Transcript Rational Users Conference 98

Using UML for Modeling Complex
Real Time System Architectures
Bran Selic
VP Advanced Technology
ObjecTime Limited
[email protected]
Overview
• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
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The Unified Modeling Language
• A general purpose OO modeling language
» combines a number of proven methods
OMT
(Rumbaugh)
UML
1.4
Mar. 1999
1996
UML
0.9
Booch
UML
1.1
Nov. 1997
OOSE
(Jacobson)
Catalysis
ROOM
3
etc.
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What is (in) the UML Standard?
• Semi-formal semantic meta-model
» defines basic modeling concepts
- object, class, etc.
» includes well-formedness rules
expressed as formal constraints in
Object Constraint Language (OCL)
• Graphical notation for modeling concepts
» 8 different diagram types
• Two predefined domain extensions
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The UML Meta-Model–Example
GeneralizeableElement
(Meta)class
isRoot:Boolean
isLeaf:Boolean
isAbstract:Boolean
Generalization association
*
Classifier
Feature
visibility:{public,
protected, private}
Compostion association
Class
isActive:Boolean
not self.isAbstract implies
OCL constraint
self.allOperations->forAll(op |
self.allMethods->exists(m |
m.specification includes (op)))
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• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
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General Real-Time Systems
• A system that maintains a continuous timely
interaction with its environment
environment
inputs
Real-Time
System
outputs
(state)
outputs = f (inputs, state)
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Complex Real-Time Systems
• Complex real-time systems characterized by:
» extreme dependability (reliability, availability)
» diverse and feature-rich functionality
» continuous feature upgrades (evolutionary
requirements)
» physical distribution
• Encountered mostly in telecommunications,
defense, aerospace, and industrial control
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Modeling Requirements for Complex RT Systems
• This complexity requires focussed modeling
support in at least the following areas:
» Architectural modeling
» Timeliness and performance modeling
» Time-aware communication models
» Concurrency management
» Resource modeling
» Distributed system modeling
» Fault-tolerance techniques
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• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
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Real-Time Software Architectures
• Architecture:
The organization of significant software
components interacting through
interfaces, those components being
composed of successively smaller
components and interfaces
• It is the key to success in:
» the initial construction of a system
» system evolution
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Architectures and Evolution
• Two functionally equivalent initial
architectures:
A
X
A
X
Mediator
B
C
B
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C
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Real-Time Architectural Specifications
• Example telecom system architecture
Structure
Channel1
TerminalA
TerminalB
Application Layer
Channel2
Services Layer
Behavior
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Architectural Component Design
Library
Channel1
System1
Terminal
TerminalA
TerminalB
Channel2
Channel
System2
Terminal
Tester
TerminalA
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Terminal
Tester
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Refining Architectures (Reuse)
Channel1
TerminalA
TerminalB
Channel1
TerminalA
TerminalB
Channel2
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Summary: Requirements for Architectural Modeling
• The ability to model and enforce:
» large-grain (architectural) components
and their interfaces
» structural compositions of architectural
components
» dynamic interaction patterns between
architectural components
» refinement of architectures
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• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
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Approach and Method
• The necessary architectural modeling
capabilities can be found in ROOM
• Express the architectural modeling concepts of
ROOM using standard UML
• Domain-specific library of UML “macros”
Business
Modeling
Library
Real-Time
Modeling
Library
(UML-RT)
...
UML Modeling Concepts
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UML Extensibility Mechanisms
• Stereotypes, constraints, tagged values
Constraint
(OCL)
Class
isActive:Boolean
not self.isAbstract implies
self.allOperations->forAll(op |
self.allMethods->exists(m |
m.specification includes (op)))
stereotype
Capsule
<“ports” >
required tag
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Real-Time Object-Oriented Modeling (ROOM)
• Domain-specific (real-time) concepts
» dynamic high-level structures
» reactive behavior (ROOMcharts)
• Executable (formal) models
• Full automatic code generation
• Field proven in a large number (>100) of
large-scale industrial projects
• Tool support available (ObjecTime Limited
and Rational Software)
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Phasing
• Basic modeling capabilities (UML 1.1)
» structural pattern modeling
(collaboration diagrams)
» state machine modeling
• Real-time specific constructs
» architectural modeling (March ‘98)
» other constructs (-June ‘99)
» collaboration: ObjecTime & Rational
• OMG standardization (1999/2000)
» RT analysis and design WG
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• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
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Capsules: Architectural Objects
• Active objects
Encapsulation
shell
Ports
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Capsules: Behavior
