[Chameleon] Contexts

[Paul Spencer]

The extraction service would extract the actual data associated with the 
visible layers and extents ...

Ken Sanderson wrote:
>>Extract Context builds a context document from the current state of the
> 
> 
>>map file and sends it to a (application-defined) extraction service
> 
> that 
> 
>>can extract data based on the layer visibility and extents provided in 
>>the context.
> 
> 
> I still don't understand this part. Why send to an extraction service if
> you can just download the context file? Think I am missing something :)
> 
> Ken
> 
> -----Original Message-----
> From: Paul Spencer [mailto:pagameba at magma.ca] 
> Sent: September 27, 2004 6:04 PM
> To: Ken Sanderson
> Cc: chameleon at lists.maptools.org
> Subject: Re: [Chameleon] Contexts
> 
> 
> Ken,
> 
> Ken Sanderson wrote:
> 
>>I have been goofing around with contexts today and it would do what I 
>>need if I was only using WMS layers, as the context saves visibility 
>>status as well as extents. I had a couple other questions about
>>contexts:
>>
>>1) Whats the real difference between Download a Context and Extract a 
>>Context? Seems one puts it right to your hard drive while the other 
>>just provides a URL for it, but the URL is to a file in a temp folder 
>>that isnt likely to be around that long. Is there a reason to use 
>>Extract vs Download?
> 
> 
> Download Context builds a context document from the current state of the
> 
> map file and allows the user to download the file to their computer. 
> Extract Context builds a context document from the current state of the 
> map file and sends it to a (application-defined) extraction service that
> 
> can extract data based on the layer visibility and extents provided in 
> the context.
> 
> 
>>2) Is it feasible to combine a context with your current map? Right 
>>now if you upload a context it replaces the map you have with the new 
>>one. Is it feasible that you could add the layers in a context to your
> 
> 
>>existing map so that you would get a combination of the two in your 
>>map window instead of just the newly loaded context?
> 
> 
> yes it is feasible.  The low level functionality is there.  MapScript 
> loads a context by replacing all the layers, but it is possible to load 
> a context into a new mapobj and then copy all the layers across.  Note 
> that while this is possible, it may not provide the best results because
> 
> of layer ordering (polygons on top of points for instance).  When 
> dealing with WMS, it is not normally possible to discover the feature 
> type of the layer, which is a disappointing limitation for client apps 
> that want to be somewhat intelligent about this sort of thing.
> 
> Cheers,
> 
> Paul
> 
> 
>>Thanks,
>>
>>Ken
>>
>>
>>-----Original Message-----
>>From: chameleon-bounces at lists.maptools.org
>>[mailto:chameleon-bounces at lists.maptools.org] On Behalf Of Paul 
>>Spencer
>>Sent: September 26, 2004 1:31 PM
>>To: Ken Sanderson
>>Cc: chameleon at lists.maptools.org
>>Subject: Re: [Chameleon] Contexts and SLD's Widgets
>>
>>
>>Ken,
>>
>>the Context widgets are to work with Web Map Contexts, an OGC spec for
>>portable map files ... it only works with WMS layers.  SLD is also an 
>>OGC spec, this one defines styling information for WMS layers.
>>
>>Neither set of widgets will help you with that.  There are no other
>>widgets that do that, either.  You will likely need to build something
> 
> 
>>to do this.
>>
>>Cheers,
>>
>>Paul
>>
>>Ken Sanderson wrote:
>>
>>
>>>What are the Context and SLD widget/tools for, ie what do they do?
>>>
>>>I am looking for a way to save a current extent, visible layers, etc
>>>so that a user can come back later and start where he left off, would 
>>>either of these be good for that? Is there any other widgets that 
>>>would work for this type of thing?
>>>
>>>Thanks,
>>>
>>>Ken
>>>
>>>
>>>
>>>_______________________________________________
>>>Chameleon mailing list
>>>Chameleon at lists.maptools.org
>>>http://lists.maptools.org/mailman/listinfo/chameleon
>>>
>>
>>
> 

-- 
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|Paul Spencer                           pspencer at dmsolutions.ca   |
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|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|
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