# Workflow definition files in HealthOmics
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You use a workflow definition to specify information about the workflow, runs, and the tasks in the runs. You create workflow definitions in one or more files using a workflow definition language. HealthOmics supports workflow definitions written in WDL, Nextflow, or CWL. 

HealthOmics supports the following choices for WDL workflow definitions: 
+ WDL – Provides a spec-conformant WDL engine. 
+ WDL lenient – Designed to handle workflows migrated from Cromwell. It supports customer Cromwell directives and some non-conformant logic. For details, see [Implicit type conversion in WDL lenient](workflow-languages-wdl.md#workflow-wdl-type-conversion).

For information about each of the workflow languages, see the language-specific detailed sections below.

You specify the following types of information in the workflow definition:
+ **Language version** – The language and version of the workflow definition.
+ **Compute and memory** – The compute and memory requirements for tasks in the workflow.
+ **Inputs** – Location of the inputs to the workflow tasks. For more information, see [HealthOmics run inputs](workflows-run-inputs.md).
+ **Outputs** – Location to save the outputs that the tasks generate.
+ **Task resources** – Compute and memory requirements for each task.
+ **Accelerators** – other resources that the tasks require, such as accelerators.

**Topics**
+ [HealthOmics workflow definition requirements](workflow-defn-requirements.md)
+ [Version support for HealthOmics workflow definition languages](workflows-lang-versions.md)
+ [Compute and memory requirements for HealthOmics tasks](memory-and-compute-tasks.md)
+ [Task outputs in a HealthOmics workflow definition](workflows-task-outputs.md)
+ [Task resources in a HealthOmics workflow definition](task-resources.md)
+ [Task accelerators in a HealthOmics workflow definition](task-accelerators.md)
+ [WDL workflow definition specifics](workflow-languages-wdl.md)
+ [Nextflow workflow definition specifics](workflow-definition-nextflow.md)
+ [CWL workflow definition specifics](workflow-languages-cwl.md)
+ [Example workflow definitions](workflow-definition-examples.md)