MITAB library

[Daniel Morissette]

Carlo Bertelli wrote:
> 
> what about fitting mitab instead of shapelib into MapServer? Could it be
> feasible. For Mapinfo users this would be extremely beneficial. What do
> you think about this issue?
> 

Carlo,

(I'll CC: my response to the MapServer list since other
MapInfo users might be interested.)

First of all, I would like to say that I can appreciate the fact that
MapInfo users would be extremely interested in using MapServer if they
could use it to serve their data directly.

Adding support for OGR in the MapServer would automatically provide
support for MapInfo TAB files.  There would be no gain in replacing the
shapefile support in MapServer by MITAB only.  Mind you, access to
MapInfo TAB files would still be quite efficient even going through OGR
since MapInfo files are quite well organized for random access.

The loss in performance that I talked about was due to the fact that OGR
uses a set of generic C++ classes defined to accomodate most formats
(while respecting the OGC Simple Feature specs), and as a consequence of
that, stuff like creating objects in memory for every feature that you
read for instance will never be as efficient as a direct C API optimized
for a specific format like shapelib.  And since MITAB is built on the
OGR object model anyways, accessing it directly will not require less
development effort nor provide much better performance than going
through OGR and support several other formats by the same way.

However, there is one thing that would have to be done in MapServer to
make MapInfo users really happy: the way MapServer works today, it could
not really take advantage of the symbology stored in a MapInfo file
(i.e. colors, line width, patterns, etc.).  So something would probably
have to be done to allow MapServer to use symbology information attached
to the data when it is available.  As part of OGR, I have started work
on specs for a generic way to carry symbology information between
formats.  So eventually the optional OGR extension for MapServer could
use that information as an alternative to defining CLASSes in the MAP
file.  How this would work exactly in MapServer is still undefined and
would have to be discussed with Steve though.

These are all very cool ideas that I would love to pursue but I have
only so much time in my hands... so I can tell you today that it is 99%
sure that MapServer will support OGR (and thus TAB files) before the end
of the summer because we have to do it for one of our clients.  On the
other hand, other changes in MapServer to take advantage of the
symbology coming from formats like MapInfo TAB will probably stay on the
ToDo list it becomes a priority for one of our clients... or if I find
the time to do it on a rainy weekend.  :-)

Best Regards,
-- 
------------------------------------------------------------
 Daniel Morissette                       danmo at videotron.ca
              http://pages.infinit.net/danmo/
------------------------------------------------------------
  Don't put for tomorrow what you can do today, because if 
      you enjoy it today you can do it again tomorrow.