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Technological developments may have made the current system redundant or outdated.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