1. Object Oriented
Analysis and Design
Conceptual
Model

2. Object Oriented Analysis and Design
Software
Requirements
Specification
What are the business needs ?
(long text)
Collaboration / sequence
Diagrams
How software objects interact to fulfill task ?
(visual)
Use Cases
What are the domain process ?
(text + visual notation)
Conceptual
Model
What are the concepts, terms ?
(visual)
Sequence
Diagrams
What are the system events, operations ?
(visual)
Contracts
What do the system operations do ?
(text)
Design
Class
Diagrams
What is the specification for the software classes ?
(visual)

3. Conceptual Model
It is a representation of real-world things, not of software components
It may show
Concepts
Association between concepts
Attributes of concepts

4. Object Oriented vs. Function Oriented Analysis
Reminder
Library Info
System
O-O A&D
Decompose by objects and concepts
Structured A&D
Decompose by functions and processes
System
Catalog
Librarian
Book
Library
Record Loans
Add Resource
Report Fines

5. Conceptual Model Concepts
What are the concepts in the Point of Sale system ?

6. Conceptual Model Concepts
Informally, an idea, thing or object
Examples:
Register
Item
Store
Sale
SalesLineItem
Cashier
Customer
Manager
Payment
ProductCatalog
ProductSpecificatin

7. Identifying Concepts Two strategies: Concept Category List
Noun Phrase List

8. Identifying Concepts Concept Category List
Create a conceptual model by making candidate concepts from a list
Contains many common categories that worth considering (not in any particular order)

9. Identifying Concepts Concept Category List
Examples
Concept Category
Physical objects
Places
Transactions
Transaction line items
Roles of people
Containers of other things
Things in a container
Other computer or electro-mechanical systems external to our system
Specifications, designs, or description of things
POST
Store
Sale, Payment
SalesLineItems
Cashier
Store, Bin
Item
CreditCardAuthorizationSystem
ProductSpecification

10. Identifying Concepts Concept Category List
Examples
Concept Category
Organizations
Events
Processes (often not represented as a concept, but may be)
Rules and policies
Catalogs
Records of finances, work, contracts, legal matters
Financial services and instruments
Manuals, books
SalesDepartment
Sale
SellingAProduct
RefundPolicy
ProductCatalog
Receipt, Ledger, EmploymentContract
LineOfCredit
EmployeeManual

11. Identifying Concepts Noun Phrase Identification
Identify nouns and noun phrases in textual description of a problem and consider them as candidate concepts or attributes
Expanded use cases are excellent description to draw concepts
Warning: a mechanical noun-to-concept mapping isn’t usually possible and words in natural language are ambiguous

12. Identifying Concepts Noun Phrase Identification
Actor Actions:
This use case begins when a Customer arrives at a POST checkout system with items to purchase
System Response:
3. Determines item price and adds item info to the running sales transaction
Description and price of the current item is presented
System Response:
3. Determines item price and adds item info to the running sales transaction
Description and price of the current item is presented
2. Cashier records the identifier
(UPC) for each item. If there is more than one of the
same item, Cashier enters
the quantity
2. Cashier records the identifier
(UPC) for each item. If there is more than one of the
same item, Cashier enters
the quantity

13. Identifying Concepts
It is better to over-specify a conceptual model with lots of fine-grained concepts, than to under-specify it
It is common to miss concepts during initial phase and discover them later (e.g., during design)
Do not exclude a concept simply because requirements do not indicate any obvious need for it
It is perfectly acceptable to have purely behavioral or attributeless concepts
Craig Larman

14. Identifying Concepts
Receipt is a record of a sale and relatively important concept in domain of sales
In general, showing a report in a conceptual model is not useful since all its info is derived from other sources
However, it has a special role in terms of business rules; customer uses it to return a previously bought item
So, what to do?

