Description
Building a state of the art high energy physics detector like CMS
requires strict interoperability and coherency in the design and
construction of all sub-systems comprising the detector. This issue
is especially critical for the many database components that are
planned for storage of the various categories of data related to
the construction, operation, and maintainance of the detector like
event data, slow control data, conditions data, calibration data,
event meta data, etc ... . The data structures needed to operate the
detector as a whole need to be present in the database before the
data is entered. Changing these structures for a database system
that already contains a substantial amount of data is a very time
and labour consuming exercise that needs to be avoided. Cases where
the detector needs to be treated as a whole are detector operation
(control, error tracking, conditions) and the interfacing of there
construction and simulation software.
In this paper we propose to use the detector geometry as the
structure connecting the various elements. The design and
implementation of a relational database that captures the CMS
detector geometry and the detector components is discussed. The
detector geometry can serve as a core component in several other
databases in order to make them interoperable. It also provides a
common viewpoint between the physical detector and its image in the
reconstruction software. Some of the necessary extensions to the
detector description are discussed.
