Basic Introduction to the TACTIC Workflow Engine

The Workflow Engine is one of the key technology components of TACTIC.  A workflow defines a set of connected process nodes.  Each node represents some work that needs to be done within the entire workflow which constitutes a job.

The workflow engine drives the entire work process forward.  It is responsible
for sending messages so that upstream and downstream process are notified of
important events.  For example, if a downstream process sets a task to complete, then all the next upstream processes will set the task to pending.

In TACTIC, any sobject can have a pipeline defined.  Fundamentally,t his means that any sobject can go through a series of processes, have tasks assigned to it and have files checked into it.

Pipeline or Workflow?

Internally, TACTIC uses word pipeline, however, this word is not commonly
recognized outside of the Visual Effects / Computer Graphics indusry.  Workflow is commonly used in every other industry, so this is the terminology that we will use from now on.

Process Node Types

By default, all nodes are manual nodes.  These nodes represent processes

where manual work must be done.  In general, a task is created which is

associated with this node.  This task will have someone assigned to it

and can have a specific start and end date.

When a task that belongs to a process changes its status, a message is

sent to that processes.  This allows the workflow engine to react to this

change in status.  For example, if a "complete" message is sent from the

task to the process, then the process "send" a pending message to all of

its output connections.  This output notification is automatic.

If the output node is another manual node, then the process will notifiy any

tasks associated with it and set them to pending.  This task would now

show up on a "pending" task list for users (who would set it to "In Progress" when working on the task)

If the output node is another node type, the behavior would be quite different.

For example, if the output node was an "action" type, then the script code

associated with that process would automatically get executed.

Action nodes are non-blocking.  They will automatically execute their programmed task and without any manual involvement from a user, when they complete, they will  send a "pending" message to the next process.

Approval node is a specific type of node that is very similar to a

manual node.  There is always an assigned task that is associated with

it however, usually, the task status options are more limited.  Also,

many widgets recognize approval nodes and adjust accordingly.

Connecting Processes

These nodes can be connected together in any combination.

manual1 -> auto1 -> auto2 -> manual2

In this example, after manual1 is set to "complete", "auto1" would automatically

execute.  On completion of "auto2" will automatically execute.  Finally,

when "auto2" completes, "manual2" will receive a "pending" signal which will

set the task in this node to a status of "pending".

The nodes can also be connected in parallel:

manual1 -> auto1 -> manual2

        -> auto2 ->

In this case, both auto1 and auto2 would be executed simultaneously.  Manual2

would not receive the pending signal until both "auto1" and "auto2" are complete.

As can be seen from these examples, the workflow engine pushes process progress

along the various steps defined in the definition of the workflow.  Users

do not need to remember to execute certain scripts in certain ways in certain

order.  This can all be hidden from the user and be executed exactly as they

were designed to do.

There are a number of other nodes in built into TACTIC which enhance how the

workflow engine behaves.  It is even possible to write custom nodes types

entirely in Python.  These nodes can be loaded in as a TACTIC plugin

and used just like a native node.