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eXAT: Software Agents in Erlang

eXAT: Software Agents in Erlang. Corrado Santoro University of Catania, Italy 11th Erlang User Conference – Stockholm, Nov. 10, 2005. Overview. Motivation Agent Characteristics and Erlang The eXAT Platform Agent Tasks Agent Intelligence Agent Communication Conclusions. Motivation.

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eXAT: Software Agents in Erlang

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  1. eXAT:Software Agents in Erlang Corrado Santoro University of Catania, Italy 11th Erlang User Conference – Stockholm, Nov. 10, 2005

  2. Overview • Motivation • Agent Characteristics and Erlang • The eXAT Platform • Agent Tasks • Agent Intelligence • Agent Communication • Conclusions Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  3. Motivation • Agents are software entities featuring • Autonomy: they are goal-oriented • Reactive: they react to environment changes • Pro-active: they build plans to achieve their goals • Social: they can communicate to each other • Can Erlang support them? • Is Erlang a good approach for agent-oriented programming? Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  4. Agent Characteristics and Erlang • Reactivity means the ability to specify a computation to be executed when an event occurs: • Symbols (Atoms)/Tuples: well suited to represent events • Function clauses: well suited to represent actions bound to events • Agent Tasks modeled as FSM: • gen_fsm and gen_event are OK, but we need something of “higher-level” and more “agent-specific” action({switch,off}) -> … action({temperature, X}) when X > 20 -> … Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  5. Agent Characteristics and Erlang • Pro-activenessmeans the ability to implement an “intelligent” reasoning process: • Atoms and Tuples: well suited to represent facts of a knowledge • Function clauses: well suited to represent production rules • Function clauses are OK to represent production rules but who “crunches” them? parent_rule({‘child-of’,X,Y},{female,Y}) -> % ..then Y is X’s mother parent_rule({‘child-of’,X,Y},{male,Y}) -> % ..then Y is X’s father Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  6. Agent Characteristics and Erlang • Social Ability means to support message passing between (local or remote) agents: • Erlang is message-oriented! • But Agent Communication requires standardized protocols. FIPA defines: • A set of “communicative acts” based on speech act theory [Searle] • “inform” act to tell something, “request” act to ask the execution of something, etc. • An Agent Communication Language (ACL) to exchange messages based on CA • A representation standard for ACL messages • Some network protocols to exchange ACL messages Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  7. eXAT A platform (runtime environment) is needed eXAT : erlang eXperimental Agent Tool Erlang Perfect for Agents? Erlang is not enough for agents as-is. Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  8. eXAT The erlang eXperiment Agent Tool An “all-in one” agent platform for agent programming • Agent Behaviors: • Agent Tasks modeled as FSM enriched with composition and specialization/extension • Agent Intelligence: • By means of the ERESYE rule processing engine • Agent Interaction: • By means of FIPA standard messaging, enriched with ontology and semantic support Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  9. eXAT Internals: Task Model Agent Tasks are modeled as FSMs A task is executed asynchronously (autonomous agent semantics) eXAT Task Model • E, the set of event types(acl, timeout, eresye, silent) • P, the set of data patterns to be associated to a certain event type • Pattern: predicate on event’s data • S, the set of states of the FSM • A, the set actions to be done Separation between event types and associated patterns to allow reuse Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  10. Start acl:(inform …) acl:(propose …) acl:(failure …) gp ev gather_inform gather_propose gather_failure acl:(refuse …) gather_refuse timeout:x evaluate_proposals silent send_cfp eXAT Task: An Example -module (contractnetinitiator). action (Self, start) -> [{cfp_event, send_cfp}]; action (Self, gp) -> [{propose_event,gather_propose}, {refuse_event,gather_refuse}, {timeout_event,evaluate_proposals}]; action (Self, ev) -> [{failure_event,gather_failure}, {inform_event,gather_inform}]. event (Self, cfp_event) -> {silent, nil}; event (Self, propose_event) -> {acl, propose_pattern}; event (Self, refuse_event) -> {acl, refuse_pattern}. pattern (Self, propose_pattern) -> [#aclmessage {speechact = ’PROPOSE’, protocol = ’fipa-contractnet’}]; pattern (Self, refuse_pattern) -> [#aclmessage {speechact = ’REFUSE’, protocol = ’fipa-contractnet’}]; ... Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  11. Start eXAT Task: Composition -module (my_task). action (Self, start) -> [{propose_event, do_propose}, {refuse_event, do_refuse}]. event (Self, propose_event) -> {acl, propose_pattern}; event (Self, refuse_event) -> {acl, refuse_pattern}. pattern (Self, propose_pattern) -> [#aclmessage {speechact = ’PROPOSE’}]; pattern (Self, refuse_pattern) -> [#aclmessage {speechact = ’REFUSE’}]. do_propose (Self, Event, Data, State) -> agent:behave (Self, b1). do_refuse (Self, Event, Data, State) -> agent:behave (Self, [b2, b3]), object:stop (Self). acl:(propose …) do_propose acl:(refuse …) do_refuse b1 b2 b3 Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  12. Start acl:(propose …) gp acl: (inform …) gather_propose acl:(refuse …) send_cfp gather_refuse silent send_cfp eXAT Task: Extension An “eXAT Task” is a class that can be extended (reused), according to object-oriented concepts Any element of a transition (event type, data pattern, associatedaction, next state) can be changed according to new requirements E.g., a contract-net initiated by the arrival of an inform message:  redefine the cfp_event -module (triggeredcontractnetinitiator). extends () -> contractnetinitiator. event (Self, cfp_event) -> {acl, inform_pattern}. pattern (Self, inform_pattern) -> [#aclmessage {speechact = ’INFORM’}]. Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  13. eXAT Intelligence: ERESYE • ERESYE is an integrated tool that allows the creation and execution of rule processing engines in Erlang • Each engine has a knowledge base and a set of rules • Facts (knowledge) are represented using Erlang tuples (or records), e.g. • {temperature, 50, ‘F’} • {father, ‘Caesar’, ‘Brutus’} • #speed { value = 30, unit = ‘km/h’} • Inference rules are written using standard Erlang functions • The Forgy’s RETE algorithm is implemented to efficiently process the rules • ERESYE engines are connected with tasks: • Task events: event activated by the assertion of a given fact in a given engine • Task action: any call to ERESYE API functions, e.g. fact assertion/retraction, rule adding/removing/activating, etc. Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  14. An ERESYE Program -module (parents). -export ([parent_rule/3, start/0]). parent_rule (Engine, {‘child-of’,X,Y}, {female,Y}) -> eresye:assert (Engine, {‘mother-of’,Y,X}); parent_rule (Engine, {‘child-of’,X,Y}, {male,Y}) -> eresye:assert (Engine, {‘father-of’,Y,X}). start () -> eresye:start (parents_engine), eresye:add_rule (parents_engine, {parent, parent_rule}). Rule Declaration Engine Identifier Conditions on facts Actions Engine creation Rule Addition (in the engine) Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  15. eXAT Communication: ACL • eXAT provides an Erlang record to represent FIPA-ACL messages #aclmessage {speechact = ‘REQUEST’, receiver = ..., ontology = ‘book-ontology’, content = #buying_action { item = #book { title = ..., author = ..., ... } } } • ACL messages are sent using functions of the acl module • A different function for each communicative act type • acl:inform, acl:request, acl:confirm, etc. • ACL messages are received by using the acl event in task specification Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  16. eXAT Communication: ACL #aclmessage {speechact = ‘REQUEST’, receiver = ..., ontology = ‘book-ontology’, content = #buying_action { item = #book { title = ..., author = ..., ... } } } • FIPA-ACL messages feature a content expressed with a given ontology • Ontology handling is needed in eXAT • FIPA-ACL messages are transferred using a proper string representations (SL = Semantic Language) (request :receiver (…) :ontology book-ontology :content (buying-action :item (book :title …) ) ) • Translation from Erlang types to SL expression is needed in eXAT Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  17. eXAT Communication: Ontologies • eXAT allows the specification of the “universe of discourse” by means of a (object-oriented) ontology • An “ontology_compiler”, provided with eXAT, translate the specification and generates: • An .hrl file containing a record definition for each