Knowledge Representation Other Examples Volker Sorge Intro to AI: - PowerPoint PPT Presentation

Intro to AI: Lecture 5 Volker Sorge Background Object Oriented Representations Example: RDF Knowledge Representation Other Examples Volker Sorge

Intro to AI: Knowledge Representation Lecture 5 Volker Sorge Background Object Oriented Representations ◮ The problem of how to represent knowledge and Example: RDF Other Examples reasoning with it or about it. ◮ Obvious questions are: 1. What is knowledge? 2. What is a representation? 3. How do we reason? We are mainly interested in the first two questions here.

Intro to AI: Implicit vs. Explicit Lecture 5 Volker Sorge Background Object Oriented Representations Example: RDF ◮ Knowledge can be learned and implicitly represented. Other Examples ◮ Examples: Neural nets, evolutionary algorithms. ◮ Knowledge can be explicitly represented. ◮ Allows for human encoding, extension and inspection. ◮ We can learn something about the knowledge, explain behaviour etc.

Intro to AI: Types of Explicit Knowledge Representation Lecture 5 Volker Sorge Background Object Oriented Representations Example: RDF ◮ Logic representation Other Examples ◮ Knowledge is represented as logical sentences. ◮ Each sentence is self-contained ◮ But representation is flat ◮ Object Oriented representation ◮ Hiearchically structured and organised ◮ Sentences are grouped ◮ Translatable to logic

Intro to AI: Semantic Networks Lecture 5 Volker Sorge Background Object Oriented Representations ◮ Hierarchies of Classes similar to object oriented Example: RDF programming. Other Examples ◮ Classes are sets of entities. ◮ Classes have properties that can be inherited. ◮ Both classes and entities can have relations. ◮ Multiple inheritance is always conjunctive. Expresses simple sentences of Object – Predicate – Subject: ◮ A bird is a vertebrae. ◮ Paul is a brother and a father.

Intro to AI: Simple Semantic Networks Lecture 5 Volker Sorge Background ◮ Semantic Networks allow for simple subclass relations Object Oriented Representations (IsA links) and properties (HasA links). Example: RDF Other Examples Source: Wikipedia

Intro to AI: Complex Relations Lecture 5 Volker Sorge Background Object Oriented ◮ More complex models can incorporate more relations. Representations Example: RDF Source: http://www.jfsowa.com/pubs/semnet.htm Other Examples

Intro to AI: Problems Lecture 5 Volker Sorge Background Object Oriented Representations ◮ Inheritance can lead to incorrect knowledge. Example: RDF Other Examples ◮ Example: ◮ Bird has the property flight. ◮ Penguin inherits from bird. ◮ Multiple inheritance can aggravate this problem and lead to contradiction. ◮ Solution: Override inheritance, where sub-class values override super-class values.

Intro to AI: RDF Lecture 5 Volker Sorge Background Object Oriented Representations ◮ W3C resource description framework for semantic web Example: RDF Other Examples applications ◮ Basic idea is to enable a semantic description of information implemented as web resources ◮ Automatic identification of different web services ◮ Sharing of data across different resources ◮ Also enables easier retrieval of similar facts

Intro to AI: RDF: Basics Lecture 5 Volker Sorge Background ◮ Resources are given by URIs Object Oriented Representations ◮ Described in Object – Predicate – Subject relations Example: RDF ◮ This effectively defines a graph with directed edges for Other Examples relations ◮ Example: :Birmingham a :City :Birmingham :inCounty :WestMidlands :Birmingham :inCountry :UK :UK :inContinent :Europe All subjects and objects could be described with Maps URLs.

Intro to AI: RDF Example: Google recipe search Lecture 5 Volker Sorge ◮ Webmasters/Authors are encouraged to use semantic Background Object Oriented markup for recipes Representations ◮ Microdata or RDF format for ingredients, cooking time, Example: RDF etc. Other Examples ◮ This enables Google search for recipes with respect to ingredients only. ◮ https://developers.google.com/ structured-data/rich-snippets/recipes < span rel= "v:ingredient" > < span typeof= "v:Ingredient" > < span property= "v:name" > White sugar < /span > : < span property= "v:amount" > 3/4 cup < /span > < /span > < /span >

Intro to AI: Example: Wolfram Alpha Lecture 5 Volker Sorge Background Object Oriented Representations Example: RDF Other Examples ◮ http://www.wolframalpha.com ◮ (Mainly) scientific knowledge base. ◮ Scientific backend of Siri. ◮ http://www.wolframalpha.com/examples

Intro to AI: Example: Google Knowledge Graph Lecture 5 Volker Sorge Background Object Oriented Representations Example: RDF Other Examples ◮ http://www.google.co.uk/insidesearch/ features/search/knowledge.html ◮ (Now only available on the wayback machine!) ◮ Scientific and general knowledge base. ◮ Mined from Wikipedia and search.