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Coupling and cohesion. Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa. Low coupling is often thought to be a sign of a well-structured computer system and a good design, and when combined with high cohesion, supports the general goals of high readability and maintainability ...
Cohesion is often contrasted with coupling. High cohesion often correlates with loose coupling, and vice versa. [2] The software metrics of coupling and cohesion were invented by Larry Constantine in the late 1960s as part of Structured Design, based on characteristics of “good” programming practices that reduced maintenance and ...
The model is named after database pioneer Charles Bachman, and mostly used in computer software design. In a relational model, a relation is the cohesion of attributes that are fully and not transitive functional dependent [clarify] of every key in that relation. The coupling between the relations is based on accordant attributes.
The dependence tree between software quality characteristics and their measurable attributes is represented in the diagram on the right, where each of the 5 characteristics that matter for the user (right) or owner of the business system depends on measurable attributes (left): Application Architecture Practices; Coding Practices
The indirection pattern supports low coupling and reuses potential between two elements by assigning the responsibility of mediation between them to an intermediate object. An example of this is the introduction of a controller component for mediation between data (model) and its representation (view) in the model-view-controller pattern.
Four types of autonomy, which promote loose coupling, are: reference autonomy, time autonomy, format autonomy, and platform autonomy. [3] Loose coupling is an architectural principle and design goal in service-oriented architectures. Eleven forms of loose coupling and their tight coupling counterparts are listed in: [4]
Example of a system context diagram. [14] Context diagrams are diagrams that represent the actors outside a system that could interact with that system. [15] This diagram is the highest level view of a system, similar to block diagram, showing a, possibly software-based, system as a whole and its inputs and outputs from/to external factors.
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).