Submissions:Literal Reification

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{{Content OP Proposal Template
{{Content OP Proposal Template
|SubmittedBy=AldoGangemi, SilvioPeroni, FabioVitali
|Name=Literal Reification
|Name=Literal Reification
|Intent=The goal of this pattern is to allow the reification of literal values within OWL.
|Intent=The goal of this pattern is to allow the reification of literal values within OWL.

Revision as of 16:24, 10 August 2010

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Current revision ID: 9814

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General description

Name: Literal Reification
Submitted by: AldoGangemi, SilvioPeroni, FabioVitali
Also Known As:
Intent: The goal of this pattern is to allow the reification of literal values within OWL.


Competency Questions:
  • What is the context in which entities refer to a particular literal value?
  • What are the meanings of a particular value considering the context in which it is used?
Solution description: Literals are reified in proper ontological individual (belonging to the class 'Literal'), expressing the literal value they refer to through a data property. This reification allows to use each 'reified literal' as subject or object of assertions.
Reusable OWL Building Block: (650)
Scenarios: A Delicious user adds the tag 'Paris' to the wiki article about Joyce's Ulysses, that represents the city in which the novel was published the very first time. Another Delicious user adds the same tag to the article about Paris Hilton, where here 'Paris' stands for a first name of a person.
Known Uses:
Web References:
Other References:
Examples (OWL files):
Extracted From:
Reengineered From:
Has Components:
Specialization Of:
Related CPs:


The Literal Reification Content OP locally defines the following ontology elements:

Literal page
hasSameLiteralValueAs page
hasLiteral page
isLiteralOf page
hasLiteralValue page

Additional information

From a Web 2.0 point of view, a tag is a non-hierarchical keyword (e.g., a string) assigned to a piece of information, such as a web document. A particular tag can have more than one meaning according to the context in which it is specified. Let us consider the following two article from Wikipedia:


The tag 'Paris' can be added to both articles, of course, but it brings with itself two different meanings, even though it is exactly the same string that has been used. In the above example, we want to say that 'Paris' is a first name of the person document 2) is about (i.e., Paris Hilton), while in document 1) 'Paris' is the name of the city in which the subject of the document (the novel 'Ulysses' by James Joyce) was published the very first time.

Using the reified literal pattern, we can express tags as proper individuals of the class 'Literal' (or of a specific subclass of it, such as 'Tag'), connecting them when refer to the same literal value. Writing the previous example down in a Turtle format, we could have:

<> a foaf:Document
	; prism:keyword :parisTag1 .
<> a foaf:Document
	; prism:keyword :parisTag2 .
:parisTag1 a litre:Literal
	; litre:hasLiteralValue "Paris"
	; a [ a skos:Concept
			; skos:definition "the name associated to a particular city"@en ] .
:parisTag2 a litre:Literal
	; litre:hasSameLiteralValueAs :parisTag1
	; a [ a skos:Concept
			; skos:definition "the first name of a person"@en ] .


Scenarios about Literal Reification
  • Used frequently in the Web 2.0, descriptive tags such as the ones used in folksonomies are keywords (e.g., strings) assigned to a particular resource, such as a web document, with the intent to describe it. Just like words in any natural language, tags may have different meanings depending on the context in which they are used. For instance, the word “Paris” may be either a name of a city or a first name of a person. Here, it is clear that the act of tagging with “Paris” both the Wikipedia pages about the Eiffel Tower and the one about Paris Hilton hides two different intents: in the former case, “Paris” denotes the city in which the tower stands; in the latter case, “Paris” denotes a particular person, i.e., Paris Hilton. Using the literal reification pattern it is possible to express descriptive tags as first class objects in OWL, by considering them as proper individuals of the class litre:Literal. Different individuals may thus represent different meanings even if their literal values are identical. >>>
  • NameHistory3.0 is a (fictional) institution that keeps track of all the names of people, and stores them as an ABox of the FOAF ontology. In particular, each person is stored as an individual of the class foaf:Person with a specific first name (data property foaf:givenName) and family name (data property foaf:familyName). On 24/09/2010, Bruce Wayne formally applied for changing his first name to Jack. Since NameHistory3.0 has to keep track of everything concerning names of people, on that date “Jack” was added as Mr. Wayne's first name. It was then that NameHistory3.0 noticed that, without any additional information, it is not possible to know which of the two first names are legally valid at any given point in time. A solution to that scenario, which avoids any modification of the ontology model and consequently of the entire triple store (operation that is obviously time-consuming and error-prone), is to use the literal reification pattern in combination with the new expressivity for punning in OWL 2. Through them, it is possible to define a literal individual as also belonging to the class foaf:givenName – that is actually defined as a data property, but may be additionally be meta-modelled as a class. We can now associate a particular time interval to each literal, so as to represent when the literal itself, i.e., the given name, is legally valid. >>>


Reviews about Literal Reification
Review article Posted on About revision (current is 9814)
OlafNoppens about Literal Reification 245545616 September 2010 1006210,062
MariCarmenSuarezFigueroa about Literal Reification 245545717 September 2010 1011010,110
EnricoMotta about Literal Reification 245545919 September 2010 1011010,110

This revision (revision ID 9814) takes in account the reviews: none

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Modeling issues

Modeling issues about Literal Reification

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