Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 1 Introduction to Software Engineering CEN 4010

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2 Objectives of the Class  Understand how to  produce a high quality software system within time  while dealing with complexity and change  Understand System Modeling  Learn UML (Unified Modeling Language)  Use Case modeling  Object Modeling  Dynamic Modeling

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 3 Course outcomes  Course Outcomes: At the end of this semester you will:  Be familiar with the Software Development Life Cycle  Master the techniques to gather and specify the requirements of a medium-size software system using UML  Master the techniques to design and implement a medium-size software system  Be familiar with software testing techniques  Be familiar with system walkthroughs  Be familiar with software documentation  Be familiar with working in a small software development team

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4 20 Software Engineering: Definition Software Engineering is a collection of techniques, methodologies and tools that help with the production of  a high quality software system  with a given budget  before a given deadline while change occurs.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5 Scientist vs Engineer  Computer Scientist  Proves theorems about algorithms, designs languages, defines knowledge representation schemes  Has infinite time…  Engineer  Develops a solution for an application-specific problem for a client  Uses computers & languages, tools, techniques and methods  Software Engineer  Works in multiple application domains  Has limited time  …while changes occurs in requirements and available technology

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6 Software Engineering: A Problem Solving Activity  Analysis: Understand the nature of the problem and break the problem into pieces  Synthesis: Put the pieces together into a large structure For problem solving we use  Techniques (methods):  Formal procedures for producing results using some well-defined notation  Methodologies:  Collection of techniques applied across software development and unified by a philosophical approach  Tools:  Automated systems to accomplish a task

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 7 Factors affecting the quality of a software system  Complexity:  The system is so complex that nobody can understand the entire system  The introduction of one bug fix causes another bug  Change:  The complexity of a software system increases with each change: Each implemented change erodes the structure of the system which makes the next change even more expensive  As time goes on, the cost to implement a change will be too high, and the system will then be unable to support its intended task. This is true of all systems, independent of their application domain or technological base.  Conformity:  Must conform to arbitrary rules  Invisibility:  Software can not be seen. Only different aspects can be described

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8 Why are software systems so complex?  The problem domain is difficult  The development process is very difficult to manage  Software offers extreme flexibility

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9 Dealing with Complexity 1. Abstraction 2. Decomposition 3. Hierarchy

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java Abstraction  Inherent human limitation to deal with complexity  The phenomena  Chunking: Group collection of objects  Ignore unessential details: => Models

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11 Models are used to provide abstractions  System Model:  Object Model: What is the structure of the system? What are the objects and how are they related?  Functional model: What are the functions of the system? How is data flowing through the system?  Dynamic model: How does the system react to external events? How is the event flow in the system ?  Task Model:  PERT Chart: What are the dependencies between the tasks?  Schedule: How can this be done within the time limit?  Org Chart: What are the roles in the project or organization?  Issues Model:  What are the open and closed issues? What constraints were posed by the client? What resolutions were made?

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java Decomposition  A technique used to master complexity (“divide and conquer”)  Functional decomposition  The system is decomposed into modules  Each module is a major processing step (function) in the application domain  Modules can be decomposed into smaller modules  Object-oriented decomposition  The system is decomposed into classes (“objects”)  Each class is a major abstraction in the application domain  Classes can be decomposed into smaller classes

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 13 Functional Decomposition Top Level functions Level 1 functions Level 2 functions Machine Instructions System Function Load R10 Add R1, R10 Read Input Transform Produce Output Transform Produce Output Read Input

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14 Functional Decomposition  Functionality is spread all over the system  Maintainer must understand the whole system to make a single change to the system  Consequence:  Codes are hard to understand  Code that is complex and impossible to maintain  User interface is often awkward and non-intuitive

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java Hierarchy  Hierarchy describes relationships between abstractions:  "Part of" hierarchy  "Is-kind-of“ (isA) hierarchy

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16 Part of Hierarchy Computer I/O Devices CPU Memory Cache ALU Program Counter

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 17 Is-Kind-of Hierarchy Cell Muscle Cell Blood Cell Nerve Cell Striate Smooth RedWhite Cortical Pyramidal

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 18 Software Lifecycle  Software lifecycle:  Set of activities and their relationships to each other to support the development of a software system  Typical Lifecycle questions:  Which activities should I select for the software project?  What are the dependencies between activities?  How should I schedule the activities?

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 19 Software Process  Software Specification – requirements elicitation (func. & non-func.) and analysis.  Software Development – systems design, detailed design (OO design), implementation.  Software Validation – validating system against requirements (testing).  Software Evolution – meets changing customer needs and error correction (maintenance).

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20 Software Specification Functionality of the software and constraints (non-functional requirements) on its operation must be defined. Involves: Requirements elicitation  The client and developers define the purpose of the system.  Output: a description of the system in terms of actors and uses cases.  Actors include roles such as end users and other computers the system needs.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 21 Software Specification  Uses cases are general sequences of events that describe all possible actions between actors and the system for a given functionality. Analysis  Objective: produce a model of the system that is correct, complete, consistent, unambiguous, realistic, and verifiable.  Model is checked for ambiguities and inconsistencies.  Output: system model annotated with attributes, operations, and associations. Described in terms of structures and dynamic interoperation  Functional model  Object Model  Dynamic Model

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 22 Software Development Software to meet the specification is produced. System Design  Goals of the project are defined.  System decomposed into smaller subsystems (architectural model).  Strategies to build system identified e.g., hardware and software platform, data management, control flow, and security.  Output: model describing subsystem decomposition and system strategies.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23 Software Development Object Design  Bridges the gap between analysis model and the strategies identified in the system design. Includes:  describing object and subsystem interfaces,  selecting off –the-shelf components,  Restructure object model to attain design goals e.g., extensibility, understandability, and required performance.  Output: detailed object model annotated with constraints and supporting documentation.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24 Software Development Implementation  Translation of the solution model into source code.  Implements the attributes and methods of each object integrating all objects such that they function as a single system.  Spans the gap between the detailed object design model and a complete set of source code files.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 25 Software Validation Ensures the software does what the customer want, i.e., that the software conforms to its specification and meets the expectations of the customer. Validation: ‘Are we building the right product?’ Ensures the software meets the expectations of the customer. Verification: ‘Are we building the product right?’ Ensures the software conforms to the specification.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 26 Software Validation  Techniques 1.Software inspections (static): analyze and check system representations e.g., requirements documents, design diagrams, and program source code. 2.Software testing (dynamic): executing an implementation of the software with test data and examining the outputs against expected results.  establishes the existence of defects.  Debugging is a process that locates and corrects these defects.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 27 Software Evolution Software must evolve to meet the customer needs. Software maintenance is the process of changing a system after it has been delivered. Reasons for maintenance:  to repair faults,  to adapt the software to a different operating environment, and  to add to or modify system’s functionality.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 28 Software Lifecycle Activities Subsystems Structured By class... Source Code Implemented By Solution Domain Objects Realized By System Design Object Design Implemen- tation Testing Application Domain Objects Expressed in Terms Of Test Cases ? Verified By class.... ? Requirements Elicitation Use Case Model Analysis...and their models

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 29 Attributes of Good Software  Maintainability  Ease of changing the software to meets the changing needs of the customer.  Dependability  Reliability, security and safety.  Efficiency  Responsiveness, processing time, and memory usage.  Usability  Appropriate user interface and adequate documentation.  Reusability  The ability to reuse components of the system in future software development projects