[Gdal-dev] Enabling PAM By Default

[Matt Wilkie]

+1, if non-developer can vote :)

As a matter of fact, just last night I was pondering for the Nth time if 
I had the wherewithal to compose a feature request for a persistent 
metadata feature be *added* to gdal. I had no idea there was something 
already there along these lines.

Most of the classGDALPamDataset page is over my head, so I don't know 
whether my particular interest is already in there or not. I'll 
elaborate a bit: one of most useful parts of the ArcGIS metadata for me 
on a consistent basis the "Process Lineage" section; exerpt below. If 
this is accomodated by PAM, I'm all for it! If not, well, it still 
sounds like a good idea. :-)

-matt

--------------
Lineage
ESRI geoprocessing history
1. Create Feature Class
Date and time: 20061119 at time 182019
Tool location: C:\Program Files\ArcGIS\ArcToolbox\Toolboxes\Data 
Management Tools.tbx\CreateFeatureclass

Command issued
CreateFeatureclass Z:\Source\PGDB\Admin250k.mdb Protected_Areas # 
region_Layer SAME_AS_TEMPLATE SAME_AS_TEMPLATE 
"PROJCS['NAD_1983_Albers',GEOGCS['GCS_North_American_1983',DATUM['D_North_American_1983',SPHEROID['GRS_1980',6378137.0,298.257222101]],PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]],PROJECTION['Albers'],PARAMETER['False_Easting',500000.0],PARAMETER['False_Northing',500000.0],PARAMETER['Central_Meridian',-132.5],PARAMETER['Standard_Parallel_1',61.66666666666666],PARAMETER['Standard_Parallel_2',68.0],PARAMETER['Latitude_Of_Origin',59.0],UNIT['Meter',1.0]];-7283252.12921423 
-6530535.15945454 139.611574189393;0 100000;0 100000" # 0 0 0 
Z:\Source\PGDB\Admin250k.mdb\Protected_Areas


2. Append
Date and time: 20061119 at time 182020
Tool location: C:\Program Files\ArcGIS\ArcToolbox\Toolboxes\Data 
Management Tools.tbx\Append

Command issued
Append region_Layer Z:\Source\PGDB\Admin250k.mdb\Protected_Areas TEST 
Z:\Source\PGDB\Admin250k.mdb\Protected_Areas


3. FeatureClassToFeatureClass_9
Date and time: 20061119 at time 182020
Tool location: C:\Program Files\ArcGIS\ArcToolbox\Toolboxes\Conversion 
Tools.tbx\FeatureClassToFeatureClass

Command issued
FeatureClassToFeatureClass 
Z:\Source\Cover\250k\boundary\qpark\region.qpark 
Z:\Source\PGDB\Admin250k.mdb Protected_Areas # "AREA AREA 
HIDDEN;PERIMETER PERIMETER HIDDEN;QPARK# QPARK_ HIDDEN;QPARK-ID QPARK_ID 
HIDDEN;PK_ID PK_ID HIDDEN;NAME NAME VISIBLE;TYPE TYPE VISIBLE" 
SAME_AS_TEMPLATE SAME_AS_TEMPLATE # 0 
Z:\Source\PGDB\Admin250k.mdb\Protected_Areas
--------------






Frank Warmerdam wrote:
> 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,


-- 
matt wilkie
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