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An IRI, or Internationalized Resource Identifier, is an extension to the URI specification to allow characters from Unicode, whereas URIs must be made up of a subset of ASCII characters. There is a mapping algorithm for translating between IRIs and the equivalent encoded URI form. IRIs are defined by rfc3987.


An item of interest that MAY be identified by an IRI.









Web Resource

A Resource that MUST be identified by an IRI, as described in the Web Architecture [webarch]. Web Resources MAY be dereferencable via their IRI.

External Resource

A Resource which is not part of the representation of the Annotation, such as a web page, a timeline, image, or video. External Resources are dereferencable from their IRI.


A feature of a Resource, that often has a particular data type. In the model sections, the term “Property” is used to refer to only those features which are not Relationships and instead have a literal value such as a string, integer or date. The valid values for a Property are thus any data type other than object, or an array containing members of that data type if more than one is allowed.


In the model sections, the term “Relationship” is used to distinguish those features that refer to other Resources, either by reference to the Resource’s IRI or by including a description of the Resource in the Annotation’s representation. The valid values for a Relationship are: a quoted string containing an IRI, an object that has the “id” property, or an array containing either of these if more than one is allowed.


Resources may be divided, conceptually, into groups called “classes”; members of a class are known as Instances of the class. Resources are associated with a particular class through typing. Classes are identified by IRIs, i.e., they are also Web Resources themselves.


A special Relationship that associates an Instance of a class to the Class it belongs to.


An element of a group of Resources represented by a particular Class.