1. Logic Modeling
Logic and timing are not represented on data flow diagrams or entity-relationship diagrams
Processes contain logic - what happens under what conditions
Logic is modeled per process
Types of logic: sequence, conditions, iteration

2. Structured English Uses a subset of English
Uses indentation similar to programming
Uses process-type verbs like READ, WRITE, GENERATE, CHECK, PRINT
Verbs and control words in CAPS
Refers to the data coming in and out of the process
No specific syntax rules

3. Structured English Examples
READ Inventory records
WHILE NOT End-of-file DO
BEGIN IF
IF Quantity-in-stock is less than Minimum-order-quantity
THEN GENERATE new order
ELSE DO nothing
END IF
END DO
READ next prescription
SELECT CASE
CASE (prescription for formulated drug)
DO send to lab station
CASE (prescription for off-the-shelf drug)
DO send to shelving station
CASE (prescription for narcotic drug)
DO send to secure station
END CASE

4. Decision Tables

5. Decision Trees Pay base salary Salaried Calculate hourly wage;
Produce absence report 1
Hourly
<40 40
Calculate hourly wage 2
>40
Calculate hourly wage;
Calculate overtime wage
Legend
1) Type of employee
2) Hours worked

6. Network Models Network Decomposition Diagram Hub Connectivity Diagrams
hubs - places where data is stored or processing is done for users at some other location
workstations - places where a user physically sits and can access the system remotely
Hub Connectivity Diagrams
simply says what hubs and external networks have to exchange data

7. Network Decomposition Diagram
System
External
Network
Hub
Hub
Hub
Workstation
Workstation
Workstation
Workstation
Set of
Workstations
Workstation

8. Hub Connectivity Diagram
50 feet
35 miles
Hub
Hub
3000 miles
External
Network

9. Simple Example 200 miles Server Server Order Takers Customer Ordering
System
Credit
Verification
Service
200 miles
Credit
Verification
Service
Server
Server
System
Administrator
Order
Takers

10. Data Dictionary Includes: Purposes descriptions of all pieces of data
relationships between pieces of data
Purposes
eliminate ambiguities
identify links between DFDs and ERD
clarify how different pieces of data are related
serves as a standard reference throughout the project
specify what is contained in data stores and flows

11. What needs to be defined
Data flows
Entities
Data stores
Relationships
are
collections of
are
collections of
Data elements
correspond to
Attributes

12. Basic parts of a definition
Name (that appears on the diagram)
Type (data flow, data store, entity, etc.)
Description (text)
Synonyms (other names used for same thing)
What it contains
What it is contained in
Constraints/data type

13. Data Flow Definition Name (that appears on the diagram)
Type = data flow
Description (text)
Synonyms
What it contains - list of data elements; lower-level data flows
What it is contained in - data flow in higher-level diagram
Constraints - source and destination

14. Example Data Flow Definition
Name: Customer Record
Type: data flow
Description: The customer information that needs to be stored in the customer DB
Synonyms: none
What it contains:
data elements:
customer ID
customer name
customer address
customer phone
lower-level data flows: none
What it is contained in: none
Constraints:
Source: Process 5, Create Customer Record
Destination: Data Store D3, Customer Master

15. Data Store Definition Name (that appears on the diagram, including ID)
Type = data store
Description (text)
Synonyms
What it contains - list of data elements
What it is contained in - n/a
Constraints - physical form, if known

16. Example Data Store Definition
Name: Customer Master
Type: data store
Description: Information on all customers who have provided this information when placing an order
Synonyms: none
What it contains:
data elements:
customer ID
customer name
customer address
customer phone
What it is contained in: n/a
Constraints: form is a database table

17. Data Element Definition
Name (does not appear on the diagram)
Type = data element
Description (text)
Synonyms (other data elements and attributes)
What it contains - n/a
What it is contained in (data stores and data flows)
Constraints (format, length, valid values)

18. Example Data Element Definition
Name: customer name
Type: data element
Description: The last name of a customer who has at one time placed an order
Synonyms: attribute Customer.name
What it contains: n/a
What it is contained in:
data flow Customer Record; data store Customer Master
Constraints: must be a character string with maximum length 15

19. Entity Definition Name (that appears on the diagram) Type = entity
Description (text)
Synonyms
What it contains (attributes)
What it is contained in - n/a
Constraints (identifier)

20. Example Entity Definition
Name: Customer
Type: entity
Description: Any individual who has at one time placed an order and purchased goods
Synonyms: none
What it contains: attributes Customer_ID, Name, Address, Phone
What it is contained in: n/a
Constraints: Customer_ID must be unique

21. Relationship Definition
Name (that appears on the diagram)
Type = relationship
Description (text)
Synonyms
What it contains (attributes, including key attributes of participating entities)
What it is contained in - n/a
Constraints (cardinality, degree, operational constraints)

22. Example Relationship ERD DFD 8 Customer_ID Phone Charge Customer
Purchase
Customer
Information
Address
Name
CUSTOMER
Account
Information
Purchase
Information
owner
type
Has
account number D5
Customer Accounts
ACCOUNT
balance

23. Example Relationship Definition
Name: Has
Type: relationship
Description: Associates individual customers with the credit accounts they have with this business, that they can use to purchase goods
Synonyms: data store D5, Customer Accounts
What it contains: attributes Customer.Customer_ID, Account.account_number, owner_type
What it is contained in: n/a
Constraints: binary; many-to-one; mandatory for accounts, but not customers

24. Attribute Definition Name (that appears on the diagram)
Type = attribute
Description (text)
Synonyms (other attributes and data elements )
What it contains - n/a
What it is contained in (entities and relationships)
Constraints (format, length, valid values)

25. Example Attribute Definition
Name: Name
Type: attribute
Description: The last name of a customer who has at one time placed an order
Synonyms: data element customer_name
What it contains: none
What it is contained in: entity Customer
Constraints: must be a character string with maximum length 15