In Taverna 2.3 and earlier, Text Constant was known as String Constant.

A Text constant service allows you to set a fixed-value input for a service or the whole workflow. This is useful for inputs that are fixed across multiple runs of the same workflow, and also for publishing your workflows since the string constant provides an example input for people wanting to try out the workflow.

Adding a Text Constant

  1. Expand Service templates under Available services in the Service Panel.
  2. Select Text constant.
  3. Drag Text constant and drop it into the Workflow Diagram.
  4. In a dialog that pops up, enter the text you want to set the Text constant to.

 

Note that you can add a Text constant from the Insert menu as well.


 

The value for a Text constant can be loaded from a file, saved to a file or cleared.

When you load the text from a file, it copies the text into the text constant. If you later change the file, then this has no effect on the text constant.

Setting a Constant (Default) Value for a Service

  1. Right-click on the input port of a service in Workflow Diagram and select Constant value.


Alternatively, you can drag in a Text Constant from the Service Templates section of the Service Panel, as explained in the previous section, and connect it to the appropriate input port of your service.