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cohesion comparison table

Subject	use	allow	have example	require	help by	has definition	have advantages	be	seek only	achieve when	simplify
communicational cohesion					the object oriented paradigm	A form of cohesion in which procedures that access the same data are kept together		more important than sequential cohesion
functional cohesion	if possible					A form of cohesion in which modules which together perform a function (a computation that returns a result and has no side effects) are kept together, and everything else is kept out	It is easier to understand a module when you know all it does is generate one specific output and has no side effects It is easier to replace a functionally cohesive module with another that performs the same computation functionally cohesive module is much more likely to be reusable	hard to assess		a module only performs a single computation, and returns a result, without having side-effects
layer cohesion		side-effects	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	that the layers must form a hierarchy - higher layers can access services of lower layers, but it is essential that the lower layers do not access higher layers		A form of cohesion in which the facilities for providing or accessing a set of services through an API or hardware interface are kept together. There must also be a strict hierarchy in which higher level layers can access only lower-level layers. In other words, the system is effectively divided into layers		hard to assess			systems
procedural cohesion						A form of cohesion in which procedures that are called one after another are kept together		weaker than sequential cohesion		you keep together several procedures that are used one after another, even though one does not necessarily provide input to the next
sequential cohesion						A form of cohesion in which a series of procedures, where one provides input to the next, are kept together		stronger than procedural cohesion		a series of procedures, in which one procedure provides input to the next, are kept together - and everything else is kept out
temporal cohesion			a designer would achieve temporal cohesion by placing together all the code used during system start-up or initialization			A form of cohesion in which aspects of a system are grouped together which are used during the same phase of execution of a program, i.e. execute close together in time		weaker than procedural cohesion	if the other types of cohesion have been achieved	operations that are performed during the same phase of the execution of the program are kept together, and everything else is kept out
utility cohesion						A form of cohesion in which utilities which cannot be logically placed in other cohesive units are kept together		the weakest kind of cohesion since it serves to group together those parts of the system that do not seem to logically belong anywhere else

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