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title: X12 EDI Connector 2.18 - Understanding the EDI Schema Language
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# X12 EDI Connector 2.18 - Understanding the EDI Schema Language

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

X12 EDI Connector uses a YAML format called EDI Schema Language (ESL) to represent EDI schemas.
Basic ESLs define the structure of Electronic Data Interchange (EDI) messages in terms of:

- structures, known as _transaction sets_ in X12 terminology

- groups, known as loops, in X12

- segments, composites, and elements

ESLs for the all [supported X12 versions](https://docs.mulesoft.com/x12-edi-connector/2.18/x12-edi-versions-x12) are included. If you are using
HIPAA, then a set of [HIPAA variations](https://docs.mulesoft.com/x12-edi-connector/2.18/x12-edi-versions-hipaa) of base X12 transaction sets are
included.

You can customize X12 schema definitions to suit your data by defining an overlay schema. An overlay
schema is a type of ESL that enables you to modify a base schema, such as an X12 4010 850 schema,
with your specific conventions. You don’t need an overlay schema if you’re using the structure
defined by the standard, but most EDI exchanges modify the base definitions in an implementation
convention.

You can define your own custom schemas, or copy and edit a base X12 schema definition to suit your
data as shown in the [EDI Schema Language Reference](https://docs.mulesoft.com/x12-edi-connector/2.18/x12-edi-schema-language-reference).

## Finding Schema Locations

To use the connector, you need to know the locations of the schemas in your project. If you’re using
out-of-the-box X12 schemas and not customizing anything, the schema location follows the
`/x12/{version}/{transaction set}.esl` convention.

For example, using the `005010` version and the 850 transaction set, the schema location is
`/x12/005010/850.esl`.

If you’re using one or more custom schemas, refer to
[XML Schema and Trading Partner Configuration](https://docs.mulesoft.com/x12-edi-connector/2.18/x12-edi-connector-config-topics) for complete
information about setting your schema locations.

## See Also

- [Introduction to Anypoint Connectors](https://docs.mulesoft.com/connectors/introduction/introduction-to-anypoint-connectors)

- [Use Exchange to Discover Connectors, Templates, and Examples](https://docs.mulesoft.com/connectors/introduction/intro-use-exchange)

- [Salesforce Help](https://help.salesforce.com)