Nepomuk Information Element (NIE): Tracker Ontology Reference Manual

Nepomuk Information Element (NIE)

Nepomuk Information Element (NIE) — Top classes in the ontology. Almost everything else is subclass of these.

Synopsis

@prefix nie: <http://tracker.api.gnome.org/ontology/v3/nie#>

Classes

DataObject, DataSource, InformationElement

Overview

Introduction

The core of the NEPOMUK Information Element Ontology and the entire Ontology Framework revolves around the concepts of DataObject and InformationElement. They express the representation and content of a piece of data. Their specialized subclasses (defined in the other ontologies) can be used to classify a wide array of desktop resources and express them in RDF.

nie:DataObject class represents a bunch of bytes somewhere (local or remote), the physical entity that contain data. The meaning (interpretation) of that entity, the information for the user contained in those bytes (e.g. a music file, a picture) is represented on the nie:InformationElement side of the ontology.

Both sides are linked using the property nie:interpretedAs (and its reverse nie:isStoredAs), indicating the correspondence between the physical element and its interpretation. There is also a property to link nie:InformationElements, representing the logical containment between them (like a picture and its album).

Common properties

Given that the classes defined in this ontology are the superclasses for almost everything in the Nepomuk set of ontologies, the properties defined here will be inherited for a lot of classes. It is worth to comment few of them with special relevance:

nie:title	Title or name or short text describing the item
nie:description	More verbose comment about the element
nie:language	To specify the language of the item.
nie:plainTextContent	Just the raw content of the file, if it makes sense as text.
nie:generator	Software/Agent that set/produced the information.
nie:usageCounter	Count number of accesses to the information. It can be an indicator of relevance for advanced searches

Dates and timestamps representations

There are few important dates for the life-cycle of a resource. These dates are properties of the nie:InformationElement class, and inherited for its subclasses:

nie:informationElementDate	This is an ''abstract'' property that act as superproperty of the other dates. Don't use it directly.
nie:contentLastModified	Modification time of a resource. Usually the mtime of a local file, or information from the server for online resources.
nie:contentCreated	Creation time of the content. If the contents is created by an application, the same application should set the value of this property. Note that this property can be undefined for resources in the filesystem because the creation time is not available in the most common filesystem formats.
nie:contentAccessed	For resources coming from the filesystem, this is the usual access time to the file. For other kind of resources (online or virtual), the application accessing it should update its value.
nie:lastRefreshed	.

URIs and full representation of a file

One of the most common resources in a desktop is a file. Given the split between Data Objects and Information Elements, some times it is not clear how a real file is represented into Nepomuk. Here are some indications:

Every file (local or remote) should generate one DataObject instance and an InformationElement instance.
Even when Data Objects and Information Elements are completely different things, for efficiency reasons in Tracker we use the same URI for both of them.
The URI will be an autogenerated ID, and the real location of the item (e.g. ''file://path/to/file.mp3'') is a property of the Data Object
Every DataObject must have the property nie:url, that points to the location of the resource, and should be used by any program that wants to access it.
There is a deprecated property in the ontology: nie:isStoredAs . We discourage its use in the code: in the best case it is a loopback to the nie:url value, but in general it can contain any value or not be set at all.

Here comes an example, for the image file /home/user/a.jpeg:

<urn:uuid:10293801928301293> a nmm:Photo, nfo:FileDataObject ;
	# Properties as nmm:Photo
	 nfo:width 49 ;
	 nfo:height 36 ;
	nmm:flash <nmm:flash-off>;
	nmm:whiteBalance <nmm:white-balance-automatic> ;
	nfo:equipment [ a nfo:Equipment ; nfo:make 'Nokia'; nfo:model 'N900'; nfo:equipmentSoftware 'Tracknon' ] ;

	# Properties from nfo:FileDataObject
	nfo:fileSize 12341234 ;

	# Mandatory for any nfo:DataObject
	nie:url <file:///home/ivan/test/CC-test-big.png> .

Related information

This explanation is just a brief extract from the original Nepomuk NIE Ontology web page.

