Nested workflows

A nested workflow is a workflow within a workflow.

A nested workflow is just another kind of service that can be added to a Taverna workflow, except that instead of it being a black box, it is a white box so you can see what is happening inside.

Nested workflow contains other services inside that together perform a certain functionality and has input and output ports just any other service in Taverna. So, if you are not interested in details of a nested workflow – you can just treat it as a black box that does something that you need.

When to use nested workflows in Taverna

It is often the case that a workflow designed for one purpose can be used again for other experiments and can be imported or merged into another workflow. Nested workflows encourage reuse and modular workflow design.

How to use nested workflows in Taverna

In the Taverna Workbench, you can:

• add a new (blank) nested workflow if you want to start creating your own,
• import an already existing workflow as a nested workflow from a file on your disk to your current workflow,
• import an already existing workflow as a nested workflow from a URL (e.g. from my Experiment) to your current workflow, and
• import a workflow already opened in the Workbench as a nested workflow to your current workflow.

Once you have added a new blank or imported an existing nested workflow to your current workflow, you can further edit it to suit your needs.

A nested workflow is normally shown in a pale blue rectangle in the workflow diagram. Inside it, you can see its composing services. This view actually shows the nested workflow as a white box.

You can also hide (collapse) a nested workflow and show it as a black box. This will hide all services inside the nested workflow and show it as a pale pink rectangle.

You can also merge a workflow into the current workflow. This  effectively copies all services, ports and links from the source workflow directly into the destination workflow. This can be useful for copying smaller workflow fragments but you loose the modularity as the copied services are not part of a nested workflow but are “blended” in the current workflow. For inclusion of larger workflows inserting them as a nested workflow may be more beneficial.