Provides an interface for application programs interacting with a contact center simulator or evaluation system. The ContactCenters library can be used to create simulators modeling complex contact centers. These simulators may be accessed from other programs, e.g., for optimization or statistical analysis. Programs may also use analytical formulas to get approximations of some performance measures, for more efficiency or for comparing with simulation. This package defines an abstract interface permitting such programs to get their data in a standardized way. Package {@link umontreal.iro.lecuyer.contactcenters.msk} provides a generic simulator implementing this interface. The defined interface, {@link umontreal.iro.lecuyer.contactcenters.app.ContactCenterEval}, represents a system capable of performing evaluations for a contact center. We define an \emph{evaluation} as a process using user-specified parameters to estimate some performance measures with analytical formulas or simulation. The interface provides a standardized mechanism to run evaluations, and obtain estimates of performance measures. It also supports evaluation options, i.e., parameters that can be changed independently of the specific implementation. The {@link umontreal.iro.lecuyer.contactcenters.app.ContactCenterSim} extends the {@link umontreal.iro.lecuyer.contactcenters.app.ContactCenterEval} interface with methods for obtaining the variance, the minimum, the maximum, and computing confidence intervals. These statistics are available only when performing several replications of a simulation, or when dividing a simulation into batches. This package also provides an enumerated type, {@link umontreal.iro.lecuyer.contactcenters.app.PerformanceMeasureType}, that represents the type of a performance measure. An element of this enum can be used as a key to several methods in this package, or queried for information such as a name, the type of estimation, etc. Facilities are also provided to format matrices containing estimates of performance measures of a given type. This package also defines some commonly-used parameter objects for storing parameters for simulation experiments, and the values of thresholds for computing service levels.