---
id: coverage.dimensions-ontology
title: Dimensions and Ontology
summary: Define reusable behavior axes and their allowed values, then inspect how cases and benchmarks cover them.
kind: reference
product_area: coverage_engineering
status: stable
updated: 2026-09-07
canonical: /docs/coverage-engineering/dimensions-ontology
---

# Dimensions and Ontology

## Definition

Dimensions are reusable project-level axes for describing how cases differ. Each Dimension contains ontology values: the named members used to classify cases and measure representation. A Dimension might be **Source condition**, with values such as **Current**, **Superseded**, **Conflicting**, and **Missing**.

Use **Project Foundations → Coverage Facets → Dimension** to create, generate, inspect, and maintain them.

## Fields, states, or lifecycle rules

### What a Dimension contains

| Element | Purpose |
| --- | --- |
| Name and description | Explain the behavior axis and its boundary |
| Ontology values | Define the values used for classification |
| Examples | Show classified cases and the reason for a value assignment |
| Statistics | Show case-pool and benchmark distribution by ontology value |
| Benchmark focus | Show whether values are required, sampled, diagnostic, or ignored in benchmark setup |

Dimensions and ontology values are project foundations. A benchmark does not copy them. **Get Started** assigns benchmark-specific roles to the project values, and **Representation** reports how the selected cases cover them.

![Dimensions and Ontology table showing Dimension definitions, ontology-value counts, Case-classification counts, and AI classification controls.](/docs-assets/assets/screenshots/dimensions-ontology-table.png)

Use the table to compare each Dimension's definition with its ontology and current classification footprint before opening the detail view.

### Create or generate a schema

Create a Dimension manually when the axis and vocabulary are already understood. Use the dimension-schema generator when project context or source material should produce a reviewable proposal. Generated proposals can include a definition, why the Dimension matters, proposed ontology members, and warnings.

A proposal is not the active schema. Review each proposed Dimension and value before accepting it. Avoid accepting near-duplicates simply because they use different wording.

> Classification boundary
>
> Creating or editing a Dimension does not instantly classify every existing case. Missing or stale classifications can be queued and monitored separately. Treat unclassified cases as missing evidence, not as an implicit ontology value.

### Design rules

- Make the Dimension answer one stable question. Split axes that mix several independent concerns.
- Give every ontology value a definition that distinguishes it from neighboring values.
- Prefer values that can be applied consistently to real cases.
- Do not use a Dimension to encode case quality, policy approval, or a desired model score.
- Review distributions after changing values. A clean schema can still leave important cases unclassified.
- Delete only after checking Case Pool and benchmark usage; removal changes the project coverage vocabulary.

### Benchmark roles

In benchmark Get Started, each Dimension and ontology value can receive a focus role:

- **Required:** the benchmark is expected to cover this value.
- **Sampled:** include it as part of the desired mix.
- **Diagnostic:** track it for analysis without making it part of the main denominator.
- **Ignored:** exclude it from the benchmark coverage intention.
- **Unset:** no explicit benchmark instruction has been recorded.

Those roles shape Coverage Story generation and interpretation. They do not alter the project-level definition of the value.

{% example-demo title="Example: source condition" %}
The project defines a Source condition Dimension with Current, Superseded, Conflicting, and Missing values. One benchmark marks all four as required; another marks Current as required and the remaining values as diagnostic. The same project vocabulary supports different benchmark intentions without duplicating the Dimension.
{% /example-demo %}

## Related task pages

{% related-card-grid title="Related task pages" %}
- [Generate a dimension schema](/docs/coverage-engineering/generate-dimension-schema)
- [Work with Project Topics](/docs/coverage-engineering/project-topics)
- [Plan Benchmark Coverage](/docs/coverage-engineering/plan-benchmark-coverage)
- [Analyze dataset representation](/docs/benchmark-datasets/representation)
{% /related-card-grid %}

## Source confidence

Code-backed: the current Dimension list, detail, settings, proposal, classification, examples, and statistics surfaces establish these fields and lifecycle boundaries.