1. CS551 UML for Distributed Objects (Engineering Distributed Objects)
Yugi Lee
STB #555
(816)
CS551 - Lecture 7

2. UML and Meta Model for Distributed Objects
Used for communicating about objects
Static vs. dynamic properties
Type vs. instance properties
UML:
Use Case Diagrams
Sequence Diagrams
Class and Object Diagrams
State Diagrams
Packages
Meta Model
CS551 - Lecture 7

3. Use Case Diagrams use case actor system boundary Plan Training Trainer
Schedule
actor
Determine League
Games
National Soccer
Manager
Association
system
boundary
Print Personal
Player
CS551 - Lecture 7
Schedule

4. Sequence Diagrams (remote) procedure call Object Name Type synchronous
Message
Tony:Tainer
BvB:Team
Teddy:Player
Stefan:Player
:Output
bookGoalies
book()
book()
printTrainingPlan
asynchronous
message
object
activation
lifeline
object
deletion
CS551 - Lecture 7

5. Class Diagrams Player -name:string -role:Position -Number:int +book()
+transfer(p:Player)
Club
-noOfMembers:int
-location:Address
Trainer
Organization
#name:string
protected
dependency
generalization
aggregation
uses
works for 1
1..*
plays in 1
11..16
has *
coaches
1..*
cardinality
composition
association
class name
attributes
Team
-name:string
+bookGoalies()
private
public
CS551 - Lecture 7
operations

6. Packages Soccer League Clubs Management National Team
CS551 - Lecture 7

7. name = “Tottenham Hotspurs”
Object Diagrams
Object Name
Object Type
Object
name = “Tottenham Hotspurs”
spurs:Team
Attribute
Name
Attribute
Value
stefan:Player
name = “Stefan Freund”
role = Defender
Number=4
name=“Jürgen Klinsmann”
role=Forward
Number = 18
klinsi:Player
Link
CS551 - Lecture 7

8. State Diagrams in team action during transition healthy composite
in match
playing
/swap
/swap
/injury
transition
reserve
[in_squad]
/play
injured
condition
[!in_squad]
/play
/recovered
/finish
/finish
indicates
default
state
training
free
/exercise
CS551 - Lecture 7

9. Parallel State Composition
Player
/unsatisfaction
/sign_contract
happy
on transfer
list
concurrent
threads
/resign
in team
final
state
CS551 - Lecture 7

10. Meta Model for Distributed Objects
Distributed Systems consist of multiple components.
Components are heterogeneous.
Components still have to be interoperable.
There has to be a common model for components that expresses
component states,
component services and
interaction between components.
CS551 - Lecture 7

11. OO Approach to Distributed Systems
Objects.
Object attributes.
Object operations.
Operation execution requests.
Exceptions.
Components
Visible component state
Usable component services Component interactions
Component service failures
CS551 - Lecture 7

12. Need for an Object Meta-model
There are many different object-oriented approaches
Distribution middleware must define object model that can serve as a common basis for heterogeneous components.
We introduce general distributed object model to capture common characteristics of object models of different distributed object-middleware.
CS551 - Lecture 7

13. Different levels of abstraction...
Meta-Object
Facility
Level 3
Meta Object
Model
Level 2
Object
Types
Level 1
Objects
Level 0
CS551 - Lecture 7

14. Object vs. Object type Has a unique identifier.
May have many different references that refer to the object.
Has a set of attributes whose names denote values.
References may denote
equal/identical objects
Is encapsulated by operations.
May raise particular exceptions.
Multiple objects may export the same properties (Attributes, operations and exceptions)
Only define the properties once!
Attributes and operations, and exceptions are defined in object types.
May raise particular exceptions.
CS551 - Lecture 7

15. <<interface>>
Samples: Object vs. Object type
<<interface>>
Player
-name:string;
-role:Position;
-Number:int;
+void book(in Date d) raises (AlreadyBooked);
klinsi:Player
name = “Jürgen Klinsmann”
role = Forward
Number = 18
CS551 - Lecture 7

16. Object type: Attributes
Attributes have a name and a type.
Type can be an object type or a non-object type.
Attributes are readable by other components.
Attributes may or may not be modifiable by other components.
Attributes correspond to one or two operations (set/get).
CS551 - Lecture 7

17. Object type: Exceptions
Service requests in a distributed system may not be properly executed.
Exceptions are used to explain reason of failure to requester of operation execution.
Operation execution failures may be
generic or
specific.
Specific failures may be explained in specific exceptions.
CS551 - Lecture 7

18. Object type: Operations
Operations have a signature that consists of
a name,
a list of in, out, or in-out parameters,
a return value type, and
a list of exceptions that the operation can raise
CS551 - Lecture 7

19. Operation Execution Requests
A client object can request an operation execution from a server object.
Operation request is expressed by sending a message (operation name) to server object.
Server objects are identified by object references.
Clients have to react to exceptions that the operation may raise.
CS551 - Lecture 7

20. Subtyping
Properties shared by several types should be defined only once.
Object types are organised in a type hierarchy.
Subtypes inherit attributes, exceptions and operations from their supertypes.
Subtypes can add more specific properties.
Subtypes can redefine inherited properties.
CS551 - Lecture 7

21. Multiple Inheritance
Means that one object type can be subtype of more than one super type
Not supported by all middleware
May lead to ambiguities
CS551 - Lecture 7

22. Multiple Inheritance Example
<<interface>>
Player
<<interface>>
Trainer
-name:string;
-role:Position;
-Number:int;
-salary:int;
+next_game():Date
+void book(in Date d) raises (AlreadyBooked);
+next_game():Date
<<interface>>
PlayerTrainer
CS551 - Lecture 7

23. Polymorphism Object models may be statically typed.
Static type of a variable restricts the dynamic type of objects that can be assigned to it.
Polymorphism denotes the possibility of assignments of objects that are instances of the static type and all its subtypes.
CS551 - Lecture 7

24. Polymorphism Example chelsea:Team name = “Chelsea” v:PlayerTrainer
d:Player
name = “Gianluca Vialli”
role = Forward
Number = 10
salary=
name = “Marcel Desailly”
role=Defender
Number=5
z:Player
name = “Gianfranco Zola”
role=Forward
Number=3
CS551 - Lecture 7