Permutation flowshop problems with initial availability constraints: characterisation and Analysis.

This paper characterises the initial availability constraint problems in a permutation flowshop layout considering different objectives: makespan, total flowtime and idle time. The goal is to analyse the structure of solutions and to discuss the managerial implications of these three problems. Also, we intend to compare the cases with availability constraint with their classical counterparts, i.e. these problems with machines available on the planning horizon. The analysis raises an important conclusion of practical application: Since for most real-life environments scheduling is performed on a periodical basis and this would naturally lead to the unavailability of machines at the starting of the scheduling period, this scheduling decision problem becomes easier than its classical‘ (i.e. without machine unavailability) counterpart.