[Gdal-dev] Enabling PAM By Default

[Frank Warmerdam]

Folks,

A mechanism called PAM (Persistent Auxilary Metadata) was engineered into
GDAL around the 1.3.0 timeframe I think.  This is essentially a mechanism
to store georeferencing, metadata, statistics and other auxilary data
in an XML file associated with a dataset for formats that don't support
the information internally.  The XML file has the extension .aux.xml.

Currently this mechanism is only enabled if the GDAL_PAM_ENABLED
configuration option (ie. env. variable) is YES.  Thus, by default we
have not been using it most of the time.  It is enabled by default in
ArcGIS and I sometimes run with it enabled.

I would like to move to having PAM turned on by default during our
development cycle and to have a build option indicating whether it is
enabled or disabled.  Shortly before 1.5 release we should be able to
make a final decision on whether we want it enabled in the 1.5.0
release depending on whether we find it is causing many problems.

My longer term goal is to have it on all the time except when explicitly
turned off - that is to have it as a default behavior.  Mainly I want this
because it is hard to be sure it is working properly when it is rarely
used except in the ArcGIS environment.  But I also think it is a valuable
facility and could be a benefit to most GDAL users if more was known about
it, and it was generally available.

Does anyone have an objection to my turning it on now, and us having a
formal motion on whether it should be enabled shortly before the 1.5
release?  Some rather brief information on PAM is available at:

   http://www.gdal.org/classGDALPamDataset.html

BTW, I have confirmed that the autotest suite runs clean (at least on linux)
with PAM enabled.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org