artificial intelligence and lisp #3 characterization of actions [chapter 5] representation language...

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

[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 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

Evaluate precondition. If failed: Instantiate variables (most of them) Insert now for current time in simulated world 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

Recall: [H- now (substance-in: g2) empty] Simplest: Look up reaction in table - but based on what? Associate reaction(s) with pattern: [H- now (substance-in: .g) empty] [H- now (substance-in: .g) .c] 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

Consist of expressions for precondition and for effect which are treated separately

Evaluation of precondition Partial evaluation of precondition Effect is ~ postcondition Match partially evaluated precondition with

postcondition/effect of another action Send expression to another agent Save expression for later reuse (learning)

Part II: Representation formalism[Read Lecture Notes, Chapter 2 for parts II-IV]

Requirements: Adequate expressivity: facts, scripts, action

laws Facilitate processing in computer Readability for humans Conciseness - avoid multiple representations Use available standards both from mathematics

and logic, and from computer world

KRF - atomic elements

Atomic entities, e.g. Plato Strings, e.g. ”Ursus ursus” Numbers, e.g. 451

KRF - composite elements

Composite entities, e.g. (age-of: Plato) Sets, e.g. {Plato Socrates} Sequences, e.g. <Caesar Augustus Nero> Records, e.g. [dispose :e glass4] Maplets, e.g. [: 45 empty] Forms, e.g. (cv (age-of: Plato)) or (+ 2 (cv (age-of: Plato)))

Composite entities vs forms

Composite entities, e.g. (age-of: Plato) Forms, e.g. (cv (age-of: Plato)) or (+ 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

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

Maplets, e.g. [: 45 empty] Used to form mappings, e.g. {[: 21 water] [: 28 empty] [: 35 beer] [: 45 empty]}

Part III: Generic Scripting Language

Used as a basis for a range of scripting languages:

Agent Scripting Language Document Scripting Language (for texts and

web pages) Operations Scripting Language ...

Scripting Expressions

Action expression, record, [verb a1 a2...] Action composition using if, soact, etc. Feature, comp.ent., (feaop: arg1 ...) Term, form, (function arg1 arg2 ...) 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

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 val-1-1] [: a2 val-1-2] ...}] [: ent-2 {[: a1 val-2-1] [: 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”]

@CommentComments may be expressed in free text, or mayuse a specialized notations as selected by thedesigner. They are preserved in textual formuntil processed by an application program.

ooooooooooooooooooooooooooooooooooo

Entityfile facilities

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 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

Milestone 1: static structure in the zoo world Milestone 2: defining actions in the zoo world What to do for the lab:

What to do for the lab(your “script”)

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 Do the work as specified Make a local check using check-lab command Upload results using upload-lab command Await final approval