Systems design chapter 6 Flashcards
Data flow diagram
Represents sys requirements as processes, external agents, data flows, and data stores
External agent
Person or org outside the sys boundary that supplies data inputs or accepts data outputs
Process
Symbol on a dfd that represents an algorithm or procedure by whih data inputs are transformed into data outputs
Data flow
An arrow on a dfd that represents data movement among processes, data stores, and external agents
Data store
A place where data is held pending future access by one or more processes
Traditional approach
System of processes, processes interact with data entities, processes accept inputs and produce outputs.
OO approach
System is collection of interacting object, objects interact with people and each other, objects send and respond to messages.
Level of abstraction
Any modeling technique that breaks the system down into a hierarchical set of increasingly more detailed models.
Context diagram
A dfd that summarizes all processing activity within the system in a single process symbol
Data flow diagram DFD
Represents sys requirements as processes, external agents, data flows, and data stores
Data flow diagram DFD
Represents sys requirements as processes, external agents, data flows, and data stores
DFD fragment
A DFD that represents the system response to one event withina single process symbol
Event-partitioned system model or diagram 0
A DFD that models system requirements using a single process for each event in a system or subsystem.
Physical and logical DFDs
DFDs can be either physical system model, a logical system model or a combination of both.
Information overload
Too much information at one time
Rule 7+-2
Modeling rule that limits the number of components or connections to no more than nine
Minimization of interfaces
Simplicity by limiting the number of of connections between model components.
Balancing
Equivalence of FAA content between data flows entering and leaving a process and data flows entering and leaving a process decomposition DFD
Black hole
Process or data store with a data input that is never used to produce a data output.
Miracle
Process or data store with a data element that is created out of nothing.
Structured English
Writing process specifications that combines structured programming techniques with narrative English.
Decision table
A table representation of processing logic containing decision variables, decision variable values and actions or formulas
Decision tree
A graphical description of process logic that uses lines organized like branches of a tree.
Data flow definition
Text description of a data flows content and internal structure.
