- Description : The Open SCheduling Architecture -
An Opportunistic Job-Shop Scheduling System
- Client : Hitachi Ltd
- Problem: Hitachi receive a large number of requests for
factory scheduling systems. This in itself makes scheduling an
important problem to the company, more so given the potential cost
saving involved if good scheduling solutions can be achieved. Most
current commercial scheduling systems which apply an essentially
simple dispatch-rule approach have various limitations most
significantly in terms of their ability to satisfy multiple,
potentially conflicting objectives, such as meeting order due dates
and restricting the overall work in process.
- Solution: A variant of the
O-Plan - Open Planning
Architecture approach was used - The Open SCheduling Architecrure (TOSCA).
TOSCA addresses the factory scheduling problem
from a constraint-based perspective. Constraints are monitored in
terms of potential threats to their satisfaction and are
opportunistically tackled through a process which iteratively refines
the schedule by restricting the resourcing and start time options.
- Main Features: TOSCA provides
- a pre-schedule analysis which serves to provide an
understanding of the feasibility of the problem in terms of its
- a high-level schedule which allocates factory operations to a
single resource and a restricted time period taking preferences into
account. This output can be treated as a full schedule which leaves
responsibility for detailed scheduling (i.e. choosing the specific
start time for operations) under human control.
- a detailed schedule which allocates factory operations to a
single resource and specific start time.
- Technical Details: TOSCA has been implemented in Common
Lisp and CLOS.
- Development Effort: The total combined effort for the
project is 5 man years over a period of 2.5 years.
TOSCA papers available through the Web
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