CS291 Software Design Studio Dr. Douglas C. Schmidt Professor of EECS Vanderbilt University Nashville, Tennessee

2 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

3 Required textbooks CS 291 Course Information CS 291 class web page ~schmidt/cs291/ My office hours in Featheringill Hall room 226 are MW 2:15-4:15 TA: Stoyan Paunov Stoyan’s office hours will be announced shortly Please send all questions to and I’ll send the answers to the class mailing list

4 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

5 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

6 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 11 Proxy 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”

7 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

8 Taxonomy of Patterns & Idioms TypeDescriptionExamples IdiomsRestricted 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

9 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 Scientific Visualization Frameworks are “semi-complete” applications

10 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 Locks IPC Math LOCAL INVOCATIONS APPLICATION- SPECIFIC FUNCTIONALITY EVENT LOOP GLUE CODE 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 Locking Logging Events

11 Overview of the ACE Frameworks Features Open-source 6+ integrated frameworks 250,000+ lines of C person-years of effort Ported to Windows, UNIX, & real-time operating systems e.g., VxWorks, pSoS, LynxOS, Chorus, QNX Large user community Acceptor Connector Component Configurator Stream Reactor Proactor Task Application- specific functionality

12 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