Introduction

Overview

Teaching: 0 min
Exercises: 0 min

Questions

• What is Common Workflow Language?

• Why might I want to learn to use CWL?

Objectives

• Learn what CWL is.

• Learn about the motivation behind the project.

CWL is a way to describe command line tools and connect them together to create workflows. Because CWL is a specification and not a specific piece of software, tools and workflows described using CWL are portable across a variety of platforms that support the CWL standard.

CWL has roots in “make” and many similar tools that determine order of execution based on dependencies between tasks. However unlike “make”, CWL tasks are isolated and you must be explicit about your inputs and outputs. The benefit of explicitness and isolation are flexibility, portability, and scalability: tools and workflows described with CWL can transparently leverage technologies such as Docker, be used with CWL implementations from different vendors, and is well suited for describing large-scale workflows in cluster, cloud and high performance computing environments where tasks are scheduled in parallel across many nodes.

Key Points

• CWL describes command line tools and workflows.

• CWL is not software.

• Descriptions in CWL aid portability between environments