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# Attributes, metrics and measures

The most general notion is "attribute":

Attribute: An attribute is a property, qualitative or quantitative, of software products or processes.

We may distinguish between the product and process cases:

Product attribute, process attribute: A product attribute is an attribute that characterizes a software product or set of products. A process attribute is an attribute that characterizes a software-related process, such as development, maintenance, documentation, management, or multiple instances of such a process.

Examples of attributes include reliability (a product attribute, non-quantitative) and total project cost (process, quantitative).

A metric is simply a quantitative attribute:

Metric: A metric is an attribute whose values are numbers (integers or reals), expressed relative to a certain unit specified as part of the metric definition.

Examples of metrics include the number of source lines of a program (product) and the total cost of a project (process). The metric tool provides by default a set of metrics, they are available in the Metric Evaluation tab of the metric tool

Attributes other than metrics will be called "qualitative":

Qualitative attribute: A qualitative attribute is an attribute other than a metric.

An example of qualitative attribute is the reliability of a software product.

The "process" vs. "product" distinction carries over to metrics:

Product metric, process metric: A metric is a product metric if it is a product attribute, a process metric if it is a process attribute.

"Relevance", as defined in the previous section, suggests that the purpose of metrics is to help us gain information about attributes that are of direct interest to us. Often these will be qualitative; for example we may want to estimate the reliability of our software. Metrics provide us with numerical values that can serve to assess or predict such attributes.

Applying a metric will give us measures:

Measure:A measure is the value of a metric for a certain process or product.