Computing and SE II Chapter 7: Software Architecture Design

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Computing and SE IIChapter 7 Software
Architecture Design

• Er-Yu Ding
• Software Institute, NJU

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Main Contents

1. Motivation of software architecture
2. What is software architecture
3. Architecture styles
4. Architecture Design

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1. Motivation of software architectureWhen
applications getting complex

• For an application based on 5 objects
• You can coding it directly and get a well product
• For an application based on 50 objects
• You should design it first and then building it
• For an application based on 500 objects
• Of course design is also needed
• But can you assure that assigning the objects
  responsibilities well and integrating them into a
  satisfied product with the help of design work?

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1. Motivation of software architecture Size(
Complexity) really does matter!
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1. Motivation of software architecture Forces
of Satisfied Software
Functionality
Cost
Compatibility

• When software getting complex
• Nonfunctional forces are very difficult to
  achieve in traditional methods!
• Because we cant see the global just with
  intuition or analysis like before
• We should control them before detail design

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1. Motivation of software architecture The way
we building software
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Where we used before
Mary Shaw, 1989 Larger Scale Systems Require
Higher-Level Abstractions --Organizing systems on
the sub-system and module level --The software
architecture level of design
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2. What is software architectureDefinition of
SW Architecture

• The SW architecture of a program or computing
  system is the structure or structures of the
  system, which comprise SW components, the
  externally visible properties of those
  components, and the relationships among them

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2. What is software architecture An Example
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2. What is software architecture Another
Example
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2. What is software architecture Why
Architecture?
The architecture is not the operational software.
Rather, it is a representation that enables a
software engineer to (1) analyze the
effectiveness of the design in meeting its stated
requirements, (2) consider architectural
alternatives at a stage when making design
changes is still relatively easy, and (3) reduce
the risks associated with the construction of the
software.
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2. What is software architecture Why is
Architecture Important?

• Representations of software architecture are an
  enabler for communication between all parties
  (stakeholders) interested in the development of a
  computer-based system.
• The architecture highlights early design
  decisions that will have a profound impact on all
  software engineering work that follows and, as
  important, on the ultimate success of the system
  as an operational entity.
• Architecture constitutes a relatively small,
  intellectually graspable model of how the system
  is structured and how its components work
  together BAS03.

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3. Architectural Styles

• Each style describes a system category that
  encompasses
• a set of components (e.g., a database,
  computational modules) that perform a function
  required by a system,
• a set of connectors that enable communication,
  coordination and cooperation among components,
• constraints that define how components can be
  integrated to form the system,
• semantic models that enable a designer to
  understand the overall properties of a system by
  analyzing the known properties of its constituent
  parts.

• Data-centered architectures
• Data flow architectures
• Call and return architectures
• Object-oriented architectures
• Layered architectures

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3. Architectural StylesData-Centered
Architecture
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3. Architectural Styles Data Flow Architecture
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3. Architectural Styles Call and Return
Architecture
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3. Architecture Styles Object-Oriented Style
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3. Architectural Styles Layered Architecture
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4. Architecture Design Architectural Patterns

• Concurrencyapplications must handle multiple
  tasks in a manner that simulates parallelism
• operating system process management pattern
• task scheduler pattern
• PersistenceData persists if it survives past the
  execution of the process that created it. Two
  patterns are common
• a database management system pattern that applies
  the storage and retrieval capability of a DBMS to
  the application architecture
• an application level persistence pattern that
  builds persistence features into the application
  architecture
• Distribution the manner in which systems or
  components within systems communicate with one
  another in a distributed environment
• A broker acts as a middle-man between the
  client component and a server component.
• Middleware platform can hide the distribution
  problem

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4. Architecture Design Organization and
Refinement

• Control
• Procedure calls (local or remote)
• Events
• Messages and message buses
• Client/server middleware
• Delegate, Adapter
• Data
• Shared Data
• Pipes
• Messages and message buses

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4. Architecture Design Architectural Design

• The software must be placed into context
• the design should define the external entities
  (other systems, devices, people) that the
  software interacts with and the nature of the
  interaction
• A set of architectural archetypes should be
  identified
• An archetype is an abstraction (similar to a
  class) that represents one element of system
  behavior
• The designer specifies the structure of the
  system by defining and refining software
  components that implement each archetype

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4. Architecture Design Architectural Context
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4. Architecture Design Archetypes
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4. Architecture Design Component Structure
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4. Architecture Design Refined Component
Structure
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4. Architecture Design Analyzing
Architectural Design
1. Collect scenarios. 2. Elicit requirements,
constraints, and environment description. 3.
Describe the architectural styles/patterns that
have been chosen to address the scenarios and
requirements module view process view
data flow view 4. Evaluate quality attributes by
considered each attribute in isolation. 5.
Identify the sensitivity of quality attributes to
various architectural attributes for a specific
architectural style. 6. Critique candidate
architectures (developed in step 3) using the
sensitivity analysis conducted in step 5.
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The End

• Next Lecture
• Component Design