object

# `coupling_metric`

Computes entity efferent coupling, afferent coupling, and instability.

Author: Ebrahim Azarisooreh and Paulo Moura
Version: 0:12:0
Date: 2018-07-17
Compilation flags:
`static, context_switching_calls`
Imports:
`public` code_metrics_utilities
`public` code_metric
Uses:
list
Remarks:

> - Efferent coupling (Ce): Number of entities that an entity depends on.

> - Afferent coupling (Ca): Number of entities that depend on an entity.

> - Instability (I): Computed as `Ce / (Ce + Ca)`. Measures the entity resilience to change. Ranging from 0 to 1, with 0 indicating a maximally stable entity and 1 indicating a maximally unstable entity. Ideally, an entity is either maximally stable or maximally unstable.

> - Abstractness (A): Computed as the ratio between the number of static predicates with scope directives without a local definition and the number of static predicates with scope directives. Measures the rigidity of an entity. Ranging from 0 to 1, with 0 indicating a fully concrete entity and 1 indicating a fully abstract entity.

> - Entity score: Represented as the compound term `ce_ca_i_a(Ce,Ca,I,A)`.

> - Dependencies count: Includes direct entity relations plus calls or dynamic updates to predicates in external objects or categories.

Inherited public predicates:
all/0 all_score/1 directory/1 directory_score/2 entity/1 entity_score/2 entity_score//2 file/1 file_score/2 library/1 library_score/2 rdirectory/1 rdirectory_score/2 rlibrary/1 rlibrary_score/2

- Public predicates

- Protected predicates

- Private predicates

- Operators

## Public predicates

(no local declarations; see entity ancestors if any)

## Protected predicates

(no local declarations; see entity ancestors if any)

## Private predicates

(no local declarations; see entity ancestors if any)

## Operators

(none)