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Outcome: find the definitions your project already owns, then choose whether to query them or change them. A catalog that can be read is not necessarily a backend that can execute queries.

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1. Identify the layer

Use the configuration and extras for that backend. Keep the existing format as the source of truth; choosing Dex does not require converting it to another one.

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2. Inspect the catalog first

Read the available metrics, dimensions, entities, and physical mappings. The mapping to warehouse columns matters: it connects semantic queries to profiling and PII checks. Ask your agent:

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3. Query or author

To answer a metric question, use explore semantic query or explore semantic values on a backend that supports it. Start with the names returned by the catalog and the semantic query reference. To change definitions, ask the agent to prepare a plan using semantic define|update|plan for dbt semantic models, or the matching semantic ossie, semantic slayer, or semantic cube command for native documents. Review the plan and apply it through transform apply.
Hosted dbt Cloud semantic queries are outside Dex’s cost guard. Understand that boundary before running them. Other backends have different query capabilities; reading a native document does not authorize a hosted catalog or query request.

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A complete local example

The Apache Ossie walkthrough takes a native layer from local files through catalog inspection, exploration, a drift baseline, and authoring. It also explains the cases where metric queries are refused and how to ask a governed warehouse question instead. For exact schemas and validation limits, use the semantic layer reference, Ossie compatibility, or Cube compatibility.