ACCT 309, Ch. 3

Seven

A well-planned level 1 DFD will show a maximum of how many processes on a single page?

level 1 DFD

a DFD is created for each process in LEVEL 0; called (blank) because they have one meaningful decimal point, i.e. 1.1

data flow diagram (DFD)

a graphical representation of data sources, data flows, transaction processes, data storage, and data destinations

flowchart

an analytical technique that uses a standard set of symbols to describe pictorially some aspect of an IS in a clear, concise, and logical manner

non-standard symbol

applied in a non-standard way more than any other; it is widely used as a multi-purpose symbol, and represents different things in different organizations and applications

system flowchart

depicts the relationships among system input, processing, storage, and output

necessary flowchart labels

don't ever create a flowchart without making sure it has the author's name, date of creation, company name and title of the process being illustrated

multiple documents symbol

duplicate copies of a document are designated by multiple document symbols stacked on each other, with close spacing between the symbols; different documents which are following the same path in the flow are designated by overlapping document symbols, with more space between symbols than found multiple-copy documents

direct access storage symbol

generally obsolete and has been replaced with one of the two more common database or data file symbols described earlier

manual input symbol

generally obsolete, but may occasionally be found; was used to denote keyboard entry by a human operator into a computer, usually without feedback or instant validation or verification; denotes pure input only

display symbol

generally obsolete, but occasionally still found; used primarily by information systems designers to denote data displayed on a screen rather than printed on a printer

transmittal tape symbol

generally used to verify, substantiate, document, or support a total of some kind; generally accepts a set of documents, or comes from a process totaling or analyzing documents

information or responsibility flow

generally, the overall flow should move down and to the right on the page, arrows should generally travel vertically or horizontally only

context diagram

highest level DFD; a summary level view of a system, showing the data processing system, its input(s), and output(s), and their sources and destinations

bridge symbol

if two lines cross, you ignore the perpendicular line and continue following the line to the next shape; if there may be confusion as to the path, you can insert a bridge or crossover, which is a little bump on crossed lines; looks like a horseshoe kind of

program flowchart

illustrates the sequence of logical operations performed by a computer in executing a program

Flow and miscellaneous symbols

indicate the flow of data; where flowcharts begin or end, where decisions are made, and how to add explanatory notes to flowcharts

documentation

narratives, flowcharts, diagrams, and other written materials that explain how a system works

internal control

represented by triangles in DFDs; they are numbered and explained in an accompanying table

processing symbols

show data processing, either electronically or by hand

input/output symbols

show input or output from a system

storage symbols

show where data is stored

level 0 DFD

shows all major activity steps in system; processes are labeled 1.0, 2.0, etc. to show when activity occurs

document flowcharts

shows the flow of documents and information between departments or areas of responsibility within an organization

data source

the entity that produces or sends the data that is entered into a system; represented by a square in DFD

data destination

the entity that receives data produced by a system; represented by a square in DFD

data flow

the movement of data among processes, stores, sources, and destinations; they are labeled to show what data is moving; if two or more data flows move together, a single line is used; represented with an arrow in a DFD

data store

the place or medium where system data is stored

transformation process

the processes that transform data from inputs to outputs are represented by circles in DFDs

data input/output symbol

this denotes any type of input to a computer and/or output from a computer; generally, denotes interactive input, but it can be used for any input process; can consider it a catch for data capture

sequential access storage

this symbol, which looks like a tape reel, is generally obsolete; originally, it was used to denote an electronic data file which cannot be accessed randomly but must be read through sequentially to find a particular record; historically, these types of files were stored on magnetic tape

guidelines for drawing a DFD

understand the system; ignore certain aspects of the system if they are unimportant; determine system boundaries; develop a context diagram; identify data flows; group data flows; identify transformation processes; identify all files or data stores; identify all data sources and destinations; name all DFD elements (choose active and descriptive names, data elements should be given unique and descriptive names representing what is known about them); subdivide the DFD; give each process a sequential number; refine the DFD; prepare a final copy

alternative symbol for data storage

used by more and more organizations instead of the previous data symbol to represent data files and databases; this symbol more closely resembles the cylindrical nature of a modern data disk

pre-defined process symbol

used for a complex process which is defined, described, or even drawn at some other place; the symbol text should give the name of the person, and clearly state where the details can be found; needs an input and an output

decision symbol

used for branching; (blank) are always binary, phrased as simple "yes" or "no" questions; the question must appear in the symbol

on-page connector symbol

used to avoid convoluted pages; traditionally, they used single letters of the alphabet, starting over with "A" on each page; these connectors must be used in pairs; they should be used whenever you're going more than one column away

complex process symbol

used to denote a process whose details are not relevant to the purpose of the flowchart; use this symbol to represent a complicated set of operations when it is not necessary for the reader to know all the details of those operations

data storage symbol

used to denote an electronic file or database stored on a local computer; generally, it is used for online storage which can be accessed by the computer without intervention by a human; name of the file/database should be on the symbol; if a process is merely adding records, an arrow should go into the file; if a process is merely reading from the file, the arrow should come out of the file

manual operations symbol

used to denote any type of process, operation or work which does not involve a computer, computer system, or computerized information technology; associate it with a worktable where manual operations take place

electronic transmission symbol

used to denote electronic data transmission moving on a public infrastructure; today mainly used for data transmission, usually over the internet, dial-up or leased data lines, or other WAN architecture; often used for email

internal control flowchart

used to describe, analyze, and evaluate internal controls, including identifying system strengths, weaknesses, and inefficiencies

document symbol

used to represent almost any kind of paper containing information, including order forms, purchase orders, contracts, invoices, checks, work orders, receipts, etc.; not used for currency or transmittal tapes; must show document's origination and final destination on the flowchart

off-page connector

used to show a flow moving from one page to another; when the flow leaves the page, the symbol must show the page number where the flow is continued

entity symbol

used to start a flow; used to identify a department, an employee position, a job title or other entity which is doing the work

off-line storage symbol

widely used to denote anon-electronic file, such as a filing cabinet, a binder, a file folder, or some other physical storage location; do not need to include the word "file" in the label; A for sorted alphabetically, D for sorted by date, and N for sorted by number

narrative description

written, step by step explanation of system components and how they interact