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TOPIC 3.2 : DATA & PROCESS MODELLING - Coggle Diagram
TOPIC 3.2 : DATA & PROCESS MODELLING
1) DATA & PROCESS MODELLING CONCEPTS
a. many graphical techniques to describe an information system
c. data dictionary and process descriptions
b. DFD uses various symbols to show how the system transforms input data into useful information.
2) DATA FLOW DIAGRAM
a. Flow of data between process
b. Provide a logical model that shows what the system does, not how it does it
c. DFD symbols
:star: process symbol
i. input data & produces output that has a different content, from or both
iii. referred to as black box
ii. contain the business logic or business rules
:star: data flow symbol
i. represents one or more data items
ii. avoid
:warning: spontaneous generation
:warning: black hole
:warning: gray hole
:star: data store symbol
i. represent data that the system stores
ii. unimportant because you are concerned only with a logical model
:star: entity symbol
i. name of the entity appears inside the symbol
ii. only external entities that provide data to the system
d. Creating set of DFD
:star: guidelines for drawing DFD
:pencil2: draw a context diagram
i. a top-level view of an information system that shows the system boundaries and scope
ii. example context diagram for an order system
:pencil2: draw a diagram 0 DFD
i. repeats the entities and data flow that appear in the context diagram
ii. exploded view of process 0 and it shows considerably more detail than the context diagram
iii. example diagram 0 DFD for an order system
:pencil2: draw the lower-level diagram
you must use leveling and balancing techniques
:check: leveling example
i. uses a series of increasingly detailed DFD to describe an information system
:check: balancing example
i. ensures that the input and output data flow of the parent DFD are maintained on the child DFD
3) DATA DICTIONARY
a. Called a data item or field is the smallest piece of data that has meaning
b. Data elements are combined into records also called data structures
c. Using CASE tools for documentation
:explode: more difficult it is to maintain full and accurate documentation
:explode: modern CASE tools simplify the task
:explode: CASE repository ensures data consistency
d. Documenting the data elements
following attributes usually are recorded and described
:!: acceptable values- domain and validity rules
:!: source
:!: default value
:!: security
:!: type and length
:!:responsible user(s)
:!: alias
:!: description and comments
:!: data element name and label
e. Documenting the data flows
the typical attributes are as follow
:red_flag: alternate name(s)
:red_flag: origin
:red_flag: description
:red_flag: destination
:red_flag: data flow name or label
:red_flag: record
:red_flag: volume and frequency
f. Documenting the data stores
typical characteristic of data store are
:recycle: alternate name(s)
:recycle: attributes
:recycle: description
:recycle: volume and freaquency
:recycle: data store name or label
g. Documenting the processes
:warning: description
:warning: process number
:warning: process name and label
:warning: process description
h. documenting the entities
:fire: alternate name(s)
:fire: input data flows
:fire: description
:fire: output data flows
:fire: entity name
i. Documenting the records
:black_flag: definition or description
:black_flag: alternate name(s)
:black_flag: record or data structure name
:black_flag: attributes
4) PROCESS DESCRIPTION
Process Specification
:star: structured english
a. must conform to the following rules
:warning: use indentation for readability
:warning: use a limited vocabulary
:warning: use only 3 building blocks of sequence, selection and iteration
b. might look familiar to programming students because it resembles pseudocode
c. the primary purpose of structured English is to describe the underlying business logic
:star: decision table
a. the number of rule doubles each time you add a condition
b. 4 types of tables
:pen: table with two condition
a. Suppose you want to create a decision table based on the Verify Order business process shown in Figure 5-34
b. If both conditions are met, the order is accepted. Otherwise the order is rejected
:pen: table with three condition
a. you must fill in the Y-N patterns
b. The best way to assure that all combinations appear is to use patterns like these
:check: The second condition uses a repeating Y-YN-N pattern
:check: The pattern in the third condition is a series of Y-N
:check: The first condition uses a pattern of Y-Y-Y-Y followed by N-N-N-N
:pen: table with one condition
a. if a process has a single condition there only are 2 possibilities
YES
NO
b. either the condition is present or it is not so there are only 2 rules
:pen: table with multiple outcomes
a. decision tables can have more than two possible outcomes.
c. Decision tree
:tada: graphical representation of the conditions, actions, and rules found in a decision table.
:tada: trees show the logic structure in a horizontal form that resembles a tree with the roots at the left and the branches to the right.
:star: modular design
:fountain_pen: 3 structures are called
:lock: selection
i. the completion of one of two or more process steps based on the results of a test or condition
:lock: iteration
i. the completion of a process step that is repeated until a specific condition changes
:lock: sequesnce
i. the completion of step in sequential order, one after another
:fountain_pen: symbol
i. rectangle represents a step or process
ii. diamond shape represents a condition or decision
iii. logic follows the line in the direction indicated by the arrows
5) LOGICAL & PHYSICAL MODEL
a. structured analysis tools are used to develop a logical model for a new information system, such tools also can be used to develop physical models of an information system
b. physical model shows how the system’s requirements are implemented
c. Sequence of Models
:explode: Performing that extra step allows them to understand the current system better
d. Four-Model Approach
:<3: Develop a physical 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
