ITM 5400 Chapter 5 - Data and Process Modeling Flashcards

1
Q

What is a data flow diagram (DFD)?

A

Shows how data flows through a system. Does not show logic or processing steps.

  • Logic model
  • Does not show how transformations are done
  • Prevents any restrictions on how the processes are implemented
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2
Q

Two basic schools of DFD are?

A

Gane and Sarson

Yourdon

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3
Q

What are the four basic symbols in DFD?

A

Process
Data Store
Entity
Data Flow

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4
Q

What is the minimum number of inputs for a Process Symbol?

A

There must be at least 1 input and at least 1 output

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5
Q

What are three incorrect data flows?

A

Spontaneous generation - process has no input
Black Hole - no output flows
Gray hole - has input and output but it is obvious that in input itself is insufficient

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6
Q

What is a data store in DFD?

A

Represents data the system stores
Does not show detailed content of a data store

** Data store must be connected to a process witha data flow.

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7
Q

What is an entity symbol?

A

Shows how the system interfaces to the world
DFD shows only external entities
DFD Entities are called terminators
*** Each entity must be connected to the process by a data flow

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8
Q

What is a context diagram?

A

A high level view of a system

  • Defines boundaries of a system
  • Shows all external entities that interact with a system
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9
Q

T/F A DFD should fit on 2 pages.

A

False it should fit on one page

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10
Q

T/F A DFD should use the same name for an item whenever it is used

A

True. Student should be named student any time it is used

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11
Q

What are the three steps in developing a set of DFDs?

A
  1. Draw the Context Diagram
  2. Draw the Level 0 DFD
  3. Decompose Level 0 DFD into lower level DFDs until processes are decomposed to lowest level
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12
Q

What is a data dictionary

A

Central storehouse of information about a systems data

  • Describes contents of each data flow
  • Describes contents of each data store
  • ID the data elements or data items within a system
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13
Q

What is used to build the data dictionary of a system?

A

A CASE tool

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14
Q

What is the lowest piece of data called?

A

Data Element - eg. customer name

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15
Q

Data elements are grouped into records based called

A

Data structures based on some common attribute, ig customer record contains customer name, phone number, address etc

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16
Q

What contains individual records which use all the same data structures?

A

Data store - customer data store contains one record for each customer

17
Q

What information should be collected for each data element?

A
  1. Data element name
  2. Alias
  3. Data type
  4. Length of field
  5. Default value - value if nothing is entered
  6. Acceptable values
  7. Source
  8. Security - who can add or delete or view element
  9. Responsible users
  10. Description or comments
18
Q

What should be collected for each data flow?

A
Name
Description
Alias
Origin
Destination
Record - what data structure is used
Volume and Freqencies
19
Q

What items should be collected for each data store?

A

Name
Description
Alias
Volume and freq

20
Q

What should be collected for each process?

A

Name
Descri[tion
Process number
Process description

21
Q

What should be collected for each record

A

Name
Definition
Alias
Attributes

22
Q

What does a process description describe?

A

The processing steps and business logic in each functional primative

23
Q

Processes are generally describe as using what 3 things?

A

English
Decision tables
Decision trees

24
Q

What are processes broken down into?

A

Related steps called modules

25
Q

What is used to break processes down info a series of logic structures?

A

Modular design

  • each structure has single entry and exit point
  • control structures are sequence, selection and iteration (loop)
26
Q

COntrol structures have three types

A

Structured - steps completed in order
Selection - based on results of a test
Iteration - executed until a condition is met

27
Q

A decision table is a logical structure that shows every combination of conditions and outcomes.

A

True

  • Used to insure all possible situations have been considered
  • Number of rules double each time a condition is added
  • `Very effective in describing complex conditions
28
Q

What is a graphical representation of conditions, actions and rules found in decision table

A

Decision tree

29
Q

What is 4 model approach

A

Develops models to describe the current system before developing models of a new system

30
Q

What are the 4 models in the 4 model approach

A

Physical model of current system
Physical model of new system
Logical model of current system
Logical model of new system

31
Q

What are the 3 main tools used for data process modeling?

A

DFD
Data Dictionary
Process Description