different design techniques

7/23/2019 Different Design Techniques

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Term Paper

Analysis and Design of

Infor

mation Systems

Topic: Different design techniques

Rishab Mehta Reg. No.

3450070062Roll No.59 Section: c1802

Declaration:

I declare that this assignment is my individual work. I have not

copied from any other students work or from any other source

except where due acknowledgment is made explicitly in thetext, nor has any part been written for me by another person.

Students Signature:


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Rishab Mehta

Index

1. Introduction 3

a. What is a system?

b. SDLC

2. System Design..........................................................................................................4

a. Preliminary or general design

b. Structure or detailed design

i. Flowchart -4

ii. Data flow diagram (DFDs) -5

iii. Data dictionary -6

iv. Structured English -6

v. Decision table -6

vi. Decision tree -7

3. Techniques7

4. Bibliography.8


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1. Introduction:

Before discussing the different design techniques used in system designing we are going to

discuss some basic terms used and there meaning.

a. What is a System?

A collection of components that work together to realize some objective forms a system.Basically there are three major components in every system, namely input, processing and

output.

b. Briefing System Development Life Cycle (SDLC)

The Software Development Lifecycle (SDLC) is a conceptual model used in projectmanagement that describes the stages involved in an information system development

project, from an initial feasibility study through maintenance of the completed application.

The figure below shows the different phases followed in SDLC:

Here the design phase can be divided into two parts:

System design

Coding


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2. System Design

Based on the user requirements and the detailed analysis of a new system, the new system

must be designed. This is the phase of system designing. It is a most crucial phase in the

development of a system. Normally, the design proceeds in two stages:

c. Preliminary or general design

d. Structure or detailed design

a. Preliminary or general design: In the preliminary or general design, the features of the

new system are specified. The costs of implementing these features and the benefits to bederived are estimated. If the project is still considered to be feasible, we move to the

detailed design stage.

b. Structure or Detailed design: In the detailed design stage, computer oriented work

begins in earnest. At this stage, the design of the system becomes more structured. Structuredesign is a blue print of a computer system solution to a given problem having the same

components and inter-relationship among the same components as the original problem.

Input, output and processing specifications are drawn up in detail. In the design stage, theprogramming language and the platform in which the new system will run are also decided.

There are several tools and techniques used for designing. These tools and techniquesare:

i. Flowchart

ii. Data flow diagram (DFDs)

iii. Data dictionary

iv. Structured English

v. Decision table

vi. Decision tree

i. Flowcharts

Systems flowcharts are graphic illustrations of the physical flow of information through the entire

accounting system. A systems flowchart is commonly used in analysis and design. Flow-lines

represent the sequences of processes, and other symbols represent the inputs and outputs to a


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process. Accountants use system flowcharts to describe the computerized processes, manual

operations, and inputs and outputs of an application system. Auditors use system flowcharts to

identify key control points in an accounting systems internal control structure.

It is nothing but a diagrammatic representation of the various steps involved in designing a

system. Some of the boxes which are used in flowcharts are:

A flowchart consists of a set of flowchart symbols connected by arrows. Each symbol

contains information about what must be done at that point & the arrow shows the flow of

execution of the algorithm i.e. they show the order in which the instructions must be

executed. The purpose of using flowcharts is to graphically present the logical flow of data

in the system and defining major phases of processing along with the various media to be

used.

Flowcharts are of three types:

a. System flowcharts

b. Run flowcharts

c. Program flowcharts

ii. Data Flow Diagram

Data flow diagrams illustrate how data is processed by a system in terms of inputs and outputs. The

main merit of DFD is that it provides an overview of what data flows in a system, whattransformations are done on the data, what files are used and where results flow. It is a good

documentation aid which is understood by both programmers and non-programmers (i.e.,


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laypersons). As DFD specifies only what processes are performed and not how they areperformed it is easily understood by a non-programming user.

