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[udig-devel] Re: clem 
Hi Rob,
Long time no see. If you are in Melbourne sometime it would be good to catch up for a coffee. Or if you want to save on hotel bills I have a spare room in St Kilda if you are willing to slum it :-) 

Rob Atkinson wrote:

Hi John,
(again? - I think we discussed this a while back on OpenSDI, no?)

I'd forgotten about that.  Some good links too.  Taa.


Hi again Bryce
You guys are touching some spaces where there is some existing work, and ongoing work that I suspect needs your input :-)
As you know I am a big fan of the ISO/OGC standards effort. However 19109/19110 seems a bit clunky. Is that just me? What is the best way to get involved?
There is detailed discussion of the state of play in terms of formal methods to model features in UML at 

https://www.seegrid.csiro.au/twiki/bin/view/AppSchemas/WebHome
There are a number of threads where we aim to develop and promote improved experience and power of the tools: 

Under way:
1) Support for a common, formal, mechanism to allow simplified views (typically GML Level 0,1 profiles) and legacy views against a shared conceptual model 2) Eclipse plugin for the "UGAS" (aka ShapeChange) UML -> GML schema automation tool (using ISO 19118 rules) 
Looks good
3) Modularisation of the modelling framework to allow external models and schemas to be effectively imported 

In research and planning:
4) geoserver WCS / geotools coverage /FM branch convergence
5) Supporting the Observations and Measurements patterns with easy configuration capabilities
FYI I have been pouring UML models using O&M and ISO base packages into the Geoserver "complex-features" branch for a while, and am waiting for FM to come home so that I can start to exercise and debug it.
Can you please be more specific? http://svn.codehaus.org/geoserver/branches/complex-features/???
We'd be most interested to share thoughts about the relationships between coverages and FM, since Bryce has probably looked much deeper into this than anyone else.
When I say "we" - there is a group of people who include key players in the OGC and ISO specs world, and one sponsor of some effort in the UK Met Office, who faces the task of creating sensible data standards and appropriate tools to handle them for the meteorology domain. So, UK MO will be the gatekeepers for my effort in the short term, but they have significant internal capability and project partners with resources willing to look into these matters.
Specifically, we want a Geoserver capability able to support coverages via WFS and WCS, and also the general feature model - time-series, objects with multiple geometries. I'd have thought a sensible, comprehensive, test case would be the ability to create a function that intersected a locus (3D trajectory) with a 4-D coverage and created a profile, and was able to serve profile this as an XML encoded GML feature or a binary-encoded "coverage" format. This function doesnt need to be defined or managed at run-time - it can be plugged in as code if necessary, but the feature model has to allow passing the input locus as a feature into the function, and the serialisation of the result as GML or a binary object.
I take it you are not talking here about profiles in the sense of the UML extension mechanism?
At the very least, we'd appreciate it if you could identify the functionality you are targetting, and propose some test cases that can be used to test whether anything we plan is going to break what you need, or if what you are doing is going to serve our needs in the short term.
Depends what you mean by short term. I'm not going to get a chance to do much work on this before December unless someone funds me for a day's work per week so I can give up my boatbuilding job!
PS - I also want to get my head around this to fulfil expectations of my role on the Geoserver Project Steering Committee :-) Help me help you!
NB The ShapeChange tool currents reads XMI, and it would take a bit of effort to make it read directly from an in-memory model, and the UML plug-ins for Eclipse didnt look worth the effort yet. Adam Flaherty at the UK Met Office has looked deeper into this and may be able to provide more explicit insight into the issues here. 
Which version of Eclipse and the UML plugins did you look at?


Nevertheless, this is not such an issue since:
a) any modelling tool ought to be able to serialise the model into XMI for management, transfer and archiving b) GML schema is a lossy serialisation - the model will contain more information than can be expressed unambiguously in GML/XML schema c) UML -> XMI -> GML is not that onerous and could be automated within Eclipse I'd have thought
The big issues informing models are how to modularise them. I strongly suggest you look at the HollowWorld template provide at the website above. 
That looks very similar to what I was thinking of.
If you dont want to buy Enterprise Architect then it should be possible to use ArgoUML or some other tool - and it would be a useful contribution to test this out. 


