Domain Model
Domain Model
Lecture 3
Lecture 3
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Agenda
Agenda

Recap

Case Requirements

Elaboration process

Domain model
–
Introduction and definition
–
How to create a domain model
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Recap
Recap

Inception activities

Different types of requirements

Scenario & Use case

Writing Use Cases


around the squares of the board
–
Implement a start Up use case as necessary
to support the initialization needs of the
iteration
–
Two to eight players can play
–
A game is played as a series of rounds
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Case requirements
Case requirements

Monopoly (cont)
–
Play the game for only 20 rounds
–
After the dice are rolled, the name of the player and
the roll are displayed. When the player moves and
lands on a square, the name of the player and the
name of the square that the player landed on are
displayed.
–
In iteration-1 there is no money, no winner or loser, no
properties to buy or rent to pay, and no special
squares of any kind
–
Square name will be “Go”, “Square 1”, “Square 2”,
…“Square 39”
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–
Last only one week
–
Most actors, goals and use cases named
–
Most use cases written in brief format; 10-20% of the use cases are
written in fully dressed detail
–
Recommendations on what components to buy/build/reuse, to be
refined in elaboration

Technical proof-of-concept prototypes and other
investigations to explore the technical feasibility of
special requirements/

High-level candidate architecture and components
proposed – NOT necessary to be final or correct

Plan for the first iteration
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Process: on to Elaboration
Process: on to Elaboration

What happens in Elaboration
–
The core, risky software architecture is programmed
and tested
–
The majority of requirements are discovered and
stabilized

Domain models

Illustrates noteworthy concepts in a
domain

Drawn with UML class diagram

As with all things in an agile modelling and
UP spirit, a domain model is optional

Input
–
Problem Description, Use Cases, …

Output
–
A set of class diagrams
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Example
Example
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Register
Item
Store
address
name
Sale
date
time
Payment


A domain model is a visual representation of
conceptual classes or real-situation objects in a
domain.
–
Various names

conceptual models, domain object models, analysis object
models

A domain model is illustrated with a set of
CLASS DIAGRAMS in which no operations
(method signatures) are defined
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Domain models is a visual dictionary
Domain models is a visual dictionary

Domain model provides a conceptual
perspective
–
Domain objects or conceptual classes
–
Associations between conceptual classes
–
Attributes of conceptual classes

The information it illustrates could
alternatively have been expressed in plain
text
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date
time
print()
What are conceptual classes
What are conceptual classes

A conceptual class may be
considered in terms of
–
Symbol – words or images
representing a conceptual
class
–
Intension – the definition of
a conceptual class
–
Extension – the set of
examples to which the
conceptual class applies
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Sale
date
time
concept's symbol
"A sale represents the event
of a purchase transaction. It
has a date and time."
concept's intension
sale-1
sale-3

amount: Money
getBalance(): Money
Sale
date: Date
startTime: Time
getTotal(): Money
. . .
Pays-for
UP Domain Model
Stakeholder's view of the noteworthy concepts in the domain.
UP Design Model
The object-oriented developer has taken inspiration from the real world domain
in creating software classes.
Therefore, the representational gap between how stakeholders conceive the
domain, and its representation in software, has been lowered.
1
1
1
1
A Payment in the Domain Model
is a concept, but a Payment in
the Design Model is a software
class. They are not the same
thing, but the former inspired the
naming and definition of the
latter.
This reduces the representational
gap.
This is one of the big ideas in
object technology.

Use a category list
–
Identify noun phrases
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Use a category list
Use a category list

Use a conceptual class category list:
–
Physical or tangible objects
Register, Airplane
–
Specifications, descriptions of things
ProductSpecification, FlightDescription
–
Places
Store, Airport
–
Transactions
Sale, Payment, Reservation
–
etc. (see Table 9.1 for a fuller list)
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Noun Phrase Identification
Noun Phrase Identification

Noun Phrase Identification [Abbot 83]
–
Analyse textual description of the domain


model components
model components
Part of speech Model component Examples
Proper noun Instance Alice
Common noun Class Customer, toy
Doing verb Operation Buy, recommend
Being verb Inheritance Is a kind of, is one
of
Having verb Aggregation
(Composition)
Has, consists of,
includes
Modal verb Constraints Must be
Adjective attributes Attributes 3 years old
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Example: find and draw conceptual
Example: find and draw conceptual
classes
classes

Case study: POS Domain
–
Input

fully dressed use case model (excellent textual
description of the domain)

Iteration-1: success (cash-only) scenario of Process
Sale use case.
–