Required System Dfd
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Required System Logical Data Flow Modelling
CSC 2202 Systems Analysis and Design
1
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.
CSC 2202 Systems Analysis and Design
2
Business & Technical System Options 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) CSC 2202 Systems Analysis and Design
3
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.
CSC 2202 Systems Analysis and Design
4
Business System Options (BSOs) Develop 2-6 options. Using RC, project team establish & develop a list of : Minimum Functional Requirements (which all options must satisfy) & Non-Functional Requirements. CSC 2202 Systems Analysis and Design
5
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. CSC 2202 Systems Analysis and Design
6
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)
CSC 2202 Systems Analysis and Design
7
BSOs - consider the following factors: • Approximate cost of each option • Development time scale • Known technical constraints • Organisation of the system - types of access (online or off-line), interfaces with other systems • Approximate data and transaction volumes • Training requirements • Benefits & impact on the organisation CSC 2202 Systems Analysis and Design
8
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. CSC 2202 Systems Analysis and Design
9
Technical System Options (TSOs) Addresses how the req. system is to be implemented. Define the TSOs: Identify constraints - external & internal Develop outline options (Up to 6) Select 2 or 3 main options for detailed dev’t Refine selected options - check performance Select the final TSO: Present options Fully document selected TSO (rationale for the selected option) CSC 2202 Systems Analysis and Design
10
Technical System Options (TSOs) Each Full TSO contains 5 main parts: • • • • •
Technical environment description System description Impact analysis Outline development plan Cost / Benefit analysis
CSC 2202 Systems Analysis and Design
11
Current System DFDs Has 2 versions Current PHYSICAL DFD Representation of the current system as it is. May show letters, filing cabinets, manual data stores etc. Current LOGICAL DFD Removes all physical references to the system. The process is referred to as Logicalisation. CSC 2202 Systems Analysis and Design
12
Steps in Logicalisation • 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). CSC 2202 Systems Analysis and Design
13
• 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 CSC 2202 Systems Analysis and Design
14
Required System Logical DFMs: Current Physical DFM
Requirements Catalogue
Selected BSO
Current Logical DFM
Required Logical DFM
CSC 2202 Systems Analysis and Design
15
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.
CSC 2202 Systems Analysis and Design
16
Required System Logical DFMs - Method Step1 Decide which processes on the current logical DFD are needed, then include these on the required logical DFD. Step 2 Look 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. CSC 2202 Systems Analysis and Design
17
Current Logical Context Level DFD: Customer
Membership request Mem. card
Video + Mem. card
Manager Mang. reports Video System
Add new video
Payment request
Payment
Payment rec. + Mem. card + video
Return video Customer Reserve video
CSC 2202 Systems Analysis and Design
18
Current Logical Level 1 DFD: Customer
1
Membership request
Customer
Mem. card
Record Member details
* Member details
Customer
D1
Customer
Member
Video + Mem. card
Payment request 2
Customer
Payment
Payment rec. + Mem. card + video
Record Video Loan
Customer
*
5 Customer
Record Video details
3
Return video
Record return video
*
*
D2
Video
Add new video
4 D1
Member Produce report *
Mang. reports
Manager Manager
6 Reserve video
Reserve video
Customer
*
CSC 2202 Systems Analysis and Design
19
Requirement Catalogue entries: • Manager can produce a list of members monthly, and then select members who will be eligible for monthly bonuses. • Generate and send monthly bonus letters to selected members. • 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. CSC 2202 Systems Analysis and Design
20
Requirements Catalogue Requirements 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. CSC 2202 Systems Analysis and Design
21
Process 7 DFD D4
Customer
Loan details Monthly bonus letter
Previous month details 7 Produce monthly bonus letter
Membership details
D1
Member
Mem. bonus list
Monthly mem. list
Manager
CSC 2202 Systems Analysis and Design
22
Required System Logical DFMs Method Step3 To maintain data, new data stores may need to be added. Identify these and add to the required logical DFD.
