<div dir="ltr"><div><div><div><div><div>No, it's not global, but applied to the datasets that satisfy the query.<br></div>Though instrument and exposure time do not change, the off-axis<br></div>parameter does. In the case of a cone search, for instance, it is<br></div>the angle between the center of the cone and the direction of the<br></div>optical axis.<br><br></div> - Arnold<br></div><div class="gmail_extra"><br clear="all"><div><div class="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 Mon, Apr 27, 2015 at 11:03 AM, Markus Demleitner <span dir="ltr"><<a href="mailto:msdemlei@ari.uni-heidelberg.de" target="_blank">msdemlei@ari.uni-heidelberg.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Arnold,<br>
<span class=""><br>
On Mon, Apr 27, 2015 at 09:43:46AM -0400, Arnold Rots wrote:<br>
> Yes, you need an observatory-specific model to calculate a score.<br>
> By its very nature, therefore, it will only be a relative score.<br>
> Example:<br>
> For Chandra we implemented a score that is based on instrument, exposure<br>
> time, and off-axis angle<br>
> (PSF degrades with increasing off-axis angle).<br>
<br>
</span>Well, yes, that could be part of it, but the way I understand<br>
things --<br>
<br>
[...] the general idea is that the better a candidate dataset<br>
matches the query, the higher the score it receives. (1.1, P.27)<br>
<br>
-- TOP's intended function is essentially like Google's ranking: it<br>
gives "how well" a given returned row matches a data set. Hence, for<br>
a given dataset score would be different for different queries, and<br>
while a global quality measure might play a role, it certainly<br>
wouldn't be expected to dominate the response. Or am I completely<br>
off here?<br>
<br>
And regarding Walter's interjection:<br>
<span class=""><br>
> I thought that the difference between MAXREC and TOP is that MAXREC<br>
> requires an overflow indicator, while TOP would prohibit it.<br>
<br>
</span>Interesting thought -- is it intended to work this way? [it doesn't<br>
in DaCHS, and a quick search in the 1.1 specs didn't give me anything<br>
pointing in that direction]<br>
<br>
Cheers,<br>
<br>
Markus<br>
<br>
</blockquote></div><br></div>