Provides facilities for creating contact-by-contact traces in simulators. For debugging or computing custom statistics such as quantiles, obtaining a trace of every contact generated by a simulator can be useful. This package provides some classes to collect the relevant information about contacts, and store it into a file or database. The tracing facility is represented by an object implementing the interface {@link umontreal.iro.lecuyer.contactcenters.app.trace.ContactTrace}. Implementations of this interface are available for traces in text files, Excel spreadsheets, or any database for which a JDBC driver is available. The {@link umontreal.iro.lecuyer.contactcenters.app.trace.FileContactTrace} class provides a static convenience method for creating the call trace object from parameters read from an XML file. To use this facility, a simulator simply needs to create an instance of a class implementing \texttt{ContactTrace}, and call the \texttt{writeLine} method for every contact. Usually, this is done in an exited-contact listener.