What We Need for Describing Web-based Services

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What We Need for Describing Web-based Services

• Drew McDermott, Dejing Dou
• Yale
• Mark Burstein
• BBN
• Doug Smith
• Kestrel

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Whats an Agent?
For our purposes, an agent is a program
accompanied by descriptive material that allows
other programs to know what it does and how to
interact with it.
In other words, agents are run-time
composable programs.
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Example
Agent told Buy paperback edition of Robo Sapiens
for less than 25.
Steps

• Find partner agent (brokering)
• Get its service description (in DAML? or
  OIL?)
• Translate ontologies if necessary
• Find interaction plan

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Example, cont.
Buy Robo Sapiens for less than 25.
(do-for-some (b Book a Agent p Price)
(and (title b Robo Sapiens) (sells a b
1 p) (lt p (dollars 25))) (buy b a 1
p))
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Brokering
Find advertisements by other agents that use
terms found in the current goal description (buy,
book, ...)
Agent Interoperation Across Multagent System
Boundaries J.A. Giampapa, M. Paolucci, and
K. Sycara Proceedings of the Fourth
International Conference on Autonomous
Agents (Agents 2000),
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Now What...?
Each agent must have an behavior description, a
formal description of what it does and how to
interact with it.
Internal and external forms Logic (book-isbn
book21 0-262-13383-0) DAML ltrdfDescription
aboutbook21gt ltpubbook_isbngt0-262-13383-0
lt/pubbook_isbngt lt/rdfDescriptiongt
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Ontology Mismatch
What if two agents dont speak the same
language? -- I.e, dont share the same
ontology. This translation problem was to be our
main focus, but existing ontologies arent
interesting enough yet.
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Now what? (cont.)
Satisfy Agent1s goal by finding a series of
actions that, according to Agent2s behavior
description, will achieve that goal. This is a
planning problem Given a system description, and
initial-state description, find a way of
achieving the goal using available actions.
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Agent Behavior Description
Two sorts of things

• Legal actions, including preconditions and
  effects
• Scripts Hierarchical structures of actions

The latter allow for easier planning, the former
for more robust planning.
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Scripts vs. Actions
Script example How to buy a book from
Amazon.com. (series (tag s1 (send Amazon
(tuple in-stock? isbn-number)))
(tag s2 (receive Amazon (step-value s1)))
(test ( (step-value s2) book-in-stock)
(series (send credit-card...)
...)))
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Scripts vs. Actions, cont.
Action example Definition of send and
receive (action (send ?agt Agent ?msg -
DAML-list) value (?i - Send-id) effect
(reply-pending ?i ?msg)) (action (receive ?agt
Agent ?i Send-id) precond (reply-pending
?i ?msg) value (?reply DAML-list)
effect (when ( ?reply book-in-stock)
(know-val-is (in-stock)
true)))
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Note Merchants might prefer us to use scripts,
so all we can do is buy something. Third
parties might supply finer-grained
behavior descriptions in terms of actions (for
comparison shopping, seeing if a book is in
print, etc.).
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How Do We Move Forward?
Obstacles to planning in DAML-S

• There are too many notations around (DAMLOIL,
  RDF, N3, XML, RuleML, .).
• None of them is a likely candidate, mainly
  because all are shy about expressivity.
• There are specialized subfields (e.g., planning)
  where people find reasonable tradeoffs between
  expressivity and tractability.
• These subfields have little apparent role in the
  Semantic Web.

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Some Constructive Suggestions

• Let DAMLOIL be mainly a type-declaration
  sublanguage
• Agree on (a) a notation that has no obvious
  expressivity limitations (b) an XML
  serialization of that notation.
• Define official chunks of the language that
  not everyone will be able to handle. Tools can
  advertise which chunks they claim to be able to
  cope with.i

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Is Planning Hard in the DAML-S Universe?
Hot stuff!
Apparently not too hard. Its not as if
Amazon.com wants to present a challenging puzzle
to its customers. The main new wrinkles are
Come to Daml-s Demo!

• Have to plan to gather information (e.g.,
  product id numbers)
• May have to loop
• Many plans will plausibly work, but will require
  run-time replanning

Challenges!
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Extensions to Unpop

• New information is generated by some actions,
  capture as (step-value step-3)
• During regression and projection, assume
  normal step values where appropriate. (Yes,
  weve got that.)
• Insert steps to verify that normal value actually
  occurred if not, replain from new situation.

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An Example
(series (tag s1 (send Amz
(in-stock Wind Done Gone)))
(tag s2 (receive Amz
(step-value s1))) (verify ( (first(step-value
s2)) in-stock)) (tag s3 (send
Amz (buy 1
(second (step-value s2))))))