Components of DFD

DFDs are constructed using four major components:

External entries

Data stores

Processes andData flows

iii. Data Dictionary

A data dictionary is a collection of descriptions of the data objects or items in a data modelfor the benefit of programmers and others who need to refer to them. A first step in

analyzing a system of objects with which users interact is to identify each object and its

relationship to other objects. This process is called data modeling and results in a picture of

object relationships. After each data object or item is given a descriptive name, itsrelationship is described (or it becomes part of some structure that implicitly describes

relationship), the type of data (such as text or image or binary value) is described, possible

predefined values are listed, and a brief textual description is provided. This collection canbe organized for reference into a book called a data dictionary.

iv. Structured English

Structured English is a way of describing the flow of a process. The two building blocks of Structured

English are (1) structured logic or instructions organized into nested or grouped procedures,and (2) simple English statements such as add, multiply, move, etc. (strong, active, specific

verbs)

Five conventions to follow when using Structured English:

1. Express all logic in terms of sequential structures, decision structures, or iterations.

2. Use and capitalize accepted keywords such as: IF, THEN, ELSE, DO, DO WHILE,DO UNTIL, PERFORM

3. Indent blocks of statements to show their hierarchy (nesting) clearly.4. When words or phrases have been defined in the Data Dictionary, underline those

words or phrases to indicate that they have a specialized, reserved meaning.

5. Be careful when using "and" and "or" as well as "greater than" and "greater than or

equal to" and other logical comparisons.


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v. Decision Tables

The decision table is a chart with four sections listing all the logical conditions and actions.

The condition stub contains a list of all the necessary tests in a decision table. In the lower

left-hand corner of the decision table we find the action stub where one may note all theprocesses desired in a given module. Thus Action Stub contains a list of all the processes

involved in a decision table.

The upper right corner provides the space for the condition entry - all possible

permutations of yes and no responses related to the condition stub. The yes and no

possibilities are arranged as a vertical column called rules.

vi. Decision Tree

The decision tree defines the conditions as a sequence of left to right tests. A decision tree

helps to show the paths that are possible in a design following an action or decision by theuser.

Four major steps in building Decision Trees:

1. Identify the conditions2. Identify the outcomes (condition alternatives) for each decision

3. Identify the actions

4. Identify the rules.

3. Techniques:

The three most important techniques that are used in designing are:

a. Logical Data Modeling

This is the process of identifying, modeling and documenting the data requirements

of the system being designed. The data are separated into entities (things aboutwhich a business needs to record information) and relationships (the associations

between the entities).

b. Data Flow Modeling

This is the process of identifying, modeling and documenting how data moves

around an information system. Data Flow Modeling examines processes (activitiesthat transform data from one form to another), data stores (the holding areas for

data), external entities (what sends data into a system or receives data from a

system), and data flows (routes by which data can flow).


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c. Entity Behavior Modeling

This is the process of identifying, modeling and documenting the events that affecteach entity and the sequence in which these events occur.

System-Level Design Techniques addresses the development and validation of co-synthesis

techniques that allow an effective design of embedded systems. Here we have an overviewof a system-level co-design flow, illustrating through examples how system performance is

influenced at various steps of the flow including allocation, mapping, and scheduling. We

are specially emphasizing upon system-level co-synthesis techniques for architectures that

contain voltage scalable processors, which can dynamically trade-off betweencomputational performances. Throughout, the introduced co-synthesis techniques, which

target both single-mode systems and emerging multi-mode applications, are applied to

numerous benchmarks and real-life examples including a realistic smart phone.

4. Bibliography

1. http://www.wikipedia.org

2. http://www.springer.com/computer/information+systems+and+applications/

3. http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.html

4. Analysis and Design of Systems - P.S. Awadh

5. Information System design and Techniques Bob McCarthy
http://www.wikipedia.org/http://www.springer.com/computer/information+systems+and+applications/http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.htmlhttp://www.wikipedia.org/http://www.springer.com/computer/information+systems+and+applications/http://www.comp.glam.ac.uk/pages/staff/tdhutchings/chapter3.html

different design techniques

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