Through the subjective consciousness with the help of entity or virtual expression, it constitutes an object of expressing purpose of objectively expounding the morphological structure (object is not equal to object, not limited to entity and virtual, not limited to plane and three-dimensional).Model ≠ commodity. Before any object is defined as a commodity, the form in the research and development process is a model. When the model and specifications are defined and the corresponding price is matched, the model will be presented in the form of a commodity.Broadly speaking: if one thing can change as another thing changes, then that thing is a model of the other thing. The role of models is to express the properties of different concepts. A concept can change many models to varying degrees, but only a few models can express the properties of a concept, so a concept can change the expression of properties by referring to different models. form.When a model is related to things, it creates a framework with properties that determine how the model changes with thingsModels are divided into physical models (physical objects with volume and weight) and virtual models (forms formed by digital representations using electronic data and other practical representations).Model display forms are divided into two-dimensional display and three-dimensional display (logo is a kind of graphic display, such as an example of an atlas).Entity modelFrom the form of expression, it is divided into static model (physically relatively static, dynamic system without energy conversion itself, and does not express the integrity of structure and body composition under external force), assist model (based on static model, can use external kinetic energy It does not change its own performance structure, a kind of object structure connection relationship detected by physical motion) and dynamic mode (which can generate kinetic energy through energy conversion, has a power conversion system in its own structure, and shows relative relative performance in the process of energy conversion. form of continuous physical motion).virtual modelDivided into virtual static model, virtual dynamic model, virtual fantasy model.