SOEN 343 Software Design Computer Science and Software

SOEN 343 Software Design Computer Science and Software Engineering Department Concordia University Fall 2004 Instructor: Patrice Chalin SOEN 343, © P. Chalin SOEN 344, © P. Chalin

Agenda – Lecture 11 b • • Exercise Set 8: finishing up GRASP: Indirection Interfaces (& Larman’s example of Composite) From Requirements to Design 10/3/2020 SOEN 343, © P. Chalin, 2

Sample JSP: Hello. jsp – Exercise Set 8 used View. Task. List. jsp <%@ page content. Type=“…" import=“…" %> <html> <% String full. Name = (String) request. get. Attribute("full. Name"); %> <head><title>Hello</title></head> <body> <h 1>Hello <%= full. Name %>!</h 1> </body> </html> 10/3/2020 SOEN 343, © P. Chalin, 3

GRASP • • • … Polymorphism. Pure Fabrication. Indirection. Protected Variations. 10/3/2020 SOEN 343, © P. Chalin, 4

GRASP: Indirection Problem • Where to assign a responsibility to avoid direct coupling between two (or more) things? How to decouple objects so that low coupling is supported and reuse potential remains higher? Solution • Assign the responsibility to an intermediate object to mediate between other components or services so that they are not directly coupled. Can you think of an example from EA? 10/3/2020 SOEN 343, © P. Chalin, 5

Do-it-all Transaction Script 10/3/2020 Page Controller redesign Domai Presentati Data Source on n Redesigning Do-it-all TS (6 classes) Template View Person Transaction Script Person Mapper Table Data Gateway SOEN 343, © P. Chalin, 6

Indirection Mapper • Mapper isolates Person from TDG and TDG from Person. 10/3/2020 SOEN 343, © P. Chalin, 7

Interfaces • A class defines both – A type, and – A (complete or partial) implementation. • An interface defines only a type. • An interface contains only – Non-static, public methods, or – Static, public final fields. 10/3/2020 SOEN 343, © P. Chalin, 8

Happy Interface public interface Happy { int i = 0; void happy(); } • Actually represents this (which is also legal) public interface Happy { static final int i = 0; /* non-static */ abstract void happy(); } 10/3/2020 SOEN 343, © P. Chalin, 9

Interfaces: Illustration (Realization of multiple interfaces) (Diagram given in class) • Person, HS_Person • Happy, Sad interfaces. 10/3/2020 SOEN 343, © P. Chalin, 10

Composite Pricing Strategies • Interface • Realization 10/3/2020 SOEN 343, © P. Chalin, 11

Recall … • Way back in week 5 b we asked the question … How do I come up with a design? 10/3/2020 SOEN 343, © P. Chalin, 12

How Do I Come Up With a Design? • What are the inputs to the activities of design? • What are the outputs? 10/3/2020 SOEN 343, © P. Chalin, 13

Design Activities: Inputs & Outputs • Product requirements • Architectural factors … • Architecture Document • Project plan – Architectural Style(s) • … 10/3/2020 SOEN 343, © P. Chalin, 14

Design Input: SRS • What is contained in the SRS? (name some of its parts) 10/3/2020 SOEN 343, © P. Chalin, 15

Design: From SRS to. . . • Domain Model • Design Model • Use Case Model • Control Style / Pattern • User-interface design … 10/3/2020 SOEN 343, © P. Chalin, 16

Design Model Classes • Domain Model often used as first approximation to Design Model. • Domain Model contains – Conceptual classes • Conceptual classes used as basis for similarly named design classes. • (E. g. Larman, Chapter 16, p. 222. ) 10/3/2020 SOEN 343, © P. Chalin, 17

Domai Presentati Data Source on n EA Patterns Page Controller Template View Front Controller Transform View Transaction Script Domain Model Data Mapper Active Record Table Module Row Data Gateway Table Data Gateway 10/3/2020 SOEN 343, © P. Chalin, 18

Enterprise Applications: Domain Model • Requirements Domain Model 10/3/2020 • Design Model: classes Domain Model pattern SOEN 343, © P. Chalin, 19

From Requirements to Design Requirements artifacts: e. g. Design artifacts: e. g. • Software Architecture Document • Domain Model • Design Model • Use Case Model 10/3/2020 • User-interface design … SOEN 343, © P. Chalin, 20

Conceptual Classes to Design Classes • Domain Model pattern 10/3/2020 SOEN 343, © P. Chalin, 21

Representational Gap • Larman, Section 17. 2: The object developer has taken inspiration from the real-world domain in creating software classes. Therefore, the representational gap between how stakeholders conceive the domain, and its representation in software, has been lowered. 10/3/2020 SOEN 343, © P. Chalin, 22

From Rich Conceptual Domain Model to Rich set of Domain Model classes 10/3/2020 SOEN 343, © P. Chalin, 23

Tutorial • Support for A 2. • A 3 will be posted shortly. 10/3/2020 SOEN 343, © P. Chalin, 24