15. Writing Concepts a graphical representation
In UML, conceptual model is illustrated via a set of static structure diagrams in which no operations are described
Concept
Attribute1
Attribute2 ….
Concept

16. Writing Concepts a graphical representation
What are the concepts in the Point of Sale system ?
POST
Item
Store
Sale
SalesLineItem
Cashier
Customer
Manager
Payment
ProductCatalog
ProductSpecificatin

17. How to make a conceptual model
List candidate concepts using Concept Category List and noun phrase identification related to current requirements under consideration
Draw them in a conceptual model
Add associations necessary to record meaningful and interesting relationships between concepts
Add attributes necessary to fulfill information requirements

18. Conceptual Model Associations
Definition:
An association is a relationship between concepts that indicates some meaningful and interesting connection
association name
Records-current
Post
Sale

19. Associations Associations to Consider
Knowledge of the relationship needs to be preserved for some duration
Need-to-know associations
Sale – SaleLineItem ?
Sale – Manager ?
Associations derived from a Common Associations List

20. Associations to Consider Common Associations List
A is physical part of B
Drawer - POST
A is a logical part of B
SalesLineItem – Sale
A is physically contained in/on B
POST – Store, Item – Shelf
A is logically contained in B
ItemDescription – Item
A is a line item of a transaction or report B
A is known/ logged/ recorded/ reported/ captured in B
Sale – POST
A is a member of B
Cashier – Store
*High priority associations

21. Associations to Consider Common Associations List
A uses or manages B
A communicated with B
A is related to a transaction B
A is transaction related to another transaction B
A is next to B
A is owned by B
A is an organizational subunit of B
Cashier – POST
Customer – Cashier
Customer – Payment
Payment – Sale
POST – POST
POST - Store
Department - Store

22. Associations How to name an association ?
Records-current ?
Post
Sale ?
Flies-to
Flight
City
Use TypeName – VerbPhrase - TypeName format
VerbPhrase is the name of the association
Start an association name with a capital letter

23. Conceptual Model Associations rules
Each end of an association is called a rule. A rule may optionally have:
Name
Multiplicity expression
navigability
navigability
Flies-to
Flight
City
destination * 1
multiplicity
role name

24. Association rules Multiplicity
Defines how many instances of a type A can be associated with one instance of type B
Example:
One Store stocks many Items
Stocks
Store
Item 1 *

25. Association rules Multiplicity values

26. Associations examples

27. Associations examples Multiple Associations
Flight * 1
Flies-to
Airport
Flies-from
Person
Drives
Car
Washes
Starts
Stops

28. Association & Concepts Tips:
Run through the concepts and associations gathered
Keep in mind: It is more important to identify concepts than associations
Focus on “need-to-know” associations
High priority associations are strongly “need-to-know”

29. Association & Concepts Tips:
Use the vocabulary of domain when naming the concepts
Exclude irrelevant features
Exclude concepts in the problem domain not relevant to the requirements
Do not add things that are not there
Exclude things not in the problem domain under consideration

30. Build a conceptual model for Point of Sale
ProductCatalog
ProductSpecificatin
SalesLineItem
Store
Item
Sale
Register
Manager
Payment
Customer
Cashier

35. How to make a conceptual model
List candidate concepts using Concept Category List and noun phrase identification related to current requirements under consideration
Draw them in a conceptual model
Add associations necessary to record meaningful and interesting relationships between concepts
Add attributes necessary to fulfill information requirements

36. Conceptual Model Attributes
Definition:
An attribute is a logical data value of an object
Include attributes when requirements (e.g., use cases) suggests or imply a need to remember information
Recall a conceptual model is a representation of real-world things.

37. Conceptual Model Attributes
Sale
date
startTime:Time
Attributes shown in the
second section of
the concept box.
Type info is optional

38. Conceptual Model Derived attributes
Some attributes might be derived from other attributes or from the multiplicity value of the relationship
Date Range
start: Date
end: Date
/duration: Days
Derived attribute

39. Conceptual Model Derived attributes

40. Conceptual Model Attributes
Since a cashier is placed in a certain post it might be represented as follows:
Is this the best way to represent it ?
Cashier
name
currentPost

41. Conceptual Model Attributes
Keep Attributes Simple
Attributes should preferably be simple attributes or pure data values
Common attribute types examples:
Boolean, Date, Number, String/Text, Time
Color, Phone Number, enumerated types

