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[udig-devel] Local File Format
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One of the things our recent MoF project has highlighted to me is
that as we start adding serious geoprocessing abilities to uDig we
are not going to be able to dodge the need for a local file format to
hold intermediate results. The MoF project was lucky in that Shape
format was not too constraining, and there was really only no
intermediate file anyways.
We have sort of initially drifted towards the idea of using a beefed
up version of the existing hsql datastore, adding some spatial
indexing ability. I want to put another, better (harder!) option on
the table.
How about using Spatial Data Format (SDF)?
What is SDF? It is the "native" format that the new Autodesk
Mapguide Open Source uses.
Why would we want to use it? Let me count the ways:
- There is already support for SDF being added to OGR and FME, so
people who create SDF files in uDig can translate them easily to
other formats using tools other than uDig. This will not be true if
we roll our own on hsql.
- The whole Autodesk product line has support for SDF, so even
AutoCAD will be able to open uDig files.
- The SDF format lives behind an abstraction called FDO (Feature Data
Objects). If we can read/write from SDF via FDO, we can read/write
from all the other FDO formats too. Because OGR is getting an SDO
bridge, this also provides us a route into all the OGR formats as
well. (From an implementation PoV, this also gives us two routes to
choose from: implement an OGR datastore and get to SDF via OGR's FDO
support; implement an FDO datastore and do the reverse.)
I think the "network effects" argument for doing SDF (and FDO) is
very compelling.
Why not use it? I guess the problem of doing more C++ wrapping is
part of it. And ignoring an hsql datastore that is 80% done hurts too.
Another option would be to use the new ESRI Geodatabase format, which
does not use Access any more. That format is not fully baked yet
though, and I do not think it is an open one. In general though, I
am becoming enthralled with the idea of using, not inventing, a local
format.
P
