此枚举定义了建筑内部或建筑外部的不同类型的空间边界。
IFC2.0中的增加的新枚举
IFC4更改枚举不再适用于IfcSpace。添加以下枚举数：外部土、外部水、外部火。
| Constant | Description |
|---|---|
| INTERNAL | The space boundary faces a physical or virtual element where there is an internal space on the other side. |
| EXTERNAL | The space boundary faces a physical or virtual element where there is an external space on the other side. |
| EXTERNAL_EARTH | The space boundary faces a physical or virtual element where there is earth (or terrain) on the other side. |
| EXTERNAL_WATER | The space boundary faces a physical or virtual element where there is water (water component of terrain) on the other side. |
| EXTERNAL_FIRE | The space boundary faces a physical or virtual element where there is another building on the other side. |
| NOTDEFINED | No information available. |