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The basic components of OWL are classes, properties, individuals and the relationships between them. Classes are the basic building blocks of an OWL ontology arranged in a taxonomic hierarchy. For example Patients and Diseases are 2 good candidates for a top level class in a dermatology ontology. Properties can be categorized as object properties, which relate individuals to other individuals and datatype properties, which relate individuals to datatype values, such as integers, floats, and strings. A property can have a domain and range associated with it. There are various special types of properties such as functional, inverse functional, symmetric and transitive. A functional property can take only one value while two different individuals cannot have the same value in an inverse functional property. If a symmetric property links A to B, then one can infer that it links B to A. If a property links A to B and B to C, then if one can infer that it links A to C, that property is transitive. Individuals are instances of classes; properties can relate one individual to another. Various restrictions can be applied to classes and properties. Cardinality restrictions specify the number of relationships in which a class of individuals can participate. Existential restriction specifies the existence of at least one relationship along a given property to an individual that is a member of a specific class. To restrict the relationship for a given property to individuals that are members of a specific class, a universal restriction must be used. Detailed information about the OWL syntax is available from the W3C website . Ò²Ðí»áÓÐÓÃ~

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º¯ÊýÊôÐÔ(Functional Property)¡ª¡ªÍ¨¹ýÕâ¸öÊôÐÔÖ»ÄÜÁ¬½ÓÒ»¸ö¸öÌå¡£hasBirthMother ·´º¯ÊýÊôÐÔ(Inverse Functional Property)¡ª¡ª¼´Õâ¸öÊôÐԵķ´ÊôÐÔÊǺ¯ÊýÊôÐÔ£¬Ò²¾ÍÊǶÔÓÚÒ»¸ö¸ø¶¨µÄ¸öÌ壬ֻÓÐ×î¶àÒ»¸ö¸öÌåÄÜͨ¹ý¸ÃÊôÐÔÁ¬½ÓÄǸö¸öÌå¡£isBirthMotherOf ´«µÝÊôÐÔ(Transitive Property)¡ª¡ªhasAncestor ¶Ô³ÆÊôÐÔ(Symmetric Property)¡ª¡ªhasSibling,Èç¹ûÒ»¸öÊôÐÔÊǶԳƵÄÄÇôËü¾Í²»ÄÜÊǺ¯ÊýÊôÐÔ¡£ £¨Protege-OWL½Ì³Ì±Ê¼Ç£©

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E9: Create inverse properties Create a new object property called isIngredientOf Press ¡°Set inverse property¡± button, Select ¡°hasIngredient¡± Then the inverse relation has been set up. Select hasBase Create the isBaseOf as the inverse property of hasBase isBaseOf is the subproperty of isIngredientOf, why? Select hasTopping create isToppingOf as the inverse property. isToppingOf is the subproperty of isIngredientOf, why? Functional Properties If a property is functional, for a given individual, there can only be at most one individual to be related via this property. For a given domain, range must be unique Functional properties are also known as single valued properties. Inverse Functional Properties If a property is inverse functional, then its inverse property is functional. For a given range, domain must be unique. Functional vs. inverse functional properties FunctionalProperty vs InverseFunctionalProperty hasID: A hasID B, C hasID B A=C For a given range Domain is unique InverseFunctionalProperty hasFather: A hasFather B, A hasFather C B=C Range is unique For a given domain Functional Property example range domain Transitive Properties If a property is transitive, and the property related individual a to individual b, and also individual b to individual c, then we can infer that individual a is related to individual c via property P. Symmetric Properties If a property P is symmetric, and the property relates individual a to individual b, then individual b is also related to individual a via property P. E10: Make the hasIngredient property transitive Select the hasIngredient property Tick the transitive tick box Select the isIngredientOf property, make sure that the transitive tick box is ticked. E11: Make the hasBase property functional Select the hasBase property Tick the ¡°functional¡± tick box OWL-DL does not allow datatype properties to be transitive, symmetric or have inverse properties. Property domains and ranges Properties link individuals from the domain to individuals from the range. OWL uses domain and range as axioms in reasoning. ¿ÉÄܲ»´óÃ÷Îú£¬ÏêÇé²é¿´http://edogdu.etu.edu.tr/course/bil546/lectures/ProtegeTutorial.ppt Ï£ÍûÄÜÓÐËù°ïÖú^_^

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