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Systems Analysis 1

OHP Masters

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The Systems Life Cycle

Objectives: To learn the stages in the systems life cycle To understand the role of the systems analyst

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The systems life cycle

Maintenance

Installation

Feasibility Study

Design

Analysis

Programming

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Why introduce a new system?

The current system may no longer be suitable for its purpose.

Technological developments may have made the current system redundant or outdated.

The current system may be too inflexible or expensive to maintain, or may reduce the organisation’s ability to respond quickly enough to customer’s demands.

Better management information is required for decision-making.

The provision of better customer service.

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The role of the systems analyst

investigating and analysing the existing system to establish how things work currently

performing a feasibility study to judge whether a new computer system is feasible

designing the new system, specifying programs, hardware, and procedures to be followed

testing and overseeing the installation of the new system

making sure that all user and technical documentation is complete

evaluating the performance of the new system to make sure it fulfils the requirements

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The feasibility study

Technical feasibility

Economic feasibility

Legal feasibility

Operational feasibility

Schedule feasibility

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Investigating the current system

Interviewing staff Examining current business and systems

documents and output. Sending out questionnaires and analysing

responses Observation of current procedures, by

spending time in various departments.

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Design

The hardware platform The software The outputs The inputs The user interface The modular design of each program in the

application The test plan and test data Conversion plan Documentation including systems and operations

documentation. Later, a user manual will be produced.

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Programming, installation and maintenance

Programs written, tested and documented Data loaded from old system to new system Staff trained on new system May be parallel running of both systems for a

while System maintained by keeping it up-to-date,

solving any problems and writing new programs when required.

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Initial Systems Investigation

Objectives: To write a statement of purpose for a new

system To write a definition of the scope of a

proposed new system To learn about methods of fact-finding To plan an interview to ascertain user

requirements

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Case Study

Statement of scope and objectives

Investigation Feasibility Study

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Statement of scope and objectives

e.g:– Project title– Date– Current problems– Objectives– Constraints– Plan of action

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Systems Investigation

You need to establish: how the existing systems work what personnel are involved the organisational, social and economic

environment within the organisation

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Methods of finding out about the current system

Interviews Studying documentation Questionnaires Observation

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Data Flow Diagrams

Objectives: To define what is meant by structured

analysis To define the symbols used in a Data Flow

Diagram (DFD) To draw a context diagram (Level 0 DFD) for

a given scenario To refine a DFD to a more detailed (lower-

level) view

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Structured analysis

A widely-used top-down method for defining system inputs, processes and outputs. It shows how information flows through a system, using several diagrams showing progressively more and more detail at each level. The primary tool of structured analysis is the Data Flow Diagram (DFD).

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Data Flow Diagrams

The following four symbols are used in data flow diagrams:

 

External entity  

 

Process  

 

Data store 

Data flow

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Data flow diagram of a travel agent booking system

CustomerTravel-query

Booking confirmation

Available flights

Booking

flightsBook flight

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Data flow diagram of part of an order processing system

Customer

Order

Invoice

Available stock stock

Process order

Out-of-stock noticeUnfilled order

backorders

Warehouse

Despatch note

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Context diagrams

a top-level DFD shows the least amount of detail and is known as a Level 0 DFD or context diagram.

Customer

Order

Invoice

Process orderOut-of-stock notice

Picking ListWarehouse

Order rejection notice

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Level 0 or context diagram shows a system as a single process with inputs and outputs flowing to or from external entities.

Level 1 DFD will split up that single process into subsystems and show more detail about the data flows and data stores.

Level 2 DFD may decompose a single subsystem even further.

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Process Specifications

Objectives: To produce a process specification using

structured English To produce a process specification using a

decision table To produce a process specification using a

flow chart

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Structured English (pseudocode) Constructs:

–Sequence–Iteration or ‘loop’–Selection

• If….Then….Else• Case

Relational operators= equal to< less than> greater than<= Less than or equal to>= greater than or equal to<> not equal to

Logical operators–AND, OR, NOT

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Decision tables

A decision table specifies in tabular form the actions to be carried out under a given set of conditions. It has the general format shown below.

Heading

The format of a decision table

Condition stub Condition Entries

Action Stub Action Entries

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Logical Data Modelling Techniques

Objectives: To define data modelling terms including entity,

attribute, primary key, foreign key, relationship To represent the relationship between entities using

an entity-relationship diagram (ERD) To normalise data to first, second and third normal

form To produce a data dictionary comprising the entities

in a system, their attributes and the relationship between them

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Entity-relationship modelling

Three distinct sorts of object are used in entity-relationship modelling:An entity is a thing of interest to an organisation about which data is to be held. Examples of entities include Customer, Employee, Stock Item, Supplier.An attribute is a property or characteristic of an entity. Examples of attributes associated with a Customer include Customer ID, Surname, Initials, Title, Address, Credit Limit.A relationship is a link or association between entities.

– One-to-one

– One-to-many

– Many-to-many

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Entity-relationship diagrams

Employee Company cardrives (One-to-one)

Ward Patientholds (One-to-many)

Album Singersfeatures (Many-to-many)

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Primary and Foreign keys

The primary key is an attribute that uniquely identifies a particular occurrence of an entity

A foreign key is where the primary key in one of two related tables appears as an attribute of the related table.

