Backbone adding data from model A to Collection with model B

Question

In a model I have one some attributes. I would like one of the attributes to be placed in a seperate collection with another model, after I altered the data.

Now altering the data is not a problem and I know how to create the new object. However I don't know what the best way to go is with:

1. where to alter the data
2. how to get it in my collection.

I tried several things from sending the complete attribute to the collection, where I do I have a parse which should give back a new object. This however fails.

I also tried to do the same with the model and a parse.

Then I tried to just return the object in the 'url' section of the collection. but as expected this does not work either. After which I tried to stringify the object to json, but this didn't work either.

So now I am thinking it might be the best way to start altering the data in Model A, after the data has ben received, and then push or add the data to the collection.

Maybe anyone else has a better idea of doing this? And how do I know the data is in Model A, so I can start running the script?

First try in the collection: by URL

SatPhotoDataCollection = Backbone.Collection.extend({

    model: SatPhotoDataModel,

    url: function() {

        var obj = satPhotoModel.attributes.Layer;
        var layerNames = {};

        for (var i = 0; i < obj.length; i+=1) {

            //do some massive things filling layerNames

        }

        return layerNames;

    }

});

Same thing, not using URL but parse, sending the 'satPhotoModel.attributes.Layer' to the collection using:

SatPhotoDataCollection.add(satPhotoModel.attributes.Layer);


SatPhotoDataCollection = Backbone.Collection.extend({

    model: SatPhotoDataModel,

    url: "",

    parse: function(data) {

        var layerNames = {};

        for (var i = 0; i < data.length; i+=1) {

            //do some massive things filling layerNames

        }

        return layerNames;

    }

});

Of course I did the same in the model satPhotoDataModel (model B) in the URL and Parse, however I must the 'layerNames' I return is really a collection of 'layers', so hence the need for a collection ;)

Now in the satPhotoModel (model A) which will have the Layer in it's attributes I could also try something like:

SatPhotoModel = Backbone.Model.extend({

    initialize: function() {

    },

    url: "http://geoservertest/geoserver/DIWADIS/ows?service=WMS&version=2.0.0&request=GetCapabilities",

    sync: function(method, model, options) {

        options.dataType = "xml";
        options.crossDomain = true;
        options.contentType = 'application/json; charset=utf-8';

        return Backbone.sync(method, model, options);
    },

    //we are expecting an XML since we want a normal object, we do this with parsing
    parse: function(data) {

        var obj = $.xml2json(data);

        this.parseLayers(obj.Capability.Layer);          

        return obj.Capability.Layer;

    },

    defaults: {

        Abstract: "",
        BoundingBox: {},
        CRS: [],
        Ex_GeographicBoundingBox: {},
        Layer: [],
        Tile: ""

    },

    parseLayers: function(data) {


        var layerNames = {};

        for (var i = 0; i < data.length; i+=1) {

            //do some massive things filling layerNames

        }

        SatPhotoDataCollection.add(layerNames);


    }

});

I am just doubting if that is really the correct way to go. So any help and enlightenment would be awesome :-)