Build a flow

A Flow is the blueprint of a complex calculation where the outputs of one Model become the inputs to the next. We call them ‘virtual deployments’, because they are built using Model Schemas not the model code.

Model selection

First click ‘Build a flow’ on the menu or home page. The next step is to filter the list of candidate models.

Pick the ones which you want to include in the flow and click ‘Load models’.

On the next page you will see the selected models listed, plus the data inputs and outputs, which have been inferred those models’ the schemas.

If you want to change the model selection, add more using ‘Select models’ or ‘Remove’ from the list.

Down the page is a first draft of the Flow TRAC has built. The graph has an internal link where an output of one Model has the same Key as an input for another. Any inputs that cannot be sourced with an internal link are treated as inputs (orange).

If you selected models with common Keys, you should see a diagram like this…

If you selected models with no common Keys, it might look more like this…

Both are technically correct and can be executed. The first pattern is more commonly what people aim for.

Intermediates

The ‘Save’ toggle on the list of Outputs allows you to change a node in the Flow between Intermediate (grey) and Output data (blue). Intermediates are not included in the results when the Flow is run.

Labels and categories

Label is a reader-friendly version of the Key which is displayed in the UI when using a Flow.

Categories are used to group Models and Data on the pages from which you launch a Job. They are optional and are only useful if a Flow has a very large number of inputs which can be meaningfully categorised into groups, to improve the user experience when launching a job.

Re-wiring

You can edit the default wiring using the Advanced options drop-down.

The rewiring tool allows you to replace Input data (orange) with an internal link, by manually mapping the Key of a Model’s output to the Key of another Model’s input. Manual rewiring works if the data sets have different Keys but their schema’s are consistent.

The dustbin allows you to remove a rewired link and return to the default Flow.

Saving the flow

Once you are happy with the Flow, provide the general attributes and click ‘Upload’. If the upload is successful you can find the flow via (Search Page) and use it to (Run a flow).

The two most common reasons for being unable to save a new flow are missing name and description fields and schema inconsistency along one of the internal links. A warning message should inform you of these issues.