[mapguide-internals] MapGuide RFC 15 - New Query Features API

Sat Feb 3 00:41:16 EST 2007

There is really no way for the server to know what it is going to run 
into prior to executing a query, unless it starts remembering stats per 
feature source and class, which would be a truly interesting piece of 
work (probably some database theory available on this topic somewhere).

In the meantime, I'd like to figure out how to monkey wrench this one 
in. This is default behavior in ArcIMS and apparently that user base 
considers this functionality quite useful. So I guess the key questions are:

- Do we really need both the old and new behavior?
- Assuming we need both, what should the default behavior be?
- How is it controlled, by the end user or application developer?
- What should it be called?

Thanks,
Bob

Andy Morsell wrote:
> I do like the proposed behavior change.  I think it will come in handy.
> And, the user can clear their selection if they don't like the ugly blue
> blobs (or we can do it programmatically for them).  I do like the idea of
> this not being a forced behavior, but I do think it should become the
> default as I would find it more useful than the existing behavior.  There
> definitely are concerns of too many objects being displayed and selected
> based on the query.  For instance, all of the parcels in Canada over $100k
> in value would probably blow up the server and the resultant selection
> display would be horrible.  I see that there is a maxFeatures parameter to
> the methods, but the optimal value for this will change depending on the
> data source.  I'm not sure the best way to handle these potential abuses,
> but there needs to be some internal checking before allowing the query to
> execute. 
>
>
> Andy 
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org
> [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Bruce
> Dechant
> Sent: Friday, February 02, 2007 4:37 PM
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] MapGuide RFC 15 - New Query Features API
>
> Jason,
>
> You are correct for both situations you have described.
> Perhaps this needs to be optional behavior with the new APIs only instead of
> forced.
>
> Thanks,
> Bruce
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org
> [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
> Sent: February 2, 2007 5:24 PM
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] MapGuide RFC 15 - New Query Features API
>
> Yes, but that means that when users select parcels at 1:10k, when they zoom
> out, they will see ugly blue blobs on my beautiful map.  They might
> say:  "Are they new lakes?" :-)
>
> I'd really prefer not to have this behaviour by default.  It changes
> existing behaviour for users familiar with MG 6.5, and existing MGOS/MGE
> installs, requiring a certain level of end-user retraining.
>
> What happens if they select a feature when they are zoomed out that is not
> visible by default when they zoom in?  Is the detailed view obscured by the
> large selection blob from a generalized feature that is not supposed to be
> visible at the large scale?
>
> Jason 
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org
> [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Bruce
> Dechant
> Sent: Friday, February 02, 2007 16:13
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] MapGuide RFC 15 - New Query Features API
>
> Jason,
>
> The following assumes you are using the existing API.
>
> The selected parcels only show up if you zoom/pan after you have already
> selected them. As soon as you do a new selection at the zoomed out level
> where the parcels are not visible they will not be selected. This is more
> for convenience so that you can see a parcel you have selected while you
> zoom to more of an overview display.
>
> Now if you are not careful with the NEW API you could end up with lots of
> features selected. :)
>
> Thanks,
> Bruce
>
>
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org
> [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
> Sent: February 2, 2007 5:06 PM
> To: MapGuide Internals Mail List
> Subject: RE: [mapguide-internals] MapGuide RFC 15 - New Query Features API
>
> I think this is a great idea, but...
>
> Will there be any way to disable this behaviour in the viewer?  I don't know
> if I want selected parcels showing up on the map at extreme zoom levels.
> Talk about ugly.
>
> This is not a feature request.  From a cartographic standpoint I'd love to
> see something like this:
>
> Representation thresholds.  Set zoom levels where adjacent polygonal
> features are merged into a single polygon, and then turn into a symbolized
> point feature.  For instance, consider a Hospital:
> - at 1:5000, all buildings in the hospital complex are represented, and
> labelled with the word "Hospital"
> - at 1:10000, these buildings are aggregated into a single rubber-band
> polygon, labelled with the letter "H" in a blue circle
> - at 1:15000, the hospital is represented by a letter H in a blue circle,
> positioned at the center of gravity of the original features
>
> The trick is that all just different representations of the same feature, so
> selection would be maintained, and geometry operations would be applied to
> the true geometry, not the simplified representation.
>
> I'm already doing this to a certain extent manually, but it would be nice to
> not have to maintain multiple copies of the same data just for display's
> sake, and with this method there is no way of maintaining selection status
> from one scale range to the next.
>
> Jason 
>
> -----Original Message-----
> Subject: [mapguide-internals] MapGuide RFC 15 - New Query Features API
>
> Hi Everyone,
>
> We would like to submit the following RFC for open discussion and
> comments:
>
> http://www.osgeo.org/trac/mapguide/wiki/MapGuideRfc15
>
> Please respond to the list with any feedback and we will be happy to
> respond.
>
> Thanks,   
>
> Bruce
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