Hi,
These groups describe the inheritance relationship between classes. They can be used while inspecting a DXF list.
For example, the DXF list of an attribute reference:
((-1 . <Nom d 'entité: 7ffffb06a50>)
(0 . "ATTRIB")
(330 . <Nom d 'entité: 7ffffb06a40>)
(5 . "1E45")
(100 . "AcDbEntity")
(67 . 0)
(410 . "Model")
(8 . "0")
(62 . 0)
(6 . "ByBlock")
(370 . -2)
(100 . "AcDbText")
(10 129.005 313.129 0.0)
(40 . 2.5)
(1 . "test")
(50 . 0.0)
(41 . 1.0)
(51 . 0.0)
(7 . "Arial_std")
(71 . 0)
(72 . 4)
(11 131.819 314.331 0.0)
(210 0.0 0.0 1.0)
(100 . "AcDbAttribute")
(280 . 0)
(2 . "ATT1")
(70 . 8)
(73 . 0)
(74 . 0)
(280 . 1)
)
The AcDbAttribute class inherits from the AcDbText class which inherits from the AcDbEntity class (which inherits form AcDbObject).
Before the (100 . "AcDbEntity") are the common properties for all AcDbOject instances.
Between (100 . "AcDbEntity") and (100 . "AcDbText") are the AcDbEntiy specific properties which are common to all entities (all AcDbObject aren't entities i.e. layer, BlockTable, dictionaries...)
Between (100 . "AcDbText") and (100 . "AcDbAttribute") are the AcDbText specific properties (attribute definitions and attribute references, for example, inherit from AcDbText)
After (100 . "AcDbAttribute") are the attribute specific properties.