an object repersents an entity, either physical, conceptual or software
an object has state
an object has behavior
an object has identity
basic principles of object orientation:
abstraction
encapsulation(封装)
modularity(模块化)
hierarchy(等级制)
an object is represented as a rectangle with an underlined name
just like this
a class is represented using a rectangle with three compartments:
the class name
the structure(attributes)
the behavior(operations)
attributes
operations:
polymorphism(多态)
generalization
package:
organize elements into groups
diagram depiction
规格说明：
元素的特征和语义的文本描述
修饰：
建模元素暴露的信息项以表现某个要点
公共分类：
类元：classifier 和 实例
扩展机制：
约束：形式：{约束条件}
构造型（stereotypes）：基于已有的建模元素引入新的建模元素
标记值：形式：{属性名=值}
构架（architecture）
