CS291CS291

Software Design StudioSoftware Design Studio

Dr. Douglas C. Schmidtd.schmidt@vanderbilt.edu

www.dre.vanderbilt.edu/~schmidt/cs291/

Professor of EECS Vanderbilt University Nashville, Tennessee

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CS 291 Course Philosophy

Good design and programming is not learned by generalities, but by seeing how significant programs can be made clean, easy to read, easy to maintain and modify, human-engineered, efficient, and reliable, by the application of good design and programming practices. Careful study and imitation of good designs and programs significantly improves development skills.

- Kernighan and Plauger

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•Required textbooks

CS 291 Course Information•CS 291 class web page

•www.dre.vanderbilt.edu/ ~schmidt/cs291/

•My office hours in Featheringill Hall room 226 are

•MW 2:15-4:15

•TA: Stoyan Paunov

•s.paunov@vanderbilt.edu

•Stoyan’s office hours will be announced shortly

•Please send all questions to d.schmidt@vanderbilt.edu and I’ll send the answers to the class mailing list

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CS 291 Course Contents•Focus on topics important to developing & maintaining quality software:

•Reuse of patterns & software components

•Developing, documenting, testing, & applying reusable classes & object-oriented frameworks using C++

•Patterns will be taught to provide good role models for software designs & to clearly articulate design tradeoffs

•Object-oriented techniques will be taught to show how to build software architectures that decouple inter-dependencies between components

•I assume you already know C++!!!

•The course will cover object-oriented techniques that address:

•Decentralized software architecture

•Architectural and design patterns

•Class interface definition

•Component reuse

•Module decomposition

•Hierarchical classification

•Extensible object-oriented application frameworks

•Several case studies will be used in class to illustrate the OO design & programming process

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CS 291 Course Work•There will be 5-6 programming assignments

•Can be done on Windows or Linux

•Must be done individually

•Programs will be graded as follows:

•40% execution correctness

•30% structure (e.g., modularization, information hiding, etc.)

•10% insightful programming (e.g., developing reusable class components, etc.)

•10% Consistent style (e.g., capitalization, indenting, etc.)

•10% appropriate commenting style

•There will be a 5 point deduction (out of a possible 100 points) for each day that your program is late

•Programs turned in later than two calendar days after the due date will receive a 0

•There will be weekly quizzes (starting today)

•There will be a comprehensive final exam

•The relative weighting of each portion of the course is :

•40% Programming projects

•35% Quizzes

•25% Final Exam

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•Present solutions to common software problems arising within a certain context

Overview of Patterns

•Capture recurring structures & dynamics among software participants to facilitate reuse of successful designs

The Proxy Pattern

1 1Proxy

service

Service

service

AbstractService

service

Client

•Help resolve key software design forces

•Flexibility•Extensibility•Dependability•Predictability•Scalability•Efficiency

•Generally codify expert knowledge of design strategies, constraints & “best practices”

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Overview of Pattern Languages

Benefits of Pattern Languages• Define a vocabulary for talking about software

development problems• Provide a process for the orderly resolution of

these problems• Help to generate & reuse software architectures

Motivation•Individual patterns & pattern catalogs are insufficient

•Software modeling methods & tools largely just illustrate how – not why – systems are designed

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Taxonomy of Patterns & Idioms

Type Description Examples

Idioms Restricted to a particular language, system, or tool

Scoped locking

Design patterns

Capture the static & dynamic roles & relationships in solutions that occur repeatedly

Active Object, Bridge, Proxy, Wrapper Façade, & Visitor

Architectural patterns

Express a fundamental structural organization for software systems that provide a set of predefined subsystems, specify their relationships, & include the rules and guidelines for organizing the relationships between them

Half-Sync/Half-Async, Layers, Proactor, Publisher-Subscriber, & Reactor

Optimization principle patterns

Document rules for avoiding common design & implementation mistakes that degrade performance

Optimize for common case, pass information between layers

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Overview of Frameworks

Framework Characteristics

Application-specific functionality

•Frameworks exhibit “inversion of control” at runtime via callbacks

Networking Database

GUI

•Frameworks provide integrated domain-specific structures & functionality

Mission Computing E-commerce

ScientificVisualization

•Frameworks are “semi-complete” applications

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Comparing Class Libraries, Frameworks, & Components

Class Libraries

Frameworks

Macro-levelMeso-levelMicro-level

Borrow caller’s thread

Inversion of control

Borrow caller’s thread

Domain-specific or Domain-independent

Domain-specific

Domain-independent

Stand-alone composition

entities

“Semi-complete”

applications

Stand-alone language entities

Components

Class Library Architecture

ADTs

Strings

LocksIPC

Math

LOCAL INVOCATIONSAPPLICATION-

SPECIFICFUNCTIONALITY

EVENTLOOP

GLUECODE

Files

GUI

A class is a unit of abstraction & implementation in an OO

programming language

Framework Architecture

ADTs

Locks

Strings

Files

INVOKES

A framework is an integrated set of classes that collaborate to produce a reusable architecture for a family of applications

Reactor

GUI

DATABASE

NETWORKING

APPLICATION-SPECIFIC FUNCTIONALITY CALLBACKS

Middleware Bus

Component Architecture

A component is an encapsulation unit with one or more interfaces that provide

clients with access to its services

Naming

LockingLogging

Events

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Overview of the ACE Frameworks

Features•Open-source•6+ integrated frameworks

•250,000+ lines of C++•40+ person-years of effort

•Ported to Windows, UNIX, & real-time operating systems

• e.g., VxWorks, pSoS, LynxOS, Chorus, QNX

•Large user community

www.cs.wustl.edu/~schmidt/ACE.html

Acceptor Connector Component

Configurator

Stream

Reactor Proactor

Task

Application-specific

functionality

Local AreaNetwork

NYSE

NASDAQ

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Pattern Benefits

• Preserve crucial design information used by applications & middleware frameworks & components

• Facilitate reuse of proven software designs & architectures

• Guide design choices for application developers

The POSA2 Pattern Language