Software Development, Lab Reports of Software Development Methodologies

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Unit- 1

Introduction to Software Design and Architecture

Overview

1.1 Overview of software design and architecture 1.2 Design levels: Architectural vs. detailed design 1.3 Design principles (modularity, abstraction, separation of concerns) 1.4 The role of the software architect 1.5 Key design goals: Performance, scalability, maintainability 1.6 Relationship between software design and software architecture 1.7 Object Oriented Software Development: Unified Software Development Process.

Vitruvius - De architectura

• Marcus Vitruvius Pollio (born c. 80-70 BC, died after c. 15 BC)
• author of De Architectura , known today as The Ten Books on

Architecture

• carefully described existing practices, not only in the design and

construction of buildings, but also in what are today thought of as

engineering disciplines

• Vitruvius is famous for asserting that a structure must exhibit the

three qualities of firmitas, utilitas, venustas - that is, it must be strong

or durable, useful, and beautiful.

Roman house plan after Vitruvius

More Architectures

Taj Mahal

Build a Palace?

Build a Palace?

?

Software Development

• Lists
• Arrays
• Class
• Object
• Procedures
• Functions
• Algorithms
• Etc.

Large-Scale, Complex software Systems…

• Large(Distributed) system
• Many people working on the

same problem

• Overly Complex
• Millions of Code…
• Should be delivered on time and

within budget!

Adding More Programmers… ??

Mythical Man-Month

• Fred Brooks, The Mythical Man-Month( 1975 )
• “Adding manpower to a late software project makes it later.”
• Conceptual Integrity
  • To make a user-friendly system, the system must have conceptual integrity, which can only be achieved by separating architecture from implementation.
  • A single chief architect... decides what goes in the system and what stays out.
  • "Having a system architect is the most important single step toward conceptual integrity...after teaching a software engineering laboratory more than 20 times, I came to insist that student teams as small as four people choose a manager, and a separate architect."

The Architect…

Structure Matters - Dijkstra 1968

• Dijkstra, 1968
  • "...Correct arrangement of the structure of software systems before simple programming..."
• Layered Structure
  • Programs are grouped into layers
  • Programs in one layer can only communicate with programs in adjoining layers
• With easier development and maintenance Focused on Structure of Programming Edsger W. Djikstra 1930 - 2002 A.D.