Transcript 07-communication

Communication Model
The Communication Plan
Specifying agent-agent transactions
Transaction patterns
Role of Communication Model
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specifies knowledge/information transfer procedures
top-level control over task execution
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additional communication tasks
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multiple knowledge-intensive tasks
explanation facilities
example: basic system-user interaction
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Relation to other models
task selected in feasibility study
and further detailed in
Task and Agent Models
organiz ation model
task model
agent model
communication
model
knowledgeintensive
task
design
model
knowledge
model
Communication Model
requirements
specification
for interaction functions
requirements
specification
for reasoning functions
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Input for communication
modeling
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Task Model
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Knowledge Model
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list of leaf tasks carried out by the considered agents
transfer functions
Agent Model
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description of relevant agents: capabilities, responsibilities
constraints.
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Information systems:
communication
More and more, IS are becoming information +
communication systems:
 distributed applications (telematics)
 virtual organizations
 CSCW
 intelligent multi-agent systems
 workflow management
 concurrent engineering
 business chain management and integration
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Communication between actors
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Information modeling must cover:
– Organizational/Business analysis
– Task/Workplace analysis
– Actor/Agent analysis (both human and system)
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Usually, several actors cooperate in a business
process or task, so
– Communication model intends to capture agent interactions
within a joint task
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Communication Model = conceptual specification of:
what kind of information objects are exchanged between
agents in cooperating in and carrying out a task, and how?
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Communication model:
overview
Task Model
Focuses on
modeling the
dialogue between
agents
Agent Model
Task
Agent
I/O info objects
.....
capabilities
.....
involved-in
Transaction
Communication
Plan
part-of
dialogue diagram
transaction control
Structured, semiformal approach
involved-in
identifier/name
I/O info objects
agents involved
communication plan
constraints
info exchange spec
part-of
Information
Exchange
Specification
communication type
message content
message control
info form/medium
involved-in
Task structure
transfer functions
.....
Knowledge Model
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Communication Model:
overview
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Layered approach to Communication Modeling
Three levels:
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1. The overall communication plan, which governs the full
dialogue between two agents
2. The individual transactions that link two (leaf) tasks
carried out by two different agents
3. The information exchange specification that details the
internal message structure of a transaction
Start to construct the global overview, and fill in the
details later
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Sample application
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Energy market
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dynamic pricing of energy
enables companies to do load management
HOMEBOTS: intelligent electrical agents
requires two-way communication system
kWh
kWh
utility
utility
customer
customer
utility
utility
&
customer
customer
info
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Transaction
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key component of Communication Model
describes what information objects are exchanged
indicates agents and tasks involved
go-between of two tasks carried out by different
agents
building blocks for the full dialogue between two
agents
transactions have an internal structure
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example: obtain
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Other CM concepts
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Communication plan
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governs the full dialogue between the agents
organization of transactions
Information exchange specification
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details transaction structure
consists of messages
only necessary for complex communications
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Communication Plan
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easiest to begin with the overall communication plan
describes full top-level dialogue
typical transactions
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data input
asking or answering questions
presentation of reasoning results
explanation of results
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Communication plan activities
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for each agent: list all tasks
for each task: identify set of associated agent-agent
transactions
results combined in “dialogue diagram"
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DD depicts transactions between two agents
draw a DD for each combination of two agents that
exchange a reasonable amount of information
specify control over the transactions
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Dialogue Diagram: general
structure
Agent A
(e.g. user)
Note: agent's
(leaf) tasks
are key entry
to dialogue
diagram
construction
Dialogue
Task A1
Agent B
(e.g. system)
Task B1
Transaction
Tr. 1
Task B2
Task A2
Transaction
Tr. 2
Task A3
Transaction
Tr. 3
Task A4
Task B3
Transaction
Tr. 4
Task A5
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Task B4
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New Customer Services:
ICT Technology
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Through networked microprocessors, devices can
'talk to', 'negotiate', 'make decisions', and 'cooperate'
with one another.