class of the ontology • A .erl file containing some Erlang function usefull to maintain the hierarchy • A .erl file containing the SL/Erlang codec for message content • Ontology types can be also used in ERESYE engines to represent fact: a very important connection between “intelligence” and “communication” Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  18. eXAT Communication: A Sample Ontology -ontology(book). class (book) -> { title = [ string , mandatory , nodefault], author = [ string , mandatory , nodefault], genre = [ string , mandatory , nodefault]}; class (‘adventure-book’) -> is_a(book), { genre = [ string , mandatory , default (adventure)] }; class (‘thriller-book’) -> is_a(book), {genre = [ string , mandatory , default (thriller)] }; class (buying_action) -> {item = [book, mandatory, nodefault] }. Capability to use OWL or RDF available in future eXAT releases Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  19. eXAT and ACL Semantics • FIPA-ACL specification defines for each communicative act • Feasibility Precondition: a predicate that must be true before sending the message • Eg: <i, confirm (j, X)>  BiX  BiUjX (agent i believes X and believes that j is uncertain on X) • Rational Effect: a predicate that must be true after the message has been send/delivered • Eg: <i, confirm (j, X)>  BjX  BiBjX (agent j believes X and agent i believes that j believes X) • FIPA-ACL semantics allows the development of “true rational agents” • It is the real link between intelligence and communication • But no agent platforms currently support FIPA-ACL semantics Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  20. eXAT and ACL Semantics eXAT represents the first attempt (initiated in 2003) to implement FIPA-ACL Semantics • An ERESYE engine to represent agent mental state (from ontologies, we can use the same Erlang types for facts and message contents) • Each time a message is sent and received, an actions is performed onto the agent’s mental state, according to FIPA-ACL semantics ERESYE Engine (agent mental state) ACL Module (encoding and transport) Semantics Module (resoning) Task (agent Behavior) Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  21. Conclusions • Erlang seems designed “for software agents”! • But people in the agent community still want to use Java • But a real agent programming language is needed (see AgentLink III RoapMap) • A proposal: an agent-oriented language including the main characteristics of both Erlang and Java? Is it too hard? • eXAT needs: • A better way to express tasks (the use of action, event and pattern functions is not so simple) • To be (more) OTP-compliant • An improved documentation (sorry)! • Some applications and test-beds that prove eXAT/Erlang effectiveness Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  22. Our Next Action • To use eXAT in the implementation of a robot for Eurobot 2006 competition (http://www.eurobot.org/) • The game is a “funny golf” • Will be the first Erlang-enabled robot? We are searching for sponsors, anyone interested here ? Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  23. eXAT Thank you for your attention! Contact Info Corrado Santoro University of Catania, Engineering Faculty Viale Andrea Doria, 6 - 95125 - CATANIA - ITALY EMail: csanto@diit.unict.it Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  24. eXAT Internals: the Agent Model eXAT Agent User-defined Interfaces to external world Agent Actions (assert/retract facts) Agent Intelligence (ERESYE Engines) Agent Tasks Triggering Events (fact assertion) Agent Actions (ACL Message Sending) Triggering Events (ACL Message Arrival) Rational Effects (ACL Semantics) ACL Module Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

  25. Reasoning process (Fact assertion) ERESYE Engine A single event specification (“eresye” event) to capture both cases Rational Effect (Fact assertion) Agent inform Linking Interaction and Mental States • Writing an agent that does something when it knows the age of Corrado {age-of, ‘Corrado’, 39} • The knowledge can be obtained by • A result of a reasoning process (e.g. by knowing the year in which Corrado was born) • An “inform” message from another agent: • (inform … :content (age-of Corrado 39) … ) This is the first attempt (initiated in 2003) to implement FIPA-ACL Semantics Corrado Santoro, "eXAT: Software Agents in Erlang", Erlang User Conference 2005, Stockholm, Sweden, Nov. 10, 2005

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