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Systems Analysis and Design Ch 5
Terms in this set (41)
Shows what the system must do, regardless of how it will be implemented physically.
Describes how the system will be constructed.
Data Flow Diagram (DFD)
Shows how data moves through an information system but does not show program logic or processing steps.
Symbol sets in DFDs
- Gane and Sarson
DFDs use 4 basic symbols to represent each of these functions:
- Data flows
- Dats stores
Receives input data and produces output that has a different content, form, or both.
Business logic or business rules
Transform the data and produce the required results.
In DFDs it is what is called to a process symbol because the inputs, outputs, and general functions of the process are known, but the underlying details and logic of the process are hidden.
Is a path for data to move from one part of the information system to another.
3 data flow and process combinations that should be avoided:
- Spontaneous generation
- Black hole
- Gray hole
A process that produces output, but has no input data flow.
Process that has input, but produces no output.
Process that has at least one input and one output, bu the input is insufficient to generate required output.
Is used in DFD to represent data that the system stores because one or more processes need to use the data at a later time.
Another name given to DFD entities because they are data origins or final destinations.
An entity that supplies data to the system.
An entity that receives data from the system.
Is a top-level view of an information system that shows the system's boundaries and scope.
Context diagram or entire information system.
It shows the details inside the black box (context diagram).
Diverging data flow
Is a data flow in which the same data travels to two or more different locations.
Is the higher-level diagram when a DFD is exploded.
Is the lower-level diagram when a DFD is exploded.
Is a process that consists of a single function that is not exploded further.
Is the process of drawing a series of increasingly detailed diagrams, until all functional primitives are identified.
Is also called exploding, partitioning, or decomposing
Maintains consistency among a set of DFDs by ensuring that input and output data flows align properly.
Data dictionary or data repository
Is a central storehouse of information about the system's data.
Data element, data item, or field
Is the smallest piece of data that has meaning within an information system.
Records or data structures
Is a meaningful combination of related data elements that is included in a data flow or retained in a data store.
Any name other than the standard data element name.
Refers to whether the data element contains numeric, alphabetic, or character values.
Is the maximum number of characters for an alphabetic or character data element.
Is the set of values permitted for the data element.
documents the details of a functional primitive, and represents a specific set of processing steps and business logic.
Is based on combinations of three logical structures, sometimes called control structures, which serve as building blocks for the process.
3 logical structures
- Interaction or looping
is a subset of standard English that describes logical processes clearly and accurately.
is a logical structure that shows every combination of conditions and outcomes.
Outcomes in a decision table
- one condition
- two conditions
- three conditions
- mutliple outcomes
is a graphical representation of the conditions, actions, and rules found in a decision table.
Many analysts follow these approach which means that they develop a physocal model of the current system, a logical model of the current system, a logical model of the new system, and a physical model of the new system.