Implementation of topology-network approach

[Pierre HARDY]

Hello Felipe,

I am highly interested in implementing such feature for an application in
hydraulics network modelling (check EPANET) some implementations of the
topology-network logic in postgis contrib packages would be nice to amswer
this need.

To answer your points:

1. I agree, but PgRouting does not provide editing functions, this is a
high limitation and make PgRouting not suitable for easy and reliable
topology edition from a desktop client such as QGIS  without implementing
some additional logic outside.

2. After reading the standard I agree with you, and suggest that ST_
function described by the standard must be implemented as a first step. In
a second step we should plan to combine them in more "smart"
functions/logic that can handle real user needs for edition from a desktop
client.

3. For a first implementation, a 2D support is sufficient to the
application I knows in water supply modelling.

Le mer. 20 nov. 2024, 02:24, Felipe Matas <felipematas at yahoo.com> a écrit :

> Ufff, I also wanted this time ago, and still want it! is just there is
> some things to take care.
>
> 1. PGRouting already has Topologies, they do not follow the SQL/MM
> standard, also do not have the functions for a user be able to use it
> 2. The standard is well defined, is just actually do not define anything
> else, functions that take advantage of a Network Topology to make them
> useful, would be great be able to at least list functions for that, the
> standard is like SF without any spatial operation.
> 3. Personally, I think in this case 2D Points are a very hard constrains,
> one very useful case for a Network Topology are roads, but in a lot of
> places int he world, to have a valid Network Topology you need 3D Points,
> this causes to one of the most useful uses would be impossible.
>
> From my perspective the ideal is have a Standard v2, and be implemented on
> PGRouting instead of Postgis.
>
> Thx!
>
> El martes, 19 de noviembre de 2024, 11:23:04 a. m. GMT-3, Pierre HARDY <
> pierre.hardy5 at gmail.com> escribió:
>
>
> Hello PostGIS devs,
>
> It seems that "postgis_topology" extension does not support
> topology-network approach.
> Here are my sources:
>
>    1. What is topology-network:
>    https://www.gaia-gis.it/fossil/libspatialite/wiki?name=topo-intro
>    2. Source no1 indicating that Postgis does not support
>    topology-network approach:
>    https://gis.stackexchange.com/questions/122636/prevent-postgis-topology-from-splitting-edges-on-line-insert
>    3. Source no2 indicating that Postgis does not support
>    topology-network approach:
>    https://terragis.net/docs/other/MASTERING_POSTGIS.pdf => p253
>
> "Before we start working with topology, we need to discuss the key
> concepts behind the PostGIS topological data model. PostGIS topology
> implementation is based on ISO standard 13249 - Information technology -
> Database languages - SQL multimedia and application packages - Part 3:
> Spatial. The standard name is often abbreviated as ISO SQL/MM. This
> standard defines two data models for topology: TopoGeometry and
> TopoNetwork; PostGIS implements only the former."
>
>
> I could verify this by testing on a basic local setup with QGIS and *Postgis
> version 3.3*.
> I guess this feature was not added since.
>
> I did not found any issues regarding this missing feature.
>
> Is an issue already openned to request this new feature or should I create
> one ?
>
> Best regards,
> --
> Pierre HARDY
>
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