Course Summary

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 2 Topics (1) Families of specification methods, evaluation criteria Safety and liveness Expressing properties in predicate calculus (logic) Input/output assertions, partial correctness, Hoare logic, invariants Z notations: dom ran and special symbols Z schemas: defining the state, operations Z examples: symb. table, Unix files, telephone,...

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 3 Topics (2) Schema calculus: modularity, hiding,... Refinement in Z: applying mapping functions, data and operation refinement, applicability and correctness State machine: pure graph, traces, using Z for state machines Statecharts: superstates, parallelism, joint transitions, history, micro-steps, activities Temporal logics, linear: [], <>,..., next Anchored version, past operators, classes of properties, fairness

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 4 Topics (3) Branching time: E, A, F, G, X, CTL Real time: TIME, Zeno, ranges, bound vars. with temp. logic; for statecharts Lamport ’ s textual state machines: open versus closed system, critical moment Allowed changes, parameter passing Fault tolerance, lossy queue and fairness, alternating bit protocol impl. of queue Process algebras and LOTOS Nondeterminism, gates, actions, Process declaration and instantiation

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 5 Topics (4) Parallel comp.: |||, |[ gates ]|, | |, hiding Offering (!) and accepting (?), negotiation Stop, hiding, i, and multiway gates Semantic views: bisimulation equivalence, testing equiv., trace equiv. Algebraic specification and Larch, algebraic axioms, initial/final algebra Generated by, partitioned by, converts Shared versus Interface Languages

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 6 Three kinds of specifications Data and transition modeling: Z vrs. Larch shared lang.; For individual steps; textual, sequential Control: Statecharts vrs. LOTOS (vrs. Esterelle vrs...) For concurrency, overlap, synchronization Global liveness (and safety too): Temporal logic in some version

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 7 Present Use of Formal Specifications Invariants and I/O assertions: added to UML designs, appear as run-time checks, assert statements and checkers (in recent systems, around 10% of Microsoft code) Elements of Z are in OCL (Object Constraint Language) extension of UML Software model checkers Bandera, accepts Java programs annotated with a version of temporal logic SLAM, a Microsoft product for checking temporal logic assertions about driver software; now SDV Java Pathfinder: NASA tool for model checking Java

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 8 Present use (cont.) Feasibility checks for Java applets >No memory segment violations, no illegal operations Legal requirements for formal specification and verification using a tool, in addition to testing >Aircraft control >Railway control in Europe and the US >Software controlling nuclear reactors in Europe Description languages for test data generation Hardware (design) verification using model checking and/or simulation: widely used in Intel, IBM, Motorola

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 9 Trends Use formal methods selectively for problem areas Develop tools with clear added value Use for error detection as well as showing correctness Set up environment where methods can be combined (not yet widespread): >VeriTech: project to translate among verification tools and their specification notations >AOSD Formal Methods Lab: apply specification notations and verification tools to Aspect-Oriented Programming

© Katz, 2007 Formal Specifications of Complex Systems-- Real-time 10 Realistically.... Potential benefits are known. Problems with formal methods have become evident. Modeling and tools have helped on real projects in particular application areas. Software development is in so much trouble, there is new willingness to invest in formal methods.