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CP2236 Information Systems Design

Business & Technical System Options

Required System Logical

Data Flow ModellingLarger versions of slides 17,20,23,24 & 28

can be found at the end of of this handout

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Business & Technical System Options

• Rare for only one solution to be possible.• Analyst/Designer should be able to suggest several

solutions to the business’s requirements.• Business Systems Options (BSOs) provide a range

of possible solutions for the business to consider.• Each BSO may have more than one way of being

implemented technically. These are known as Technical System Options (TSOs)

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Business System Options (BSOs)Aim - To agree the functionality of the req. system.

•BSOs - done after the Requirements Catalogue (RC) has been formalised. Each entry in RC is considered, if any are excluded - document reasons.

•Develop 2-6 options.

•Using RC, project team establish & develop a list of : Minimum Functional Requirements (which all options must satisfy) & Non-Functional Requirements.

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Functional Requirements - dictate what the system should do.

What facilities are required & what activities the system should carry out:

• descriptions of required functions• outline of reports - hard/soft copies• on-line queries & updates• data storage, retrieval & transfer, etc.

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Non-Functional Requirements - address other facilities (limitations & constraints)

• Required Service/Performance Levels (response times for on-line functions, rate of data transfer)

• Security & Access Requirements• Technical Constraints (make use of existing

hardware)• Project Constraints (system delivery deadlines &

cost limits)• Quality of user interfaces (how intuitive and

easy to learn, and to use the technology to perform the task)

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BSOs - consider the following factors:

•Approximate cost of each option•Development time scale•Known technical constraints•Organisation of the system - types of access (on-line or off-line), interfaces with other systems

•Approximate data and transaction volumes•Training requirements•Benefits & impact on the organisation

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Business System Options

•Upto 3 shortlisted. Each Option presented formally to the management. •Strengths & Weaknesses explained to facilitate a decision. Opportunity to reassess the viability of the project (to carry on / cancel it).•Selected BSO could be one option or an hybrid.•Document selected BSO (reasons for selection & rejection others). •Form the basis for the rest of the project and for the final system.

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Technical System Options (TSOs)Addresses how the req. system is to be implemented.Define the TSOs:Identify constraints - external & internalDevelop outline options (Up to 6)Select 2 or 3 main options for detailed dev’tRefine selected options - check performance

Select the final TSO:Present optionsFully document selected TSO (rationale for the selected option)

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Technical System Options (TSOs)

Each Full TSO contains 5 main parts:

• Technical environment description• System description• Impact analysis• Outline development plan• Cost / Benefit analysis

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Current System DFDs

There are 2 versions of this:1. Current PHYSICAL DFD

Representation of the current system as it is. May show letters, filing cabinets, manual data stores etc.

2. Current LOGICAL DFD Removes all physical references to the

system. The process is referred to as Logicalisation.

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Steps in Logicalisation (revision)

• Replace Physical Data Stores with main Logical Data Stores.

• Remove Transient Data Stores

• Remove/separate out processes that cannot be automated and/or require subjective decisions or will remain subjective.

• Remove processes which only reorganise data (e.g. sorting).

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• Combine processes which are joined by a data flow only, and which form part of the same or a very similar process

• Combine processes performing the same functions (appear separate only because of physical location).

• Minimise Data Flow Contents.

• Remove all physical references.

• Remove processes which do not alter data (ad hoc retrievals without creation or update.

• Remove processes which exist due to tradition or politics

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Required System Logical DFMs:

Current Physical DFM

Current Logical DFM

Required Logical

DFM

RequirementsCatalogue

Selected BSO

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Required System Logical DFDs

The broad aim is to take the current logical DFD and to map the Requirements Catalogue and BSO’s on to it.

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Required System Logical DFMs - Method

Step1Step1Decide which processes on the current logical DFD are needed, then include these on the required logical DFD.

Step 2Step 2Look at the requirements catalogue, see what new processes are needed to meet the new requirements, add these to the required logical DFD.

Generally, any process that could be done by computer is a candidate for automation.

Any process that requires human judgement must be ruled out.