Class Details

DataObject

Description

A unit of data that is created, annotated and processed on the user desktop. It represents a native structure the user works with. The usage of the term 'native' is important. It means that a DataObject can be directly mapped to a data structure maintained by a native application. This may be a file, a set of files or a part of a file. The granularity depends on the user. This class is not intended to be instantiated by itself. Use more specific subclasses.

Class hierarchy

    rdfs:Resource 
        nie:DataObject

Properties

Name	Type	Description
`byteSize`	integer	File size in bytes
`created`	dateTime	Date of creation of the DataObject. Note that this date refers to the creation of the DataObject itself (i.e. the physical representation). Compare with nie:contentCreated
`dataSource`	DataSource	Marks the provenance of a DataObject, what source does a data object come from
`interpretedAs`	InformationElement	Links the DataObject with the InformationElement it is interpreted as
`isPartOf`	InformationElement	Generic property used to express containment relationships between DataObjects. NIE extensions are encouraged to provide more specific subproperties of this one. It is advisable for actual instances of DataObjects to use those specific subproperties. Note to the developers: Please be aware of the distinction between containment relation and provenance. The isPartOf relation models physical containment, a nie:DataObject (e.g. an nfo:Attachment) is a 'physical' part of an nie:InformationElement (a nmo:Message). Also, please note the difference between physical containment (isPartOf) and logical containment (isLogicalPartOf) the former has more strict meaning. They may occur independently of each other
`lastRefreshed`	dateTime	Date when information about this data object was retrieved (for the first time) or last refreshed from the data source. This property is important for metadata extraction applications that don't receive any notifications of changes in the data source and have to poll it regularly. This may lead to information becoming out of date. In these cases this property may be used to determine the age of data, which is an important element of it's dependability
`url`	string	URL pointing at the location of the resource. In cases where creating a simple file:// or http:// URL for a file is difficult (e.g. for files inside compressed archives) the applications are encouraged to use conventions defined by Apache Commons VFS Project at http://jakarta.apache.org/ commons/ vfs/ filesystems.html.

DataSource

Description

A superclass for all entities from which DataObjects can be extracted. Each entity represents a native application or some other system that manages information that may be of interest to the user of the Semantic Desktop. Subclasses may include FileSystems, Mailboxes, Calendars, websites etc. The exact choice of subclasses and their properties is considered application-specific. Each data extraction application is supposed to provide it's own DataSource ontology. Such an ontology should contain supported data source types coupled with properties necessary for the application to gain access to the data sources. (paths, urls, passwords etc...)

Class hierarchy

    rdfs:Resource 
        nie:DataSource

InformationElement

Description

A unit of content the user works with. This is a superclass for all interpretations of a DataObject.

