This section has not yet been upgraded to match Cylc 8 changes.

What Is A Workflow?

A workflow consists of an orchestrated and repeatable pattern of business activity enabled by the systematic organization of resources into processes that transform materials, provide services, or process information.


In research, business and other fields we may have processes that we repeat in the course of our work. At its simplest a workflow is a set of steps that must be followed in a particular order to achieve some end goal.

We can represent each “step” in a workflow as a oval and the order with arrows.

digraph bakery { "purchase ingredients" -> "make dough" -> "bake bread" -> "sell bread" "bake bread" -> "clean oven" "pre-heat oven" -> "bake bread" }

What Is Cylc?

Cylc (pronounced silk) is a workflow engine, a system that automatically executes tasks according to their schedules and dependencies.

In a Cylc workflow each step is a computational task, a script to execute. Cylc runs each task as soon as it is appropriate to do so.

digraph Mini_Cylc { a -> b b -> c d -> f b -> d f c e -> f }

Cylc can automatically:

  • Submit tasks across computer systems and resource managers.

  • Recover from failures.

  • Repeat workflows.

Cylc was originally developed at NIWA (The National Institute of Water and Atmospheric Research - New Zealand) for running their weather forecasting workflows. Cylc is now developed by an international partnership including members from NIWA and the Met Office (UK). Though initially developed for meteorological purposes Cylc is a general purpose tool as applicable in business as in scientific research.

Cylc provides a variety of command line and GUI tools for visualising and interacting with workflows.