A pipeline key is a value that's created every time an entry field is created. That means that any entry field created in Atlas Play gets its own signpost. That signpost you can then use throughout your process mapping to recall the contents of that field later on in the process or even within a sub process. This means that data input by a user in a task can become the basis for output later on.
How pipeline keys are created
It's important to understand how pipeline keys are created, because once they've been set you are not able to edit them.
When creating a field in a task you'll be asked to name it. This will become the label of the field, which is editable, but also the pipeline key. Atlas Play will automatically make the pipeline key lower case and replace each space with an underscore, so it's ready to be copy pasted into other elements including tasks and expressions.
How pipeline keys can be used
As mentioned already, you can use your pipeline key to recall data that has been input by users or otherwise generated by a task field within Atlas Play.
This could be the result of an option selected by a user, or it could be a file uploaded by a user. It may even be the result of an External Service Call Task, meaning data could be pulled from outside of Atlas Play to provide an output later on in your process.
Adding pipeline keys as an output
To add a pipeline key as an output, you simply need to select that as an option when configuring a task further on in your process.
For example, if you wish to have a Text Display Field, rather than choosing to enter the text yourself by using the Display Text Data Source Type, you can select the Pipeline Key Data Source Type.
Here you can enter the pipeline key you've copied over from your previous task. By using the pipeline key as your Data Source Type, Atlas Play will display whatever the result was from the field whose pipeline key you've used!
For data that is process context this may displayed as tags against the process by configuring that key as a tag.
Passing a pipeline key into an External Service Task
For example, if your Service Task Function needs an input the relevant pipeline key can be inserted in the Data Item Key field against the relevant Parameter Key used by the function.
Once configured, the Parameter Key is displayed against the Key icon. Whereas, the Data Item Key (Pipeline Key) is displayed against the Cloud icon.