Ch08-Architecture Design

Systems Analysis and DesignSystems Analysis and Design
5th Edition5th Edition
Chapter 8. Architecture DesignChapter 8. Architecture Design
Alan Dennis, Barbara Haley Wixom, and Roberta Roth
8-1© Copyright 2011 John Wiley & Sons, Inc.

Chapter 8 Outline
Elements of an architecture
design.
Creating an architecture design.
Hardware and software
specification.
© Copyright 2011 John Wiley & Sons, Inc. 8-2

INTRODUCTION
 Architecture design
– Plans for how the system will be distributed across
multiple computers and what hardware, operating
system software, and application software will be
used for each computer.
 Key factors in architecture design
– Nonfunctional requirements developed early in the
analysis phase play a key role in architecture design.
 Hardware and software specification
– Defines what hardware and software are needed for
the new system.

ELEMENTS OF AN ARCHITECTURE
DESIGN
 The objective of architecture design
is to determine how the software
components of the information
system will be assigned to the
hardware devices of the system.

Architectural Components
 The major architectural components of any system
are the software and the hardware.
 All software systems can be divided into four basic
functions:
- Data storage.
- Data access logic: the processing required to access
stored data.
- Application logic: the logic documented in the DFDs,
use cases, and functional requirements.
- Presentation logic: the display of information to the
user and the acceptance of the user’s commands.

(cont’d)
The three primary hardware
components:
- Client computers: Input-output devices
employed by users (e.g., PCs, laptops,
handheld devices, smart phones)
- Servers: Larger multi-user computers
used to store software and data.
- The network: Connects the computers.

Client-Server Architectures
Client-server architectures balance the
processing between client devices and one or
more server devices.
The client is responsible for the presentation
logic, whereas the server is responsible for the
data access logic and data storage.
A thick or fat client contains all or most of
application logic; whereas a thin client
contains a small portion of the application
logic.

(cont’d)

(cont’d)
 Client-server architectures have four important
benefits.
- Scalable
- Can support different types of clients and servers
through middleware.
- The presentation logic, the application logic, and the
data processing logic can be independent.
- If a server fails, only the applications requiring that
sever are affected.
 The major limitation of client-server architectures is
their complexity.

Client-Server Tiers
 There are many ways in which the
application logic can be partitioned
between the client and the server.
The arrangement in Figure 8-1 is
called two-tiered architecture.

(cont’d)
Three-tiered architecture

(cont’d)
n-tiered architecture

Less Common Architectures
Server-Based Architectures

Client-Based Architectures

Advances in Architecture
Configurations
Advances in hardware, software, and
networking have given rise to a
number of new architecture options.
- Virtualization.
- Cloud computing.

Virtualization
 Virtualization refers to a creation of a virtual
device or resource, such as a server or storage
device.
 Server virtualization involves partitioning a
physical server into smaller virtual servers.
 Storage virtualization involves combining
multiple network storage devices into what
appears to be single storage unit.

Cloud Computing
 Cloud computing – everything from
computing power to computing
infrastructure, applications, business
processes to personal collaboration can be
delivered as a service wherever and whenever
needed.
The “cloud” can be defined as the set of
hardware, networks, storages, devices, and
interfaces that combine to deliver aspects of
computing as a service.© Copyright 2011 John Wiley & Sons, Inc. 8-17

(cont’d)
 Cloud computing can be
implemented in three ways:
- private cloud,
- public cloud, and
- hybrid cloud.
 At this time, cloud computing is in
its early stage of development.

(cont’d)
 Advantages of cloud computing
1. The resources allocated can be increased or
deceased based on demand.
2. Cloud customers can obtain cloud resources
in a straightforward fashion.
3. Cloud services typically have standardized
APIs (application program interfaces).
4. The cloud computing model enables
customers to be billed for resources as they
are used. © Copyright 2011 John Wiley & Sons, Inc. 8-19

Comparing Architecture Options
Most systems are built to use the existing
infrastructure in the organization, so often
the current infrastructure restricts the
choice of architecture.
Each of the architectures discussed has its
strengths and weaknesses.
Client-server architectures are strongly
favored on the basis of the cost of
infrastructure.

CREATING AN ARCHITECTURE DESIGN
 Creating an architecture design begins with
the nonfunctional requirements.
Refine the nonfunctional requirements into
more detailed requirements for the
selection of architecture.
The nonfunctional requirements and the
architecture design are used to develop the
hardware and software specification.

Operational Requirements

Performance Requirements

Security Requirements

Cultural and Political Requirements

Designing the Architecture
In many cases, the technical environment
requirements as driven by the business
requirements define the application
architecture.
If the technical environment requirements do
not require the choice of a specific
architecture, then other nonfunctional
requirements become important for designing
the architecture.

(cont’d)
Nonfunctional Requirements and
Their Implications for Architecture
Design

HARDWARE AND SOFTWARE
SPECIFICATION
The design phase is also the time to
begin selecting and acquiring the
hardware and software that will be
needed for the future system.
The hardware and software
specification is a document that
describes what hardware and software
are needed to support the application.

(cont’d)
 Sample hardware and software specification

(cont’d)
 First, you define software
– Define the operating system and any special purpose
software
– Consider additional costs such as training, warranty,
maintenance, licensing agreements.
 Next, you create a list of the hardware needed
– Database servers, network servers, peripheral devices,
clients, backup devices, storage components, and
others.
 Finally, you describe the minimum requirements for
each piece of hardware.

(cont’d)
Factors in hardware and software selection

SUMMARY
Application architecture.
- Client-server architecture.
- Advances in architecture configurations:
virtualization and cloud computing.
Architecture Design.
- Nonfunctional requirements.
Hardware and software
specification.
- A document that describes what hardware and
software are needed to support the application.

Copyright 2011 John Wiley & Sons, Inc.
All rights reserved. Reproduction or translation of this work
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information contained herein.

Ch08-Architecture Design

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