Domain Models and
Implementations
Examples of Domains
· Health Care
· Education
o Academic Records
o Scheduling
o Course Management
o Online Courses
· Enterprise
o Shipping
o Inventory/Warehouse Management
o Human Resources
o Accounting/Payroll
o E-Store
· Science
o Modeling
o System Control
· Finance/Banking/Investment
o Online Banking
o Portfolio Management
o Ledgers/Blockchains
· Entertainment/Gaming
· Manufacturing
o Factory Automation
· Software Engineering
o CASE Tools
o Language Processors
o IDEs
Example: Film
Pal
Notes
· This is a UML package diagram.
· A package is a collection of related class and interface declarations.
· Packages are name spaces.
· The dashed arrows are dependency arrows. They indicate that the source package depends on or uses stuff declared in the target package.
film
Notes
· Types-as-Objects pattern used to represent movie genre. Use this when type doesn't impact behavior.
· Actor-Role pattern used to decouple personal info from the roles played by a person.
· Bi-directional association between Film and Actor needs to be managed by one end or the other.
theater
Notes
· CreditCard is a class that implements the PaymentMethod interface.
· Actor-Role Pattern used here, too.
utilities
· How would Time and Date be implemented? How should we deal with time zones? Why does Time extend Date?
· How should Location be implemented?
Object Diagrams
A UML object diagram shows objects (instances of classes) and links (instances of associations):
· Think of an object diagram as an "instance" of a class diagram.
· Think of an object diagram as a snapshot of memory.
· Bill Smith uses his Visa card to buy three tickets to the June 4, 2020, 7:30 PM showing of Star Wars at the Coronet Theater. Draw an object diagram of this scenario.
· How is today's 7:30 PM showing of Star Wars differentiated from tomorrow's 7:30 PM showing?
Domain Patterns (Analysis
Patterns)
· Actor-Role
o A person wears many hats.
o Decouple actors (e.g., Person, Organization) from the roles they play (e.g., customer, employee, teacher, student).
· Types as Objects
o Represent types as objects (rather than classes) when type doesn't impact behavior (i.e., method implementations).
· Values
o Represent values such as quantities as immutable objects with logical equality.
· Events
o Events have location, start time, and duration.
o Events can have participants and a creator/owner.
· Service
o Members of a service class (aka utility class) are global—public and static in Java. They can be used anywhere in the program.
o Service classes are never instantiated. What would be the difference between two instances?
o A service represents a collection of related functions and variables.
o Functions are different from methods. They don't have an implicit parameter (this). Therefore they don't represent object behaviors.
· Composite
o Hierarchies (Org Charts, trees, taxonomies) and assemblies (devices, programs) are represented using the Composite Pattern:
o Component is abstract (or an interface)
o There can be many simple and composite component classes.
o Instances of the composite pattern are trees. Parent nodes are composites and leaf nodes are simples.
o Subcomponents is an example of a polymorphic collection.
Concepts,
Principles, Technologies
Value versus Reference Objects
Interfaces versus Abstract Classes
Exceptions
What happens if a patron's payment fails? For example, if his credit card is maxed out or expired?