– Smart equipment agents we call homebots (inspired by Star
Trek and Asimow's Robot Stories)
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We use this,e.g., for distributed power load
management (Further info: see separate case)
Benefits:
– handles much larger scale
– higher degree of automation & decentralized flexible approach
– proactive for the customer
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DD for energy market
Task and
transaction links in
power auction are
graphically
sketched in the
dialogue diagram:
Gives overview of
the system's
communication
plan
Utility
Customer
Announce
Express
Preferences
Assess
Award
Schedule
Bid
Implement
Monitor
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C
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M
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C
A
T
E
Monitor
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CP for the housing application
assessment finished/
report decision
application received/
order assessment
application
assessment
data needed/ask
data received / reply
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waiting for
case data
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Transactions in the
Homebots System
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Transaction list:
– 1. Kick-off the auction: sends a trigger signal to the customer
agents to commence a load management action
– 2. Submit the bids: transmits the bids from the customer
agents to the auctioneer for further processing
– 3. Present the awarded power allocation: informs the
customer agents about the results of the auction
– 4. Present the associated real-time schedule: provides the
customer agents with the calculated schedule that implements
the awarded allocation
– 5. Receive the resulting real-time implementation data:
transmits the actual metering data (Needed for billing and for
assessing the need for further load management actions)
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Transaction control notations
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state diagrams
pseudo-code with special control primitives
SEND, RECEIVE
CARRY-OUT (SEND/RECEIVE combination)
WAIT-until/while
PROCESS (task)
; (sequence)
REPEAT-until/while, IF THEN ELSE
& (AND), | (choice), V (OR)
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Homebots Dialogue Control
Reduction need?
Announce & Kick-off
Auction
Running
Auction Completed/
Awards Distributed
Next Round
Interested? N
Opt out
Interested? Y Convergence? N
Express Prefs.
Opted Out
Preferences
Calculated
Power need?
Bid & Submit
Award & Present
Convergence? Y
Allocation
Computed
Assess
Bids received?
Bid
Submitted
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Communication Model:
Middle Level
identifier
& name
Specification of individual
transactions, structured in
a number of components:
agents
involved
communication
plan
TRANSACTION
Simple worksheet
techniques are helpful
here
constraints
information
objects
information exchange
specification
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Illustration Middle Level:
Homebots System (II)
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Submit-the-bid transaction description (Worksheet CM-1)
– Identifier/Name: Transaction 2: Submit-the-bid
– Information objects: linking Bid and Assess tasks: (1) bid; (2)
going price or going allocation (depending on domain theory)
– Agents involved: (1) customer agents; (2) auctioneer/utility
agent
– Communication plan: Homebots (base version)
– Constraints: (1) decision procedure for bidding completeness;
(2) market convergence postcondition
– Information Exchange Spec: See Worksheet CM-2
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Note: this transaction contains more than one message, and
so is composite
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Transaction “Housing” (1)
Transaction name
Order application assessment
Information object
a residence application
Agents involved
Comm. Plan
data entry + knowledge system
(+ assigner)
active when application arrives.
Constraints
Prototyping: interact with user
Informtation exchange
ransaction is of the “order”
type
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Transaction “Housing” (2)
Transaction name
Obtain application data
Information object
Attribute-value pairs of an a
applicant and residence
database + knowledge system
Agents involved
Comm. Plan
Constraints
Informtation exchange
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transitions connected to the
“waiting for data” state
Ensure mapping of data
request onto DB data format
transaction is of the ask-reply
type.
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Composite Transactions
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"I'm getting cold, so could you please shut the door?''
– First part is just information: notification message
– Second part is request for action by the other agent: task
delegation message
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So, within one transaction: two messages differring in both
content and intent
Transactions not only transmit content, but also an
intended relationship between two agents. Both these
aspects must be explicitly specified.
– Compare: "Hey, idiot, shut the door, I'm getting cold!"
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Speech Acts
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Agent communication languages often inspired by
so-called speech act theory
Makes distinctions between:
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Content ('locutionary nature') of a speech act or message -what is actually being said -Intended effect ('illocutionary force') on the other agent
Actual effect ('perlocutionary force') on the other agent
– N.B. nice communication modeling exercises:
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Communication Model
"It's the economy, stupid!''
Edward Albee's Who's Afraid of Virginia Woolf?
