Architecture Modeling - SPES 2020

5.2.1.5 Platform-Based Design
Architecture Modeling
Platform-based design (PBD) was introduced in the late 1980s to capture a design process that
could encompass both horizontal and vertical decompositions and multiple viewpoints. It was
inspired by the development of personal computing and by the use of the term platform intended
to underline the importance of re-use and of building upon available results. The notion of
platform though was highly context dependent and meant different things to different people.
Thus, there was room to introduce a general approach that could be shared across industrial
domain boundaries and would subsume the various definition and design concepts.
The basic tenets of platform-based design are as follows:
• The design progresses in precisely defined abstraction layers; at each abstraction layer,
functionality (what the system is supposed to do) is strictly separated from architecture
(how the functionality could be implemented). This aspect is clearly related to layered
design and hence it subsumes it.
• Each abstraction layer is defined by a design platform. A design platform consists of
– A set of library components. This library not only contains computational blocks
that carry out the appropriate computation but also communication components that
are used to interconnect the computational components.
– Each element of the library has models that represent a characterization in terms of
performance and other non-functional parameters together with the functionality it
can support. Not all elements in the library are pre-existing components. Some may
be “place holders” to indicate the flexibility of “customizing” a part of the design
that is offered to the designer. In this case the models represent estimates of what
can be done since the components are not available and will have to be designed.
At times, the characterization is indeed a constraint for the implementation of the
component and it is obtained top-down during the refinement process typical of
layered designs. This layering of abstractions based on mathematical models is
typical of model-based methods.
– The rules that determine how the components can be assembled and how the functional
and non-functional characteristics can be computed given the ones of the components
to form an architecture. Then, a platform represents a family of designs
that satisfies a set of platform-specific constraints. This aspect is strictly related to
component-based design.
• This concept of platform encapsulates the notion of re-use as a family of solutions that
share a set of common features (the elements of the platform). Since we associate the
notion of platform to a set of potential solutions to a design problem, we need to capture
the process of mapping a functionality (what the system is supposed to do) with the platform
elements that will be used to build a platform instance or an “architecture” (how the
system does what is supposed to do). This process is the essential step for refinement and
provides a mechanism to proceed towards implementation in a structured way. Designs
on each platform are represented by platform-specific design models. A design is obtained
by a designer creating platform instances (architectures) via composing platform
components (a process that is typical of component-based design), by mapping the functionality
onto the components of the architecture and by propagating the mapped design
in the design flow onto subsequent abstraction layers and/or perspectives.
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