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.
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.
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.
Customer Bank Cash receipts process Payment Deposit Customer 1.0 Sales Clerk 3.0 Bookkeepi ng 2.0 Cashier Bank Cash Cash and register tape Deposit slip and cash Verified register tape Form 66W
Sales journal
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 Customer 1.0 Receive payment 4.0 Record sale 2.0 Compare cash and tape 3.0 Prepare deposit Bank Payment Receipts and Receipts summary Sales record Validated receipts Verified receipts summary
*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
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 e.g. PC, other data entry Note: Can also be
document / report device, key-to-disk input output; cards rarely used
2. Processing
Note: Includes inquiries e.g. Prepare document, e.g. MICR reader,
and file updates sign document key-to-disk device,
scanner, RFID reader
3. Output
Used when type of media is Unknown or for manual card files, Ledgers, batch, logs, etc.
Deposit
Bank
Document Manualkeying Punch card
Computer process Manua l proces s Offline proces s Displa y General purpose input-output
4. Data stores Filing sequence: A = alphabetical C = chronological N = numerical 5. Connectors
Note: Can also be On-page connector Off-page connector
external entity Use A, B, C, etc. Use page number
and A, B, C, etc.
Logic flow
Telecommunications link
6. Miscellaneous
Bridge for crossing flow Notice lack of arrowhead Goods, e.g., Inventory, shipment Disk Ta pe Pap er Start/stop Annotation
Examples Systems Flowchart Clerk Computer Input Document Key input Displa y Input or error Resolve discrepanci es if any Key corrections/ accept input Accept ed input Input document Edit/validate input Record input Data Store 1 Data Store 2
Scanning clerk Computer
*DFD’s and flowcharts provide us with multiple, complementary methods for describing a system Input document Scan document Update data Data Store(s )