SOEN 343 Software Design Computer Science and Software

SOEN 343 Software Design Computer Science and Software Engineering Department Concordia University Fall 2005 Instructor: Patrice Chalin SOEN 343, © P. Chalin SOEN 344, © P. Chalin

Agenda – Lecture 9 a • Architecture: 4+1 view model. – Web EA: Process, Deployment views. • GRASP: PV. • Web EA: – Applying PV, and separating concerns. – Refactoring: • From a 1 component design solution. • To a 3 component design solution. 12/27/2021 SOEN 343, © P. Chalin, 2

Architecture • … deals with the top-level structure. – Components – Interrelationships 12/27/2021 SOEN 343, © P. Chalin, 3

Documentation of Architectures • Architecture Document = View A + View B + View C + … View X + “Beyond Views” 12/27/2021 SOEN 343, © P. Chalin, 4

“ 4+1” View Model of Arch. • By Philippe Kruchten [Kruchten 95] (URL to paper given on web site. ) • Rational Unified Process. 12/27/2021 SOEN 343, © P. Chalin, 5

“ 4+1” View Model of Arch. Implementation/ Deployment/ 12/27/2021 SOEN 343, © P. Chalin, 6

Web EA: Process, Deployment Views • Given in class: – Deployment view. – Process view. 12/27/2021 SOEN 343, © P. Chalin, 7

GRASP • • • Information Expert. Creator. High Cohesion. Low Coupling. Controller. 12/27/2021 • • Polymorphism. Pure Fabrication. Indirection. Protected Variations. SOEN 343, © P. Chalin, 8

GRASP Protected Variations • Problem: How to design objects, subsystems, and systems so that the variations or instability in these elements does not have an undesireable impact on other elements? • Solution: Identify points of predicted variation or instability; assign responsibility to create a stable interface around them. 12/27/2021 SOEN 343, © P. Chalin, 9

Core PV Mechanisms • • Encapsulation. Interfaces. Polymorphism. Indirection, … (Note: we are speaking of mechanisms, not principles) 12/27/2021 SOEN 343, © P. Chalin, 10

PV: Pick Your Battles • Beware not to try to overly “future-proof” your designs. • Actually, this is true of any principle … 12/27/2021 SOEN 343, © P. Chalin, 11

Applying PV to Web EA • Consider a single servlet which offers the greeting “Hello”. • Refactor it with the goal of applying PV and separate concerns. 12/27/2021 SOEN 343, © P. Chalin, 12

Applying PV to Web EA • (Solution given in class) 12/27/2021 SOEN 343, © P. Chalin, 13

Applying PV to Web EA (given in class) • Greeting example with successively refined design solutions: 1. Start from design of 1 servlet class whose purpose is to offer a greeting. 2. Factor out domain logic to create design with: • • • Servlet in Application layer. A class in Domain Logic layer to be responsible for domain logic. How are the responsibilities of MVC distributed now? 3. Separate V and C by using JSP for V. 12/27/2021 SOEN 343, © P. Chalin, 14