Metric definitions

A metric definition holds a name, grain, numerator expression, denominator expression, unit, aggregation method, version and status. The Retail Analyst prepares this record so the reviewer can understand the measure before anyone compares values across stores or periods. A conversion number has little value when its denominator changes without a recorded decision. The approved definition gives the result a stable interpretation.

The definition can be related to a store definition and a reviewing person. A result can then reference the metric definition it used. That connection makes it possible to compare results while still finding the rule behind each value. The aggregation method is a recorded choice; the team should agree whether a ratio of sums or another method fits the reporting question.

• Grain. The grain explains the unit of observation that a result summarizes.
• Expression. Numerator, denominator and unit state how the measure is read.
• Version. Status and version separate a draft rule from an approved one and a retired one.

Write down how the business defines a session, shopper, conversion and exposure before setting the expressions. Pick an aggregation method that matches that definition. A ratio of sums can answer a different question from averaging store rates. The reviewer should see a worked example with a normal denominator and a zero denominator before approving the definition.

Agree when a new version is needed. A changed source mapping, eligibility rule or conversion event can change a metric even if its displayed name stays the same. Keep the earlier definition so historic values retain their meaning. Decide who prepares the rule and who can approve it; the reviewer should be independent from the preparer for material changes.

Use a dated store measurement with accepted basket facts. The analyst drafts a basket conversion definition, enters its grain and expressions, selects the aggregation method and gives it a version. The reviewer checks two source windows and records approval. The analyst then links a result to that approved definition and reviews its numerator, denominator, value and source row count.

Repeat the case with no eligible sessions. The result should show a clear exception reason instead of a usable conversion rate. Later, when the store changes the event mapping, retain the earlier version and prepare a new definition for the new period. Reviewers can then explain why values from different windows differ.

• Metric definitions awaiting approval — Examine draft grain, method and reviewer before use.
• Result windows — Compare values with their linked definition and period.

Follow definition to result and review the model.