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# Elementary and composite metrics

Some of our metrics will be elementary and some composite. An elementary metric is measured directly from the product or project record:

Elementary_metric
- An elementary product metric is a product metric whose values (integers) indicate the number of occurrences of a certain pattern in a product.
- An elementary process metric is a process metric whose values reflect measurements drawn directly from project records.

An example of elementary product metric is the number of source lines. An example of elementary process metric is the number of incremental compilations of a system.

Elementary metrics are provided by default by the metric tool. There is no means to remove them or to define new ones since they are not expressed as a combination of other metrics.

From these elementary metrics we may define composite ones:

Composite metric : A composite metric is a metric whose values are defined by a mathematical formula involving other metrics (elementary, or previously defined composite metrics).

A later section will introduce a number of operations for defining composite metrics out of elementary ones.

Again we may distinguish between product and process:

Composite product metric, composite process metric:
- A composite product metric is a composite metric defined entirely in terms of product metrics.
- A composite process metric is a composite metric whose definition involves one or more process metrics.

By convention, this definition treats as process metric a composite metric involving both product and process components.

The classification introduced for metrics extends to measures, so that we may talk about an elementary product measure, a composite process measure and so on.

See Also
Metrics
Scopes