Systematic OO Programming with Axiomatic Design

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Systematic OO Programming with Axiomatic Design

• Sung-Hee Do
• Nam P. Suh,
• Axiomatic Design

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Axiomatic Design

• Offers a systematic and orderly way to proceed
  through the software development process
• Provides for a methodology that ensures
  developers make the best design decisions by
  providing decision-making criteria in the form of
  2 axioms
• The independence axiom
• The information axiom

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Independence Axiom

• Suggests that the best designs maintain the
  independence of the functional requirements,
  ensuring that the design can achieve each
  function without inadvertently affecting any
  other functions.
• (Coupling)

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Information Axiom

• Suggests that the best designs minimize their
  information content. Thus the solution with the
  greatest likelihood of success is the simplest
  solution.

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Benefits of Axiomatic Design

• The quality of design can be determined upon the
  degree to which it satisfies the defined
  functional requirements
• The design ensures that each function is
  satisfied independently and that coupling does
  not occur
• (cont.?)

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Benefits of Axiomatic Design (cont.)

• Job assignment and team management is easier
  because they can use the system architecture
  diagram to assign tasks and define the
  inter-relationships between various modules or
  classes
• Software change orders can be handled quickly and
  easily because the system architecture identifies
  the modules affected by a change

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The Process
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Investigate customer attributes to discover
customers needs.
Note these needs and determine the designs
functional requirements (FRs) by answering the
question What must this design do to satisfy
the customers needs?
Developers determine the answers and record the
results as FRs in the left column of a design
matrix.
(here)
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Developers record the design parameters (DPs)-
physical solutions that satisfy each functional
requirement.
More than one design DP may satisfy each FR, but
the information axiom will help determine the
best solution.
This process is recorded across the top of the
design matrix.
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Developers may indicate a relationship between
the FRs and the DPs with an X in the matrix or
with an equation. The matrix checks that each DP
satisfies only one FR.
Developers decompose the design, working through
each part to determine the subfunctional
requirements and subdesign of their previous
design until theyve completed the entire design.
Axiomatic development pushes the development team
to define the problem explicitly, envisioning the
entire design before writing a single line of
code.
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Axiomatic Development Process
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Axiomatic Design Example

• The authors make use of a case study to
  illustrate the effectiveness of axiomatic design.
  The Acclaro design software is the first
  implementation of a software design package using
  axiomatic design principles.

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State tasks in terms of what the software must
accomplish at the highest level.
Highest level FR to help developers succeed
with software design.
Find associated DPs choose most feasible
solution create axiomatic design
software
Define next level of FRs and DPs
P in the leftmost column represents the parent
level items in numbered rows below it represent
highest level DPs and FRs
Continue from system level down to individual
modules in increasing specific detail until the
design is decomposed into manageable pieces.
The matrix tracks decomposition ensuring that
DPs satisfy the FRs and are not coupled.
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Fourth level branch of Acclaro
Xs represent specific functions.
Outmost FRs and DPs are parents.
Numbers are assigned to the first level that
further define the parent level. Sub FRs and Sub
DPs acquire additional numbers.
Compare these numbers with those in Table1.
(Relationship)
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Module 1141 excerpt. (4th level branch)
-Outermost layer is 1141, next deeper is
11412.
-Module 1141 has sub-module 11411- Module
11412 is five layers deep
-Only diagonal Xs describe independence of
FR-DP relationships (ie 114121 and 114122
are independent of one another)
-Module 114123 is decoupled- its impacted
by 114121 and 114122. Developers make
decisions about 114123 only after making
those for 114121 112122.
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Corresponding system architecture for example
design matrix. Circled Ss represent summations
of modules the circled Cs represent control
points that indicate one step must precede the
other.
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System architecture

• Serves as a graphical representation of the
  matrix
• Gives order in which to make design decisions
• Indicates how those decisions will impact other
  design functions

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Development Ordering

• Core functions are diagonal matrix Xs and should
  be developed along the diagonal in order
• Off-diagonal terms do not represent core
  functions-but are considered in development
• The matrix helps developers establish and
  organize the relationships

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Object Orientation

• DP leaves can represent attributes, methods, or
  arguments of a specific class
• One or two levels up, the DPs can also be defined
  as a class combining the leaves below.
• Once classes are defined, developers can define
  attributes and operations, then create interfaces
  by establishing relationships bewteen objects and
  operations, using the design matrices.

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???Questions???