Artificial Intelligence and Lisp #3
Characterization of Actions [Chapter 5]
Representation Language [Chapter 2]
Lab Assignment 2
Part I: Working with action laws
[Read Lecture Notes Chapter 5 for this,
but read Chapter 2 first]
Effect law for pour action
[Do .t [pour .fr .to]] =
[if [and [H- .t (substance-in: .to) empty]
(not [H- .t (substance-in: .fr)
Empty ])]
[coact [H! .t (substance-in: .to)
(cv (substance-in: .fr)) ]
[H! .t (substance-in: .fr)
Empty ]]
[soact] ]]
Notation on previous slide
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[H- time feature val] is a logical expression
which is true if the value of feature at time-1 is
val
[H time feature val] is a logical expression which
is true if the value of feature at time is val
[H! time feature val] is a low-level “action” that
assigns val as the value of feature at time
Use of effect law in simulator
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Check whether precondition is satisfied
If so, execute the 'then' clause in the
environment.
A composite action (coact) always takes one
timestep. A sequence (soact) takes one
timestep per component.
If precondition is not satisfied, then execute the
'else' clause.
Report success or failure, failed precondition,
and culprit of the failure (so that the agent has a
chance to fix the problem)
Precondition for pour action
[Do .t [pour .fr .to]] =
[if [and [H- .t (substance-in: .to) empty]
(not [H- .t (substance-in: .fr)
empty ])]
[coact [H! .t (substance-in: .to)
(cv (substance-in: .fr)) ]
[H! .t (substance-in: .fr)
empty ]]
[soact] ]]
Failed precondition as reported by simulator:
[H- now (substance-in: g2) empty]
Operations done on the precondition
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Evaluate precondition. If failed:
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Instantiate variables (most of them)
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Insert now for current time in simulated world
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Identify which (one or more) of the conjuncts
has the value false
Return both entire instantiated precondition,
and failed conjuncts
More complicated operation if the precondition
is more complicated
Agent's response to failed
precondition: alternatives
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Recall: [H- now (substance-in: g2) empty]
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Simplest: Look up reaction in table - but based on what?
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Associate reaction(s) with pattern:
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[H- now (substance-in: .g) empty]
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[H- now (substance-in: .g) .c]
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Check postconditions of all available actions to find one
with desired effect:
dispose
[H! .t (substance-in: .e) empty]
Find sequence of actions (a plan) whose combined effect
will be the desired one.
Operations on action expressions
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Consist of expressions for precondition and for
effect which are treated separately
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Evaluation of precondition
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Partial evaluation of precondition
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Effect is ~ postcondition
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Match partially evaluated precondition with
postcondition/effect of another action
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Send expression to another agent
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Save expression for later reuse (learning)
Part II: Representation formalism
[Read Lecture Notes, Chapter 2 for parts II-IV]
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Requirements:
Adequate expressivity: facts, scripts, action
laws
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Facilitate processing in computer
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Readability for humans
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Conciseness - avoid multiple representations
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Use available standards both from mathematics
and logic, and from computer world
KRF - atomic elements
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Atomic entities, e.g. Plato
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Strings, e.g. ”Ursus ursus”
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Numbers, e.g. 451
KRF - composite elements
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Composite entities, e.g. (age-of: Plato)
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Sets, e.g.
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Sequences, e.g. <Caesar Augustus Nero>
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Records, e.g.
[dispose :e glass4]
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Maplets, e.g.
[: 45 empty]
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Forms, e.g.
(cv (age-of: Plato))
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or
{Plato Socrates}
(+ 2 (cv (age-of: Plato)))
Composite entities vs forms
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Composite entities, e.g. (age-of: Plato)
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Forms, e.g.
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or
(cv (age-of: Plato))
(+ 2 (cv (age-of: Plato)))
Composite entities can have attributes and
values
Forms are replaced by their value during
evaluation - composite entities are not
KRF - records
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Records, e.g.
[dispose :e glass4]
More generally:
[oper arg1 arg2... :tag1 val1
:tag2 val2 ... ]
Alternative, equivalent:
[oper :tag1 val1 :tag2 val2 ...
^ arg1 arg2... ]
KRF - mappings
[: 45 empty]
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Maplets, e.g.
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Used to form mappings, e.g.
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{[: 21 water]
[: 28 empty]
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[: 35 beer]
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[: 45 empty]}
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Part III: Generic Scripting Language
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Used as a basis for a range of scripting
languages:
Agent Scripting Language
Document Scripting Language (for texts and
web pages)
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Operations Scripting Language
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...
Scripting Expressions
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Action expression, record, [verb a1 a2...]
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Action composition using if, soact, etc.
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Feature, comp.ent., (feaop: arg1 ...)
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Term, form, (function arg1 arg2 ...)
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Query, form, is a kind of term
Atomic propos., record, [pred a1 a2 ...]
Composite propos., form, (and p1 p2 ...)
and similarly for or, not, etc.
Part IV: Entity-files
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Entity-files are used in Leonardo for persistent
storage of information between sessions
In principle, each entityfile is a two-level
mapping:
{[: ent-1
{[: a1
[: a2
val-1-1]
val-1-2] ...}]
[: ent-2
{[: a1
val-2-1]
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[: a2
... ... }
val-2-2] ...}]
Practical representation of entityfiles
------------------------------------ entity-1
[:
[:
[:
[:
type sometype]
a1 “value of attribute a1 for entity-1”]
a2 (symbfun: a5)]
(attrfun: color) {red green}]
------------------------------------ entity-2
[: type sometype]
[: a1 “value of attribute a1 for entity-2”]
@Comment
Comments may be expressed in free text, or may
use a specialized notations as selected by the
designer. They are preserved in textual form
until processed by an application program.
ooooooooooooooooooooooooooooooooooo
Entityfile facilities
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Each entity in the file must have a value for the
type attribute. That value must again be an
entity in a file, and so on.
Entityfiles can be written and read back.
Only attributes that are included in the
attributes attribute of the type are written to
the file
Entities not having a value for any of the
attributes of their type, are not written to file
Notice the use of properties, e.g. Comment
Some additional aspects
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An entity of type section can be used for
partitioning an entityfile into parts separated by
a =================== line
The in-categories attribute is always
optional and should have a set of entities as
value
The command sortfil myfile sorts the
entities in a file in alphabetical order
The name of an entityfile is always the first
entity in the file
Lab 2: Defining a Zoo Miniworld
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Milestone 1: static structure in the zoo world
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Milestone 2: defining actions in the zoo world
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What to do for the lab:
What to do for the lab
(your “script”)
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Read lab instructions on the course webpage:
page on labserver access and lab 2 definition
Start a session with your Leonardo agent
Download lab materials from labserver using
commands getlabs and getlab lab2a-kb
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Do the work as specified
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Make a local check using check-lab command
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Upload results using upload-lab command
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Await final approval