[postgis-devel] Oracle SDO_GEOMETRY vs PostGIS WKT

[Jorge Arévalo]

On Wed, Aug 25, 2010 at 1:19 PM, Nicklas Avén
<nicklas.aven at jordogskog.no> wrote:
> Yes, that was a great link.
>
Sorry if the question sounds "silly", but as I understand it, both
extensions (PostGIS and Oracle Spatial) provide topological
operations, so, they both have topological models to define
relationships between objects. My point is I think Oracle uses a more
complicated way to define these objects (for example, a polygon).

I don't really think the reason is the Oracle's way is better for some
kind of operations (calculate intersections, or whatever), because I'm
talking about the way of representing data for the user, not the way
the data are stored.

This is, I find Oracle's "presentation" format much more complicated
than PostGIS one. Without any logic (for me) reason. They probably
have good reasons, related with their own object data model, for
example. Maybe it's a waste of time asking this kind of questions...
In that case, my apologies.

> Paul, do you have any thoughts to share about PostGIS and topology:
> http://opengeo.org/products/coredevelopment/postgis/topology/
>
> Olivier is also thinking about topological aspects of 3D as discussed some
> week ago.
>
> Jorge, do you have a link to that Oracle documentation? I think this an
> interesting topic too, but I know far to little about it.
>
Yes, sorry. I forgot it:
http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28399/toc.htm
(is for the version I'm using, 11gr1)

Jorge

> /Nicklas
>
>
>
> 2010-08-25 Jorge Arévalo wrote:
>
> Reply to myself: good link to read
> http://bgis.sanbi.org/gis-primer/page_22.htm
>>
>>Useful to avoid mixing concepts or missunderstandings.
>>
>>2010/8/25 Jorge Arévalo :
>>> Hi,
>>>
>>> On Wed, Aug 25, 2010 at 12:43 PM, Nicklas Avén
>>> wrote:
>>>> Hallo
>>>>
>>>>>
>>>>>Yep, like other companies developing propietary software. The point is
>>>>>I don't understand why using a mix of numbers and arrays whose
>>>>>elements index tables to simply represent a polygon. Saving storage
>>>>>space? I don't know. The PostGIS way, closer to OGC standard, is much
>>>>>easier, IMHO.
>>>>>
>>>>
>>>> I don't know what this Oracle representation looks like but from above
>>>> it
>>>> sounds like it might be about some topological model.
>>>> In PostGIS representation I guess it is difficult to describe two
>>>> neighbor
>>>> polygons without repeating the shared vertexes for both polygons?
>>>>
>>>> /Nicklas
>>>>
>>>
>>> Yes, Oracle Spatial's data model seems to be a topological model [1].
>>> Thanks for pointing me to that fact. As I said, I find it some
>>> tangled, and I'm looking for the reason. Or am I talking non-sense?
>>>
>>> Best regards,
>>> Jorge
>>>
>>>>
>>>>
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>>>
>>
>>
>>
>>--
>>Jorge Arévalo
>>DEIMOS Space
>>Internet & Mobilty Division
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>>28760 Tres Cantos (Madrid)
>>Tel: +34 91 806 34 50 - ext: 155
>>jorge.arevalo at deimos-space.com
>>http://gis4free.wordpress.com
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