Tools for Verification of Specification Given by Basic Protocols

1. Tools for Verification of Specification Given by Basic Protocols Oleksandr Letychevskyi, Ph.D. Glushkov Institute of Cybernetics of Ukrainan Academy of Sciences email: Alexander.Letichevsky.jr@iss.org.ua Telephone: +38(044)200-84-24

2. VRS Tools Algebraic Programming System Verification of Requirements System (academic version) Client (academic version) Verification of Requirements System (business version) Client

3. Precondition I1 I2 Process S R Postcondition Basic Protocols – Input of Verification System Basic protocol in MSC form x S(x)->A(x) . R(x) Action A will be performed if S is true and then condition R will be true after A

4. Example of industrial formalization

5. Formalization of Wimax requirements Transition system specifications Wimax (802.16 protocol) specifications are very close to basic protocols and could be converted easily Basic protocol format Environment description

6. Some basic protocols for 802.16 protocol

7. Basic Protocols Technology Formalized requirements Concrete Trace Generator Symbolic Trace Generator Static Requirements Checker Verdict, set of traces

8. Concrete Simulation • Concrete Trace Generator (CTG) simulates system behavior which is restricted by set of basic protocols and filters. • Simulation is performed by checking of PRE conditions and applying POST conditions. • During simulation CTG detects deadlocks, non-determinisms, safety violations, unreachable requirements, usage of uninitialized attributes and admitted region attribute overflow. • CTG generates counterexamples for detected inconsistencies and set of traces correspondingly to filter settings.

9. Symbolic Generation • Symbolic Trace Generator (STG) simulates set of basic protocol by applying of possible protocols that present behavior of system without computing of concrete environment state. • Simulation is performed by proving of existing of solution of formula in PRE-condition. If solution does not exist – the corresponded counterexample with symbolic values will be presented. • During simulation STG shall detect deadlocks, safety violations, and non-determinisms without initial values of attributes. • STG shall generate counterexamples by means of backward generation for inconsistencies that were detected by static requirements checking. These inconsistencies may be not reached by concrete trace generation.

10. Common Scheme of Symbolic Modeling Environment Description Set of Basic Protocol Initial State of Environment Safety Condition Selection of Basic Protocol Checking of Basic Protocol Applicability Proving Machine If not applicable If applicable: Change State of Environment Checking of Properties (safety, reachability) Trace Creating Set of Traces Verdict New Trace

11. Backward Trace Generation Initial state Initial state If we’ll use backward trace generation we could reach initial state by means of deductive tools Inconsistency or incompleteness could be unreachable by means of direct trace generation Inconsistency or safety violation Inconsistency or safety violation

12. Static Requirements Checking • Static Requirements Checker proves the following properties: • Consistency; • Completeness; • User-defined safety conditions;

13. Piloting and verification by VRS (CDMA) Piloting Statistics

14. Piloting and verification by VRS (CDMA) Efforts Spent and Defects Found 22% of defects are of HIGH severity! 2.2 hours per defect; 3.2 hours per accepted defect