CSC 2202 Systems Analysis and Design
23
Requirements Catalogue Requirement 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. CSC 2202 Systems Analysis and Design
24
Process 8 DFD Order payment
8 Supplier
Purchase order
Purchase & Payment New Videos Order details
Order & invoice
CSC 2202 Systems Analysis and Design
D3
Video order
25
Required Logical Level 1 DFD: 1 Membership request
Customer
Record Member details
D1
Member
*
Mem. card
D4
Video + Mem. card
Loan details
2 Record Video Loan
Payment request Payment Customer
*
D2
Payment rec. + Mem. card + video
Video
3 Record return video
Return video
* 5
D1
Member
Record Video details
4
Reserve video
Produce report
*
Add new video
* Mang. reports D2
Manager
Video
6 Reserve video
Customer
* D4
Loan details
8
Order payment
Monthly Bonus letter Produce Monthly Bonus letter
*
7 Supplier
Purchase & payment new videos
Purchase order
D1 Monthly mem. list
* Mem. bonus list
Order+Invoice
Member
D3
Manager
Video order
CSC 2202 Systems Analysis and Design
26
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.
CSC 2202 Systems Analysis and Design
27
Required Logical Context Level DFD: Customer
Monthly mem. list
Membership request
Add new video
Manager
Mem. card Mem. bonus list Video + Mem. card Payment request
Mang. reports
Video System
Return video Order+Invoice Order payment
Payment
Purchase order
Payment rec. + Mem. card + video Reserve video
Supplier Monthly Bonus letter
Customer
CSC 2202 Systems Analysis and Design
28
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.
CSC 2202 Systems Analysis and Design
29
Requirements CatalogueStorecard holders should have the facility to close their account. Manager Cardholder details
1 Register new customer
Account No.
Cardholder details
D2
Cardholder Account
D1
Transacts. & payments
Balance
2
Cardholder details
Record transactions and payments
Payments
Transaction details
Cardholder
CSC 2202 Systems Analysis and Design
Merchant
30
CSC 2202 Systems Analysis and Design
1
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.
CSC 2202 Systems Analysis and Design
2
Business & Technical System Options 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) CSC 2202 Systems Analysis and Design
3
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.
CSC 2202 Systems Analysis and Design
4
Business System Options (BSOs) Develop 2-6 options. Using RC, project team establish & develop a list of : Minimum Functional Requirements (which all options must satisfy) & Non-Functional Requirements. CSC 2202 Systems Analysis and Design
5
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. CSC 2202 Systems Analysis and Design
6
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)
CSC 2202 Systems Analysis and Design
7
BSOs - consider the following factors: • Approximate cost of each option • Development time scale • Known technical constraints • Organisation of the system - types of access (online or off-line), interfaces with other systems • Approximate data and transaction volumes • Training requirements • Benefits & impact on the organisation CSC 2202 Systems Analysis and Design
8
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. CSC 2202 Systems Analysis and Design
9
Technical System Options (TSOs) Addresses how the req. system is to be implemented. Define the TSOs: Identify constraints - external & internal Develop outline options (Up to 6) Select 2 or 3 main options for detailed dev’t Refine selected options - check performance Select the final TSO: Present options Fully document selected TSO (rationale for the selected option) CSC 2202 Systems Analysis and Design
10
Technical System Options (TSOs) Each Full TSO contains 5 main parts: • • • • •
Technical environment description System description Impact analysis Outline development plan Cost / Benefit analysis
CSC 2202 Systems Analysis and Design
11
Current System DFDs Has 2 versions Current PHYSICAL DFD Representation of the current system as it is. May show letters, filing cabinets, manual data stores etc. Current LOGICAL DFD Removes all physical references to the system. The process is referred to as Logicalisation. CSC 2202 Systems Analysis and Design
12
Steps in Logicalisation • 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). CSC 2202 Systems Analysis and Design
13
• 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 CSC 2202 Systems Analysis and Design
14
Required System Logical DFMs: Current Physical DFM
Requirements Catalogue
Selected BSO
Current Logical DFM
Required Logical DFM
CSC 2202 Systems Analysis and Design
15
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.
