The NSCL event builder is a two stage pipeline. The first stage of the pipeline puts event fragments from an arbitrary number of event sources into a total time order. A mechanism exists to allow analysis applications to look at these fragments directly. The second stage of the pipeline assembles fragments that lie within some specified coincidence window into events.
This chapter describes:
The philososphy of the event orderer
How to start up the event orderer using the standard start script
How to write an event orderer startup script
The set of packages available to scripts that interact with the event orderer.
In addition to this chapter, please see the reference information in the part 1evb. That part of the reference material provides detailed information about the event builder Tcl package.
The event orderer was designed to support user written extensions and user interfaces. Support for this was in the specification from the start. One reason is the wide variety of possible meanings that can be attributed to exceptional conditions like data late, or mixed and incomplete barriers.
The orderer accomplishes this by wrapping it's C/C++ core with a Tcl/Tk interface. Furthermore some standard Tk components are provided along with a Tcl application program interface that allowws you to intervene at key points in the event orderer's execution.
If you think of the event orderer as a set of Tcl commands that encpasulate the C/C++ core you'll have a good picture of the final structure.