Class hierarchy

    rdfs:Resource 
        nie:InformationElement

Properties

Name	Type	Description
`characterSet`	string	Characterset in which the content of the InformationElement was created. Example: ISO-8859-1, UTF-8. One of the registered character sets at http://www.iana.org/assignments/character-sets. This characterSet is used to interpret any textual parts of the content. If more than one characterSet is used within one data object, use more specific properties
`comment`	string	A user comment about an InformationElement
`contentAccessed`	dateTime
`contentCreated`	dateTime	The date of the content creation. This may not necessarily be equal to the date when the DataObject (i.e. the physical representation) itself was created. Compare with nie:created property
`contentLastModified`	dateTime	The date of the last modification of the original content (not its corresponding DataObject or local copy). Compare with nie:lastModified
`contentSize`	integer	The size of the content. This property can be used whenever the size of the content of an InformationElement differs from the size of the DataObject. (e.g. because of compression, encoding, encryption or any other representation issues). The contentSize in expressed in bytes
`copyright`	string	Content copyright
`depends`	DataObject	Dependency relation. A piece of content depends on another piece of data in order to be properly understood/used/interpreted
`description`	string	A textual description of the resource. This property may be used for any metadata fields that provide some meta-information or comment about a resource in the form of a passage of text. This property is not to be confused with nie:plainTextContent. Use more specific subproperties wherever possible
`disclaimer`	string	A disclaimer
`generator`	string	Software used to 'generate' the contents. E.g. a word processor name
`hasLogicalPart`	InformationElement	Generic property used to express 'logical' containment relationships between InformationElements. NIE extensions are encouraged to provide more specific subproperties of this one. It is advisable for actual instances of InformationElement to use those specific subproperties. Note the difference between 'physical' containment (hasPart) and logical containment (hasLogicalPart)
`hasPart`	DataObject	Generic property used to express 'physical' containment relationships between DataObjects. NIE extensions are encouraged to provide more specific subproperties of this one. It is advisable for actual instances of DataObjects to use those specific subproperties. Note to the developers: Please be aware of the distinction between containment relation and provenance. The hasPart relation models physical containment, an InformationElement (a nmo:Message) can have a 'physical' part (an nfo:Attachment). Also, please note the difference between physical containment (hasPart) and logical containment (hasLogicalPart) the former has more strict meaning. They may occur independently of each other
`identifier`	string	An unambiguous reference to the InformationElement within a given context. Recommended best practice is to identify the resource by means of a string conforming to a formal identification system
`informationElementDate`	dateTime	A point or period of time associated with an event in the lifecycle of an Information Element. A common superproperty for all date-related properties of InformationElements in the NIE Framework
`isLogicalPartOf`	InformationElement	Generic property used to express 'logical' containment relationships between DataObjects. NIE extensions are encouraged to provide more specific subproperties of this one. It is advisable for actual instances of InformationElement to use those specific subproperties. Note the difference between 'physical' containment (isPartOf) and logical containment (isLogicalPartOf)
`isStoredAs`	DataObject	Links the information element with the DataObject it is stored in
`keyword`	string	Adapted DublinCore: The topic of the content of the resource, as keyword. No sentences here. Recommended best practice is to select a value from a controlled vocabulary or formal classification scheme
`language`	string	Language the InformationElement is expressed in. Users are encouraged to use the two-letter code specified in the RFC 3066
`legal`	string	A common superproperty for all properties that point at legal information about an Information Element
`license`	string	Terms and intellectual property rights licensing conditions.
`licenseType`	string	The type of the license. Possible values for this field may include 'GPL', 'BSD', 'Creative Commons' etc.
`links`	DataObject	A linking relation. A piece of content links/mentions a piece of data
`mimeType`	string	File Mime Type
`plainTextContent`	string	Plain-text representation of the content of a InformationElement with all markup removed. The main purpose of this property is full-text indexing and search. Its exact content is considered application-specific. The user can make no assumptions about what is and what is not contained within. Applications should use more specific properties wherever possible.
`relatedTo`	DataObject	A common superproperty for all relations between a piece of content and other pieces of data (which may be interpreted as other pieces of content).
`rootElementOf`	DataSource	DataObjects extracted from a single data source are organized into a containment tree. This property links the root of that tree with the datasource it has been extracted from
`subject`	string	The subject or topic of the document
`title`	string	The title of the document
`usageCounter`	integer
`version`	string	The current version of the given data object. Exact semantics is unspecified at this level. Use more specific subproperties if needed

Credits and Copyright

Authors:

Ludger van Elst, DFKI, <elst@dfki.uni-kl.de>
Michael Sintek, DFKI, <michael.sintek@dfki.de>
Leo Sauermann, DFKI, <leo.sauermann@dfki.de>
Antoni Mylka, DFKI, <antoni.mylka@dfki.de>

Editors:

Antoni Mylka, DFKI, <antoni.mylka@dfki.de>

Contributors:

Christiaan Fluit, Aduna, <christiaan.fluit@aduna-software.com>
Evgeny 'phreedom' Egorochkin, KDE Strigi Developer, <stexx@mail.ru>

Upstream:

Upstream version

ChangeLog:

Tracker changes