CSC 2202 Systems Analysis and Design
16
Required System Logical DFMs - Method Step1 Decide which processes on the current logical DFD are needed, then include these on the required logical DFD. Step 2 Look 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. CSC 2202 Systems Analysis and Design
17
Current Logical Context Level DFD: Customer
Membership request Mem. card
Video + Mem. card
Manager Mang. reports Video System
Add new video
Payment request
Payment
Payment rec. + Mem. card + video
Return video Customer Reserve video
CSC 2202 Systems Analysis and Design
18
Current Logical Level 1 DFD: Customer
1
Membership request
Customer
Mem. card
Record Member details
* Member details
Customer
D1
Customer
Member
Video + Mem. card
Payment request 2
Customer
Payment
Payment rec. + Mem. card + video
Record Video Loan
Customer
*
5 Customer
Record Video details
3
Return video
Record return video
*
*
D2
Video
Add new video
4 D1
Member Produce report *
Mang. reports
Manager Manager
6 Reserve video
Reserve video
Customer
*
CSC 2202 Systems Analysis and Design
19
Requirement Catalogue entries: • Manager can produce a list of members monthly, and then select members who will be eligible for monthly bonuses. • Generate and send monthly bonus letters to selected members. • 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. CSC 2202 Systems Analysis and Design
20
Requirements Catalogue Requirements 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. CSC 2202 Systems Analysis and Design
21
Process 7 DFD D4
Customer
Loan details Monthly bonus letter
Previous month details 7 Produce monthly bonus letter
Membership details
D1
Member
Mem. bonus list
Monthly mem. list
Manager
CSC 2202 Systems Analysis and Design
22
Required System Logical DFMs Method Step3 To maintain data, new data stores may need to be added. Identify these and add to the required logical DFD.
CSC 2202 Systems Analysis and Design
23
Requirements Catalogue Requirement 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. CSC 2202 Systems Analysis and Design
24
Process 8 DFD Order payment
8 Supplier
Purchase order
Purchase & Payment New Videos Order details
Order & invoice
CSC 2202 Systems Analysis and Design
D3
Video order
25
Required Logical Level 1 DFD: 1 Membership request
Customer
Record Member details
D1
Member
*
Mem. card
D4
Video + Mem. card
Loan details
2 Record Video Loan
Payment request Payment Customer
*
D2
Payment rec. + Mem. card + video
Video
3 Record return video
Return video
* 5
D1
Member
Record Video details
4
Reserve video
Produce report
*
Add new video
* Mang. reports D2
Manager
Video
6 Reserve video
Customer
* D4
Loan details
8
Order payment
Monthly Bonus letter Produce Monthly Bonus letter
*
7 Supplier
Purchase & payment new videos
Purchase order
D1 Monthly mem. list
* Mem. bonus list
Order+Invoice
Member
D3
Manager
Video order
CSC 2202 Systems Analysis and Design
26
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.
CSC 2202 Systems Analysis and Design
27
Required Logical Context Level DFD: Customer
Monthly mem. list
Membership request
Add new video
Manager
Mem. card Mem. bonus list Video + Mem. card Payment request
Mang. reports
Video System
Return video Order+Invoice Order payment
Payment
Purchase order
Payment rec. + Mem. card + video Reserve video
Supplier Monthly Bonus letter
Customer
CSC 2202 Systems Analysis and Design
28
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.
CSC 2202 Systems Analysis and Design
29
Requirements CatalogueStorecard holders should have the facility to close their account. Manager Cardholder details
1 Register new customer
Account No.
Cardholder details
D2
Cardholder Account
D1
Transacts. & payments
Balance
2
Cardholder details
Record transactions and payments
Payments
Transaction details
Cardholder
CSC 2202 Systems Analysis and Design
Merchant
30
