A car's ignition switch serves several purposes. First, it allows you to control the power to many of the car's accessories, preventing accessories from running down the car's battery when the car is parked for a long period of time.
Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation. In the common data architecture, cardinality is documented with data integrity but not with data structure. There are several types of cardinality defining relationships between occurrences of entities on two sides of the line of relationships.
1 In software design, modularity refers to a logical partitioning of the software design that allows complex software to be manageable for the purpose of implementation and maintenance.2  The logic of partitioning may be based on related functions, implementation considerations, data links, or other criteria. In cognitive science, the idea of modularity of mind holds that the mind is composed of independent, closed, domain-specific processing modules. 2  Specifically, see visual modularity, for an article relating to the various putative visual modules.