[webmap-discuss] Re: Using JSON instead of XML for OGC documents

Allan Doyle adoyle at eogeo.org
Fri Nov 17 16:32:56 EST 2006

On Nov 17, 2006, at 14:37, Cameron Shorter wrote:

> The biggest win for web browsers (performace wise) would be if Web  
> Feature Services could return GML in JSON format. I'd imagine this  
> would be relatively easy to incorporate into the WFS spec.

AFAIK the WFS spec allows for alternate return formats. I know some  
people have used WFS's to return shapefiles. It should be a matter of  
declaring a MIME type in the capabilities or something.

> Disclaimer: I still haven't done any performance tests with JSON.
> Raj Singh wrote:
>> Martin echoes my initial reaction. The bigger picture is the  
>> reliance  on XML data structures for information content. I don't  
>> think it's a  good idea to consider abandoning such a flexible,  
>> well-understood,  expressive format just because it's not ideal  
>> for one platform (Web  browsers), even if that platform is perhaps  
>> the primary parser of  some document types.
>> Maybe a good long term strategy is to go with XML as the  
>> canonical  document format, but have some sort of "header" section  
>> that points  to other formats (or services that produce  
>> alternative formats). And  make that header easy enough to read  
>> that text parsers can easily  pull out enough information to avoid  
>> the rest and go get their  preferred document format. This  
>> strategy could apply not only to  static document formats like  
>> Context and SLD, but also to service  responses like GetCapabilities.
>> ---
>> Raj
>> On Nov 16, 2006, Martin Daly wrote:
>>> We've also looked into JSON a bit, although not for Context  
>>> documents.
>>> In this case not using XML for the first step seems to be just   
>>> delaying
>>> the inevitable?  That is, after you have the context data, the  
>>> next  step
>>> is always to get the capabilities of the server (see the recent e- 
>>> mail
>>> trail about, for example, GetMap and GetCapabilities not sharing the
>>> same URL root).
>>> Unless all of the references services/data area also returned as  
>>> JSON,
>>> then you will be parsing XML sooner rather than later.
>>> M
>> On Nov 16, 2006, at 5:34 PM, Cameron Shorter wrote:
>>> Context working group,
>>> Regarding: http://json.org
>>> There has been discussion amongst http://openlayers.org  
>>> developers  about using JSON instead of XML for storing OGC  
>>> documents (like OGC  Context, WMC, and probably a host of other  
>>> documents too).
>>> The reason for considering JSON over XML are:
>>> * In Web Browsers, XML support is patchy.
>>> * Consequently extra code is required to be downloaded to cover  
>>> all  browsers.
>>> * In browser clients, code size is a major consideration as   
>>> size=bandwidth=speed.
>>> * JSON is reportedly faster to process.
>>> JSON reportedly has all the other advantages of XML like being   
>>> structured, easy to read, is supported by multiple languages etc.
>>> One thing discussed is standing up XML<->JSON services.
>>> I'd be interested to hear comments from OGC participants on  
>>> these  ideas.
>>> Feel free to foward onto others more appropriate.
>>> -- 
>>> Cameron Shorter
>>> http://cameron.shorter.net
> -- 
> Cameron Shorter
> http://cameron.shorter.net
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Allan Doyle
adoyle at eogeo.org

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