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In-Depth Information
IF
We require for all we interface behaviors F
α, ρ
: IF
IF f o r w h i c h
ρ
(F) is defined
(F))
Clearly not every mapping between interfaces is to be called an abstraction.
Particular behavioral properties are required. We require for all we interface behaviors
F
F =
α
(
ρ
IF
α
(F) ~> IF F
and that
F ~> IF F'
only holds if there is an granularity abstraction
α
with
(F')
Nevertheless, this form of refinement should be compatible with composition and
abstraction, too.
F =
α
α IF (M')
The following property can expected only for abstraction functions
M ~> SM M' ⇒
α IF (M) ~> IF
α 1 and
α 2 that fit
together:
IF F 2
Property refinement should be a special case of granularity refinement
M ≈> SM M' ⇒ M ~> SM M'
Note that implementation refinement is a special case of property refinement while
granularity refinement is a generalization. In principle, we could work with only one
refinement relation that is a generalization of all of the refinement relations
introduced above. However, the individual refinement relations are more appropriate
to reflect the role of these relations in the development process. This allows us to
characterize refinement steps.
We assume a general granularity refinement relation on systems
α 1 (F 1 )
IF
α 2 (F 2 ) ~> IF F 1
IB
It formalizes the idea of granularity refinement for the set of all systems. It is based
on the idea of interface abstraction and granularity of interface abstraction:
~> : HCS
×
HCS
α IF (M')
For interfaces we assume that the mapping
M ~> M'
α IF (M) ~> IF
is the identity. This way granularity
interface refinement is used as a reference relation for granularity refinement for all
kinds of systems.
α
4.3.4 Deployment
Typically composed software systems are distributed over a network of hardware
units on which they are executed. Each software component is located on one
particular hardware unit. We speak of deployment. It is one of the decisive steps in
software development to determine the deployment of a system especially for
distributed and embedded systems.
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