Alliyah EvangelistaSystems Analysis & Design, Chp. 5 - Data and Process Modeling
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What is data modeling?
The process of creating a visual representation (data model) of an information system. It's a conceptual representation of the Data objects and its association between different data objects, and the rules (processes, input, output, etc.).
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What does a data model help reduce?
Helps reduce missing data (data omission). Missing data can lead to incorrect results and faulty reports.
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A data model helps to better portray a ___.
business requirement.
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What does a data model help identify?
Helps in identifying redundant, duplicate, and missing data. And helps improve data quality. It also defines relational tables, stored procedures and primary and foreign keys.
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Describe a logical and physical model.
Logical: shows what the system must do, regardless of how it will be physically implemented.
Physical: describes how the system will be physically constructed and how the system's requirements will be implemented.
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What is a four-model approach?
1. Physical model of the current system
2. Logical model of the current system
3. Logical model of the new system
4. Physical model of the new system
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What are the pros and cons of a four-model approach?
Advantages:
- provides a clear picture of the current system's functions before any modifications are made.
- important because mistakes occurring in the early stages will affect later stages and can result in unhappy users and additional costs.
Disadvantages:
- extra time and cost to do it for the current system.
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What does Data flow diagram (DFD) show?
Shows how the system transforms input data into useful information. How data moves through an information system, but not the program logic.
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Processes contains the business logic that transforms the data. What is a business logic.
The rules determining how a system handles input data and produces useful information.
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The name of the process should be written in ___ and is a ___.
CAPITAL LETTERS, verb
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In DFDs a process symbol can be referred to as a black box. Why might that be the case?
Because the inputs, outputs and general functions of the processes are known, but the underlying details and logic of the process are hidden. By showing processes as black boxes, SA can avoid unnecessary detail and clutter.
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Spontaneous generation, black hole, and gray holes are process combinations that must be avoided. Define all three of them.
Spontaneous generation: produces output with no input data flow.
Black hole: has input but no output.
Gray holes: has at least one input and output, but the input is insufficient to generate the output shown. Ex. DATE OF BIRTH --> CALCULATE GRADE --> FINAL GRADE
How does someone's birthdate create their final grade?
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What does a data store represent?
Stores data that can be used at a later time by a process.
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A data store must be connected to a ___ with a data flow.
process
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What should a data store have?
An incoming and outgoing data flow connected to at least one process.
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External entities ___ data or provide ___.
receive data, provide data.
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External entities are also known as ___. This is because they can what starts the flow of data or be their final destinations.
terminators
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An entity that supplies data is a ___. An entity that receives data is a ___. An entity can be both.
source, sink
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What is correct and incorrect in this diagram?
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The name of the process is the name of the ___.
information system
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What is the difference between a Context Diagram and Diagram 0.
Context Diagram: the first diagram created for the system and the middle process is process 0. No processes are blown up and is the basic view of the system. No data stores.
Diagram 0: the inside view of process 0, showing more processes and a more detailed view of the system (blown up). Visible data stores.
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To create lower-level diagrams, leveling and balancing techniques must be used. Define the terms.
Leveling: progressively drawing a series of diagrams until all primitive functions are identified. "Partitioning, blowing/exploding up". Drawing a context diagram and then diagram 0 is part of the process of leveling. Diagram 0 can also be decomposed into more detailed processes.
Balancing: maintaining a consistency among a set of DFDs by ensuring that input and output data flows align properly. External entities will also remain the same.
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What is the purpose of a data dictionary?
The data dictionary is used to collect, document and organize specific facts about a system. It defines and describes all data elements and meaningful combinations of data elements (also called data item or field).
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What is a data element?
The smallest piece of data that has meaning in an IS. Ex. student grade, salary, SIN#, name, etc. A factor that isn't related and connected to anything, YET.
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Modular design is based on a combination of three logical structures. What are they and define them.
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Correctly identify what logical structure each figure is showing.