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Current Logical Context Level DFD:

VideoSystem

Customer

Manager

Customer

Membershiprequest

Mem. card

Video + Mem.card

Payment request

Payment

Payment rec. + Mem.card + video

Return video

Mang. reports

Add new video

Reserve video

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Current Logical Level 1 DFD:

Customer

Customer

Customer

Manager

Customer

Customer

Customer

Customer

Manager

Customer

*

RecordMemberdetails

1

MemberD1

*

RecordVideoLoan

2

VideoD2

*

Recordreturnvideo

3

MemberD1

*

Producereport

4

*

RecordVideodetails

5

*

Reservevideo

6

Mem. card

Payment request

Payment rec. + Mem.card + video

Mang. reports

Membershiprequest

Video + Mem.card

Payment

Return video

Add new video

Reserve video

Member details

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Requirement Catalogue entries:

1. Manager can produce a list of members monthly, and then select members who will be eligible for monthly bonuses.

2. Generate and send monthly bonus letters to selected members.

3. Incorporate purchasing of new videos from suppliers - an order for new videos is generated and sent to suppliers. Suppliers send the invoice and the videos to the store. A payment is sent to the supplier on receipt of the invoice.

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Requirements CatalogueRequirements 1 & 2

• A new process (7) is added to incorporate requirements 1 & 2.

• The existing Loan details and Member data stores are included.

• Members details are sent to the manager and a bonus list is generated.

• The bonus letter is sent to the customer.

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Process 7 DFD

Producemonthlybonusletter

7

Loan detailsD4

Previous monthdetails

Customer

Monthly bonusletter

Manager

MemberD1Membershipdetails

Monthly mem.list

Mem. bonus list

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Required System Logical DFMs - Method

Step3Step3

To maintain data, new data stores may need to be added. Identify these and add to the required logical DFD.

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Requirements CatalogueRequirement 3

• Another process (8) is needed to incorporate Requirement 3 into the logical DFD.

• In this example, a new data store ‘Video order’ is also added.

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Process 8 DFD

Purchase& PaymentNew Videos

8

Videoorder

D3

Order details

Supplier

Order payment

Order & invoice

Purchase order

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Required Logical Level 1 DFD:

Customer

Customer

Manager

*

RecordMemberdetails

1

MemberD1

*

RecordVideoLoan

2

VideoD2

*

Recordreturnvideo

3

MemberD1

*

Producereport

4*

RecordVideodetails

5

*

Reservevideo

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Supplier

Customer

Manager

*

Purchase& paymentnew videos

7

VideoorderD3

Loan detailsD4

*

ProduceMonthlyBonusletter

8

MemberD1

Loan detailsD4

VideoD2

Mem. card

Payment request

Payment rec. + Mem.card + video

Mang. reports

Membershiprequest

Video + Mem.card

Payment

Return video

Add new video

Reserve video

Purchase order

Order payment

Monthly Bonusletter

Monthly mem.list

Order+Invoice

Mem. bonus list

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Context Diagram

The Context Level required system logical DFD. follows same principles as for current physical and current logical DFDs.

• Any Level 1, Level 2 diagrams should balance with the context diagram.

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Required Logical Context Level DFD:

VideoSystem

CustomerManager

Customer

Supplier

Membershiprequest

Mem. card

Video + Mem.card

Payment request

PaymentPayment rec. + Mem.

card + video

Return video

Mang. reports

Add new video

Reserve video

Purchase order

Order+Invoice

Order payment

Mem. bonus list

Monthly Bonusletter

Monthly mem.list

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Exercise

Incorporate the following entry from the Requirements Catalogue into the required

system DFM

Requirements Catalogue

Storecard holders should have the facility to close their accounts.

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Requirements CatalogueStorecard holders should have the

facility to close their account.

Registernew

customer

1

Recordtransactionsand payments

2

CardholderAccount

D1

Manager

Cardholderdetails

Account No.

Cardholderdetails

D2

Cardholderdetails

Balance

Cardholder Merchant

Transactiondetails

Payments

Transacts.& payments

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PRINT INSTRUCTIONS

Handout-

pp 1-16,18,19,21,22,25,26,27

2 per page for 17,20,23,24,28