• Optional hierarchical state machine (signal
handler with run-to-completion semantics)
transitionS1toS2:
{int x;
x = 0;
p2.send(s1);
p3.send(s2);
…
};
S1
S2
S3
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Capsules: UML Modeling
• Stereotype of Class concept («capsule»)
with specialized (executable) semantics
• Class diagram representation:
«capsule»
CapsuleClassX
#counter : int
#x : char
ports
+portB : ProtocolA::master
#portC : ProtocolB
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Protocols: Contractual Behavior Patterns
• Interaction contracts between capsules
» e.g., operator-assisted call
Caller
Operator
Callee
call
ack
number
call
ack
transfer
talk
time
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Protocol Specifications
• A special form of collaboration
Alice
caller
OperatorAssisted
Call
callee
Bob
protocol state machine
significant sequences
caller
operator
callee
operator
initial
Charlie
Dexter
connecting
connected
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Protocol Roles
• Specifies one party in a protocol
significant sequences
Incoming signals
caller
signal
source
call
caller
number
caller
ack
callee
operator
callee
OperatorRole
Outgoing signals
signal
target
call
callee
transfer
caller
ack
caller
role state machine
initial
connecting
connected
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Protocol Refinement
• Using inheritance
Incoming signals
Incoming signals
signal
source
call
caller
caller
number
caller
callee
ack
callee
reply
caller
signal
source
call
caller
number
ack
OperatorRole
Outgoing signals
Outgoing signals
signal
target
call
callee
transfer
caller
ack
caller
Extended
OperatorRole
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signal
target
call
callee
transfer
caller
ack
caller
query
caller
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Protocols: UML Modeling
• Collaboration stereotype: «protocol»
• Classifier Role stereotype: «protocolRole»
1
«protocolRole»
caller
«protocol»
incoming
OperatorAssisted
Call
ack
transfer
outgoing
call
number
talk
1
1
«protocolRole»
«protocolRole»
operator
callee
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Ports: Boundary Objects
• Fully isolate a capsule’s implementation from
its environment (in both directions)
Capsule
S1
Environment
S2
Created and destroyed along with their capsule
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Ports and Protocols
• Each port realizes a single protocol role
(type)
» Multiple ports with same type possible
«capsule»
CapsuleClassX
ports
+portA : ProtocolA::master
#portB : ProtocolB
+portC : ProtocolB~
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Ports: Collaboration Diagram Notation
portA : ProtocolA::master
«capsule»
anX:CapsuleClassX
1
portC : ProtocolB~
«port»
portA:ProtocolA::master
• Shorthand notation for capsule instances
» iconified form
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Combining Capsules
• Using connectors
remote : FaxProt
«capsule»
sender : Fax
«capsule»
remote : FaxProt
receiver : Fax
Connector
Connectors model communication channels
Each connector supports a single protocol
Static typing rules apply (compatible protocols)
Modeled as association classes in UML
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Composition:
Structural Patterns as (Reusable) Dynamic Components
Relay
port
sendCtrl : Control
c : Control
receiveCtrl : Control
c : Control
remote:FaxProt
«capsule»
sender:Fax
«capsule»
receiver:Fax
Remote:FaxProt
FaxCall
• The composite is also a first-class object!
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Composite Capsule Semantics
• Architectural assertion mechanism: the static
elements of the internal structure of a
composite capsule are automatically created
(and destroyed) along with the capsule
» applies recursively down to the
innermost leaf capsule level
» only explicitly prescribed architectural
structures can be instantiated
• This also significantly reduces the complexity
of the model since all the code used to
establish these structures is eliminated
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End Ports: Where Structure and Behavior Meet
• Ports directly connected to the state machine
Implementation
End Port
c : SystemControl
senderCtrl : Control~
capsule state machine
Public End
Port
receiveCtrl : Control~
initial
connecting
c : Control
c : Control
connected
«capsule»
sender:Fax
«capsule»
receiver:Fax
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Decomposition: Class Diagram View
• Alternative representation
» More abstract
1
sender
«capsule»
Fax
1
«capsule»
receiver
FaxCall
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• The Unified Modeling Language (UML)
• Complex real-time systems
• Requirements for modeling architectures of
complex RT systems
• Approach and method
• Architectural modeling constructs
• Summary
39
Bran Selic
Summary (1)
• Complex real-time systems phenomena
require specialized modeling support
• The ROOM language has industry-proven
support for modeling complex real-time
architectures
• The benefits of both UML and ROOM are
gained by expressing the ROOM constructs
as UML stereotypes
» UML-RT : a UML extension for the
complex real-time domain
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Summary (2)
• Only four UML stereotypes are sufficient
(include formally defined constraints that
ensure consistency/executability)
Stereotype
UML Metaclass
«protocol»
Collaboration
«protocolRole»
ClassifierRole
«port»
Class
«capsule»
Class
 supplemented by an optional custom notation
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Bibliography
• Real-time architectural modeling whitepaper
by B. Selic and J. Rumbaugh:
» http://www.objectime.com
• OMG’s UML 1.1 standard
» http://www.rational.com
• ROOM
» B. Selic, G. Gullekson, and P. Ward,
“Real-Time Object-Oriented Modeling”,
» John Wiley & Sons, NY, 1994.
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