<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div>Mark,</div>
<div><br></div><div><br></div><div>Thank you for the meeting notes.</div><div><br></div><div>I would just comment on the following point:</div><div><br><blockquote type="cite"><div>On 20 Feb 2025, at 15:31, CresitelloDittmar, Mark via dm <dm@ivoa.net> wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> o [MCD] restatement of concern..</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> EpochPosition is a 2nd mode of representing content which can be done</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> with the Measurement types. This is generally considered bad practice.</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> I would be MUCH happier with the object if it were associated with </font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> GAIA data, more than the "Epoch Propagation" use case. i.e. that it</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> is an object which supports the very complex GAIA (or GAIA-like) data</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> which the Measurements model is currently unable to support.</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> That would give providers/clients a more clear picture of WHEN to use</font></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><font face="monospace"> this Object over the PhysicalProperty representation.</font></div><br class="Apple-interchange-newline"></div></blockquote></div><br><div>- There is no doubt that the EpochPosition class complies with the GAIA use-case.</div><div>But describing the position of stars in a 6D space is a physical reality that we need to model with something describing these vectors and the way their coordinates can be correlated.</div><div>For this reason, I do not think we should rename the class “EpochPosition” as “GAIAsomething” (if this is what you propose) .</div><div>PROPOSAL : make the link with GAIA very explicit in the class description as well the reason why it is flatten.</div><div><br></div><div>- I agree with you that having to different ways to model the same quantity is not desirable, but the fact is that one property (EpochPropagation) encloses the other (meas:LonLatPosition), thus, the use-cases overlap. </div><div> Faced with this situation, I reaffirm that importing one model from another is done first by sharing the same description for the same quantities, which is done for EpochPosition vs Meas:*, and that making these imports machine-operable comes as an extra-feature which may cost a lot. Therefore, it is wise to keep EpochPropagation as a MANGO native (complicated) class and meas:LonLatPosition as an imported one.</div><div>PROPOSAL: recommend to use meas:LonLatPosition for simple positions (but the model cannot enforce such a rule).</div><div><br></div><div>Laurent</div></body></html>