Suggestion: include more discussion on the Xmatch syntax logic.

[mtaghiza]

After reading the docs:Query section, I was missing some more discussion on the logic of the Xmatch syntax. For example, a new user might ask why there are 3 parameters given for ERROR, but only 2 that define a POINT (which are ra and dec).

Is there a comprehensive document that lists the specifications and all capabilities of the new syntax?

I downloaded both papers mentioned in the docs:Info section:

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6475925
http://arxiv.org/pdf/1206.5021v1.pdf

but only one query is shown, and has a somewhat different syntax as that shown in the docs:Query section.
By the way, It would be nice for the user to have direct download links to those papers shown in both sections.
thanks.

EDIT: just realized that the syntax changed and that the User's guide will be updated with an explanation of the new grammar.