1 of 20 Octopus: document handling Document handling: three modeling approaches Marc Voorhoeve Venkatesh Kannan TUE

2 of 20 Octopus: document handling Octopus project Broker: EESI Industry partner: Océ Researchers: Nijmegen TUE - Electrical Engineering TUE - Computer Science

3 of 20 Octopus: document handling Data path: concurrent job execution scan control print retrieve Image Processing store IP1 IP2 resources user

4 of 20 Octopus: document handling Engineering decisions: - resource capacity - scheduling rules Octopus aim: Engineering support Frameworks: - TA (Timed Automata) - SDF (Synchronous Data Flow) - CPN (Colored Petri nets) Simulation State space exploration Approaches

5 of 20 Octopus: document handling Timed automata: labeled transition system with clock variables, that can be set and tested. states, actions (maybe silent), clock assignments, clock conditions. idlebusy recover start? 

6 of 20 Octopus: document handling Kind of merge with synchronization of clocks. idlebusy recover start?   s0s1 start! s2 start! (idle,s0)(busy,s1) (recover,s1) (idle,s1)(busy,s1) (recover,s1) (idle,s2) Temporal predicates (CTL) can be assessed, e.g. existence of execution path with duration D.

7 of 20 Octopus: document handling CPN (colored Petri nets): Petri net with arc inscriptions, firing conditions and subnet hierarchy. Eager firing. idlebusy recover start x x x x ( )( ) s0 s1 s2 a b

8 of 20 Octopus: document handling SDF: action-based, Petri net subclass (marked graph) Firing delays fast optimal schedule computation

9 of 20 Octopus: document handling Special challenge: modeling USB storage/retrieval. unidirectional capacity: H, bidirectional capacity: L capacities L,H in MB/sec satisfying L < H < 2L. Suppose 3H upstream; after 1 sec L downstream timing diagram: (H-L)/H H L 2L

10 of 20 Octopus: document handling USB model: hybrid system. Discrete approximation in TA possible. Exact CPN model by data manipulation. SDF model is still under construction.

11 of 20 Octopus: document handling Experiences so far: - coordination via regular meetings - agreement on parameters of common model - mutual validation has been achieved (despite several difficulties) Next stages: - validation with current project - exploration of engineering alternatives - adaptivity?

12 of 20 Octopus: document handling CPN tradeoff: structure in net vs. color more structure visual model low-level less flexible structure in color opaque high-level flexibility TA tradeoff: model vs. predicate constraints in model smaller state space more models constraints in predicate larger state space less models (flexibility) Some difficulties were caused by the solutions that the various frameworks allow.

13 of 20 Octopus: document handling CPN model therefore opts for flexibility. Other difficulties caused by unstable requirements. color set JOB: sequence of tasks. a b [a,b] x != [ ] x tail(x)

14 of 20 Octopus: document handling jobQ JOB scannerscanIPIP1IP2USBprintIP started Job JOB scheduler Job Generator new Job JOB memory INT

15 of 20 Octopus: document handling start do free jobQ JOB started Job JOB comp Info paper Info end parameters structure of scanner, scanIP, IP1, IP2, printIP

16 of 20 Octopus: document handling job in join trigger USB jobList update job out Job Rate LastUpdateTime JOB structure of USB subnet

17 of 20 Octopus: document handling x H L 2L Depicted USB scenario: 0 U H03 1 UL13+x DL12 2UH2 3UH3 3+x- time job rate last_update_timetrigger x=(H-L)/H

18 of 20 Octopus: document handling TA, SDF: find "optimal" schedule within state space for a given job sequence CPN: nondeterministic eager execution Mutual validation of models: - remove freedom - model within intersection - compare generated schedules (traces) Mutual validation: do the models match?

19 of 20 Octopus: document handling Modeling power vs. analysis options: CPN: most power, least analyzable. SDF: least power, analysis limited but fast TA: wide range of analysis options danger of state space explosion Possible developments for Océ: - competition - cooperation

20 of 20 Octopus: document handling Conclusions: Combination of formal frameworks interesting, but time-consuming. More time needed for assessment. Questions?