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Communication Model:
Detail Level
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Detailed message specification:
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1. Content (locution): by means of a propositional
statement
2. Intention (illocution): by means of typing a message
Predefined types:
– Task Delegation: Request; Require; Order; Reject-td
– Task Adoption: Propose; Offer; Agree; Reject-ta
– Pure Information Exchange: Ask; Reply; Report; Inform
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Note: Intention = purpose x commitment
– Cf. performatives in KQML (DARPA Knowledge Sharing Effort)
and esp. COSY (Daimler-Benz)
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Communication types
Task delegation Task adoption Information
exchange
Request
Propose
Ask
Require
Offer
Reply
Order
Agree
Report
Reject-td
Reject-ta
Inform
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Semantics of
Communication Types
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Request/Propose: potential for cooperation, but agent wishes to negotiate on
the terms. Loosely: `I have an interest, but not yet a commitment'.
Require/Offer: agent already has made a pre-commitment, and intends to
prompt the receiving agent for its commitment. This type thus denotes a
conditional commitment.
Order/Agree: agent has made a commitment, and thus will act accordingly.
Reject-td/ta: denote that the agent does not want to commit or cooperate.
Ask/Reply: have as intent a query for information from another agent, and
delivery of information in return.
Report: types a message sent after an agent has acted towards a (previously)
agreed task goal, with the intention to let the other agent know the status of
achievement (e.g. success, failure, outcome of the action).
Inform: refers to a message type that just delivers information objects to
another agent. Indicates an independent informative action: no previous request
or agreement involved.
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Typed Message Patterns
Not only typing of single messages possible.
Also, natural chains of message types can be formed (cf. COSY):
Communication type patterns
Communication Patterns
INFORM
ORDER
1)
REPORT
REQUIRE
AGREE
AGREE
REPLY
REPORT
2)
4)
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PROPOSE
5)
3)
ASK
REJECT-ta
REQUEST
REJECT-td
6)
REJECT-ta
7)
OFFER
ORDER
OFFER
PROPOSE
REQUEST
REQUIRE
REJECT-td
8)
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Worksheet CM-2: Information
Exchange Specification
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Only needed for complex communication patterns
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energy market
Worksheet structure
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Transaction Identifier/Name
Agents involved: sender, receiver
Information items
Message specification
Message control
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Transaction “submit-the-bid”:
message specifications
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Bid-message
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type:PROPOSE
content: bid
from: customer agent
to: auctioneer
Opt-out-message
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type: REJECT-TA
content: no part
from: customer agent
to: auctioneer
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Auction-data-message
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type: INFORM
content: market data
from: auctioneer
to: customer agent
Next-round-message
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type: REQUEST
content: trigger next round
from: auctioneer
to: customer agent
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Information items
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role:
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core object
support item
– explanation texts of domain material
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rock photographs, mineral photographs
– reasoning traces
– WHY/HOW explanations
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syntactic form: data string, diagram, ...
medium: pop-up window, command-line interface,
human intervention, …
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cf. Design issues
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Control over messages
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Refinement of control in communication plan
Notations: the same
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State diagram
Pseudo code
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Transaction: submit-the-bid
REPEAT WHILE <market convergence condition not satisfied>
IF <interest in load management>
THEN PROCESS(bid-task); SEND(BID-MESSAGE)
ELSE SEND(OPT-OUT-MESSAGE)
END-IF
IF <bids received>
THEN PROCESS(assess-task)
ELSE PROCESS(decision subprocedure [e.g. WAIT...])
END-IF
SEND(AUCTION-DATA-MESSAGE) &
SEND(NEXT-ROUND-MESSAGE)
END-REPEAT
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Validation techniques
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Communication-plan walk-through
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adequacy transaction structure
completeness list of information items
need for help or explanation
Wizard-of-Oz technique
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experimental technique to validate interaction
mock-up software
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Nielsen's guidelines for
usability engineering
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Present a simple and natural dialogue
Speak the user's language
Minimize the user's memory load
Maintain consistency in terminology
Give feedback about what is going on
Show clearly marked exits from unwanted states
Offer shortcuts for the experienced user
…..
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Guidelines for balancing the
communication model
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Key inputs:
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Take agent capabilities into account (see AM)
syntactic form of media is area of both CM and DM
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leaf tasks TM
transfer function KM
guideline: in CM if conceptual reason
Decide here about support information
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not in design model
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Communication model
activities
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Identify core information objects to be exchanged
between agents
Identify associated transactions
Draw important dialogue diagrams
Combine this to a full communication plan
Specify the individual transactions
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worksheets CM-1 and CM-2
Validate and balance the model
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