1. Software Modeling SWE5441 Lecture 3 Eng. Mohammed Timraz
University of Palestine
Faculty of Engineering and Urban planning
Software Engineering Department
Software Modeling SWE5441
Lecture 3
Eng. Mohammed Timraz
Electronics & Communication Engineer

2. Two Types of Design Models
Static model:
Represents the parts, relationships, and attributes that do not change (during execution of the software )
Dynamic model:
Represents what happens during the execution of the software.

3. Software Product Designer & Engineering Designer
A software product designer is concerned with:
Product features and capabilities.
Visually appealing and easy to use user interfaces.
Fitting into users’ business processes and operability.
Product packaging.
** ( a closer tie to what is specified in the product requirements )
A software engineering designer is concerned with:
Individual functionalities and performance.
Internal structure of the software system.
Individual programs and their interfaces & interactions.
The data flow through the software system (including inputs and outputs).
System maintenance and evolution.
** (a closer tie to the internal technical design )
(similarities and differences?)

4. Software Design Team We Need both: Software Product Designer.
Software Engineering Designer.
Different sets of skills needed:
Product Designer: knowledge of:
User interface, communicating the requirements/product design, marketing, business processes, applications domain knowledge
Engineering Designer: knowledge of:
Architecture, programming, database and data structures, development platforms, networking, operating systems.

5. Software Design Design Requirements Code-Implementation
product designer
Requirements
engineering designer
Design
Code-Implementation
product designer
Test Case Design
Testing
Builds
Maintenance
(product and
engineering
redesign)

6. Software Product Design .vs. Software Engineering Design
Product Design Activity:
output is a software requirements specification document.
Answers mostly “what” the user and customer needs and wants.
formulates the problem in an organized way :
Functionalities & features
Looks and interfaces
Constraints
Engineering Design Activity:
output is a design specification document
Answers mostly “how” the software will be put together to respond to the users’ needs and wants.
formulates the solution in an organized way.
High level software:
Components and How they interact.
Rationale behind your design decisions ( * my addition )
Low level specifications of programs and data and their behavior
organize: relating these

7. Is There a Design Method?
There is no ONE design method in the form of a “recipe” for design.
There are several methods that all speak to:
Design process: a set of steps that starts with “some inputs” and transform that input to some output and eventually results in a design specification (e.g. structured method, OO-method, etc.).
Design notation: a set of symbolic representations and how the symbols are to be used (e.g. UML, etc.).
Design “heuristics”: a set of guiding rules (e.g. low coupling and high cohesion)

8. The Software Lifecycle
Systems Engineering
Requirements Analysis
Software Design
Implementation
Testing
Deployment
Evolution
The process/activities of developing and evolving software

9. The Software Lifecycle
Software Design
Requirements Analysis
Implementation
Systems Engineering
Testing
Systems Engineering
Identify needs/problems
Allocation of roles
Hardware
Procedures
Software
Feasibility studies
Deployment
Evolution

10. The Software Lifecycle
Software Design
Requirements Analysis
Implementation
Systems Engineering
Identify needs, problems and allocate roles
Testing
Deployment
Evolution
Requirements Analysis
Define goals, objectives, features of target software

11. The Software Lifecycle
“Up to 70% of all faults detected in large-scale software projects are introduced in requirements and design. Detecting the causes of those faults early may reduce their resulting costs by a factor of 100 or more.”
The Software Lifecycle
Software Design
Requirements Analysis
Implementation
Systems Engineering
Define software features
Identify needs, problems and allocate roles
Testing
Deployment
Software design
Creating a blueprint for building the software
Architectural design
Subsystem design
Detailed design
Procedural Design
User Interface Design
Database Design
Data Structures Design
Test case design
Evolution

12. The Software Lifecycle
Software Design
Requirements Analysis
Implementation
Create blueprint
Systems Engineering
Define software features
Identify needs, problems and allocate roles
Testing
Deployment
Evolution
Implementation
Creating the finished product – the program
Coding
Writing code for the classes and operations
Generate object code
Create Test cases
Create user manuals

13. The Software Lifecycle
Software Design
Create code
Requirements Analysis
Implementation
Create blueprint
Systems Engineering
Define software features
Identify needs, problems and allocate roles
Testing
Deployment
Evolution
Testing
Determining if the software has errors/fulfils its requirements
Test planning
Unit testing
Subsystem testing
Integration testing
Regression testing
Test case design

14. The Software Lifecycle
Software Design
Create code
Requirements Analysis
Implementation
Create blueprint
Systems Engineering
Define software features
Identify needs, problems and allocate roles
Testing
Deployment
Uncovering errors
Deployment
Making the software available for use
Deployment/installation planning
Develop documentation
Hardware configuration
Installation
Software distribution
Training
Evolution

15. The Software Lifecycle
Software Design
Create code
Requirements Analysis
Implementation
Create blueprint
Systems Engineering
Define software features
Identify needs, problems and allocate roles
Testing
Deployment
Uncover errors
Evolution
Managing the software
Configuration management
Controlling change as software evolves
Technical support
Software lifecycle activities
Evolution
Make software available for use

16. Inputs To Software Design
Software requirements specification
Describes WHAT system shall do not HOW.
External view of system to be developed.
Environmental constraints
Hardware, language, system usage.
Design constraints
Design method.
Design notation.

17. Outputs From Software Design
Architectural Design
Overall description of software structure, Textual and Graphical.
Specification of software components and their interfaces.
Data Design.
Detailed Design of each component
Internal logic.
Internal data structures.
Design decisions made
Design rationale.
Traces to requirements.

18. Software Design Process
Software life cycle models:
Waterfall: limitations of Waterfall Model
Incremental: evolutionary prototyping
Exploratory: throwaway prototyping
Spiral model: risk driven process model

19. Waterfall Model

20. Software Life Cycle Model (Definition)
Requirements Analysis and Specification
Analysis of user's problem.
Specification of "what" system shall provide user.
Architectural Design
Specification of "how" system shall be structured into components.
Specification of interfaces between components.
Data Design.

21. Software Life Cycle Model (Construction)
Detailed Design
Internal design of individual components.
Design of logic and data structures.
Coding
Map component design to code.
Unit Testing
Test individual components.

22. Software Life Cycle Model (Integration and Test)
Integration Testing
Gradually combine components and test combinations.
System Testing
Test of entire system against software requirements.
Acceptance Test
Test of entire system by user prior to acceptance.

23. Software Life Cycle Model (Maintenance)
Modification of software system after installation and acceptance
Fix software errors.
Improve performance.
Address changes in user requirements.
Often implies significant software redesign

24. Limitations of Waterfall Model
Does not show iteration in software life cycle.
Does not show overlap between phases.
Software requirements are tested late in life cycle.
Operational system available late in life cycle.

25. Prototyping During Requirements Phase
Problem
Software requirements are tested late in life cycle.
Solution
Use throw-away prototyping.
Help ensure requirements are understood
Also first attempt at designing system
Design of key file and data structures
Design of user interface
Early design tradeoffs

32. Spiral Process Model (SPM)
SPM consists of four main activities that are repeated for each cycle:
Defining objectives, alternatives and constraints
Analyzing risks
Developing and verifying product
Spiral planning
Number of cycles is project specific
Risk driven process
Analyze risks in second quadrant

34. Design Concepts