Lec 6 - enterprise modeling

Lec 6 - enterprise modeling - Enterprise modeling concepts...

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Unformatted text preview: Enterprise modeling concepts and tools Dr. Jacqueline Wong BA Faculty CUHK 1 Fishbone Diagram • A fishbone diagram is an analysis tool that represents the possible causes of a problem as a graphical outline. When using a fishbone diagram, an analyst first states the problem and draws a main bone with sub-bones that represent possible causes of the problem. • In the following example, the problem is unhappy workers, and the analyst has identified four areas to investigate: environment, workers, management, and machines. In each area, the analyst identifies possible causes and draws them as horizontal sub-bones. environment too hot workers training Unhappy workers too old management machines 2 Data Flow Diagrams • A data flow diagram (DFD) shows how data moves through an information system but does not show program logic or processing steps • A set of DFDs provides a logical model that shows what the system does, not how it does it 3 Data Flow Diagrams • DFD Symbols – DFDs use four basic symbols that represent processes, data flows, data stores, and entities – Symbols are referenced by using all capital letters for the symbol name 4 Symbols Symbols Name Process Example Apply Payment Calculate Commission Bank Deposit Data Flow Invoice Payment Students Data Store A/C Payable Customer Warehouse External Entity 5 Data Flow Diagrams • DFD Symbols – Process symbol • Receives input data and produces output that has a different content, form, or both • Resembles a black box or a circle, where the inputs, outputs, and general function of the process are known, but the underlying details are not shown 6 Data Flow Diagrams • DFD Symbols – Data flow symbol • Represents one or more data items • The symbol for a data flow is a line with a single or double arrowhead 7 Data Flow Diagrams • DFD Symbols – Data store symbol • Represent data that the system stores • The physical characteristics of a data store are unimportant because you are concerned only with a logical model • Symbol is a flat rectangle that is open on the right side and closed on the left side, or just a pair of parallel lines. 8 Data Flow Diagrams • DFD Symbols – Entity Symbol • Symbol is a rectangle. • Name of the entity appears inside the symbol • DFD entities also are called terminators, because they are data origins (source entity) or final destinations (sink entity). • Source entity: supplies data to the system • Sink entity: receives data from the system 9 Picking List Order CUSTOMER WAREHOUSE Order Reject Notice Invoice 0 Order System Payment Completed Order Cash Receipts Entry Commission SALES Rep ACCOUNTING 10 Order System: Context Diagram Data Flow Diagrams • Context Diagrams – Top-level view of an information system that shows the system’s boundaries and scope – Do not show any data stores in a context diagram because data stores are internal to the system – Begin by reviewing the system requirements to identify all external data sources and destinations – Record the name of the entities and the name, content, direction of the data flows – What makes one system more complex than another is the number of components, the number of levels, and the degree of interaction among its processes, entities, data stores, and data flows 11 Data Flow Diagrams • Conventions for DFDs 1. Each context diagram must fit on one page 2. The process name in the context diagram should be the name of the information system 3. Use unique names within each set of symbols 4. Do not cross lines 5. Use a unique reference number for each process symbol 12 Order 1 Fill Order Order Reject Notice Customer 2 Create Invoice Invoice D1 A/C Receivable Invoice Detail Payment Picking List Payment Detail 3 Apply Payment Warehouse Completed Order D2 Invoice Cash Receipts Entry Accounting Commission Sales Rep Diagram 0 / Level 1 DFD 13 Data Flow Diagrams • Diagram 0 – Zooms in on the context diagram and shows major processes, data flows, and data stores – Must retain all the connections that flow into and out of “process 0” – Each process has a reference number – If same data flows in both directions, you can use a double-headed arrow – Diagram 0 represents exploded view of process 0 14 Customer D3 Customers Order Reject Notice Order Credit Status 1.1 Verify Order Product Detail D4 Products Picking Detail Inventory Change Rejected Order 1.2 Prepare Reject Notice Accepted Order 1.3 Assemble Order Diagram 1 / Level 2 DFD Picking List Warehouse 15 Payment Customer Commission Earned Invoice Detail 3.1 Post Payment D1 A/C Receivable Payment Detail Customer Payment D5 Daily Payments Accounting Payment 3.2 Calculate Commission 3.3 Prepare Accounting Entry Accounting Cash Receipts Entry Commission Sales Rep Diagram 3 / Level 2 DFD 16 Data Flow Diagrams • Lower-Level Diagrams – Created using leveling and balancing techniques – Leveling • Uses a series of increasingly detailed DFDs to describe an information system – Balancing • Ensures that the input and output data flows of the parent DFD are maintained on the child DFD 17 Data Flow Diagrams • Strategies for Developing DFDs – A set of DFDs is a graphical, top-down model – With a bottom-up strategy, you first identify all functional primitives, data stores, entities, and data flows – The main objective is to ensure that your model is accurate and easy to understand – General rule of thumb is that a diagram should have no more than nine process symbols – To construct a logical model of a complex system, you might use a combination of top-down and bottom-up strategies – The best approach depends on the information system you are modeling 18 Process Description Tools • A process description documents the details of a functional primitive, which represents a specific set of processing steps and business logic • Modular Design – Based on combinations of three logical structures, sometimes called control structures which serve as building blocks for the process 1.Sequence 2.Selection 3.repetition - looping 19 Structured English version of the COMMISSION EARNED policy: • • • • • • • • • • • • If EXTRA BONUS equal to YES If PAYMENT TOTAL is greater than $50,000 Add 2% to COMMISION PERCENT Output SPECIAL LETTER Output AWARD LIST ELSE Add 1% to COMMISION PERCENT Output AWARD LIST ELSE If PAYMENT TOTAL is greater than $50,000 Add 1% to COMMISION PERCENT Output SPECIAL LETTER • Calculate COMMISSION = COMMISSION PERCENT times PAYMENT TOTAL 20 Process Description Tools • Structured English – Must conform to the following rules • Use only the three building blocks of sequence, selection, and iteration • Use indentation for readability • Use a limited vocabulary, including standard terms used in the data dictionary and specific words that describe the processing rules – Might look familiar to programming students because it resembles pseudocode 21 Decision Table (a) Commission Earned Process (b) Extra Bonus Payment Total > $50,000 Add 2% to COMMISION PERCENT Add 1% to COMMISION PERCENT Output SPECIAL LETTER Output AWARD LIST (d) 1 2 3 4 (c) YYNN YNYN X XX X X XX a) Place the name of the process in a heading at the top left. b) Enter the conditions under the heading, with one condition per line. c) Enter all potential combinations of Y/N (for yes and N) for the conditions. Each column represents a numbered possibility called a rule. d) Place an X in the action entries area for each rule to indicate whether to accept or 22 reject the order. Process Description Tools • Decision Tables – Shows a logical structure, with all possible combinations of conditions and resulting actions – It is important to consider every possible outcome to ensure that you have overlooked nothing – Can have more than two possible outcomes – Often are the best way to describe a complex set of conditions 23 Decision Tree Y  Add 2% to COMMISSION PERCENT  Output SPECIAL LETTER  Output AWARD LIST Payment Total more than $50,000? Y N Add 1% to COMMISSION PERCENT Output AWARD LIST Extra Bonus? Y N Add 1% to COMMISSION PERCENT Output SPECIAL LETTER Payment Total more than $50,000? N  No Action 24 Process Description Tools • Decision Trees – Graphical representation of the conditions, actions, and rules found in a decision table – Whether to use a decision table or tree often is a matter of personal preference 25 ...
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