A data model named DTO(Data and Tool Object) is offered to characterize a design object which is identified by four aspects: ObjectClass-id, Method, Versionand Facet.

• 它采用一个数据模型（称为DTO模型）刻划设计对象，由四个基本参量（设计对象类，设计方法，历史版本，等价视图）唯一确定。