McIlraith - Knowledge Systems Laboratory DAML/Horus Meeting 02/16/2001 Mobilizing the Web with...

McIlraith - Knowledge Systems Laboratory DAML/Horus Meeting 02/16/2001

Mobilizing the Web with

DAML-Enabled Web Services

Sheila McIlraith

Knowledge Systems Laboratory (KSL)Department of Computer Science

Stanford University

(with Son Cao Tran and Honglei Zeng)


Motivation

The Web is evolving from a provider of documents

and images …


Motivation

… to a provider of services


Overview

Problem: today’s web is designed primarily for human use.

We are developing semantic markup of • web services,• web service users’ preferences and constraints• reusable agent procedures

to make services computer-interpretable, use-apparent, and

agent-enabled.

We are developing agent technology that exploits semantic

markup to support automated web service discovery,

execution, composition and interoperation.


Web Service Markup Will Enable

Automation of:

• Web service discoveryFind me an airline service that offers flights to Tuktoyuktuk

• Web service executionBuy me “Harry Potter and the Sorcerer’s Stone” at

www.amazon.com

• Web service selection, composition and interoperationMake my travel arrangements for my IJCAI conference trip

Industry efforts growing

(we are improving with DAML)

Opportunity Area

These are the drivers for web service markup.


Semantic Markup

How is DAML adding value over XML?

Ontologies• reuse • sharing• composition • succinct web site markup

E.g.,service world-altering service purchase purchase-plane-ticket

purchase-UAL-plane-ticket purchase-book ... Information-providing service provide-schedule-info provide-flight-schedule-info...


Semantic Markup



Constraints and Rules• compact representation• ease of expression

E.g.,flight-over-3hours movieunauthorized-web-site unreliable-source


Semantic Markup



Constraints and Rules• compact representation• ease of expression

Semantics

E.g., supplier -vs- vendor due-date due-date


Web Services: An Example

• Web service discoveryFind me an airline service that offers flights to Tuktoyuktuk

• Web service executionBuy me “Harry Potter and the Sorcerer’s Stone” at

www.amazon.com

• Web service selection, composition and interoperationMake my travel arrangements for my IJCAI conference trip


Approach

Each web site provides a set of services• information providing (e.g., flight schedules, camera views) or• world-altering (e.g., booking flights, home temp. adjustment)

Web services are conceived as • functions for execution, (~Declaratively Specified API)• actions/processes for composition and interoperation.

Web sites are annotated with DAML markup, describing

services in terms of action preconditions

and effects or in terms of processes of

actions. DAML-enabled web pages


DAML Markup of Web Services

E.g.,service world-altering service purchase purchase-plane-ticket

purchase-UAL-plane-ticket parameters: c-name, origin, dest, d-date, … preconditions: know(c-name), valid(credit-card), … effects: purchased(ticket), debit(credit-card)... rent rent-car ... Information-providing service provide-schedule-info provide-flight-schedule-info...

Function and action-based markup exploits ontologies:

Web Service Ontologies

DAML-enabled web pages

Collectively they create a distributed KB of services.


Agents request services through brokers


AgentBroker


Agents communicate with DAML-enabled web sites

through Agent Brokers that request web services

and dispatch responses.

Brokers exploit the web service ontologies to assist in

locating appropriate service providers.


DAML-Enabled Agents

Agents are tasked by people, or by other agents.


AgentBroker

E-mail


...


Generic Procedures

Agents are tasked in terms of high-level, reusable “generic procedures.”

“The what not necessarily the how.”

Ontologies support sharing,reuse, and composition.



Web Procedures Ontologies

AgentBroker

E-mail ...

E.g.,Travel(cust,origin,dest,date-d,date-r,purpose) Check-purpose-related-restrictions; Book-travel(origin,dest); Book-transportation(dest); Book-hotel(dest)end;


Customizing Generic Procedures

Generic procedures can be further constrained by

DAML-defined constraints• user constraints/preferences, • group constraints, or• instance-specific constraints.



Web Procedures Ontologies

AgentBroker

E-mail

DAML-enabled personal/company

constraints and prefs...

E.g., • Bob would like to drive if the driving distance is less than3 hours.

• KSL Business air travel should be on an American carrier.

...


Instantiating Generic Procedures

Agent’s KB is automatically constructed relative to the

generic procedure and constraints. KB is updated by web

service responses.

Deductive machinery instantiates the generic procedure

wrt. constraints and world state to

generate web service requests

that the broker executes.

KB

Web Services

Service Ontologies

Procedures Ontologies

AgentBroker

Constraints & Prefs

E-mail ...


Status

DAML = First-order logic and some DAML+OIL

Agent KB representation language = Situation Calculus

Generic procedures representation language = Golog

Deductive machinery = Prolog

Agent Broker = Open Agent Architecture [SRI]

Prototype agent/agent broker constructed.

Preliminary ervice ontology constructed.

KB

Web Services

Service Ontologies

Procedures Ontologies

AgentBroker

Constraints & Prefs

E-mail ...


Travel Example

Bob Chen wants to travel from San Francisco to Monterey, departing September 2 and returning September 6. The purpose of the travel is DAML.

Our Lab’s Relevant ConstraintsKSL Business air travel must be on an American carrier.

Bob’s Relevant ConstraintsBob would like to drive if the driving distance is less than 3 hours.

Generic Procedure:Travel(customer,origin, dest, date-d, date-r, purpose) Book-travel(origin,dest); Book-transportation(dest); Book-hotel(dest); Inform(customer); Create-expense-claim;end;


Dynamic User Interface with DAML+OIL


Behind the Scenes


Agent e-mails itinerary to customer


Agent creates expense claim for customer

Writing “DAML”!


Summary of Key Features of KSL Work

DAML Markup of Web Services, User Constraints, Agent Procedures:• Computer-interpretable, use-apparent, agent-enabled services.• Ontologies facilitate construction, sharing, reuse, and composition; support succinct web site markup.• Markup not specific to particular agent implementation.

A DAML-Enabled Agent System:• DAML markup provides distributed KB for agents.• Logic-based generic procedures + constraints. • Procedures - general and easy to use. • Constraints enable customization.• Ontologies facilitate construction, sharing, reuse, composition.• Procedures are verifiable wrt. certain properties.• Deductive machinery instantiates procedures generating web service requests that are sent to the agent broker. • Procedures & deductive machinery provide middle ground between planning & programming.


Take-Away Message

• Semantic Web Services are going to revolutionize B2B and E-Commerce on the Web.

• They will also revolutionize the way companies deal with their information and business processes.

• Semantic markup (DAML markup) of web services is the key enabling technology for this revolution.

McIlraith - Knowledge Systems Laboratory DAML/Horus Meeting 02/16/2001 Mobilizing the Web with...

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