structuring user requirements
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Structuring User Requirements. IS 592 Dr. Dania Bilal Spring 2005. Recap of Systems Analysis Phase. Determining user requirements Structuring user requirements Selecting the best system design strategy. Structuring User Requirements. Data Flow Diagrams (DFDs) - PowerPoint PPT PresentationTRANSCRIPT
Structuring User Requirements
IS 592Dr. Dania BilalSpring 2005
Recap of Systems Analysis Phase
Determining user requirements Structuring user requirements Selecting the best system design
strategy
Structuring User Requirements
Data Flow Diagrams (DFDs) Analysis tool to structure user
requirements in a system Graphically represents data movement
or flow in an information system and relationships among data flow
DFDs
Show the processes that transform or change data
Focus on movement of data between processes ->DFDs are called process models Process modeling shows data flow through
the system based on an organization’s rules, decisions, and policies
DFDs
Increase software development productivity by avoiding mistakes in representing user requirements
Saving money in software cost
Based on user requirements gathered during planning stage
Evolve from the more general to the more specific
DFDs
DFDs of current system Used to understand current system
DFDs of new logical system Used to show data flow, structure, and
functional requirements of new system
DFDs Symbols
Flow of data is represented by Data flow Data Store Process Source (external entities)
DFDs Symbols
Data Flow Data in motion from one place in a
system to another Example: user query in a database
DFDs Symbols
Data store Physical location or various locations of
data in an information system Example: a data store in a circulation
system contains data about students, faculty, staff, community users, etc.
DFDs Symbols
Process Actions performed on data for
transformation, storage, and distribution May represent data in
File folder, computer-based file, notebook
DFDs Symbols
Source/sink Depicts the origin and/or destination of
data Referred to a external entity
Another organization or unit that sends and receives information from the system
A person who interacts with the system, inside or outside
Another information system that exchanges information with the system under analysis
DFDs Symbols
Source/sink Defines the system boundaries Data originates outside a system from
one or more sources, and the system produces information to one or more sinks
DFD Mechanics
How the four symbols are represented? Data flow: drawn as an arrow Data store: drawn as a rectangular Process: drawn as a circle Source/sink: drawn as a square
DFD Definitions Level-0 diagram
Represents a system’s major processes, data flow, and data stores at the highest level of detail
Context diagram Shows major flow between entities and
the system (too general) Level-N diagram
A DFD that results from a decomposed Level-0 diagram
Types of DFDs
Current logical Depicts current system
New logical Has additional functions Inefficient data flows are reorganized
New physical Depicts physical implementation of the
new system
DFDs
Examples Visit
http://www.umsl.edu/~sauter/analysis/dfd/dfd.htm
For additional information or clarification Visit
http://management.wcupa.edu/mis451/chapter08.ppt#256,1,Slide 1