:datetime in the model as</div><div>"Represents a moment in time using a date+timestamp". What was meant there is that it is not just a day/date (2017-04-18), and not just a time ("13:00:01.3"), but the fully specified moment in time. <br></div><div>In the current description it does indeed sound as if date and time must be represented, i.e. too much like a prescription for valid serializations. This was NOT intended.</div><div>ivoa:datetime is supposed to represent the concept of a Timestamp as you mention it, and it should be up to serialization prescriptions to take care of valid representations.</div><div> </div><div>So if that interpretation is given to ivoa:datetime, would that type be sufficient for your requirements?</div><div><br></div><div>Cheers</div><div>Gerard</div><div><br></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><span class="m_3105801468246703495gmail-m_-7040136663337435096m_-2145722271534925065m_2019370339920083806gmail-HOEnZb"><font color="#888888"><div class="gmail_quote"></div><div class="gmail_quote">Mark<br><br></div><div class="gmail_quote"><div class="gmail_extra"><br></div></div></font></span></div></div>
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