[Chameleon-dev] [Bug 180] New: SLD + Filter in the Web Map Context documents
Wed, 14 Jan 2004 04:02:44 -0500

           Summary: SLD + Filter in the Web Map Context documents
           Product: Chameleon
           Version: 1.1
          Platform: PC
        OS/Version: Windows 2000
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: Widget

Excellent.  Bart, if you are interested, you could file this as an 
enhancement request in Chameleon.  Not sure when we might be able to do 
it, but it definitely seems like something we should start looking for 
funding to do.

> Checking the context (1.0) specs, there seems 2 ways that the Style 
> element might be used in a context file. The first is for named styles. 
> The second option is to define and SLD. Here is the text from the sepcs 
> refering to that :
> Each <Style> element may alternatively define the style(s) of the layer 
> with a <SLD> element.
> The <SLD> element must contain required <Name> and optional <Title> 
> elements which identify the particular element of a Styled Layer 
> Descriptor to be used for this style. The <SLD> element must then 
> contain one of three alternative sources of description of a layer style:
> 1. an <OnlineResource> element describing a link to the specified SLD 
> document.
> <OnlineResource
> xmlns:xlink=""
> xlink:type="simple"
> xlink:href=">
> This reference may be to a separately referenced SLD document or to an 
> inline <StyledLayerDescriptor> in the same context document (which may 
> define the styles for multiple layers within the Web Map Context)
> 2. <StyledLayerDescriptor> element containing inline the namedStyle or 
> userStyle named in the enclosing <Style> element
> 3. <FeatureTypeStyle> element containing inline the specific feature 
> styling instructions for the enclosing <Style> element
>  Here is what can be done to support these :
>    * for the online ressource, we need to upgrade the context reader to 
> parse the SLD url and save it as a metadata on the layer. Should not be 
> too much work to do this.
>    * for the inline SLD, It requires more effort since it needed to 
> convert SLD to/from mapserver classes. There is though some mapserver 
> low level code to do this that can be used as a starting point.
> Paul Spencer wrote:
>> I'll have to get Assefa or Daniel to comment on this one, but I 
>> believe that the style element is intended as a 'NamedStyle' that 
>> would be one of the styles explicitly named by the WMS Server in its 
>> Capabilities documents.  I am not sure if there is a mechanism to 
>> specify an SLD in and/or filter with a layer in a Context document 
>> other than by modifying the connection string appropriately.  This 
>> would be a misuse of the standard, I think.
>> Cheers,
>> Paul
>> Bart van den Eijnden wrote:
>>> Hi list,
>>> I have 2 feature requests / "enhancement bugs" which in m
y opinion 
>>> would make a nice addition to Chameleon, but there is also some 
>>> overlap with PHP/Mapscript I guess. What would be the best place to 
>>> put these, Chameleon bugzilla or Mapserver bugzilla?
>>> 1. SLD/Filter in the Web Map Context
>>> I see that the Web Map Context standard already has a place (<Style> 
>>> element) for including the SLD. This would open up the possibility of 
>>> saving a selection created with the ExpressionBuilder widget into the 
>>> Web Map Context file.
>>> 2. scale dependent LegendTemplate widget
>>> The current LegendTemplate implementation does not look at the 
>>> MINSCALE and MAXSCALE values to determine if a layer is visible or 
>>> not. Would be a nice addition in my opinion to have a LegendTemplate 
>>> which looks into these values to determine whether or not to include 
>>> the layer.
>>> Best regards,
>>> Bart

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