[Mapbender-dev] Application element interaction

[Christoph Baudson (Wheregroup)]

I have already sent this mail 5 hours ago...maybe it got lost

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Hello folks,

Karim and I had been discussing how application elements could interact 
in the future. We wanted to establish a more user friendly way of 
configuring how elements collaborate. Based on that discussion I have 
made a prototypical implementation.

The scenario consists of two elements, a button for digitizing a 
polygon, and a feature list. I want the feature list to automatically 
display the polygons that are being digitized, without having to change 
the source code.

I have added an element var "inputs" for the feature list, which looks 
like this:

[{
       "type": "featureCollection",
       "method": "addFeatureCollection",
       "title": "Features that will be added to the feature list",
       "linkedTo": [
           {
               "id": "mb_digitize_polygon",
               "event": "finished",
               "attr": "featureCollection",
           }
       ]
}]

This JSON snippet specifies that the feature list has an input of a 
specific "type" ("featureCollection"), and input data can be added via 
an API "method" ("addFeatureCollection").

This input is then linked to the output of the polygon digitizer, 
specified by "id". The output is generated whenever an "event" is 
triggered ("finished"), and the listener can access the output via the 
attribute "attr" ("featureCollection") of the object passed into the 
callback.

With this approach, we can create very flexible configurations. I 
imagine an admin UI similar to Yahoo Pipes, where you can connect your 
elements by drawing a line from element A to B, complete with default 
settings and validation. The JSON above would be generated automatically.

Thanks to the Mapbender API the code necessary to do this is only about 
20 lines [1], there is no need to add code to existing elements.

What do you think about this approach? I think it would be a great 
feature and make configurations very easy, and it would also give 
element designers a structure to code to. I would love to have that in 
Mapbender 3.x, maybe for FOSS4G.

Christoph

[1] http://osgeo.pastebin.com/0SwNFUvU

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Christoph Baudson
Anwendungsentwickler

Fon: +49 (0)228 / 90 90 38 - 15
Fax: +49 (0)228 / 90 90 38 - 11
christoph.baudson at wheregroup.com
www.wheregroup.com
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