> For the complete documentation index, see [llms.txt](https://v2.dataos.info/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://v2.dataos.info/references/dataos-resources/workflow/core-concepts.md).

# Core concepts

### Workflow and DAG

A Workflow is an execution plan for batch work. The plan is expressed as a DAG.

Use a single step for simple jobs. Add more steps when work must happen in stages. Use `depends` to describe order.

{% code title="workflow\.yaml" expandable="true" collapsedlinecount="10" %}

```yaml
spec:
  dag:
    - name: extract
      spec: {}
    - name: validate
      depends:
        - extract
      spec: {}
    - name: publish
      depends:
        - validate
      spec: {}
```

{% endcode %}

### Workflow type

Workflows are typically defined as `instance` workloads.

An instance starts, processes work, and exits.

### Schedule

Use `spec.schedule` to run the Workflow automatically.

Set one or more cron expressions in `crons`. Set `timezone` to control evaluation time. Use `concurrencyPolicy` to control overlapping runs.

### Steps

Each item in `spec.dag` is a step.

Each step can define:

* a unique `name`
* optional `depends` entries
* its own runtime configuration in `spec`

This lets one Workflow mix simple and complex steps in the same DAG.

### Compute and resources

Use `compute` to choose the execution environment.

Use `resources.requests` and `resources.limits` to size each step. Set these values per step when different stages need different capacity.

### Stack and stackSpec

`stack` selects the runtime for a step. `stackSpec` contains the stack-specific configuration.

Start by designing the DAG. Then choose any stack that supports Workflow execution mode.

Use `container` for custom scripts, CLIs, and packaged batch jobs. Use another supported stack when its runtime model better fits the step.

{% code title="workflow-step.yaml" expandable="true" collapsedlinecount="8" %}

```yaml
spec:
  dag:
    - name: run-step
      spec:
        stack: ${{stack-name}}
        stackSpec:
          ${{stack-specific-configuration}}
```

{% endcode %}

### Projections and storage

Workflow steps can also consume projections and mounted volumes.

Use `use.projection` for secrets and runtime configuration. Use `use.volumes` when steps must share files across the DAG.

For projection syntax, template engines, data sources, and troubleshooting, see [Projections](/references/dataos-resources/secret/projections.md).


---

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