The following is merely a re-formatted version of the comments in the AGDD (Atlas Generic Detector Description) dtd.

Identifiers

Identifiers provide for a generalized identification scheme of positioned volumes in the detector. Identifier are specified as member elements attached to any position operator.

Generally, an identifier is composed of a set of numbers such as

/1/3/4/5/1/34

The meaning of each field is conventional and reflects the local hierarchy of volumes.

The identifier elements permit to freely specify which field(s) will be affected by the positioning operation. When single positioning is used, a single value of one or several fields will be affected by the operation. When a multiple positioning operation is considered, one or several fields will be iteratively affected. In this case, it is possible to follow the iteration by specifying a first value and a step used to compute iterated field values.

Attributes

field

a symbolic name characterizing the affected field. Legal names should be conventionally specified. Currently three symbols have been introduced :

layer

(typically R in barrels and Z in end-caps)

ring

(typically Z in barrels and R in end-caps)

sector

(typically Phi)

value

the exact value to be entered in single positioning or the first value in multiple positiong.

step

only used in multi-positioning.