Chapter 7 - Data flow diagramming. When you''ve finished studying this chapter, and completing the activities at its conclusion, you should be able to: Explain the symbols and design considerations associated with DFDs; compare and contrast flowcharts and DFDs with regard to purpose, content, structure, and use in accounting information systems; discuss the ways in which DFDs are used in AIS work; construct a leveled set of DFDs; design normalized database tables from a DFD.
Trang 1Chapter 7 Data Flow Diagramming
Trang 3Learning objectives
considerations associated with DFDs.
DFDs with regard to purpose, content,
structure, and use in accounting
information systems.
work.
a DFD.
Trang 4Nature and purpose of DFDs
accounting practice
underlies the AIS
Trang 5DFD symbols
process
external entity
data flow
data store
Trang 7Leveling and balancing
leveled sets
one before it.
that external entities and data flows at the boundary cannot “disappear” between
levels.
Trang 8Leveling and balancing
Trang 9Customer order
Invoice
Trang 101.0 Process customer order.
2.0 Bill customer.
Processed customer order
Trang 11• More detail than
the Level Zero
Level Zero diagram.
Trang 12Leveling and balancing
Customer
Customer
order
1.1 Verify customer order. Verified
customer order
1.2 Evaluate customer credit.
Customer database
Credit inquiry
Credit decision Processed customer order
Trang 13Leveling and balancing
until they are primitive
different levels.
1.2.2
Trang 14Database design
Trang 15Database design
least one table
Trang 16Database design
Student table in design view
Student table in datasheet view
Trang 17Database design
in tables and / or other queries
average)
Trang 18Database design
Query in design view
Query in datasheet view
Trang 19Database design
if they know nothing about design and
structure
Trang 20Database design
Form in design view Form in form view
Trang 21Database design
Trang 22Database design
Report in report view
Trang 23Database design
– Primary key: a field in a table that uniquely
identifies every record in that table
– Foreign key: a primary key in one table that
is included in another table for linking
purposes
– Compound primary key: two or more fields
in a table that together comprise its primary
key
Trang 24Database design
Junction table
• A table that joins together two separate tables.
• Required when the two separate tables have a
“many-to-many” relationship – Every student may enroll in many classes.
– Every class has many students.
• Named by joining the separate table names
– Student table
– Class table
– Student / class table
This is the junction table.
Trang 25Database design
Relationship grid
Trang 26Database design
Table characteristics that ensure a relational
database is organized as efficiently and
Trang 28Database design
with a “flat file” (such as a spreadsheet)
and create normalized database tables.
normalized tables “from scratch.”
23 January 2014 post on Dr Hurt’s AIS
Trang 29Normal forms
This data array is a “flat file” comprising two fields and
five records It is not normalized, as the “courses”
field includes repeating groups of data (i.e., two
courses in one field).
Trang 30• To put the array in 1NF, we need to
eliminate repeating groups.
Normal forms
This array, while not fully normalized, is closer to that state Note that we could search for specific course prefixes and / or numbers more easily than in
Student ID Prefix Number Prefix Number
Trang 31eliminate redundant data.
Normal forms
Neither table has repeating groups or redundant data;
however, we’re missing key information: which
students are in which courses?
Student table Student ID
1026 1053 1221 1270 1397
Acc 343 Bus 281 Psy 200 Eng 117 Mat 146
Course table
Trang 32marrying data from
two other tables
Trang 33that each table contains only fields that
give us more information about the
primary key.
code, phone number
classroom, section number
need any information beyond the primary
keys of the two other tables
Normal forms