Importing new VDDT model strata into existing Path projects

[ashlisky]

Is it possible to import a VDDT stratum model into an existing Path project (like you can in VDDT)? I assume one way could be to edit the Path project definitions to include the new stratum and any new states and transitions not already in the model, and then add deterministic and probabilistic transitions line by line (or edit the transitions .xls files and import them into Path). I assume you could also import the new model strata into stand-alone VDDT, then create a new Path project using the new VDDT.mdb, but this seems counterintuitive given the trend toward making VDDT a Path component rather than a stand-alone system. Am I missing anything? Thanks.

[colin-daniel]

It is a bit trickier to import a VDDT model into an existing Path project than it was in VDDT. The reason is that VDDT allowed you to have different definitions for every model. This made it easier to import and export models, but the tradeoff was that you could end up with a collection of models in a VDDT project with different definitions – which made it difficult to run all of the models together and roll up the results. In Path we only allow one set of definitions for the entire project, so all strata (ie models) need to use the same definitions. This is what allows us to easily run models for several strata together when simulating an entire landscape.
    
The result is that you must ensure that any new model you are importing into Path – whether it be from VDDT or from Excel – uses the same definitions as exist already in the Path project. Here is how you can do this:
 1.First, create a VDDT mdb that contains only the model(s) you would like to import to Path (create a copy of the VDDT mdb, then delete the unwanted models; or use the Export function in VDDT to export the models you are interested in).
2.Import the VDDT model(s) into a new Path project (using File | New From VDDT menu). This will automatically create a new set of definitions in Path corresponding to the VDDT definitions.
3.You then need to edit these new Path definitions so that they match those of your existing Path project. Note that you can open more than one instance of Path at a time, allowing you to display the definitions from the two projects side-by-side.
4.Once the definitions match then you can open both Path projects together (in a single instance of Path) and copy/paste the new model(s) from one mdb to the other. Note that you can only open multiple Path projects at once (in a single instance of Path) if all the projects have matching definitions.
 
I realize this isn’t perfect. Our plan is eventually to allow users to copy and paste models with different defintions into Path (including models from VDDT) – however this is not a trivial task, as this step requires reconciling the definitions in an intelligent way.
 
Thanks, Colin.
 

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