What does TOP mean ?

[Petr Skoda]

Dear all

during teaching VO at several universities last several weeks I have got 
and interesting question to which I cannot find answer ....

What does mean TOP in ADQL mean and how the TOP is implemented in various 
SSAP services ?


In ADQL (ver 2.0) is said only that TOP returns n records

while In SSAP 1.1 is written in 4.1.2.15 that TOP returns n TOP RANKING 
records using some score function ....

"
  Metrics such as distance from the specified position, or the degree of 
overlap with a specified bandpass or time interval, determine the score.
"

just trying randomly ADQL over TAP in Topcat to SDSS8 in Eddinburg 
it seems that TOP  on PhotoPrimaryAll where psfMag_g < 6 tries to oreder 
by the psfMag and then limit ....

But it may be just my subjective feeling .....


And does anybody implemented TOP in scoring manner in SSAP ?

Best regrads,

Petr

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*  Petr Skoda                         Phone : +420-323-649201, ext. 361 *
*  Stellar Department                         +420-323-620361           *
*  Astronomical Institute AS CR       Fax   : +420-323-620250           *
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*  Czech Republic                                                       *
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