# Data lineage diagram

Lineage answers the question that follows every wrong number: where did this come from? A lineage diagram traces a field from the source system, through each transformation, to the dashboard someone is looking at.

Generate it if your platform can. Draw it if not; an approximate lineage diagram beats none.

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## When to reach for one

* Debugging a metric nobody trusts.
* Impact analysis before changing a source system.
* Governance and audit, where provenance has to be demonstrated.

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## How to draw it in Capable

| **Route** | **Use when**                                         |
| --------- | ---------------------------------------------------- |
| Graphviz  | Generated lineage; DOT is what most tools emit.      |
| D2        | Hand-maintained lineage that needs to stay readable. |

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## A worked example

Lineage for one revenue metric:

![Data lineage diagram](https://help.gocapable.com/images/att1418592285.svg)

The source, which you can paste into a new diagram and edit:

```
digraph lineage {
  rankdir=LR;
  node [shape=box, fontname="Helvetica"];
  crm [label="CRM\n(source)"];
  billing [label="Billing\n(source)"];
  stg [label="stg_invoices\n(staging)"];
  dim [label="dim_customer"];
  fct [label="fct_revenue"];
  dash [label="Revenue dashboard", shape=note];
  crm -> dim;
  billing -> stg;
  stg -> fct;
  dim -> fct;
  fct -> dash;
}
```

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## A few things that catch people out

* Lineage at field level is far more useful than at table level, and far harder to maintain.
* Mark which hops are automated and which are somebody exporting a spreadsheet.
* Regenerate rather than edit; lineage drifts faster than almost any other diagram.

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## Related

[JSON structure diagramA payload somebody can actually read.](https://help.gocapable.com/diagrams/json-structure-diagram.html)

[Entity relationship diagramTables, keys and the lines between them.](https://help.gocapable.com/diagrams/entity-relationship-diagram.html)

[ExamplesWorking diagrams you can copy.](https://help.gocapable.com/diagrams/examples.html)

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_Get the cardinality right and the rest follows._