Classical methods are based on mathematical programming
and can solve this problem when the complexity is low. And
there are some heuristics and meta-heuristics that are able to
provide good schedules for more complex problems [9]. The
traditional scheduling and control systems propose hierarchical
and centralized architectures, where a classical scheduler
system that has a global model of the multi-project
environment makes schedules according to the current state of
the system. Hans et al. [4] review existing literature in
hierarchical approaches and propose a generic project planning
and control framework for helping management to choose
between planning methods, depending on organisational issues.
But these techniques are not flexible or robust enough, and
have difficulties to consider many real factors. In addition, real
environments undergo frequent changes (new resources, new
technologies) that force to modify the scheduling system. The
traditional scheduling and control systems, which are based on
hierarchical and centralized architectures, have not enough
flexibility to adapt themselves to the dynamism and complexity
of multi-project environments.
These issues have motivated, in last years, successive
proposals are appearing to improve the scheduling and control
in a multi-project environment. The paradigm of Multi-agent
Systems (MAS) can help to find solutions, especially in cases
where some social behaviour emerges. This paper shows an
agent-based approach for online dynamic scheduling and
control in multi-project environments that takes advantage of
the ability of agents to negotiate and adapt to changing
conditions. The MAS has basically two types of agents:
projects managers and resources managers.
Projects have scheduled work to be done by different
resources. Resources are endowed with some capabilities
(knowledge, work force, etc.) that are needed to do the work.
Projects demand resources over time and resources offer their
capabilities and time availability. There is an auction process,
and the price of resource-time slots emerges endogenously as a
result of supply and demand. The design of the auction process
uses a technique that has been proposed for distributed
scheduling in the literature [8], [14], [11].
This agent-based approach has two distinctive aspects with
respect to other works: the integration of strategic decisions(accept or reject new projects) and operative aspects (resource
allocation), and the ability to manage resource flexibility. This
allows mangers to study the advisability of increasing the
flexibility of resources.
The next section introduces the role of agent-based
modeling and simulation in project scheduling. Section 3
presents the MAS for the real-time scheduling problem, which
has been specified with an agent-oriented modeling language,
INGENIAS [10]. This has been the basis for implementing a
simulation, which is described in section 4, and whose results
are discussed in section 5. Finally, section 6 presents main
conclusions of using this agent-based modeling and simulation
approach.