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R: [udig-devel] Discussion about UDIG functionality and some prop osals
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Title: Discussion about UDIG functionality and some proposals
It
seems to me that this post should go more to the GeoTools mailing list than the
uDig one.
topology aware set of tools for editing, etc.
Paul
On Oct 5, 2005, at 10:04 AM, Jesse Eichar wrote:
> I'm afraid I dont have too many comments on this. Mainly I think
> the normal feature model should be used and either a special
> topology edit mode should be activated, at which time the TDM is
> created or there is an operation to create a TDM from a layer. I
> understand value of having a TDM for editing.
>
> Jesse
>
> Vitali Diatchkov wrote:
>
>
>> Hi!
>>
>> Continuing the discussion about Topology Data Model for vector
>> data inside
>> of UDIG.
>>
>> The following editing tools are common for every GIS system (in
>> terms of
>> feature geometry):
>> -Divide polygon
>> -Merge two adjacent polygons
>> -Cut piece of one polygon and add it to adjacent in case this
>> piece
>> is touches common border
>> -Delete polygon
>> -Move common border for adjacent polygons
>>
>> These operations should be considerable in context of topology
>> consistence
>> between different geometries.
>>
>> TDM can be built from simple feature model. It is quite expensive
>> operation
>> but it should be performed once, just build TDM. TDM will give
>> benefits
>> during next editing operations while it is much more easier to
>> deal with TDM
>> directly then each time perform validation of topology consistence
>> after
>> each atomic operation. The back building of simple feature model
>> from TDM is
>> quite straightforward operation, just traverse graph in a special
>> manner.
>>
>> We have the following "frameworks" :
>>
>> Com.vividsolutions.jts.geomgraph
>> Com.vividsolutions.jts.planargraph
>> Org.geotools.graph
>>
>> Models of those frameworks differ in terms of various involved
>> entities and
>> operations.
>> In most cases for counted editing operations needed TDM is more
>> simple and
>> Oracle Topology Data Model is the most appropriate as an example what
>> editing tools need. I suppose so, Oracle TDM is not overloaded by
>> different
>> additional constructions and objects. While feature model may be
>> huge, the
>> performance of building TDM, memory issues, etc. are important. As
>> simple
>> TDM we have and editing operations are satisfied with it so much
>> the better.
>>
>> The important issue.
>> Topology data model doesn't replace simple feature model. It
>> serves as an
>> auxiliary model for performing various complex editing operations
>> maintaining topology consistence automatically. We edit TDM and
>> reflect
>> local changes to simple feature model.
>>
>>
>
>
>> Different application requirements suppose various TDM. Having one
>> complete
>> TDM sometimes is often redundant and make influence on performance
>> where
>> just small piece of functionality is needed.
>>
>> In this proposal I consider TDM as an auxiliary model to make
>> editing of
>> vector data easier and more powerful. And TDM is used directly during
>> editing step. There are two cases:
>> -Perform any editing operations without just-in-time validation.
>> Validation of topology consistence is checked during transaction
>> committing, for example in the end.
>> -Perform editing operations over TDM directly and it maintains
>> topology consistence automatically. Validation in the end is
>> optional
>> while TDM guarantees consistence after each atomic operation.
>>
>> I choose the second case.
>>
>> What is about Luca Sigfrido Percich suggests in
>> http://docs.codehaus.org/display/GEOTOOLS/Meta+Information
>> +Infrastruct
>> and how to apply that MII to topology validation, it would be
>> quite powerful
>> framework for unified topology validation described declaratively
>> by "meta
>> information" (see attachment file).
>>
>> I talk about topology in terms of auxiliary data structure to
>> facilitate
>> editing operations.
>>
>> Any suggestions, comments, questions to find the golden mean.
>>
>>
>>
>> Vitali Diatchkov.
>>
>> ---------------------------------------------------------------------
>> ---
>>
>> _______________________________________________
>> User-friendly Desktop Internet GIS (uDig)
>> http://udig.refractions.net
>> http://lists.refractions.net/mailman/listinfo/udig-devel
>>
>>
>
> _______________________________________________
> User-friendly Desktop Internet GIS (uDig)
> http://udig.refractions.net
> http://lists.refractions.net/mailman/listinfo/udig-devel
>
