[postgis-users] PostgreSQL/PostGIS and ArcGIS Server 9.3

[Paolo Corti]

Hello Paul

it is not only a question of versioning, ArcSde - together with ArcObjects -
make possible to use the Geodatabase model in any RDBMS supported by ArcSde.

The pro of this is having a lot of out of the box functionalities, like
domains, referential integrity, relationship class, networks, topology,
constraint on data, etc... 
Customizations will be consistent whatever RDBMS you choose, so won't be
hard to switch from SQL Server to Oracle for example, or vice versa. You
will need just to transfer the data from one platform to the other (from
ArcCatalog or by the command line) without the need to rewrite triggers,
constraints, functions....

But if you are using the Geodatabase model, you are then - as you are saying
- highly tied to ArcObjects (and so to ArcMap), that meaning that you will
need to exclusively rely on Esri clients for editing and even viewing data
if you want to enjoy some of the out of the box stuff (like relationship
classes). If you just need an OGC simple feature viewer then you can read
the data without problems.
And is not only a question of making it very difficult to read and write
arcsde data from other applications, is even almost impossible to use the
RDBMS features (trigger, functions, procedures, constraints, etc...) without
compromising the database. The only way to put some intelligence in the data
is then demanded only to COM ArcObjects, from the application or by
deploying dlls that will interact with the data streamed from the database.
For example if in a PostGis table you write a trigger that after any insert
will copy in the table a value from another table under some spatial
operator criteria (for example copy a value from a polygon in which a point
is contained), and this is relatively simple - and powerful, no need for
cursors here - to make with Spatial SQL, with Geodatabase (and ArcSde) you
would need to write an ArcObjects dll and deploy that at any client. This is
even a problematic solutions, because you will have a deployment issue.

Paolo


Paul Ramsey-3 wrote:
> 
> SDE allows you to use ArcMap as a client. That's the main value
> proposition.
> 
> Secondarily, there's some stuff, most particularly versioning, that
> they implement by managing extra metadata in side tables.  This is
> where your concern regarding 3rd party edits to PostGIS data come to
> reality. If you start mucking with the data, particularly versioned
> data, outside the SDE environment, you can put it into an inconsistent
> state.
> 
> Also, you need some knowledge of the SDE scheme in order to properly
> *read* the information out of a versioned system with a 3rd party
> tool, since the data in the tables will include shapes from multiple
> versions.
> 
> In general, if you restrict yourself ot reading with 3rd party tools
> and writing with ESRI tools, or non-ESRI tools working through the SDE
> API, you should be safe.
> 
> Yes, using SDE effectively castrates the spatial database. It still
> walks and talks, but it's a shell of the man it was before.
> 
> P.
> 
> 

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