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PRODID:-//University of Liverpool Computer Science Seminar System//v2//EN
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DTSTAMP:20260416T202429Z
UID:Seminar-verification-1177@lxserverM.csc.liv.ac.uk
ORGANIZER:CN=Patrick Totzke:MAILTO:totzke@liverpool.ac.uk
DTSTART:20230626T100000
DTEND:20230626T110000
SUMMARY:Verification Series
DESCRIPTION:Isa Vialard: Measuring well quasi-orders\n\nWell-structured transition systems (WSTS) are tansition \nsystems whose set of configurations is a well-quasi order (WQO) and \nwhose transitions respect this order. Therefore, complexity of problems\non WSTSs can often be linked to the measures of the underlying wqo, \ncalled the ordinal invariants.\n\nThe ordinal invariants, i.e.,  maximal order type, height, and width, \nare measures of a wqo based on the ordinal rank of the trees of its bad\nsequences, strictly decreasing sequences, and antichain sequences, \nrespectively. Complex wqos are often built from simpler wqos through \nbasic constructions such as disjoint sum, direct sum, cartesian\nproduct, and higher-order constructions like powerset or sequences. One\nmain challenge is to compute the ordinal invariants of such wqos \ncompositionally.\n\nThis talk will focus on the width of the cartesian product.\n\nhttps://www.csc.liv.ac.uk/research/seminars/abstract.php?id=1177
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