Documenting Information System
Documenting Information System Chapter Objectives: •
Teach students to read and prepare documentation to portray aspects of business processes including their operations and information processes
Show students how to read and prepare data flow diagrams and systems flowcharts
Purposes of documentation To enable the users to understand, explain, evaluate, and improve complex business processes, information systems, and internal controls. To train personnel To understand the systems and to evaluate the systems’ controls A. DATA FLOW DIAGRAM (DFD) – a graphical representation of a system. It depicts system components; data flows among the components; and the sources, destinations, and storage of data. Data Flow Diagram Symbols 1. Bubble symbol – depicts an entity or a process within which incoming data flows are transformed into outgoing data flows.
2. Data flow symbol – represents a pathway for data.
3. External entity symbol – portrays a source or a destination of data outside the system.
4. Data store symbol – represents a place where data are stored.
Types of Data Flow Diagrams 1. Context Diagram – a top-level, or least detailed, diagram of the an information system that depicts the system and all of its activities as a single bubble, and shows the data flows into and out of the system and into and out of the external entities.
Cash receipts process
External entities are those entities outside the system that sends data, or receive data from, the system. 2. Physical Data Flow Diagram – is a graphical representation of a system showing the system’s internal and external entities, and the flows of data into and out of these entities. Customer Cash
1.0 Sales Clerk
Cash and register tape 2.0 Cashier
Form 66W Verified register tape 3.0 Bookkeepi ng
Deposit slip and cash
Blue sales book Internal entity is an entity (i.e. person, place, or thing) within the system that transforms data. It includes accounting clerks (person), departments (places), and computers (things). Physical data flow diagrams specify where, how, and by whom a system’s processes are accomplished. It does not tell us what is being accomplished. 3. Logical Data Flow Diagram – is a graphical representation of a system showing the system’s processes (as bubbles), data stores, and the flows of data into and out of the processes and data stores. It is used to document information systems because it can represent the logical nature of a system, what tasks the system is doing, without having to specify how, where, or by whom the tasks are accomplished.
1.0 Receive payment
4.0 Record sale
Receipts and Receipts summary
2.0 Compare cash and tape Verified receipts summary
3.0 Prepare deposit
Logical Data Flow Diagram versus Physical Data Flow Diagram Logical DFD users can concentrate on the functions that a system performs WHAT “ a system is doing (Logical DFD) will change less over time than “HOW” (Physical DFD) it is doing it. Logical DFD uses verbs that described actions being performed than with the nouns in Physical DFD Logical DFD portrays a system’s activities, whereas as Physical DFD depicts a system’s infrastructure
*We need both Logical DFD and Physical DFD to understand a system completely
*When two DFD’s have equivalent external data flows, they are considered as BALANCED. Only balanced set of DFD’s are correct. Compare the Context DFD and Logical DFD above; both have the same external data flows Deposit
B. SYSTEMS FLOWCHART – is a graphical representation of information processes (activities, logic flows, inputs, outputs, and data storage), as well as the related operations processes (entities, physical flows, and operation activities). It contains manual and computer activities, the systems flowchart presents a logical and physical rendering of the who, what, how, and where of operations and information processes. The systems flowchart combines the physical and logical aspects of the system as compared with Physical and logical DFD’s which depict different aspects of the system. In addition, the systems flowchart includes the operations process and management context for a system, aspects that are ignored in DFD’s. Systems Flowcharting Symbols 1. Inputs
Note: Also output also be document / report rarely used
e.g. PC, other data entry device, key-to-disk input
Note: Can output; cards
2. Processing Computer process
Note: Includes inquiries reader, and file updates device,
Manua l proces e.g. sPrepare
Offline proces s
scanner, RFID reader 3. Output
General purpose inputoutput
Used when type of media is Unknown or for manual card files, Ledgers, batch, logs, etc.
e.g. MICR key-to-disk
4. Data stores
Filing sequence: A = alphabetical C = chronological N = numerical 5. Connectors Start/stop
Note: Can also be external entity
On-page connector Use A, B, C, etc.
Off-page connector Use page number and A, B, C, etc.
Logic flow Telecommunications link
6. Miscellaneous Annotation
Bridge for crossing flow
Notice lack of arrowhead
Goods, e.g., Inventory, shipment
Examples Systems Flowchart
Data Store 1
Displa y Input or error Resolve discrepanci es if any
Key corrections/ accept input
Accept ed input
Data Store 2
Data Store(s )
*DFD’s and flowcharts provide us with multiple, complementary methods for describing a system