muto logo

Modular Unified Tagging Ontology (MUTO)

Specification of MUTO Core - 16 November 2011


Namespace URI:
http://purl.org/muto/core#
Latest version:
Version 1.0 - (RDF/XML, HTML)
Last update:
2011-11-16
Author:
Steffen Lohmann

Abstract

The Modular Unified Tagging Ontology (MUTO) is an ontology for tagging and folksonomies. It is based on a thorough review of earlier tagging ontologies and unifies core concepts in one consistent schema. It supports different forms of tagging, such as common, semantic, group, private, and automatic tagging, and is easily extensible.


Table of Contents

  1. General Characteristics
  2. Basic Design Decisions
  3. Definitions and Axioms
  4. Unified Tagging Ontologies
  5. Diagram
  6. Example
  7. Modules
  8. Classes
  9. Properties
  10. Acknowledgments
  11. References

General Characteristics [back to top]


Basic Design Decisions [back to top]


Definitions and Axioms [back to top]

Key terms related to tagging and folksonomies are defined at http://www.socialtagging.org.

There are some fundamental principles of tagging and folksonomies that must not be violated. These principles have been considered in the design of the MUTO core vocabulary and are expressed in the following axioms:

Tag axioms:

Tagging axioms:


Unified Tagging Ontologies [back to top]

MUTO is based on a review of the following tagging ontologies:

Name Release
(latest update)
Main purpose Newly introduced concepts OWL sublanguage RDF/XML URI reference
(local copy of reviewed version)
Tag Ontology 2005-03-23
(2005-12-21)
First formal tagging ontology Fundamental concepts and structure, restricted tagging OWL Full http://www.holygoat.co.uk/owl/redwood/0.1/tags/
(MUTO mirror)
Tagging Ontology 2006
(2007-01-15)
Comprehensive domain description Tagging source and note, private and group tagging OWL Full http://bubb.ghb.fh-furtwangen.de/TagOnt/tagont.owl (missing)
(author copy) (MUTO mirror)
Ontology of Folksonomy 2007
(—)
Comprehensive domain description Aggregated tag, tag position, polarity, and type OWL DL http://www.eslomas.com/tagontology-1.owl
(MUTO mirror)
Social Semantic Cloud of Tags 2007-03-23
(2008-06-13) 
TAGS extension for tag clouds Tag clouds, frequencies, coccurrences, and spelling variants OWL Full http://scot-project.org/scot/ns# (missing)
(MUTO mirror)
Meaning of a Tag  2008-01-15
(—) 
TAGS extension for semantic tagging Tag meaning, automatic tagging  OWL Full http://moat-project.org/ns#
(MUTO mirror)
Upper Tag Ontology 2008
(—) 
Upper ontology Voting via tags  OWL Lite
(OWL Full)
http://info.slis.indiana.edu/~dingying/uto.owl
(MUTO mirror) (aligned version)
Common Tag 2009-06-08
(—) 
Minimal ontology (optimized for RDFa) Author vs. reader tags  OWL Full http://commontag.org/ns#
(MUTO mirror) (CTAG mappings / MUTO mirror)
TAGora Tagging Ontology  2009
(2010)
Automatic tag sense disambiguation -- OWL Lite http://tagora.ecs.soton.ac.uk/schemas/tagging
(MUTO mirror)
NiceTag Ontology 2009-01-09
(2010-09-09)
Taggings as speech acts (intention of tags) Named graphs, tag intensions OWL Full http://ns.inria.fr/nicetag/2010/09/09/voc
(MUTO mirror)
Modular Unified Tagging Ontology 2011-09-02
(2011-11-16)
Unification, modularization -- OWL Lite http://purl.org/muto/core#

Note that only the main concepts of these tagging ontologies are included in the MUTO core vocabulary. Further concepts can be integrated as extensions (e.g. in the form of MUTO modules).


Diagram [back to top]

The following diagram shows the main concepts of the MUTO core vocabulary. A more complete UML diagram is available at http://purl.org/muto/core/muto-UML.png

compact muto diagram


Example [back to top]

The following diagram illustrates a private tagging from the tagging system example.org. User alice tagged a photo showing her friend Bob. She first entered the tag "madrid" and later added the tag "sol" as a subtag of "madrid". She gave the tag "sol" an explicit meaning by referencing the DBpedia description of "Puerta del Sol".

The tagging system automatically recognized Alice's friend Bob on the photo and added his name as a tag. It also linked the tag to his user account at the social networking website example.com. Alice decided to share this private tagging with Bob and granted him access.

compact muto diagram

Here is the RDF/Turtle representation of the described example (also available in RDF/XML).

