ARTIFICIAL INTELLIGENCE [INTELLIGENT AGENTS PARADIGM] - PowerPoint PPT Presentation

Loading...

PPT – ARTIFICIAL INTELLIGENCE [INTELLIGENT AGENTS PARADIGM] PowerPoint presentation | free to download - id: 58d8b6-ODhkZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

ARTIFICIAL INTELLIGENCE [INTELLIGENT AGENTS PARADIGM]

Description:

ARTIFICIAL INTELLIGENCE [INTELLIGENT AGENTS PARADIGM] KNOWLEDGE REPRESENTATION SCHEMAS Professor Janis Grundspenkis Riga Technical University Faculty of Computer ... – PowerPoint PPT presentation

Number of Views:618
Avg rating:3.0/5.0
Slides: 36
Provided by: MEL114
Learn more at: http://stpk.cs.rtu.lv
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: ARTIFICIAL INTELLIGENCE [INTELLIGENT AGENTS PARADIGM]


1
ARTIFICIAL INTELLIGENCEINTELLIGENT AGENTS
PARADIGM
KNOWLEDGEREPRESENTATION SCHEMAS
  • Professor Janis Grundspenkis
  • Riga Technical University
  • Faculty of Computer Science and Information
    Technology
  • Institute of Applied Computer Systems
  • Department of Systems Theory and Design
  • E-mail Janis.Grundspenkis_at_rtu.lv

2
Knowledge Representation Schemas
  • Logical schemas
  • First-order logic
  • Higher-order logic
  • Procedural schemas
  • Rule-based systems
  • Network schemas
  • Semantic networks
  • Conceptual graphs
  • Structured schemas
  • Frames
  • Scripts

3
Semantic Networks
  • Definition Semantic network (Quillian, 1967) is
    a knowledge representation schema that captures
    knowledge as a graph. The nodes denote objects or
    concepts, their properties and corresponding
    values. The arcs denote relationships between the
    nodes. Both nodes and arcs are generally labelled
    (arcs have weights).

4
Example of Semantic Network
5
Semantic Networks
  • Typical relationships
  • IS-A
  • PART-OF
  • HAS
  • VALUE
  • LINGUISTIC

6
Semantic Networks
  • Typical relationships (continued)
  • IS-A
  • Supertype type (superclass class)
  • Type subtype (class subclass)
  • Subtype instance (subclass instance)
  • PART-OF
  • Supertype type (superclass class)
  • Type subtype (class subclass)

7
Semantic Networks
  • Typical relationships (continued)
  • HAS
  • Object property
  • VALUE
  • Property value
  • LINGUISTIC
  • Examples likes, owns, travel, made of,

8
Semantic Networks
  • NETWORK EXTENSION
  • Addition of new nodes and their relationships
  • Three ways of node addition
  • Similar object
  • More specific object
  • More general object

9
Semantic Networks
  • REASONING
  • Query node
  • Answer search
  • Answer localization at the query node
  • Path construction following labels of arcs

10
Semantic Networks
  • INHERITANCE
  • Definition Inheritance is a process by which the
    local information of a superclass node is assumed
    by a class node, a subclass node, and an instance
    node

11
Semantic Networks
  • INHERITANCE (continued)
  • 1) Provides a natural tool for representing
    taxonomically structured knowledge. 2) Provides
    economical means of expressing properties common
    to a class of objects. 3) Reduces the size of a
    knowledge base. 4) Provides more compact code
  • 1) Exception handling by local priority. 2)
    Additional workload of knowledge engineer who
    must decide at which node to define common
    properties

12
Conceptual Graphs
  • DEFINITION A conceptual graph (John Sowa, 1984)
    is a finite, connected, bipartite graph
  • The nodes of the graph denote either concepts or
    conceptual relations
  • Conceptual graphs do not use labelled arcs
    instead the conceptual relation nodes represent
    relations between concepts
  • Concepts can only have arcs to conceptual
    relations, and vice versa
  • Concepts are represented as boxes and conceptual
    relations as ellipses

13
Conceptual Graphs
  • Concept nodes represent
  • Concrete concepts (objects), for instance, cat,
    telephone, book , etc. These concepts are
    characterised by our ability to form an image of
    them in our minds. Concrete concepts include
    generic concepts such as cat or book along with
    concepts of specific cats and books
  • Abstract concepts, for instance, beauty, loyalty,
    and love that do not correspond to images in our
    minds

14
Conceptual Graphs
  • Conceptual relation nodes indicate a relation
    involving one or more concepts. Some special
    relation nodes, namely, agent, recipient, object,
    experiencer, are used to link a subject and the
    verb
  • Conceptual graphs can represent relations of any
    arity
  • A relation of arity n is represented by a
    conceptual relation node having n arcs

15
Example of Conceptual Graph
16
Conceptual Graphs
  • Each conceptual graph represents a single
    proposition
  • Knowledge base contains a set of conceptual
    graphs
  • Graphs may be arbitrary complex but must be
    finite

17
Frame Based Systems
  • The term frame is coined by Minsky in 1975.
  • Frame is a static data structure used to
    represent stereotypical information about some
    concept.
  • Frame is like a template that contains generic
    information about some concept that you could
    refer to for describing a given instance of the
    concept.

