The SEESCOA
Composer Tool:
Using Contracts for
Component Composition and
Run-Time Monitoring
UML 2002
SIVOES-MONA workshop
October 1, 2002
Stefan Van Baelen,
David Urting, Yolande Berbers
K.U.Leuven
Department of Computer Science
Celestijnenlaan 200 A
B-3001 Leuven
Belgium
http://www.cs.kuleuven.ac.be
Outline
Components & Collaborations
Contracts for Components & Collaborations
UML 2002, 01/10/2002
Goals of the SEESCOA Project
The SEESCOA CCOM Composer Tool
Future Work
SIVOES-MONA Workshop
The SEESCOA Run-Time Component
System
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Goals of the SEESCOA Project
Developing applications by hierarchical
(de)composition of components
Adding QoS specification contracts onto scenarios
(resource constraint contracts)
UML 2002, 01/10/2002
Enable CBD for RT Embedded Systems
Code generation for SEESCOA component system
Monitoring resource contracts at run-time
Active scheduler based on resource contracts
For higher-end embedded systems
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Development of a run-time component system
supporting loose coupling of component
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Components & Collaborations
A logically highly cohesive, lowly coupled,
documented software module that can be used as a
unit of development, reuse, composition and
adaptation.
UML 2002, 01/10/2002
What is a SEESCOA component ?
It can be instantiated and is statefull at run-time
Component blueprint (class-like) vs. instance (object-like)
Example
a collection of objects accessible through one or more
facades, and providing a factory to instantiate them
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It provides dedicated functionality through welldefined interfaces.
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SEESCOA component modeling & hierarchical
(de)composition is based on ROOM/UML-RT
 Components = black boxes accessible through ports
 Component blueprint (class) can define a number of port
blueprints (classes)
3
Master control
1
Sampler
#
Read-out
 Ports define a bi-directional asynchronous interface to a
component
 Port specification on 3 levels
Syntactical level (in/outgoing message names & params)
Semantic level (message spec., pre & postconditions)
Synchronization level (MSC for the port)
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Settings control
UML 2002, 01/10/2002
Components & Collaborations
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Synchronization level MSC
= extended UML Sequence Diagram
 Allows specification of loops, alternative & optional messages
 Allows specification of message hooks
Sending time of message (S)
Beginning of activation (B)
:Sampler
:Env
start
End of activation (E)
S
R
B
Return value passing
= distinct message
E
LOOP
update
S
OPT
R
request
R
S
S
resend
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Receival time of message (R)
UML 2002, 01/10/2002
Components & Collaborations
R
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Component instances can have a number of port
instances, to which other component/port
instances can be connected
reader 1
settings control
secondary
sampler
UML 2002, 01/10/2002
Components & Collaborations
read-out
reader 2
master control
MSC’s of connected components must be
compliant (MSC conformance checking)
Mapping of names (resolving name mismatches)
Mapping of LOOP / OPT / ALT blocks
“Unified” collaboration MSC as a result
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master
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Components & Collaborations
c2
env
env
c1
a
a’
LOOP
b’
b
LOOP
c
e’
d
OPT
d’
LOOP
c’
e
c2
c1
a/a’
b/b’
LOOP
d/d’
e/e’
c/c’
Resulting MSC associated with the connector
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ALT
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MSC conformance checking
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Components & Collaborations
But multi-connectors can also be modeled
consumer
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Connectors are mostly binary
producer
producer
mediator
OPT
LOOP
LOOP
start
send
deliver
ok
consumer
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mediator
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Components & Collaborations
UML 2002, 01/10/2002
UML SEESCOA Profile
 Meta-model extension
Classifier
Instance
Port
1
0..n
S_Component
Instance
Connection
Port Instance
1
0..n
Plus additional restrictions
(inheritance, features, …)
2..n
0..1
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S_Component
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Timing contracts on a collection of connectors
Memory contracts on a component
Can be seen as contract between component & the
component system, restricting the dynamic memory usage
of the component
sampling
read-out
reader 1
Timing Contract
Memory Contract
Timing Contract
prod
MW
cons
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QoS contracts can be attached to components &
connectors
UML 2002, 01/10/2002
Contracts for Components &
Collaborations
‹#›
Contracts for Components &
Collaborations
UML 2002, 01/10/2002
QoS contracts
Based on Real-Time Logic (RTL)
Time-stamped events: occurrence relation
R(event, occurrence, time)
Can make use of message hooks
:Sampler
Beginning/End of activation
msg.B[] - msg.S[] < 10 ms
:Env
start
S
R
B
E
LOOP
update
S
OPT
R
request
R
S
S
resend
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Sending/Receival of message
R
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Contracts for Components &
Collaborations
Occurrence maps to MSC loop
ping.S[i+1] - ping.S[I] <= 50 ms
c2
env
LOOP
ping
Nesting of MSC loops supported
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QoS contracts & LOOP / ALT / OPT constructs
“*” (all occurrences)
response.S[*][1] - request.S[*][1] <= 10 ms
LOOP
LOOP
request
response
ALT & OPT expressions have meaning if event
occurred
“-” (any one occurrence)
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c2
env
‹#›
Contracts for Components &
Collaborations
Deadline constraints (worst-case duration):
b[]-a[] <= t
Lower-bound timing constraints: b[]-a[]>= t
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Typical QoS contracts supported by templates
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Periodicity constraints:
period*(i-1) <b[i]-a[]< period*i
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Components send messages via component
system
Component system is responsible for
starting/stopping/swapping components
Component system is responsible for message
delivery
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The SEESCOA Run-Time
Component System
Each component has its own message queue
Messages run to completion per component
Active components simulated by self-directed
messages
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No direct component interaction => loose coupling
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QoS constraint monitor layer within component
system
Gathers timing information of specified events.
External RTL checker analyses information
UML 2002, 01/10/2002
The SEESCOA Run-Time
Component System
Restricted intrusion
QoS Monitor Layer
reader 1
RTL
Checker
event
occurrence
reporting
SEESCOA Component System
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sampling
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The SEESCOA CCOM
Composer Tool
Specification of connections
Specification of timing contracts
Code Generation for component connection &
interaction
UML 2002, 01/10/2002
Specification of components, ports & MSC’s
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Code Generation for contract checking (monitor)
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Future Work
Based on timing contracts
Memory constraints
Specification & monitoring
UML 2002, 01/10/2002
Active component scheduler
Memory resource broker
Distributed QoS Monitor
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Run-time component system
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