Insertion Modeling: Technology for Modeling Distributed Systems

1. Семинар «Образный компьютер» 10 Мая 2011 Инсерционное моделированиеА.Летичевский

2. Содержание • Инсерционное моделирование • Математические основания • Инсерционные машины • Базовые протоколы • Верификация в системе VRS Образный компьютер

3. Инсерционное моделирование: Технология построения и исследования моделей многокомпонентных распределенных систем, представленных с помощью композиции агентов и сред Формально Агенты и среды: Атрибутные транзиционные системы Композиция:непрерывная функция погружения, характеризующая изменение поведения среды в результате погружения агента Образный компьютер

4. Исторические замечания Идея «Взаимодействия агентов и сред» появилась в 1996 году в результате совместных исследований с Д.Гильбертом в Сити Университете в Лондоне. С 2000 она использовалась при разработке средств верификации требований краспределенным программным системам. Реализована в системе VRS, разработанной по заказу Моторолы. В настоящее время используется компанией Uniquesoftдля создания новых средств разработки программных cистем. Одновременно в ИК разрабатывается система инсерционного моделирования IMS Образный компьютер

5. Insertion modeling paradigm • The world is a hierarchy of environments and agents inserted into them. • Environments and agents are entities evolving in time. • Insertion of agent into environment changes the behavior of environment and produces new environment which is ready for insertion of new agents (if there is a room). • Environments as agents can be inserted into higher level environment. • Agents can be inserted from external environment as well as from internal agents (environments). • Agents and environments can model another agents and environments on the different levels of abstraction environment Insertion function agent environment agent agent Образный компьютер

6. Mathematical foundations Transition systems Agents Behaviors and behavior algebras Environments and insertion function Insertion equivalence of agents Process algebras Образный компьютер

7. Transition systems Agents and environments are labeled or attributed transition systems considered up to bisimilarity (bisimilar states have the same behavior that is cannot be distinguished by an observer). b b b a a a a a a a a b b b b b a a b a a Образный компьютер

8. Поведение транзиционной системы: множество последовательностей действий, которые она может совершить (?) s s' Образный компьютер

9. a a s s t t R R R R a a Бисимуляционная эквивалентностьbisimilarity (Milner 1980, D.Park 1981) Отношение бисимуляции (bisimulation): bisimulation => bisimilarity (бисимуляционная эквивалентность) Образный компьютер

10. x a a ┴ b y:Δ a a Δ Agents Attribued transition systems with divergence and terminal states considered up to bisimularity. x:(a.0)+a.(b.(y:(a.0+a. Δ + Δ)) + bot) Behaviors Elements of continuous complete behaviour algebra F(A) over a set of actions A (a kind of process algebra). Extensions: functions defined by recursive definitions in F(A) Sates as behaviors. Образный компьютер

11. n Environments and insertion functions is a complete behavior algebra over action algebra (a kind of process algebra). Insertion function must be continuous Insertion of several agents Multilevel insertion Образный компьютер

12. Insertion equivalence Semigroup of environment transformations Equivalence Образный компьютер

13. Traditional algebras of communicating processes(CCS, CSP, ACP, π-calculus,...) can be obtained by selection of an environment and its insertion function. Образный компьютер

14. Look-ahead insertion (прогнозирующее погружение) Head insertion (префиксное погружение) Classification of insertion functions One-step insertion continuous continuous continuous Образный компьютер

15. Insertion machines: implementation of insertion models Real time insertion machines Analytical insertion machines Образный компьютер

16. Real time insertion machine Model driver External environment External insertion function Unfolding recursive definitions Input model Agent behavior unfolder Environment interactor Computing insertion function and making nondeterministic choice Образный компьютер

17. Analytical insertion machine Goal state Filters Search control Model driver Unfolding recursive definitions Output traces Input model Agent behavior unfolder Environment interactor Computing insertion function Образный компьютер

18. IMS is an environment for the development of insertion machines (new project of Glushkov Institute of Cybernetics) Образный компьютер

19. Some insertion machines developed previously Semantics of MSC (2002, 2005) Glushkov evidence algorithm (2002, 2003) Semantics of Basic Protocols (2005) Trace Generators for VRS (2008) Checking security protocols (2009) Creatures and substance (2009) Proving program correctness and generating invariants Образный компьютер

20. BPSLBasic Protocol Specification Languageused in VRS Образный компьютер

21. Basic protocol Combination of Hoar triples with the model of interaction of agents and environments. A method to define insertion function (look-ahead) by representing its local properties. First order quantifier with typed variables Precondition Postcondition Finite process (behavior) of attributed environmentwith inserted agents Properties of environment Environment property Образный компьютер

22. BPSL implemented in VRSenvironment description + set of BPs Types: Data types simple: int, real, Bool, enumerated, symbolic (free terms), agent behaviors (process algebra) lists: list of τ(simple) functional: (simple, arrays are considered as functional types with restrictions on the domains of indexes) Agent types: defined by the set of typed agent attributes Agent behaviors: defined by recursive equations Environment attributes: used as functional symbols (simple= arity 0) Agent attributes: typed names Образный компьютер

23. Preconditions and postconditions Environment description defines a signature of multisorted algebra and domains for types (sorts). Precondition is a first order formula over signature defined by environment description. Postcondition is a formula + assignments + update operators for lists. Assignments and updates are considered as a temporal logic formula. Formulas for lists: u=(t1,t2,…) or Exist x(u=p*x*q). Existential quantifiers are allowed in formulas. Образный компьютер

24. VRS toolsConcrete Trace Generator (CTG)Symbolic Trace Generator (STG)Static Requirements Checker (SRC) Образный компьютер

25. Concrete trace generatoranalytical insertion machine for concrete models All attributes have concrete values in the state of environment and agents states. Each instantiated basic protocol defines single-valued transformation of environment state: Analog: model checker for BP-specifications Goal state, safety conditions Filters and search control, LTL, Symmetry, dynamic abstraction,… Образный компьютер

26. Symbolic trace generator analytical insertion machine for concrete models Possible values of environment and agent attributes are defined by means of logic formulas. Transition rules defined by means of corresponding deductive system Predicate transformer computes the strongest postcondition. Образный компьютер

27. Static requirement checker algorithms based on predicate transformer Proving properties of requirements without generating traces. Completeness Consistency Safety Reachability (reduced to safety) Образный компьютер

28. Future development of IMS Models, defined by local properties (generalization of basic protocols) Proving correctness of programs Solving constraint problems Developing new cognitive architecture on a base of IMS Образный компьютер