18
Frame Based Systems
  • A frame has
  • Name frame identification information.
  • Slots with labels describing the attributes and
    possible values for each attribute.

19
Frame Based Systems
  • The slots contain
  • Frame identification information
  • Relationship of this frame to other frames
  • Frame default information (slot values that are
    taken to be true when no evidence to the contrary
    has been found)
  • New instance information (slots may be left
    unspecified)
  • Procedural information (procedural code may be
    attached to the slot)
  • Descriptors of requirements for frame match

20
Frame Based Systems
  • ATTRIBUTES
  • STATIC
  • DYNAMIC
  • VALUES
  • NUMERIC
  • SYMBOLIC
  • BOOLEAN

21
Frame Based Systems
  • Sources of attribute values
  • Initialize
  • Database
  • Procedure
  • Expert System
  • User
  • Inheritance
  • Other Frame (object)

22
Frame Based Systems
  • CLASS
  • Definition Class is a collection of objects that
    share some common properties (attributes).
  • A class frame contains
  • A descriptive name of the concept
  • A set of attributes that are characteristic of
    all its associated objects
  • Attribute values that considered common to these
    objects
  • It may contain 1) An explicit reference to all
    of its associated subclasses 2) Information
    describing the behaviour of the concept.

23
Frame Based Systems
  • SUBCLASSES
  • Definition Subclasses are classes that represent
    subsets of higher level classes.
  • Three kinds of class relationships
  • Generalization Kind of relationship
  • Aggregation Part of relationship
  • Association Semantic relationship

24
Frame Based Systems
  • INSTANCE
  • Definition Instance is a specific object from a
    class of objects.
  • AN INSTANCE FRAME
  • Describes
  • A specific object from its related class.
  • Contains
  • All of the characteristics of the class frame as
    well as a specific information (specific features
    and property values).

25
Example of Frame Based System
truck truck
class vehicle class vehicle
reg. number
producer
model
owner
tonnage
part of basket
superclass vehicle superclass vehicle
reg. number
producer
model
owner
basket basket
dimensions 231.5
material tin
car car
class vehicle class vehicle
reg. number
producer
model
owner
number of doors 4
horse-power
Johns car Johns car
class car class car
reg. number LV97
producer BMW
model 520
owner John
number of doors 2
horse-power 150
John John
age 22
length of driving 2
26
Frame Based Systems
  • INHERITANCE
  • Definition Inheritance is the process by which
    the characteristics of a parent frame are assumed
    by its child frame.
  • Note In general, a child frame will inherit
    information from its parents, grandparents,
    great-grandparents, etc.
  • MULTIPLE INHERITANCE
  • An object could inherit information from more
    than one parent (in this case objects relate to
    different worlds)

27
Frame Based Systems
  • INHERITANCE
  • Practical value
  • Easier coding of the system
  • Easier modification of information in a frame
    (adding new property to the class frame it will
    be inherited automatically by all of its
    instances)
  • Potential problem exception handling
  • Any frame that is an exception from the norm,
    that is, the frame has some property value unique
    to itself, this value must be explicitly encoded
    in the frame.

28
Frame Based Systems
  • FACETS
  • Definition A facet is an extended knowledge
    about a frames property.
  • Facets provide additional control over property
    value and the operation of the system.

29
Frame Based Systems
  • A facet extends the information in the following
    ways
  • TYPE Defines a type of value that can be
    associated with the property
  • DEFAULT Defines a default value, i.e., an
    initial value for the property
  • CONSTRAINT Defines the allowable value

30
Frame Based Systems
  • MINIMUM CARDINALITY Establishes min number of
    values
  • MAXIMUM CARDINALITY Establishes max number of
    values
  • IF-NEEDED Specifies action to be taken if the
    propertys value is needed
  • IF-CHANGED Specifies action to be taken if the
    propertys value is changed

31
Frame Based Systems
  • METHODS (1)
  • Definition Method is a procedure attached to an
    object, that will be executed whenever requested.
  • An IF-NEEDED method is written in order to obtain
    the propertys value only when it is needed.
    IF-NEEDED facet executes some method only when it
    is needed (method acts like a demon).

32
Frame Based Systems
  • METHODS (2)
  • An IF-CHANGED method is written in order to
    change an objects property value, access
    database, etc. IF-CHANGED facet executes some
    method that performs some function in the event
    the property's value changes.
  • Methods designed to perform both operations can
    be inherited.

33
Example of Methods
Temperature sensors
Name
Unknown
Value
Unknown
Value If-Needed Method
Value If-Changed Method
Unknown
Critical Value
Get-Value (Self.Name)
IF Self.Value gt Self.Critical Value THEN
Self.Status Alert
Status If-Changed Method
Status
Unknown
IF Self.Status Alert THEN Sound-Alert
34
Frame Based Systems
  • COMMUNICATION BETWEENOBJECTS (1)
  • Interobject communication using facets
  • Using facet methods objects can communicate with
    one another. A change to only one property value
    may cause a series of changes in a number of
    objects (frame system is dynamic!). Objects can
    influence the property values in other objects,
    or even itself.

35
Frame Based Systems
  • COMMUNICATION BETWEENOBJECTS (2)
  • Message passing
  • Definition Message passing is a signal to an
    object to which the object responds by executing
    a method.
  • Sending messages involves using a function
  • (SEND message-name, object-name, arguments)
About PowerShow.com