@prefix muto: <http://purl.org/muto/core#> .
@prefix sioc: <http://rdfs.org/sioc/ns#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
<http://example.org/tagging/tagging1> a <http://purl.org/muto/core#PrivateTagging>;
    muto:taggedResource <http://example.com/photos/photo1>;
    muto:hasCreator <http://example.org/user/alice>;
    muto:hasTag <http://example.org/tag/tag1>,
        <http://example.org/tag/tag2>,
        <http://example.org/tag/tag3>;
    muto:taggingCreated "2011-11-11T11:11:11Z";
    muto:taggingModified "2011-11-12T09:43:03Z";
    muto:grantAccess <http://example.org/user/bob>;
    sioc:has_container <http://example.org/tagging/taggings>;
    sioc:note "Photo showing Bob in downtown Madrid." .
<http://example.org/tag/tag1> a <http://purl.org/muto/core#Tag>;
    muto:tagLabel "madrid" ;
    muto:nextTag <http://example.org/tag/tag2>.
<http://example.org/tag/tag2> a <http://purl.org/muto/core#Tag>;
    muto:tagLabel "sol";
    muto:tagCreated "2011-11-12T09:43:03Z";
    muto:tagMeaning <http://dbpedia.org/resource/Puerta_del_Sol>;
    skos:broader <http://example.org/tag/tag1> .
<http://example.org/tag/tag3> a <http://purl.org/muto/core#AutoTag>;
    muto:tagLabel "bob";
    muto:autoMeaning <http://example.org/user/bob> .
<http://example.org/tagging/taggings> a <http://rdfs.org/sioc/ns#Container>;
    sioc:has_space <http://example.org> .

Modules [back to top]

The MUTO core vocabulary can be extended by modules that describe specific parts of tagging and folksonomies in more detail (e.g. tag categories, resource types, etc.) or provide alignments to related vocabularies. There is only one mappings module at the moment, but more modules are planned for the future. Feel free to contribute with your module.

MUTO Mappings Module

This module provides mappings between the MUTO core vocabulary and other tagging ontologies (Version 0.1 is limited to alignments with TAGS).

Namespace URI:
http://purl.org/muto/mappings#
Latest version:
Version 0.1
Last update:
2011-11-16
Author:
Steffen Lohmann

Classes (4) [back to top]

The MUTO core vocabulary introduces the following four classes. See the formal RDF/XML specification for more details.

Automatic Tag | Private Tagging | Tag | Tagging


Automatic Tag [back to top]

URI:
http://purl.org/muto/core#AutoTag
Subclass of:
muto:Tag
Description:
An automatic tag is a tag that is automatically associated with a resource (e.g. by a tagging system), i.e. it is not entered by a human being.

Private Tagging [back to top]

URI:
http://purl.org/muto/core#PrivateTagging
Subclass of:
muto:Tagging
Description:
A private tagging is a tagging that is only visible to its creator (unless the creator has not granted access to others via muto:grantAccess). Every tagging that is not an instance of muto:PrivateTagging is public by default.

Tag [back to top]

URI:
http://purl.org/muto/core#Tag
Subclass of:
skos:Concept
Description:
A Tag consists of an arbitrary text label. Note that tags with the same label are NOT merged in the ontology.

Tagging [back to top]

URI:
http://purl.org/muto/core#Tagging
Subclass of:
sioc:Item
Description:
A tagging links a resource to a user account and one or more tags.

Properties (17) [back to top]

automatic tag meaning | creator of | grant access | has access | has creator | has tag | meaning of | next tag | previous tag | tag created | tag label | tag meaning | tag of | tagged resource | tagged with | tagging created | tagging modified


automatic tag meaning (object property) [back to top]

URI:
http://purl.org/muto/core#autoMeaning
Domain:
muto:Tag
Subproperty of:
muto:tagMeaning
Description:
This subproperty indicates that the meaning of a tag has been automatically defined (e.g. by a tagging system), i.e. it has not been defined by a human being. The default case is disambiguation by users via muto:tagMeaning.

creator of (object property) [back to top]

URI:
http://purl.org/muto/core#creatorOf
Domain:
sioc:UserAccount
Range:
muto:Tagging
Subproperty of:
sioc:creator_of
Inverse of:
muto:hasCreator
Description:
A user account can have a (theoretically unlimited) number of taggings. Use sioc:member_of to define groups for group tagging or link to foaf:Agent, foaf:Person, or foaf:Group via sioc:account_of.

grant access (object property) [back to top]

URI:
http://purl.org/muto/core#grantAccess
Domain:
muto:Tagging
Description:
A (usually private) tagging can be linked to one or more user accounts or user groups that should have access to it (apart from the creator). This property can also be used in public tagging to link a user account or user group to a tagging (e.g. if the creator of a tagging wants to suggest the tagging to another user).

has access (object property) [back to top]

URI:
http://purl.org/muto/core#hasAccess
Range:
muto:Tagging
Inverse of:
muto:grantAccess
Description:
A user account or user group can have access to a private tagging from another user if the access is explicitly permitted by the creator of the tagging. This property can also be used in public tagging to link a user account or user group to a tagging (e.g. if the creator of a tagging has suggested the tagging to another user).

