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Software Design: An Overview Guy Tremblay and Anne Pons

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Software Design: An Overview Guy Tremblay and Anne Pons EEL 6883 Software Engineering Vol. 1 Chapter 4 pp.191-208 Presenter: Sorosh Olamaei 1 Introduction Design as a ... – PowerPoint PPT presentation

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Title: Software Design: An Overview Guy Tremblay and Anne Pons


1
Software Design An OverviewGuy Tremblay and
Anne Pons
  • EEL 6883
  • Software Engineering Vol. 1 Chapter 4 pp.191-208
  • Presenter Sorosh Olamaei

2
1 Introduction
  • Design as a life cycle activity bonds the
    requirements to construction
  • Process of breaking down the system into
    components, defining interfaces and defining
    components to a level of detail that enables
    their construction
  • Blueprint of the solution to be implemented
  • Usually not unique

3
Scope of the paper
  • DeMarcos terminology
  • Decomposition design ( D-design ) mapping of a
    system into its component pieces
  • Family Pattern design (FP-Design) goal is to
    establish exploitable commonalities over a family
    of systems
  • Not covered User Interface design, Invention
    design (I-design) a conceptualization of a
    system to satisfy discovered needs and
    constraints

4
2 Software Design Concepts
  • Design key concepts (car example)
  • Goals
  • Constraints
  • Alternatives
  • Representations
  • Solutions ( to wicked problems lack of test to
    determine when the problem is indeed solved)

5
2.2 Software Design Context
  • Software design is bounded to
  • Requirement analysis
  • Construction (coding and unit testing)
  • Integration and qualification testing
  • Linear or Incremental life cycle models

6
2.3 Software Design Process
  • Software architectural design
  • Software detailed design

7
3 Software Structure and Architecture
  • Definition of software architecture
  • The fundamental organization of a system
    embodied in its components, their relationships
    to each other, and to the environment, and
    principles guiding its design and evolution.
  • Reuse of generic design knowledge
  • Architectural Styles
  • Design Patterns
  • Product Lines

8
3.1 Architectural Structures and Views
  • Key purpose of software architecture is
    communication among stakeholders
  • Design View
  • A collection of models that represent an aspect
    of an entire system.
  • Represent a partial aspect of software
    architecture that shows specific properties of a
    software system
  • Overall organization of an SDD is composed of a
    number of design views each of which contains a
    subset of the various attributes describing
    design entities
  • View model by IEEE
  • Decomposition, Dependency, Interface , detailed
    description
  • 41 view model by RUP
  • Logical, Implementation, Process ,Deployment
    ,Use-case

9
Architectural Structures and Views
  • Views can be classified into 3 categories called
    Viewtypes
  • Module viewtype
  • Component-and-connector viewtype
  • Allocation viewtype
  • Software architecture is a multifaceted artifact
    produced by the design process and composed of a
    set of relatively independent and orthogonal
    views

10
3.2 Macro/Micro architectural Patterns
Architectural Styles Versus Design Patterns
  • A pattern is a common solution to a common
    problem in a given context
  • Goal is to codify and document recurring
    solutions to typical problems
  • Attributes to ensure transferability
  • Pattern name
  • The context in which the pattern may apply
  • Example illustrating need
  • Essence of the general problem
  • Underlying solution
  • Implementation guidelines
  • Related patterns
  • Advantages and disadvantages

11
Macro/Micro architectural Patterns Architectural
Styles Versus Design Patterns
  • Pattern Classification based on scope and level
    of abstraction
  • Architectural Styles
  • Design Patterns
  • Coding Idioms ( part of software construction not
    explained in this paper)

12
Macro/Micro architectural Patterns Architectural
Styles Versus Design Patterns
  • An architectural style expresses a fundamental
    structural organization schema for software
    systems. It provides a rich set of predefined
    subsystems, specifies their responsibilities, and
    includes rules and guideline for organizing the
    relationship between them
  • Major Architectural Styles
  • General structure
  • Distributed systems
  • Interactive systems
  • Adaptable systems
  • Other Styles
  • Choice depends on quality attributes that must be
    satisfied. Heterogeneous styles are possible.

