===== Before the Lab =====
Read:
  * [[http://www.cs.uu.nl/docs/vakken/smw/lectures/Reasoning%20on%20the%20Web.pdf|Reasoning on the Web]]
  * [[http://www.inf.unibz.it/~debruijn/teaching/swt/lecture-6-handouts.pdf|OWL vs. RDF, DL, DL rules, DLP]]
  * {{:pl:dydaktyka:piw:2010:sw:rulesonthesw-2009-tutorial2.pdf|Rules on the Semantic Web}}

Reasoning on the Web - summary:
  * queries
    * SPARQL (see [[.:rdf2|RDF lab]])
  * DL reasoning
    * more powerful than querying, DL reasoning tasks
    * example reasoner: http://clarkparsia.com/pellet/, demo: http://pellet.owldl.com/owlsight/ 
  * rules over ontologies 
    * [[http://ruleml.org/|RuleML]], [[http://www.w3.org/2005/rules/wiki/RIF_Working_Group|RIF]] - rule interchange formats
    * [[http://www.w3.org/Submission/SWRL/|SWRL]] Semantic Web Rule Language based on OWL 
  * [[http://www.w3.org/TR/owl2-profiles/#OWL_2_RL|OWL 2 RL]] - new version of OWL, additional constructs for expressing rules in the ontology

===== Lab instruction =====

==== DL Reasoning ====
  * Analyze the [[http://owl.man.ac.uk/2003/why/latest/|reasoning examples in OWL DL]]
  * Use the [[http://www.co-ode.org/downloads/pizzafinder/|Manchester Pizza Finder]] to see the results of implementing your ontology from the [[.:owl|previous lab]]
  * Browse sample ontologies with [[http://pellet.owldl.com/owlsight/|OwlSight]] (using Pellet as a DL reasoner)
    * Find all inconsistencies of the example ontologies.
    * Read the explanations of the inconsistencies - how could one repair the ontologies?



==== SWRL ====
In this exercise we will use Protege editor with the [[http://protege.cim3.net/cgi-bin/wiki.pl?SWRLTab|SWRLTab plugin]].

Depending on the configurations, Pellet/Jess may be used to execute SWRL rules.
=== Family rules ===
  - Read {{:prv:tasks:newsemweblabs:reasoning:swrl2009protegeconference.pdf|about SWRLTab in Protege}}
  - Download [[http://swrl.stanford.edu/ontologies/examples/family.swrl.owl|family ontology with rules]]. 
  - Open it in Protege (run ''protege3''), in SWRLTab analyze the rules. Click on **J** button to enable Jess rule engine. Run the rules iteratively. Check the inferred axioms.

=== Implementing SWRL ===
  - Open Protege editor and enable SWRL Tab (Project->Configure in Protege 3.4.4)
  - Implement an example [[https://ai.ia.agh.edu.pl/wiki/_media/pl:prolog:prolog_lab:animal_kb.pl?id=pl%3Aprolog%3Aprolog_lab%3Aprolog_lab_metaprog&cache=cache|expert system]] - an expert system for recognizing animals:
    - define Classes used in the system (look for ''isa'' predicate): Mammal, Bird, Carnivore, etc.
    - define characteristics of the animals (There Is More Than One Way To Do It!)
      * as Properties, e.g.: has
      * as Classes, e.g. Swims
    - Make assertions about individuals, e.g. has(dennis,hair). parent(dennis,diana). Swims(denzel).
    - Define rules of the system 
    - Express the initial data as appropriate assertions
    - Run Pellet/Jess to execute the rules. Observe the inferred facts. Execute the rule engine iteratively, till no more information can be concluded.
    -**extra task**: add more rules to the system, use built-in SWRL predicates.

===Examples===
<code>
rule id1: 
  [1: has(X,hair)]
  ==>
  [assert(isa(X,mammal)),
   retract(all)].
</code>
has(?x,"hair") -> Mammal(?x)

<code>
rule id4: 
  [1: flies(X),
   2: lays_eggs(X)]
  ==>
  [assert(isa(X,bird)),
   retract(all)].
</code>
Flies(?x) ∧ Lays_eggs(?x) -> Bird(?x)

===Initial data===
<code>
initial_data([
	has(dennis,hair),
	has(dennis,hoofs),
	has(dennis,black_stripes),
	parent(dennis,diana)
	]).
</code>

==== Rules in OWL2RL ====
Read: [[http://www.semantic-web-book.org/page/KI_2009_Tutorial|OWL 2 and Rules]] slides

Control questions:
  * How to express rules using ''owl:subClass'' relationships?
  * what is a property chain axiom?


  - Run Protege, version 4: ''protege4''
  - Create a new ontology in Protege
  - Model the family ontology with rules using OWL 2 constructs ([[http://www.semantic-web-book.org/page/ESWC09_Tutorial|See OWL2 tutorials]])
  - **extra task**: if there is enough time, model the animals expert system in OWL 2 RL

===== If you want to know more =====
Further reading:
  * [[http://www.debruijn.net/publications/deri-tr-2006-06-03.pdf|Logics for the Semantic Web]] - FOL, DL, LP & F-logic
Test cases for OWL2 (incl.OWL2RL):
  * http://www.w3.org/2007/OWL/wiki/Test_Suite_Status


===== Komentarze =====

Z braku lepszego miejsca tutaj studenci wpisują komentarze natury ogólnej do tego lab. 8-)

Za dużo materiału do przerobienia. Gdy wybiła godzina końca zajęć, ja dotarłem do Family Rules (podpunkt 3), czytając wcześniej jedynie Reasoning Examples in OWL DL (co zajęło ponad 45 minut).