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Normalisation

Normalisation is the process of ensuring that the database is designed in the best possible way, so that:there is a minimum of data duplicated in different tables.inconsistencies between data items are eliminated it is as easy as possible to extract information from the database.

The stages of normalisation are known as first, second and third normal form.

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The stages of normalisation

First Normal form

Definition: A database in first normal form must not contain repeating attributes. Second normal form

Definition: A table is in second normal form if it is in first normal form and no column that is not part of a primary key is dependent on only a portion of the primary key. Third normal form – Non-key dependence test

Definition: A table in third normal form contains no ‘non-key dependencies’.

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The data dictionary

A data dictionary describes all the data components in a system. It will show, for example:the entities in a systemthe name and description of each attributethe relationship between the entities

Atomic attributes

An atomic attribute cannot be broken down any further

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The Input Specification

Objectives: To define the data sources and methods of

data capture for an application To define the verification and validation

methods used on the input data To design a data input form To design an input screen layout To describe different methods of data capture

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The source of data

For example in a sales order processing system:What kind of order form does a customer use? What information needs to be entered into the system from a customer order?When orders are telephoned, does the person answering the telephone have a pad of standard order forms on which they record the order? If so, what form does the order form take? Alternatively, are they typed into the computer system immediately by the person taking the order without the need for a paper form?Or, are all (telephoned and mailed) orders collected into a batch and entered later?

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Data items for a system

Customer data Sales order data

Batch processing

A data control clerk has the responsibility of: counting the documents checking each one visually to see that the customer

has entered essential details calculating a control total filling in a batch header document logging the batch in a book kept for this purpose

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Data verification

This is the process of double-checking that data entry is correct.

Data validation

Validation is done by a computer program, and checks as far as possible that the data is accurate.

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Data validation

Presence check Format check (also called picture check) Range check. The expiry date of a credit card

must have a month number between 1 and 12, and the date must be later than today’s date

File lookup check Check digit check Batch header checks

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Designing an input screen Some basic rules:

– the form should be given a title to identify it– the form should not be too cluttered – spaces and blanks

are important– it should give some indication of how many characters can

be entered in each field of data– the user should be given a chance to go back and correct

any field before the data is accepted– items should appear in a logical sequence to assist the user– default values should wherever possible be prewritten onto

the form so that a minimum of data entry is required– lower case in a display is neater and easier to read than all

upper-case– colours should be carefully chosen to be legible and easy on

the eyes

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Methods of data capture

Keyboard:Disadvantages include:– it is easy to make transcription errors – that is,

copy the data wrongly from the document– it is time-consuming– data entry operators who enter data all day every

day are prone to repetitive strain injury (RSI)

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Other methods of data capture

Voice data entry Scanners and OCR Magnetic Ink Character Recognition (MICR) Optical Mark Recognition (OMR) Magnetic stripe Bar code reader or scanner Hand-held input devices Touch screen EDI

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Designing Output

Objectives: To examine what types of output are needed

from a system To distinguish between operational output

and management information To design a screen report layout To design a printed report layout

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Types of output

Operational information e.g:– customer invoices and delivery notes– stock order list showing which items of stock need

reordering– daily sales journal (showing all the sales for one

day) Management information e.g:

– total sales analysed by month– sales for a given product– sales for a given customer

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Output from a system Invoice Stock reports Screen reports Graphical reports Designing your own reports – decide on:

– the contents of the report– whether it is to be screen-based or paper-based– the layout of the report – in columns or an alternative format,

portrait or landscape etc.– page and/or column headings– any grouping of data, for example all transactions relating to one

product may be grouped together, before moving on to the next product

– any subtotals and final totals that are to appear on the report– any parameters that the user will be able to specify, for example

which products or customers the report will list, or the range of dates that will apply

– fonts and (on a screen report) colours used.

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The Feasibility Report

Objectives: To select a suitable project for study To plan the sections of the feasibility report To write a feasibility report

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Choosing a project

A few suggestions: a simple library system for books and borrowers – maybe a

departmental, rather than a school, library; a booking system for holiday cottages; a system to record which personnel have been on which training

courses; a vet’s system for recording owners, pets and treatments; a database for a builder keeping records of customers and jobs; a stock control system for a school shop; a hairdresser’s database to keep records of treatments that customers

have had; a database for a garage to keep records of work done for customers; an estate agent’s database to keep records of houses for sale,

purchasers and sellers; an art gallery’s records of paintings and artists and maybe buyers.

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The contents of a feasibility report

Title page Statement of purpose of the system A definition of system scope Deficiencies of the current system Statement of user requirements Costs and benefits of development Conclusion and recommendations

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Systems Specification A description of the proposed system and its objectives. Database specification including:

– database structure

– a data dictionary

– menu structure

Input specification including:– methods of data capture

– validation methods

– data-input form or screen layouts

Output specification including:– data required for output

– screen report layouts

– printed report layouts

Process specifications showing details of the processes that need to be carried out on the data to generate the required output

Test plan and test data with expected results Conclusion, including a discussion of:

– software

– hardware

– possible constraints

– personnel