Multi-agent interactions on the Web through Linked Data Notifications

Jean-Paul Calbimonte • Davide Calvaresi • Michael Schumacher

Institute of Information Systems

University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis)

European Conference on Multi-Agent Systems EUMAS

Evry, December 2017

@jpcik

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HES-SO: University of Applied Sciences and Arts Western Switzerland

Institute of Information Systems

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Use Case: an example

wellbeing

monitoring

health

recommendations weather

information

point-of-care

restauration

services

point-of-interest

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A Web of Agents

Agent

Agent

Agent

Agent

Agent

Agent

Agent

Web Standards?

Rich Semantics?

Decentralized?

Agent identifiers?

Metadata?

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RequirementsR1: Standard and extensible messaging.

R2: Standard metadata.

R3. Asynchronous and distributed communication.

R4. Standard Web protocols.

R5. Web identifiers.

R6. Semantic representation.

• any type of data

• different formats

• representations

• Web standards

• participants, time constraints, performatives, conditions, etc.

• send and receive messages

• coordination

• no central entity

• Web Standards: HTTP

• not excluding others

• no commitments to a particular agent implementation

• URL/URI/IRIs

• unicity and de-referenceability.

• Web standards (e.g. OWL, RDF),

• extensibility and high expressiveness.

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Linked Data Notifications• Recently endorsed W3C Recommendation

• Decentralized data interchange of notifications on the Web

• Generic and simple mechanism to send and consume data

• Based on the Linked Data principles • Use URIs to name things• Use HTTP URIs• Get relevant data by dereferencing a URI • URIs linked to other URIs

• Usage of RDF for data representation.

• Virtually any type of notifications

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LDN: Basics

Notifications are

to/about itSends notifications

Exposes notifications through inbox

Creates notifications in inbox

SenderTarget

Consumer

Receiver

Consumes notifications

inbox

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LDN: interactions

GET/HEAD

Sender

Target

Consumerinbox

GET/HEAD

inbox

Receiver

inbox

POST GET

notifications

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LDN: example

GET/HEAD

Sender

Agent

Jean-Paul

Consumer

Agentinbox

Receiver

Agent

inbox

POST GET

notifications

http://w3id.org/people/jpcik/me

http://w3id.org/people/jpcik/inbox

{"message": "Your Talk

at EUMAS is at 11:00"}

Container of received

messages

Get all messages

Get one particular

message

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HTTP-based communication

• LDN is entirely based on HTTP requests and responses

• Natural candidate for most types of exchanges

• Other protocols could be used in certain circumstances• e.g. WebSockets for push-subscriptions.

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Agent Identification

• URIs (or IRIs) are used to identify all entities involved.• Agents identified with URIs

• de-referenceable to obtain more information • agent visibility• perception of agent’s environment can be enriched

GET http://example.org/agents/health-agent

• Response: • include metadata about the agent, • e.g. name, scope, endpoint, ontologies, etc.

• Each agent can provide an endpoint inbox• Not necessary located within the same environment

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Endpoint Discovery

• An agent may advertise its inbox• e.g. JSON-LD message content:

• Indicates inbox location/other useful metadata• Discovery phase: first interaction between two agents that

wish to establish a conversation or initiate a negotiation

{

"@context": "http://www.w3.org/ns/ldp",

"@id": "http://example.org/agents/health-agent",

"inbox": "http://example.org/agents/health-agent/inbox"

}

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RDF data representation• Any representation format and/or model. • LDN agents: use RDF as standard representation framework.

• use of URIs for identifiers• using extensible vocabularies• possible to attach explicit semantics

• Metadata annotations should be expressed in RDF,• i.e. sender, receiver, performative, protocol, date-time,

reply information, conversations, etc.

• e.g. (JSON-LD serialization) information about an agree message, indicating the sender agent, receiver, conversation information, etc.

{

"@id": "ex:agree_request1",

"ag:permormative": "ag:Agree",

"ag:sender": "ex:agent1",

"ag:receiver": "ex:agent2",

"ag:reply-to": "ex:agent3",

"ag:protocol": "ag:RequestWhen",

"ag:conversationId": "ex:conv321",

"ag:inReplyTo": "ex:conversation1",

"ag:ontology":

"http://example.org/ontology#",

"ag:content":

"..."

}

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Sending agent notifications• LDN agent may POST notifications to an agent inbox endpoint• JSON-LD representation of a call for proposals agent message:

POST /agents/health-agent/inbox HTTP/1.1

Host: example.org

Content-Type: application/ld+json

{

"prov:generatedAtTime": "2017-09-14T04:00:00.000Z",

"@id": "ex:callForProposals1",

"@graph": [

{ "@id": "ex:cfp1",

"ag:permormative": "ag:CallForProposals",

"ag:sender": "ex:agent1", "ag:protocol": "ag:ContractNet",

"ag:ontology": "http://example.org/healthOntology#",

"ag:content": "..." }

],

"@context": {

"prov": "http://www.w3.org/ns/prov#", "ex": "http://example.org#",

"ag": "https://w3id.org/rdfagents/msg#"}

}

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Interaction protocols

• example: the Request Interaction Protocol (FIPA)

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Interaction Protocols

• call for proposals made available to an agent inbox.

• accessed by the inbox owner / participants

• allows participants to respond to it by sending proposals

• proposals can be accepted by the initiator agent.

• all messages conform to an agreed RDF structure

• exchanged preferably through HTTP, with GET and POST

POST

GET

Inbox

Initiator Participant

call-for-proposals

propose

proposal

accept-proposal

GET

POST

POST

cfp

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Publishing inbox elements

• Consumers may access an agent inbox • Obtain the messages available there through HTTP requests.

• GET over an inbox: return notification URIs• URIs for collections of notifications• URIs for individual notifications• Notification URIs referenced with LDP ldp:contains predicate.

• Security, privacy and ownership schemes should be enforced

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Agent reasoning

• LDN adoption do not affect traditional reasoning engines

• Guarantee the retro-compatibility with already existing mechanisms

• Foster the development of new ones

• Increased capabilities due to the semantic expressiveness

• Simplified and extended interactions.

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LDN for Agents: Challenges• Adoption of semantically rich messaging mechanisms (e.g. RDF-based)

among Agents on the Web.

• Usage of ontologies and vocabularies that link existing Web protocols (e.g. LDN) and Agent-communication standards (e.g. FIPA ACL).

• Definition and agreement of system-agnostic Agent communication primitives, based on existing MAS languages.

• Provision of agent discovery, selection and orchestration services, based on existing standards.

• Implementation and adoption of best practices of agent-based mechanisms for Web interactions.

gracias! ¿tienes preguntas?

Jean-Paul CalbimonteUniversity of Applied Sciences and Arts Western Switzerland

HES-SO Valais-Wallis

@jpcik