layer | communicates using procedure calls or by inter-process communication where the lower layers can become servers and the higher layers can become clients | |
has definition A subsystem that provides a set of services and has layer cohesion | |
has example The set of related services which could form a layer might include:- Services for computation
- Services for transmission of messages or data
- Services for storage of data
- Services for managing security
- Services for interacting with users
- Services provided by an operating system
- Services provided directly by the hardware
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has well-defined interface that is used by layer immediately above | |
is a subtopic of 9.2 - Principles Leading to Good Design | |
is often divided into smaller subsystems | |
is part of multi-layer system | |
is a kind of component | |
only communicates with the layer immediately below it | |
sees a lower layer as a set of services it can use | |
usually provides services through an API | |
component | is reusable if it can be used in several different systems with little or no modification | |
may perform a special-purpose function such as the user interface for a particular system | |