特殊图标的含义（Protégé中）

一、The class hierarchy contains two types of icons: Solid yellow icons and yellow icons with three white lines through the middle, representing the equivalence symbol.

The icons containing the equivalence symbol (three white lines) denote classes thatare asserted to be equivalent to some other class expression.These are known as defined classes.

An example of a defined class(定义类的一个例子)

The solid yellow icons denote classes that are not defined classes (i.e.aren’t asserted to be equivalent to some other class expression). These classes are known asprimitive classes.

An example of a primitive class（原始类的一个例子）

二、Bolding（高亮）
本体中的公理是公认的事实（或推理规则），是用来知识推理的。
The class hierarchy view may show some names in a bold font and others in a regular font. Roughly speaking, classes whose names are shown in a bold font are described using axioms in the active ontology. This means that the class appears on the left hand side of a SubClassOf axiom, in an EquivalentClasses axiom, in a DisjointUnion axiom or in a DisjointClasses axiom. Classes whose names are shown in a regular weight font are merely referenced in the imports closure of the activeontology.

An example the bolding used in the class hierarchy. Class B is shown in bold because the active ontology contains axioms that describe it. Class A is not shown in bold because it is merely referenced by the active ontology (in the description of class B).

三、Cycles
Classes that appear in a cycle of SubClassOf axioms, for example A SubClassOf B, B SubClassOf C and C SubClassOf A will be collapsed and shown together, with one tree node for each class in the cycle so that each class may be selected. An example is shown below.

An example of a cycle in the class hierarchy. Classes in the cycle are displayed as equivalences, with a node for each class.

The reason for this notation is that a cycle in the class hierarchy between two or more classes states that the classes in the cycle are equivalent. This is because A EquivalentTo B is an abbreviation for the two axioms A SubClassOf B and B SubClassOf A.