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Software
Architectural Design
by:
Dr. Bharat V. Chawda
Computer Engineering Department,
BBIT, VVNagar, Gujarat, India
1

Overview
 Introduction
 Architectural Design Decisions
 Architectural Views
 Architectural Patterns
 Application Architectures
(As per GTU Curriculum – Diploma in Computer/IT Engineering)
Based on Books:
1. Software Engineering – by Ian Sommerville
2

Introduction
 Architectural Design
 Concerned with –
 Understanding: how a system should be organized &
 Designing: the overall structure of the system.
3

Architectural Design Decisions
 Some fundamental questions…
 Is Generic application architecture available?
 What is the fundamental approach to structure
system?
 What architectural patterns or styles might be used?
 Which architecture is best: Non-fun requirements?
 How: system is distributed across cores &
processors?
 How: Structural components  sub-components?
 What Strategy will be used to control op of
components?
 How architectural design will be evaluated?
 How sys architecture will be documented?
4

Architectural Views
 Logical View
 Shows key abstractions in system as Objects or Classes
 System requirements r related to entities
 Process View
 Shows: how sys is composed of interacting processes
 Useful 4 making judgments about non-functional req.
 Development View
 Shows: how SW is decomposed for development
 Useful for SW managers and programmers
 Physical View
 Shows: sys HW; How SW components r distributed…
 Useful 4 sys engineers : planning a system deployment
5

Architectural Patterns
 MVC (Model-View-Controller) Architecture
 Layered Architecture
 Repository Architecture
 Client-Server Architecture
 Pipe and Filter Architecture
6

MVC Architecture: Concept
 Concept
 Separates presentation and interaction from sys data
 Model: Manages system data & associated operations
 View: Manages how data is presented to the user
 Controller: Manages user interactions; passes to M, V
 When used
 There are multiple ways to view & interact with data
 Future requirements for interaction and presentation of
data are unknown
9

MVC Architecture: Ad-Disad
 Advantage
 Allows data to change independently of its
representation and vice versa
 Supports presentation of the same data in different
ways
 Disadvantage
 Can involve additional code and code complexity: when
data model and interactions are simple
10

Layered Architecture
 Concept
11

Layered Architecture: Example
 Library System
12

Layered Architecture: Concept
 Concept
 Organizes the system into layers: Each layer has some
functionality
 A layer provides services to the layer above it
 Lowest-level layers provide core services: likely to be
used throughout the system
 When used
 Building new facilities on top of existing systems
 Development is spread across several teams…
 Requirement for multi-level security
13

Layered Architecture: Ad-Disad
 Advantage
 Allows replacement of entire layer without affecting
system
 Redundant facilities can be provided in each layer to
increase dependability; Ex: Authentication
 Disadvantage
 Providing clean separation between layers is difficult
 Service request is processed at each layer  May affect
the performance
14

Repository Architecture: Ex
 IDE
15

Repository Architecture: Concept
 Concept
 All data in a system is managed in a central database
(repository) : accessible to all components
 Components do not interact directly; but through
repository
 When used
 Systems having large volumes of data/info : need to be
stored for a long time
16

Repository Architecture: Ad-Disad
 Advantage
 Components can be independent – do not need to
know existence of other components
 Consistent data management
 Changes made by one component can be propagated
to all components
 Disadvantage
 Repository is a single point of failure
 Distributing repository across several computers may
be difficult
17

Client-Server Architecture: Ex
 Film/Video Library
18

Client-Server Arch: Concept
 Concept
 Functionality of the system is organized into services:
each service delivered from a separate server
 Clients are users of these services; Access servers to
make use of them
 When used
 Data in shared database need to be accessed from a
range of locations
 Load on a system is variable: As servers can be
replicated
19

Client-Server Arch: Ad-Disad
 Advantage
 Servers can be distributed across a network
 General functionality can be available to all clients: No
need to be implemented by all services: Ex – Printing
Service
 Disadvantage
 Each service is a single point of failure: Denial of
Service; Server Failure
 Unpredictable performance: depends upon network +
system
 Management prob possible: servers r owned by diff org
20

Pipe & Filter Architecture: Ex
 Invoice Management
21

Pipe n Filter Arch: Concept
 Concept
 Processing of data : Set of components  Filters
 Filters: discrete, transforms data
 Data flows from one component to another as in pipes
 When used
 In data processing applications : Inputs are processed
in separate stages to generate related outputs
 Ex: Batch processing, Transaction-based processing
22

Pipe n Filter Arch: Ad-Disad
 Advantage
 Easy to understand; Supports transformation reuse
 Evolution by adding transformations is straight forward
 Can be implemented: Sequential or Concurrent
 Disadvantage
 Data need to be parsed or unparsed as per format of
different components
 This increases system overhead
 Transformation can’t be reused if uses incompatible
data structures
23

Application Architectures
 What?
 Applications –
 As a starting point for the architectural design process
 As a design check list
 As a way of organizing the work of the development
team
 As a means for assessing components for reuse
 As a vocabulary for talking about types of applications
24

App Arch: Transaction Processing Sys
 Example: ATM System
25

App Arch: Information Systems
 Example: Hospital System
26

App Arch: Language Processing Sys
 Example: Language Processing System
27

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