LIRa session: Declan Thompson

Speaker: Declan Thompson

Date and Time: Thursday, February 13th 2020, 16:30-18:00

Venue: ILLC Seminar Room F1.15, Science Park 107.

Title: Local Fact Change, Memory Logic and Expressive Power


Local fact change logic (LFC) models the notion of a unilateral change in a network structure. It adds a single, innocent-looking model change operator to the basic modal logic, allowing the valuation at a single point in the model to change. This small addition results in undecidability, which can quickly be shown via a satisfaction-preserving translation from memory logic (ML). The lack of a direct translation raises the question of the relative expressive power of LFC and ML.

In this talk, I will investigate the relative expressive power of LFC and ML. Such comparisons are often made by either providing a direct translation from one logic to the other, or demonstrating a pair of models which one of the logics can distinguish and the other cannot. In the case of LFC and ML, these two approaches come apart. We are left with a somewhat messy picture of how the two compare.