From QED

The CIDOC Conceptual Reference Model defines an open ontology, that is, additional classes and properties may be defined in accordance with certain principles (e.g. strict inheritance).

For example, MPEG-7 is regarded as a compatible extension — see Combining the CIDOC CRM and MPEG-7 to Describe Multimedia in Museums.

QED defines the CRM classes as categories in the Category: namespace using exactly the same names, e.g. Category:CRM Entity corresponds to the root class.

QED also has extensions to support the Dublin Core Metadata Element Set, including categories for the defined values of Category:Type.

A graphical representation of key classes in the class hierarchy with Dublin Core extensions may be found here. The QED source for this graph can easily be modified to produce similar graphs emphasizing a different set of classes.

QED currently uses Version 4.2 of the CIDOC/CRM.

Contents 1 Principles 1.1 Classification 2 Overview 3 Some Classes of Interest 3.1 Category:Actor E39 3.2 Category:Collection E78 3.3 Category:Information Carrier E84 3.4 Category:Conceptual Object E28 3.5 Category:Information Object E73 3.6 Category:Type E55 3.7 Category:Event E5

Principles

Classes are arranged in a conventional superclass-subclass hierarchy. For CRM objects, there is a single root class, which is called CRM Entity and which corresponds to the QED category: Category:CRM Entity. With the exception of this class, and a similar class for primitives, every CRM class has one or more CRM superclasses. Most predefined classes have only one predefined superclass, and most subclasses of a class are mutually disjoint.

The classes are numbered, e.g.

• E5 (entity number 5) is Category:Event.

Properties are also numbered:

• P52 is the property "has current owner", as in:

  E18 Physical Thing - has current owner - E39 Actor.

Every named property has a named inverse, e.g. the inverse of P52 is "is current owner of".

The numbering scheme does not reflect structure.

Classification

QED pages should be classified in the lowest level applicable class, including any QED-specific extensions.

No QED page should be included in an abstract category.

Overview

One of the main distinctions is between physical objects (e.g. my copy of the 2005 XYZZY Annual Report) and their abstractions ("The 2005 XYZYY Annual Report")

Another important distinction is between objects, object identifiers, and appellations.

The CRM has several classes for time periods (historical eras, etc) and events (transfer of custody, etc).

Many relationships ("X destroyed Y") are defined in terms of an Event object, rather than as attributes of X or Y. This is partly because most such events can occur more than once, e.g.

"An earthquake destroyed Lisbon in 1531"

"An earthquake destroyed Lisbon in 1755"

The main reason is that many events have a variety of attributes worthy of being catalogued.

Some Classes of Interest

Category:Actor E39

An Actor is a superclass of both Category:Person and Group and corresponds closely to the concept of an agent.

"Individual people should be documented as instances of Person, whereas groups should be documented as instances of either Group or its subclass Legal Body."

An Actor is identified by an Category:Actor Appellation (E82).

Category:Collection E78

A Collection is an aggregation of physical items that are assembled and maintained (curated, preserved) over a period of time by an identifiable Actor.

Other types of aggregations would be defined in terms of E55 Type.

Category:Information Carrier E84

An Information Carrier is a physical man-made object that was made with the purpose of carrying the information of an Information Object (E73).

Examples:

• the physical object known as the Rosetta Stone
• a book, i.e. the physical thing that can be placed on a bookshelf

Category:Conceptual Object E28

A Conceptual Object is a Man-Made Thing considered in the abstract, e.g. a specific novel, a musical composition, an algorithm, or a specific legal right held by a particular Actor, e.g.

• The copyright held by XYZZY over the 2005 XYZZY Annual Report

Category:Information Object E73

An Information Object is a Conceptual Object that is recognized and documented as a single entity. Its predefined subclasses and some of their subclasses are:

  E29 Category:Design or Procedure
  E31 Category:Document
  E33 Category:Linguistic Object
  E36 Category:Visual Item
  E37 Category:Mark
  E38 Category:Image
  

Examples:

• Beethoven's Ode to Joy (an instance of E73 Information Object)
• The 2004-2005 XYZZY Annual Report (an instance of E31 Document)

Category:Type E55

An instance of Type is a class, that is, it defines a set of entities.

For example, Language E56 (the class of natural languages) is a subclass of Type, and thus includes Xhosa (xh:), Yakut (sah:) and Zuni (zun:).

Category:Event E5

An Event is an occurrence that took place during a definite (if unspecified or unknown) interval of time. The Yalta Conference is regarded as an Event, even though it can be decomposed into a sequence of constituent events.

Activity (E7) is a subclass of Event and corresponds to events such as Acquisition, Transfer of Custody, and Attribute Assignment.