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CHIP contributes to secure handling of Smart Cards, a SLIGOS Application ! GHOST (Gestion des Horaires des Services Téléphoniques) developed by Sligos, organizes the daily and weekly roster of operators at Carte Bleue VISA (smart card) Call Centers, who validate important purchases every minute of the year.
GHOST in action, at the Carte Bleue Call Centers of Sligos GHOST in action, at the Carte Bleue Call Centers of Sligos


Screens from the GHOST application
Screens from the application


New flexible working hours make staff assignment a very complex, time-consuming and recurring work for the manager. There are many kinds of constraints e.g. due to union laws, worker availability, or temporary over-loads. The system can handle temporary workers, part-timers as well as full-timers, for which the planning and tracking creates new problems for the manager.

GHOST provides daily forecasts of calls, hour by hour, based on several years' historical data and other calender information such as vacation dates of the various academic zones, holidays, as well as economic information on tendancies. Based on these work load forecasts and the availabilities of permanent staff, GHOST calculates the needs of complementary staff, while respecting the working regulations involved.

For over a year now, GHOST is used operationnally by managers at two Carte Bleue Call Centers at Vineuil and Beaubourg/Paris. Each system manages several dozens of operators. Plans are underway for installating this application in many other centers of the Groupe Sligos. Sligos expects a very strong growth in needs for Call Centers in France.


Developed by the Advanced Technology Development Center of Sligos, GHOST is based on UNIX

CHIP is used to implement the staff planning and assignment engine and the optimisation of the use of complementary staff. This is an example of CHIP application where both discrete and rational variables are used. An initial approximate solution is found using the CHIP's incremental rational solver, giving bounds on discrete variables. A second pass will calculate the best discrete solution with the lowest cost.

Other software used together with CHIP include:

  • D.O.M (Delphia Object Modeler) is used for the modeling and development of the overall system.
  • The Forecasting Module uses neural networks from Neuristique, to forecast work loads.

GHOST is the “living” proof that CHIP, the Constraint Programming Tool par excellence, can be integrated into mainstream object-oriented programming environment for analysis, design and development, together with avant-garde methods such as neural networks.

GHOST Application Architecture

  • Forecasting Module: Produces the work-load forecasts, based on historical data, for each hour of the day.
  • Time Base Module: Manages the working hours of the permanent staff, taking into account day-off, leave, etc, and produces the available workers for a given day.
  • Complementary Staff: Constructs the duty roster according to work regulations, and optimises the affectation of complementary workers for a given day, for a given list of available permanent workers and for a previsional work-load.
  • Quality Tracking: Keeps track of some quality factors. This module also calculates the size of teams to improve the factors.Other Modules and functionalities are planned, such as Batch Sizing and/or Long Term Planning, Taking into account different services and productivity differences among workers, Taking into account Overdue Work.

GHOST Application Architecture

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