has creator (functional property) [back to top]

URI:
http://purl.org/muto/core#hasCreator
Domain:
muto:Tagging
Range:
sioc:UserAccount
Subproperty of:
sioc:has_creator
Description:
Every tagging is linked to at most one user account. This property can be omitted for automatic taggings. In contrast to its superproperty sioc:has_creator, it is functional and with an explicit domain. Use sioc:member_of to define groups for group tagging or link to foaf:Agent, foaf:Person, or foaf:Group via sioc:account_of.

has tag (object property) [back to top]

URI:
http://purl.org/muto/core#hasTag
Domain:
muto:Tagging
Range:
muto:Tag
Description:
A tagging consists of a (theoretically unlimited) number of tags. A tagging may also consist of no tags, e.g. if the system allows its users to mark a resource first and add tags later.

meaning of (object property) [back to top]

URI:
http://purl.org/muto/core#meaningOf
Range:
muto:Tag
Inverse of:
muto:tagMeaning
Description:
The number of tags that can be linked to one and the same meaning is theoretically unlimited.

next tag (functional property) [back to top]

URI:
http://purl.org/muto/core#nextTag
Domain:
muto:Tag
Range:
muto:Tag
Description:
This property indicates the tag that follows next in the list of tags. It can be used to describe the order in which the tags have been entered by the user.

privious tag (functional property) [back to top]

URI:
http://purl.org/muto/core#previousTag
Domain:
muto:Tag
Range:
muto:Tag
Inverse of:
muto:nextTag
Description:
This property indicates the tag that is preceding in the list of tags. It can be used to describe the order in which the tags have been entered by the user.

tag created (functional property) [back to top]

URI:
http://purl.org/muto/core#tagCreated
Domain:
muto:Tag
Range:
xsd:dateTime
Subproperty of:
dcterms:created
Description:
The creation date and time of a tag. This property can be omitted if muto:taggingCreated = muto:tagCreated (i.e. in the common case that a tag has been created along with a tagging, not in a later edit of the tagging). The datatype of this property is xsd:dateTime (in contrast to it superproperty dcterms:created which has range rdfs:Literal).

tag label (functional property) [back to top]

URI:
http://purl.org/muto/core#tagLabel
Domain:
muto:Tag
Range:
rdfs:Literal
Description:
Every tag has exactly one label (usually the one given by the user) - otherwise it is not a tag. Additional labels can be defined in the resource that is linked via muto:tagMeaning.

tag meaning (object property) [back to top]

URI:
http://purl.org/muto/core#tagMeaning
Domain:
muto:Tag
Description:
The meaning of a tag can be expressed by a link to a well-defined resource. This can be any resource that clarifies the meaning of the tag (e.g. some DBpedia resource).

tag of (functional property) [back to top]

URI:
http://purl.org/muto/core#tagOf
Domain:
muto:Tag
Range:
muto:Tagging
Inverse of:
muto:hasTag
Description:
Every tag is linked to exactly one tagging. This results from the fact that tags with same labels are NOT merged in the ontology.

tagged resource (functional property) [back to top]

URI:
http://purl.org/muto/core#taggedResource
Domain:
muto:Tagging
Subproperty of:
sioc:about
Description:
Every tagging is linked to exactly one resource. This can be any kind of resource (i.e. all subclasses of rdfs:Resource), including tags and taggings.

tagged with (object property) [back to top]

URI:
http://purl.org/muto/core#taggedWith
Range:
muto:Tagging
Inverse of:
muto:taggedResource
Description:
A resource can have several taggings from different users. Tags are never directly linked to resources but can be inferred from the taggings.

tagging created (functional property) [back to top]

URI:
http://purl.org/muto/core#taggingCreated
Domain:
muto:Tagging
Range:
xsd:dateTime
Subproperty of:
dcterms:created
Description:
Every tagging has exactly one creation date and time. The datatype of this property is xsd:dateTime (in contrast to its superproperty dcterms:created which has range rdfs:Literal).

tagging modified (datatype property) [back to top]

URI:
http://purl.org/muto/core#taggingModified
Domain:
muto:Tagging
Range:
xsd:dateTime
Subproperty of:
dcterms:modified
Description:
A tagging can have multiple modification dates, as the number of times a tagging can be edited (e.g. to add or remove tags) is theoretically unlimited. The datatype of this property is xsd:dateTime (in contrast to it superproperty dcterms:created which has range rdfs:Literal).

Acknowledgments [back to top]

This work has been conducted in the context of the UrThey project funded by the Spanish Ministry of Science and Innovation (TIN2009-09687).


References [back to top]

Lohmann, S., Díaz, P., Aedo, I.: MUTO: The Modular Unified Tagging Ontology. Proceedings of the 7th International Conference on Semantic Systems (I-SEMANTICS 2011), pp. 95-104. ACM, New York, NY, USA, 2011. [DOI] [BibTex]


Creative Commons License
DEI logo