42. Conceptual Model Attributes
What are pure data values ?
Their unique identity is not meaningful
It does not make sense to distinguish separate instances of them, for example:
number 5
string “cat”
phone numbers that contain the same number
address that contain the same address

43. Conceptual Model Concept vs. Attribute
Do not represent something as an attribute when it should have been a concept
Guideline
If X cannot be considered as number or text in real world, X is probably a concept, not an attribute
When in doubt, make it a separate concept

44. Concept vs. Attribute Flight Example
Worse
Better
Flies-to
Flight
destination
Flight
Airport 1 1
destination is a
complex concept
Relate concepts with an association, not an attribute

45. Concept vs. Attribute Cashier-Post Example
Worse
Better
Cashier
name
currentPost
Cashier
name
Post
number
Uses 1 1
currentPost is not
a simple attribute
Relate concepts with an association, not an attribute

46. Concept vs. Attribute Cashier-Post Example
name
currentPost
Cashier
name
Post
number
Uses 1 1
Cashier
name
currentPostNumber
Maybe:
Even worse
Do not use kind of Foreign Keys in the Real World !!!

47. Concept vs. Attribute Cashier-Post Example
name
currentPost
Cashier
name
Post
number
Uses 1 1
In the implementation: Will A Cashier class will hold the current post it uses as a complex attribute (Post class) ?
It should not be decided at this stage !!!

48. Concept vs. Attribute non-primitive attributes
Consider an attribute as non-primitive type when:
It is composed of separate sections (phone number)
There are operations associated with it such as parsing or validation (ss#)
It has other attributes (promotional price that has start/end dates)
It is a quantity with a unit (payment amount has currency)

49. Concept vs. Attribute non-primitive attributes
ProductSpecification
upc:UPC
ProductSpecification 1 *
UPC
Store
address:Address * 1
Store
Address
… depends on your style

50. Concept vs. Attribute An Item Concept Example
Item instance represents a physical item in a store
Item has a description, price and UPC which are not recorded anywhere else
Item
Description
Price
SerialNumber
UPC

51. Concept vs. Attribute Problems with Item Concept
Duplicate data (description, price, UPC)
Very space inefficient
Assume store sells out Item X,
Can we answer a question like: “how much item X cost”?

52. Concept vs. Attribute Problems with Item Concept
Solution to Item concept problem is to add a new concept called ProductSpecification
It represents a description of information about items
Worse
Better
Item
Description
Price
SerialNumber
UPC
ProductSpecification
Description
Price
UPC
Item
SerialNumber 1 *
Describes

53. Concept vs. Attribute Flight Example
date
number
Route
Time
Airport
name
Flies-to 1 *
All the flights are cancelled for 6 months
How can you get record of flight routes?

54. Concept vs. Attribute Flight Example
Worse
Better
Flight
date
time
Described-by
FlightDescription
Number
Route
Flight
date
number
Route
Time
Airport
name * 1
Flies-to 1 * *
Describes-flies-to 1
Airport
name

55. Concept vs. Attribute Specification Concept
In general, add a description or specification concept when
Deleting instances of things they describe results in loss of information that needs to be maintained
It reduces redundant or duplicate information

56. Add attributes in Point of Sale conceptual model
SalesLineItem
ProductCatalog
ProductSpecificatin
Register
Item
Sale
Store
Manager
Payment
Customer
Cashier

59. Conceptual Model glossary
Lists all terms used in the conceptual model to improve communication
Should be created from the start and filled along the way
Records terms from:
Uses cases
Conceptual model: Type and Attributes
Contracts (later)

60. Conceptual Model glossary
Commentsa
Category
Term
Description of the process of a customer buying items in a store
use Case
Buy Item
A short description of an item in a sale and its associated ProductSpecification
attribute
Productspecification.Description : Text
An item for sale in a Store.
type
Item
A sales transaction
Sale
The grand total of the Sale
Sale.total : Quantity
Terms are orders alphabetically
In the comments when using another term, mark it by italics