Sequential Project Portfolio

[danhu]

Hello everyone,

Using Vensim Professional I'm working on a model concerning project portfolio management. Meaning I’m considering an array of projects to be done with different workloads. These projects get processed in an aging chain consisting of different work steps.
The projects should get processed one at a time and the next project should enter the aging chain, meaning getting processed, when the latter is finished. Meanwhile the surrounding variables should retain its values.

Now I’m looking for a possibility to bring the sequential logic of a project portfolio into the model. Unfortunately I didn’t found such a structure in the literature.
I’ve tried out subscripts but couldn’t come up with a solution to the sequential logic. This basic model you can find in the attachment.

Do you have any ideas or recommendations to this problem?
I would be very grateful for any suggestions!

[tomfid]

This sounds like the kind of thing we designed Ventity for.

I think the key question is, what does a project in the portfolio look like? Are you modeling it with full dynamic detail? Or just as a simple thing with specified duration, resources, etc.?

[danhu]

Thanks a lot for your reply!

The projects in the portfolio should just be a simple thing with attributes like you described. They should all interact with the same surrounding dynamics.

Thinking in programming language I would say a part of the model, namely the aging chain of work steps, should act as an object being able to process given information and return values to other modeling variables. Also a little bit of logic and matrices would be necessary to implement the arrays and the sequential process.
Having now read the concept of Ventity I think it could be a good solution to this problem.

Do you see any other solutions directly in Vensim or maybe using VBA?

[tomfid]

I think this can be done in Vensim.

The first step would be to build a single-project model. Then add an array dimension for the set of all projects. You end up simulating some zeroes (for projects that haven't started yet), but that's not much of a burden.

Where Ventity would really help is with multiple projects, each with multiple tasks and prerequisite relationships. The key advantages would be that you don't have to create projects until they start, and you only need to specify the task-to-task relationships that exist.

I wouldn't recommend VBA or any other language, because you lose unit checking and other essential quality control and usability features.