Modeling Exceptions in Real Time Systems through ObjectProcess

Modeling Exceptions in Real Time Systems through Object-Process Methodology מידול חריגות במערכות זמן אמת באמצעות תהליכים - מתודולוגיית עצמים Yudit Somekh M. Sc. Research supervised by Prof. Dov Dori and Dr. Mor Peleg

Real Time Systems (RTS) l Play an important role in many technological advent such as telecommunications, aerospace, defense, medical etc. l Typically tend to be large and extremely complex a sound and simple design methodology is needed

OPMT real time extension The ability of OPM in showing the objects and the processes together in one intuitive diagram is very important and appropriate for designing RTS. The complexity of the system is handled using the hierarchic nesting mechanisms.

OPM/T main functionality l Triggering events – External – Internal (state entrance, state change etc. ) l Guarding conditions l Temporal constraints – Process duration constraint – State duration constraint – Reaction time constraint l Timing exceptions Example 1 Example 2

OPM/T issues Issues concerning real time systems that needs further discussion: l Priorities between events and corresponding processes l Parallelism and concurrency between processes l Processes sequences – currently default scenarios are supported l Exceptions - currently predicted and time exceptions are supported in OPM/T

Exceptions Dealing with exceptions is a major issue in the concurrent processing characteristics of real time systems. Exceptions classification: l Predictability l Synchronicity l Impact size

Research Goals l Create case studies of large and complex real time systems. l Identifying missing features in OPM/T. l Classification of exception types. l Extending OPM to full exceptions support – includes detection and handling mechanisms.

OPM/T: Triggering event and guarding condition example Room Temperature >=18 deg Switch off <15 deg e Cooling (1. 5, 2. 5) e Heating c Heating system: Triggering event and guarding condition of the Heating process On

OPM/T: Temporal constraint and timing exception example Heating System off On (0, 3600) Shut-off An exception link associated with the upper bound of a state duration constraint