An STC "when" and "where" example

[Roy Williams]

Arnold

I have stripped out some of your data to leave only what is below. It just a postion, 
and has RA and Dec in ICRS coordinate system. Please can you tell me if this is a 
valid STC document? If so, it would seem quite easy to parse. If not, what are the 
other parts that must be in it?

Roy
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Specifically I removed:
-- Observatory location, I assume this defaults to the center of the Earth.
-- Time of observation, I assume this defaults to 1/1/2000.
-- I changed coord_system_id="ICRS-TT-WAVELENGTH-TOPO" to be just "ICRS", is that OK?
-- Error on the position, I assume it defaults to zero error.
-- Wavelength information, please can you explain why this is in with the space-time 
coordinate systems?

And here is the minimal document to say RA=148.88821, Dec=69.06529:

<?xml version="1.0" encoding="UTF-8"?>
<ObsDataLocation
xmlns="http://www.ivoa.net/xml/STC/stc-v1.20.xsd"
xmlns:crd="http://www.ivoa.net/xml/STC/STCcoords/v1.20"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    <ObservationLocation ID="TaxTimeEvent">
        <crd:AstroCoords coord_system_id="ICRS">
            <crd:Position2D unit="deg">
                <crd:Name>RA,Dec</crd:Name>
                <crd:Value2>148.88821 69.06529</crd:Value2>
            </crd:Position2D>
        </crd:AstroCoords>
    </ObservationLocation>
</ObsDataLocation>