System-defined Properties

ApertureDB defines a set of properties known as system-defined properties. These properties are either used in object definitions or computed internally by the system. To distinguish them from user-defined properties, all system-defined properties start with "_" prefix. Some properties are present in all objects (e.g., _uniqueid), while others are specific to certain object types (e.g., _label for BoundingBox, Polygons, or Descriptors). System-defined properties cannot be updated by users, except in cases where the Update command explicitly supports modification through defined parameters. However, these properties can be used as keys in constraints.

Here we detail the set of properties for each Object:

Object	Properties	Type	Param for Update Command	Can Be Used in constraints	Notes
All Objects	_uniqueid	string		Y	Unique id for the object
	_create_txn	number		Y	Transaction id that created the object
Connection	_src	string		N	unique_id of the src of the connection
	_dst	string		N	unique_id of the dst of the connection
DescriptorSet	_name	string		Y	Name of the set
	_dimensions	number		Y	Dimensionality of the Descriptors
	_engines	array		N	List of engines available for KNN
	_metrics	array		N	List of metrics available for KNN
	_count	number		Y	Number of Descriptors in the Set
	_segment_size	number		Y	Number of Descriptors on each segment
	_max_segments	number		Y	Maximum number of segments
	_splits	object		N	Number of splits
Descriptor	_label	string	label	Y
	_set_name	string		Y	Name of the set the Descriptor belongs to
BoundingBox	_label	string	label	Y
	_coordinates	rect	rectangle	N
	_area	number		Y	Area (in pixels) of the BoundingBox
Polygon	_label	string	label	Y
	_vertices	poly	polygons	N
	_area	number		Y	Area (in pixels) of the Polygon
	_bounds	rect		N	The smallest rectangle containing the Polygon
Video	_fps	number		Y	Average frames per second
	_frame_count	number		Y	Number of frames in the video
	_frame_width	number		Y	Width of the frame
	_frame_height	number		Y	Height of the frame
Frame	_label	string	label	Y
	_frame_number	number	frame_number	Y
	_time_offset	string	time_offset	Y
	_time_fraction	number	time_fraction	Y
Clip	_label	string	label	Y
	_range_type	number		Y	Type describing what type of range (time,frame,pct)
	_range_start	number		Y	Start of Clip range
	_range_stop	number		Y	End of Clip range

NOTE: Only properties having 'Param for Update Command' are modifiable by the user.

NOTE: Only the "==" and "in" operators are supported for "_uniqueid".