Properties used for annotating classes (terms) in the NPO OWL file are listed below:

[rdfs:label] preferred name

[rdfs:comment] The property preferred name is used to indicate the preferred name of a class or a class-level association in the NPO.

[rdfs:label] definition

[rdfs:comment] The property definition is used to indicate the meaning or definition of a class or a class-level association in the NPO.

[rdfs:label] synonym

[rdfs:comment] The property synonym is used to indicate an alternate name of a class or a class-level association in the NPO.

[rdfs:label] dBXrefID

[rdfs:comment] The property dBXrefID is used to indicate the reference ID of a class from an external CV /  ontology / database.

[rdfs:label] code

[rdfs:comment] The property code is used to indicate a unique identification code for every class in the NPO.

[rdfs:comment] It begins with the prefix "NPO_" followed by a number (e.g., NPO_250). The smallest code value is NPO_100 of class Cylinder.