What is a single source of truth for product data?

One authoritative record per fact, with every other system reading from it rather than holding its own copy. For product data that means one place where a description, a dimension, or a GTIN is authored, and channels rendering from it. Where two systems can both edit the same field, there is no source of truth.

The test is what happens when two systems disagree. If the answer requires a person to decide which is right, the fact is stored twice, whatever the integration diagram claims.

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