Historical Coverage Gap

A required reporting period has no valid historical row.

Historical models often assume that every required period is covered by at least one valid record. But in real source systems, histories are often incomplete.

Records may start too late, end too early or contain missing intervals. When reporting depends on a missing period, joins fail, facts lose attributes or snapshots become incomplete.

Customer C1 has history for January to March and May to December, but April is missing.

Try this Historical Coverage Gap case in Target Table Validation

Use these sample target tables to test the validator:

1. Copy one of the target tables below.
2. Open Target Table Validation.
3. Paste the copied table as your target output.
4. Check whether the April coverage gap is marked or incorrectly hidden as covered.

customer_id,snapshot_date,customer_status,valid_from,valid_to,coverage_status
C1,2024-01-31,Active,2024-01-01,2024-01-31,covered
C1,2024-02-29,Active,2024-02-01,2024-02-29,covered
C1,2024-03-31,Active,2024-03-01,2024-03-31,covered
C1,2024-04-30,Unknown,2024-04-01,2024-04-30,coverage_gap_marked
C1,2024-05-31,Active,2024-05-01,2024-05-31,covered

customer_id,snapshot_date,customer_status,valid_from,valid_to,coverage_status
C1,2024-01-31,Active,2024-01-01,2024-01-31,covered
C1,2024-02-29,Active,2024-02-01,2024-02-29,covered
C1,2024-03-31,Active,2024-03-01,2024-03-31,covered
C1,2024-04-30,,2024-04-01,2024-04-30,coverage_gap_unmarked
C1,2024-05-31,Active,2024-05-01,2024-05-31,covered

Each individual row can look valid while the timeline is incomplete.

Coverage gaps usually appear between otherwise valid records. The problem often only becomes visible when another source, fact table or snapshot date needs that missing period.

Make historical coverage explicit before joining.

Validate coverage against the periods your reports actually need.

The Workbench can surface coverage gaps as validation findings.

Coverage gaps are easy to miss and expensive to debug later.

Historical gaps are easy to miss because each individual record can look valid.

The problem only appears when the model is queried for a missing period or joined against another historical source. Coverage validation makes these gaps visible before they create incorrect reports.