Regards

Rob Atkinson


John Reid <sdiowl@xxxxxxxxxxxx> wrote on 07/25/2006 09:02:18 AM:



> Guess I should start by introducing myself properly  :-)   My name's
> John Reid.


Welcome aboard!



> > Hmmm... a _graphical_ modeling tool, or an Ecore adapter?



> Bryce, you nailed it.  From a quick initial read of docs I think
> I'll need both.  My initial idea was to:
> 1. Define a UML profile for geographic features
> 2. Use a (possibly customized) heavy-weight UML 2.0 graphical
> modeling tool to do the hard work. I'm currently looking at Visual UML 
> 3. Use XMI and UML 2.0 Diagram Interchange files for native model
> persistence and publishing
> 4. Provide adapters to read/write ISO compliant XML schemas


I'm getting lost in terminology.  This happens to me a lot.   :)
1] My understanding is that the UML encoding of Geographic features was
handed to us from on high in 19109, Clause 8 (I think).  Are you talking
about drawing out the required UML (e.g. '107, '108, '111, '112, '115...)
in a specific UML tool?  Or are you talking about something else when you
say a "profile"?  Perhaps drawing out a particular subset of '107, etc.

2&3 ] Bravo!

4] ? Which ISO compliant XML schemas?  GML 3.2.0 / ISO 19139?
Beware of the GT/GeoAPI Feature Model. You may get some data which is not 
strictly ISO compliant (making it difficult to encode it in an ISO
compliant way.)  Jody insisted on allowing for non-OGC non-ISO features
merely because customers generate all manner of garbage XML and he's afraid 
to call them wrong.   :)   Due to much whining on my part, they made
allowances for people who play by the rules, but I think this is optional. 
It has been a while since I looked at the Feature Model.  I suggest you
examine it to ensure that you can extract an appropriate guarantee that
feature schema you receive will be encode-able...Pay particular attention
to duplicate feature attributes. Jody, can you direct this fine young man 
to the ISO subset of the feature model?

Also beware of GML.  Making an XML schema seems to invite people to
disregard all else. The XML Schema for GML permits more than is allowed by 
the text of the GML standard, and also more than is allowed by the data
model GML is supposed to represent.  People will argue that anything that
validates against the schema should be considered "legal" even if it
conflicts with the text of the GML standard or the model that GML encodes. 
You're going to have to defend your #4 from incorrect allegations of it
being broken and resist the temptation to break your codec for everyone
just because someone has produced or needs to receive data which is broken 
in a specific way.  Down that road lies madness.

Not that I have any strong feelings on the issue.  :)  Nope not me.



> I had hoped that a direct mapping could be established between a UML
> profile and ISO 19109, however I'm now unsure if this is possible.
> At least not with the "natural" way to use UML profiles...  It looks
> like an additional layer will be needed to map from the Eclipse UML2
> model to the GeoAPI interfaces and 4) can be handled by the
> Geotools/uDig implementation of these interfaces.


Again, I'm not sure I understand the word profile in this context.
I think Eclipse UML2 would only be necessary because you want to use UML2.0 Diag. Int. Files. Ecore is much smaller and I'm nearly certain it contains everything required to be ISO compliant (including references, inheritance, etc.) Is there a converter between the two? The only reason I mention it 
is because Coverages are being built as Ecore models, which should
kickstart your profileing.

The next two paragraphs are intended to convince you that you need to
declare your scope before it explodes. :) Don't get discouraged! I want to 
see UML schema representations happen!!

How do you intend to handle Operations?  When a geographic feature is
specified to have some sort of behavior, how do you want to match it up
with a local version of code in the current environment? Can't code it in 
UML!

More generally, say you have a shapefile containing roads which came from
some random source.  Separately, you have an ISO compliant Roads schema
which you have been working with (maybe even coding against: routing
algorithms and whatnot.)  Can you map the feature attributes in your
shapefile to identically-defined "standard" attributes in the Roads schema, 
thereby making all your hard "routing" work available to you?

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