13
Macro/Micro architectural Patterns Architectural
Styles Versus Design Patterns
  • Gamma et al.
  • Creational patterns
  • Structural patterns
  • Behavioral patterns
  • Buschmann et al.
  • Structural decomposition patterns
  • Organization of work patterns
  • Access control patterns
  • Management patterns
  • Communication patterns

14
3.3 Design of Families of Systems and Frameworks
  • Based on software product lines and software
    components
  • Software production line A collection of
    systems sharing a managed set of features
    constructed from a common set of core software
    asset
  • Building a common set of software assets involves
    identifying the key commonalities encountered
    among the various members of the possible family
    of product- done through domain analysis as well
    as accounting for their possible variability -
    done by identifying and defining reusable and
    customizable components
  • In an object-oriented context, a related notion
    is that of framework, a partially complete
    software subsystem that can be extended by
    instantiating specific plug-ins or hot spots

15
4 Software design quality analysis and evaluation
  • Software Quality The totality of features and
    characteristics of a software product or service
    that bear on its ability to satisfy stated or
    implied needs
  • Properties of Software Quality
  • Functionality
  • Usability
  • Efficiency
  • Maintainability
  • portability

16
Software design quality analysis and evaluation
  • 4.1 Design Quality Attributes
  • Run-time qualities
  • Development-time qualities
  • Impact of architectural choices
  • Conceptual integrity which concerns the
    architectures intrinsic quality architecture
    reflects one single set of design ideas leading
    to simplicity, consistency and elegance
  • 4.2 Measures (quantitative estimates)
  • Depends on selected design approach
  • Function-oriented (structured) measures
  • Objected-oriented measures
  • 4.3 Quality Analysis and Evaluation Tools
  • Quality attributes are hard to quantify
  • Software design reviews
  • Simulation and prototyping

17
5 Software design notations and documentation
  • Budgen categorization
  • Black-box notation external properties of the
    elements of a design model
  • White-box notation describing some aspect of
    the detailed realization of a design element
  • Alternative categorization
  • Structural/Static properties
  • Behavioral/dynamic properties
  • 5.1 A selection of Design Notations (UML)
  • Class and object diagrams
  • Component diagrams
  • Deployment diagrams
  • Structure charts
  • Structure (Jackson) diagrams

18
Software design notations and documentation
  • 5.2 Behavioral Descriptions (Dynamic view)
  • Activity diagrams
  • Interaction diagrams sequence and collaboration
    diagrams
  • Data flow diagrams
  • State transition diagrams and statechart diagrams
  • Pseudo code and program design languages (PDLs)

19
5.2 Design Documentation
  • Coherency of the design documentation depends on
    many aspects stakeholders, software development
    methods
  • Key practice is selection of an appropriate set
    of views which satisfies different stakeholders
    needs
  • Project manager detailed allocation views
  • Developer detailed module and component-and-conne
    ctor views

20
Design Documentation
  • View documentation also involves describing
    interfaces of the element from that view
  • A key characteristic of any interface
    specification must be two-way which means what
    the element provides and what it requires
  • Another key idea design should be presented and
    documented in a rational way the rationale
    behind the key decisions should also recorded ex.
    The design alternatives that were considered and
    rejected should be described

21
6 Software Design strategies and methods
  • 6.1 General Strategies and Enabling Techniques
  • Software design strategies can be described in
    terms of enabling techniques independent of
    specific software development method
  • Abstraction
  • Coupling and cohesion
  • Divide and conquer
  • Information hiding and encapsulation
  • Sufficiency

22
Software Design strategies and methods
  • 6.2 Function-oriented (Structured) Design
  • Divide and conquer approach toward identifying
    major system function in a top-down approach.
  • Structured analysis produces DFDs of the various
    system functions together with associated process
    descriptions, that is, descriptions of the
    processing performed by each subtask, usually
    using informal Pseudocode.
  • Entity-relationship diagrams describing the data
    stores can also be used.
  • Key strategies to help derive a software
    architecture from a DFD
  • Transaction analysis triggers
  • Transformation analysis identifying the central
    transform, structure chart
  • Key concept of structured design are those of
    coupling and cohesion restrict coupling to
    normal types data, stamp, control coupling.
    Avoid common and contest coupling

23
Software Design strategies and methods
  • Additional Heuristics to improve the quality of
    resulting design
  • Fan-in/Fan-out high / low or moderate ( 5-7 max)
  • Decision splitting (avoid separating them into
    files)
  • Balanced systems top-level modules deal with
    logical and abstract data independent of the
    implementation format

24
Software Design strategies and methods
  • 6.3 Object-oriented Design
  • Object based (no inheritance or polymorphism) Vs
    object oriented design
  • OO design (solution domain) Vs requirement
    analysis ( problem domain)
  • Class diagrams Vs Integration diagrams (sequence
    or elaboration diagrams)
  • 6.4 Data-structured-oriented Design (Jackson
    Structured Programming)
  • Emphasis is on the data that a program
    manipulates rather than the functions it performs
  • Motivated by stability in data rather then
    functions that need to be performed
  • Restricted to the design of data-processing
    programs using sequential ( batch-style) files
    and processes
  • Jackson System Development (JSD) approach
    similar to OOD to address more complex
    interacting processes

25
My views about the paper
  • Comprehensive overview which does not get the
    reader lost
  • Gets the reader motivated to read the following
    design papers
  • Lack of references to sources that expand on
    topics

26
  • Questions !?
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