User:Peak/CRM

The CIDOC Conceptual Reference Model is intended to be "open", that is, additional classes and properties may be defined in accordance with certain principles (e.g. strict inheritance). This is one of the strong points of this particular ontology.

Background
Classes are arranged in a conventional superclass-subclass hierarchy. There is a single root class, which is called CRM Entity. With the exception of this class, every class has one or more 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 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".

Unfortunately, the numbering scheme does not reflect structure.

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 quite a few classes for time periods (historical eras, etc) and events (transfer of custody, etc), but I won't cover that in detail here, except to point out that 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.

Actor E39
An Actor is a superclass of both 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 Actor Appellation (E82).

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 Type.

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

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

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 Design or Procedure E31 Document E33 Linguistic Object E36 Visual Item E37 Mark E38 Image Examples:
 * Beethoven's Ode to Joy (an instance of Information Object)
 * The 2004-2005 XYZZY Annual Report (an instance of Document)

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:).

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.