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<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2>1) Table _catalog menat to hold the database name, but in
most cases postgis just leaves that blank since there is a geometry_columns
table per database. I'm not quite sure if the specs require that be filled
in though. In theory it should since the standard ANSI SQL
information_schema tables require it filled in.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2>2) Well as you may have noticed - Postgis doesn't follow
the MM Part 3 spec yet as for as these meta tables are concerned e.g. they don't
start with ST_ yet and geometry_columns is a physical table. I haven't
taken that close a look at the specs to see if they really</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2>require SRS_Name be the primary key. Are you sure
that is the case. Most systems I know of based on my limited understanding key
off of the SRS_SRID.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2>Having the SRS_NAME be unique however doesn't seem like a
bad idea since it would prevent equivalent spatial reference systems from having
2 different identities.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=740283110-09072008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=740283110-09072008></SPAN><FONT face=Arial><FONT
color=#0000ff><FONT size=2>Hope that helps,</FONT></FONT></FONT></DIV>
<DIV><FONT><FONT color=#0000ff><FONT size=2><SPAN
class=740283110-09072008></SPAN></FONT></FONT></FONT><SPAN
class=740283110-09072008></SPAN><FONT face=Arial><FONT color=#0000ff><FONT
size=2>R<SPAN
class=740283110-09072008>egina</SPAN></FONT></FONT></FONT><BR></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <B>On Behalf Of
</B>zhangmb<BR><B>Sent:</B> Wednesday, July 09, 2008 5:44 AM<BR><B>To:</B>
postgis-users@postgis.refractions.net<BR><B>Subject:</B> [postgis-users]
questions about geometry_columns base table!<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV><FONT size=2>
<DIV><FONT size=2>Hello,I have some questions about SQL/MM part
3:spatial.</FONT></DIV>
<DIV><FONT size=2>1. In the definition of st_geometry_columns base table, what
is the meaning of the TABLE_CATALOG and what it should store exactly? what is
the meaning of the unqualified schema name and the qualified
identifier?</FONT></DIV>
<DIV><FONT size=2>2. In the definition of st_spatial_reference_systems base
table, why using SRS_NAME as primary key as opposed to using
SRS_SRID?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Thanks a lot!</FONT></DIV>
<DIV> </DIV>
<DIV>--zhangmb</DIV></FONT></DIV></BODY></HTML>
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