<div dir="ltr">Hi Walter,<div>taking freely from latest TAP PR (work in progress), but the concepts</div><div>remain the same as the ones in TAP-1.0:</div><div><br></div><div>==</div><div><div>The principal, indexed, and std columns are boolean values implemented</div><div>as integers. As such, the value must be 0 or 1; no other values are allowed.</div><div><br></div><div>The principal flag indicates that the column is considered a core part</div><div>of the content; clients can use this hint to make the principal column(s)</div><div>visible, for example by selecting them by default in generating an ADQL</div><div>query. In cases where the service selects the columns to return (such as a</div><div>query language without an explicit output selection), the principal column</div><div>indicates those columns that are returned by default.</div><div class="gmail_extra">==</div><div class="gmail_extra"><br></div><div class="gmail_extra">So, there's no intention, I think, to make it map VERB or trying to set</div><div class="gmail_extra">up a set of levels of principal, it's simply a flag to declare a column as</div><div class="gmail_extra">a special one among others.</div><div class="gmail_extra"><br></div><div class="gmail_extra">Cheers,</div><div class="gmail_extra"> Marco</div><div class="gmail_extra"><br><div class="gmail_quote">2017-10-10 0:32 GMT+02:00 Walter Landry <span dir="ltr"><<a href="mailto:wlandry@caltech.edu" target="_blank">wlandry@caltech.edu</a>></span>:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Everyone,<br>
<br>
In the current TAP PR, TAP_SCHEMA.columns.principal is an integer. Is<br>
the intention to make that map to the same meaning as SCS's VERB? It<br>
seems that the meaning is somewhat inverted. So<br>
<br>
SCS VERB TAP principal<br>
1 2<br>
2 1<br>
3 0<br>
<br>
If that is the case, should the meaning (and perhaps the actual<br>
mapping) be put into the TAP PR? To be concrete, the wording could be<br>
<br>
The "principal" number indicates the importance of a column. Clients<br>
can use this hint to make some columns visible, for example by<br>
selecting them by default in generating an ADQL query. A value of<br>
'2' is for columns that the provider considers a bare minimum that<br>
are useful in describing the returned objects. A value of '1' is<br>
for columns that may be generally useful, but not always necessary.<br>
A value of '0' is for columns that are probably only of use to<br>
specialized audiences. These values correspond to VERB levels 1, 2,<br>
and 3 in Simple Cone Search (Plante & Molinaro et al 2017).<br>
<br>
Thanks,<br>
Walter Landry<br>
</blockquote></div><br></div></div></div>