Stefan Van Baelen, David Urting, Yolande Berbers K.U.Leuven Department of Computer Science

1. 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 BerbersK.U.Leuven Department of Computer Science Celestijnenlaan 200 A B-3001 Leuven Belgium http://www.cs.kuleuven.ac.be

2. Outline • Goals of the SEESCOA Project • Components & Collaborations • Contracts for Components & Collaborations • The SEESCOA Run-Time Component System • The SEESCOA CCOM Composer Tool • Future Work

3. Goals of the SEESCOA Project • Enable CBD for RT Embedded Systems • Developing applications by hierarchical (de)composition of components • Adding QoS specification contracts onto scenarios (resource constraint contracts) • Development of a run-time component system supporting loose coupling of component • Code generation for SEESCOA component system • Monitoring resource contracts at run-time • Active scheduler based on resource contracts • For higher-end embedded systems

4. Components & Collaborations • What is a SEESCOA component ? • A logically highly cohesive, lowly coupled, documented software module that can be used as a unit of development, reuse, composition and adaptation. • It provides dedicated functionality through well-defined interfaces. • 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

5. Settings control 3 Sampler # Read-out Master control 1 Components & Collaborations • 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) • 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)

6. Components & Collaborations • Synchronization level MSC = extended UML Sequence Diagram • Allows specification of loops, alternative & optional messages • Allows specification of message hooks • Sending time of message (S) • Receival time of message (R) • Beginning of activation (B) • End of activation (E) • Return value passing = distinct message :Sampler :Env start S R B E LOOP update S R OPT request R S S R resend

7. Components & Collaborations • Component instances can have a number of port instances, to which other component/port instances can be connected • 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 reader 1 settings control secondary read-out sampler reader 2 master master control

8. a’ d/d’ a a/a’ d’ d Components & Collaborations • MSC conformance checking env c2 c1 env LOOP b b’ LOOP ALT LOOP c e’ OPT e c’ c1 c2 b/b’ LOOP e/e’ c/c’ Resulting MSC associated with the connector

9. consumer producer mediator Components & Collaborations • Connectors are mostly binary • But multi-connectors can also be modeled mediator producer consumer OPT start LOOP send LOOP deliver ok

10. Components & Collaborations • UML SEESCOA Profile • Meta-model extension • Plus additional restrictions (inheritance, features, …)

11. read-out sampling reader 1 Memory Contract Timing Contract Contracts for Components & Collaborations • QoS contracts can be attached to components & connectors • 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 Timing Contract cons prod MW

12. Contracts for Components & Collaborations • QoS contracts • Based on Real-Time Logic (RTL) • Time-stamped events: occurrence relation R(event, occurrence, time) • Can make use of message hooks • Sending/Receival of message • Beginning/End of activation • msg.B[] - msg.S[] < 10 ms :Sampler :Env start S R B E LOOP update S R OPT request R S S R resend

13. request Contracts for Components & Collaborations • QoS contracts & LOOP / ALT / OPT constructs • Occurrence maps to MSC loop • ping.S[i+1] - ping.S[I] <= 50 ms • Nesting of MSC loops supported • “*” (all occurrences) • response.S[*][1] - request.S[*][1] <= 10 ms • ALT & OPT expressions have meaning if event occurred • “-” (any one occurrence) env c2 LOOP ping env c2 LOOP LOOP response

14. Contracts for Components & Collaborations • Typical QoS contracts supported by templates • Deadline constraints (worst-case duration): b[]-a[] <= t • Lower-bound timing constraints: b[]-a[]>= t • Periodicity constraints: period*(i-1) <b[i]-a[]< period*i

15. The SEESCOA Run-Time Component System • Components send messages via component system • Component system is responsible for starting/stopping/swapping components • Component system is responsible for message delivery • No direct component interaction => loose coupling • Each component has its own message queue • Messages run to completion per component • Active components simulated by self-directed messages

16. The SEESCOA Run-Time Component System • QoS constraint monitor layer within component system • Gathers timing information of specified events. • External RTL checker analyses information • Restricted intrusion sampling reader 1 RTL Checker QoS Monitor Layer eventoccurrencereporting SEESCOA Component System

17. The SEESCOA CCOM Composer Tool • Specification of components, ports & MSC’s • Specification of connections • Specification of timing contracts • Code Generation for component connection & interaction • Code Generation for contract checking (monitor)

18. Future Work • Active component scheduler • Based on timing contracts • Memory constraints • Specification & monitoring • Memory resource broker • Run-time component system • Distributed QoS Monitor