Ais Chapter 6

Front 1

Data flow diagrams

Back 1

incorporate fewer symbols and different rules than flowcharts.

Front 2

Process

Back 2

A set of procedures an organization uses to gather data, change the data into information, or report the information to system users. Every process in a data flow diagram has 2 identifying characteristics. A number and a name.

Front 3

Every process in a data flow diagram has at least how many identifying characteristics and what are they?

Back 3

2. A number and a name.

Front 4

process names

Back 4

should always be verb phrases, that is, they should start with an action word like approve, record, calculate or check.

Front 5

external entity

Back 5

Any person or organization outside the boundary of an information system. Boundaries are a matter of management judgment and external entities lie outside boundaries. Whether or not a erson or organization is an external entity depends on your definition of the system not your definiton of the organization.

Front 6

Data store

Back 6

A data store is a place for collecting data; you might think of it as a file whether paper based or electronic. Data stores are labeled with noun phrases such as customer data, vendor data, or inventory data. Data stores can be linked to processes or external entities in a data flow diagram. They cannot be linked to one another.

Front 7

Data flow

Back 7

A data flow is represented by a directional line in a data flow diagram. Data flows should have only one arrow on one end to conform to DFD design conventions. Data flows, like data stores, are labeled with noun phrases: desired information, accounts payable data, customer order data and the like.

Front 8

DATA FLOW RULES

Back 8

1. All processes should have unique names
2. The inputs to a process should differ from the outputs of a process.
3. Any single DFD should have no more than 7 processes.
4. No process can have only outputs. This would imply it was making information from itself. If an object has only outputs it must be an external entity.
5. No process can have only inputs. If it has only inputs, it must be a data store.
6. A process has a verb phrase.
7. Data cannot be moved directly from one data store to another data store. Data must be moved by a process.
8. Data cannot move from an external entity to a data store. Must be removed by a process.
9. Data cannot move directly from an external entity to a data store. Data must be moved by a process.
10. A data store has a noun phrase label.
11. Data of any concern to the system cannot move directly from one external entity to another external entity. They must be moved by a process. If they flow directly without they are outside the system boundary and should be excluede.
12. An external entity has a noun phrase label.
13. A data flow has only one direction between symbols.
14. A data flow cannot go directly back to the same process it leaves.
15. A data flow can go directly into a data store When it does, it signifies an update. (delete, add, or change).
16. A data flow has a noun phrase label.

Front 9

Symbols in a DFD

Back 9

Only 4: circle (process), line (data flow), rectangle (external entity), parallel lines ( data store).

Front 10

lines in a data flow diagram

Back 10

represent data, they are labeled with noun phrases

Front 11

Focus of a DFD and flowchart

Back 11

DFD's focus on data and how they move between business processes, external entities, and data stores.
Flowcharts are concerned with data and also with doucments and processing tools.

Front 12

Systems flowcharts often show

Back 12

More detail than a DFD.

Front 13

leveled sets in DFD's

Back 13

DFD's have leveled sets.

Front 14

How many processes should a single DFD have?

Back 14

No right answer however generally less than 7.

Front 15

When do you stop breaking down a process?

Back 15

You stop breaking down a process when it's "self-explanatory". At that point, the process is said to be primitive, meaning it cannot be broken down any further.

Front 16

Does each process have to be decomposed to the same level?

Back 16

No.

Front 17

What other documents support the leveled set of DFDs?

Back 17

In most IS systems, you'll find some specialized terminology that needs to be defined. You'd normally prepare a system's dictionary for that purpose.

Front 18

What's the relationship between levels?

Back 18

The DFDs at various levels must be balanced. In other words, things cannot magically appear and disappear between the levels.

Front 19

Database tables how are they organized?

Back 19

Database tables are organized in rows and columns, much like the rows and columns of a spreadsheet.

Front 20

Primary Key

Back 20

Each record in a datbase must have a unique identifier referred to as a primary key

Front 21

foreign keys

Back 21

a foreign key in one table is nothing but a primary key in another.

Front 22

queries

Back 22

organizing the data in a relational database would allow users to ask questions and create output reports that reflect information.

Front 23

What do database quaries store?

Back 23

Queries store instructions not data. Each time a query is "run" it looks at the current data to get the answer to its questions.

Front 24

Data normalization

Back 24

Data normalization allows database creators and users to minimize database size, optimize table design, and acess the data more quickly and efficiently.

Front 25

normal form

Back 25

when a database follows the rules of normalization, it is said to be in normal form.

Front 26

First Normal Form

Back 26

Eliminates repeating groups. For every row/column cell, there is only one value, not multiple values.

Front 27

Second Normal Form

Back 27

redundant data is eliminated Junction tables created to link two primary key tables. More efficient and compact, easy to query and calculate.

Front 28

Third normal form

Back 28

Designed so that table columns are not duplicated in any related tables. Primary key contains all shared information for maximum efficiency. Nothing is ever duplicated. This is the most efficient database.

Front 29

What is the most efficient database form?

Back 29

Third normal form is the most efficient.

Front 30

Levels in DFD

Back 30

Context level (numbered as process 0) This is kind of like a title to what the broad process is all about.
1. Level zero (numbered as process 1.0, 2.0) Think of an outline, and this is the main items in an outline.
2. Level 1 (Numbered as process 1.1, 1.2 ect) Next level details on process 1.0
3. Level 2 Subheadings of subheadings in an outline.