[Fwd: Re: [webmap-discuss] zoomlevels in OWSContext?]

[Steven M. Ottens]

Hi all,

As Tom said, we've to decide for ourselves what the extension should
look like. From what I understood is the following extension correct, so
I propose we use it:

<wms-c:ZoomLevels>128,64,32,16,8,4,2,1</wms-c:ZoomLevels>
where xmlns:wms-c="http://wiki.osgeo.org/index.php/WMS_Tile_Caching"

Note that the zoomLevels go from big to small numbers. Also <ZoomLevels>
is a child of <Layer>

regards,
Steven

Kralidis,Tom [Burlington] wrote:
> (Thanks Daniel for forwarding this to me, I'm now a part of this list
> again :))
>
>
>   
>> Steven M. Ottens wrote:
>>     
>>> Currently we store out layers in a WMC document, but we're 
>>>       
>> switching 
>>     
>>> to OWSContext to allow for more types of layers then just 
>>>       
>> WMS layers. 
>>     
>>> Since the zoom levels are depending on the server, it makes 
>>>       
>> sense to 
>>     
>>> me to store these levels in OWSContext. Are there any OWSContext 
>>> experts around who can tell me if that's already in the standard,
>>>       
>> No, that's not part of the OWSContext schema. I participated 
>> in the OWS Context IE and don't remember the question of 
>> storing multiple zoom levels even being raised at all. Note 
>> that WMS doesn't support the concept of fixed zoom levels 
>> either, so before multiple zoom levels can be added to OWS 
>> Context some work will be required upstream in WMS.
>>
>>     
>
> Correct.  Since OWSContext is based on OGC specifications, this doesn't
> apply.
>
>   
>>> if not, what would be a proper place and name
>>> for such a thing?
>>>
>>>       
>> If I remember correctly an extension mechanism was included 
>> in the schema that could possibly be used for that. I think 
>> Tom Kralidis would be the best one to answer on this. I CC'd 
>> him in case he is not on this list.
>>
>>     
>
> There is an extension element in the OWSContext schemas (schema chunk
> below) which allows this:
>
> 	<xs:complexType name="ExtensionType">
> 		<xs:annotation>
> 			<xs:documentation>This allows additional
> elements to be added to support non WMS Layer
> services.</xs:documentation>
> 		</xs:annotation>
> 		<xs:sequence>
> 			<xs:any namespace="##any"
> processContents="lax"/>
> 		</xs:sequence>
> 	</xs:complexType>
>
> Yes, fairy dust :)
>
> The basic approach is to define your own namespace in the root element
> of the OWSContext instance doc (i.e. xmlns:foo="http://foo/foo"), and
> then use that prefix within the document when applying your own
> constructs, i.e.:
>
> <foo:zoomLevels>1,2,4,8,16,32,64</foo:zoomLevels>
>
> Having said this, if you are going to be adding extensions, I would
> suggest that these be agreed upon in some way, so at the least the
> extensions are defacto; so it's great that it's being discussed here.
>
> ..Tom
>
>
>   
>> Daniel
>> -- 
>> Daniel Morissette
>> http://www.mapgears.com/
>>
>>
>>     
>
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>   


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