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Dominic Hughes

Publications and source records attributed to Dominic Hughes.

11 recordsLinked to original sources
arXiv2021

Combinatorial Proofs and Decomposition Theorems for First-order Logic

We uncover a close relationship between combinatorial and syntactic proofs for first-order logic (without equality). Whereas syntactic proofs are formalized in a deductive proof system based on inference rules, a combinatorial proof is a syntax-free presentation of a proof that is independent from any set of inference rules. We show that the two proof representations are related via a deep inference decomposition theorem that establishes a new kind of normal form for syntactic proofs. This yields (a) a simple proof of soundness and completeness for first-order combinatorial proofs, and (b) a full completeness theorem: every combinatorial proof is the image of a syntactic proof.

cs.LO↗
arXiv2021

Federated Evaluation and Tuning for On-Device Personalization: System Design & Applications

We describe the design of our federated task processing system. Originally, the system was created to support two specific federated tasks: evaluation and tuning of on-device ML systems, primarily for the purpose of personalizing these systems. In recent years, support for an additional federated task has been added: federated learning (FL) of deep neural networks. To our knowledge, only one other system has been described in literature that supports FL at scale. We include comparisons to that system to help discuss design decisions and attached trade-offs. Finally, we describe two specific large scale personalization use cases in detail to showcase the applicability of federated tuning to on-device personalization and to highlight application specific solutions.

cs.LG↗
arXiv2016

MALL proof nets identify proofs modulo rule commutation

We show that the proof nets introduced in [Hughes & van Glabbeek 2003, 2005] for MALL (Multiplicative Additive Linear Logic, without units) identify cut-free proofs modulo rule commutation: two cut-free proofs translate to the same proof net if and only if one can be obtained from the other by a succession of rule commutations. This result holds with and without the mix rule, and we extend it with cut.

cs.LO↗
arXiv2012

Simple free star-autonomous categories and full coherence

This paper gives a simple presentation of the free star-autonomous category over a category, based on Eilenberg-Kelly-MacLane graphs and Trimble rewiring, yielding a full coherence theorem: the commutativity of diagrams of canonical maps is decidable.

math.CT↗
arXiv2010

A minimal classical sequent calculus free of structural rules

Gentzen's classical sequent calculus LK has explicit structural rules for contraction and weakening. They can be absorbed (in a right-sided formulation) by replacing the axiom P,(not P) by Gamma,P,(not P) for any context Gamma, and replacing the original disjunction rule with Gamma,A,B implies Gamma,(A or B). This paper presents a classical sequent calculus which is also free of contraction and weakening, but more symmetrically: both contraction and weakening are absorbed into conjunction, leaving the axiom rule intact. It uses a blended conjunction rule, combining the standard context-sharing and context-splitting rules: Gamma,Delta,A and Gamma,Sigma,B implies Gamma,Delta,Sigma,(A and B). We refer to this system M as minimal sequent calculus. We prove a minimality theorem for the propositional fragment Mp: any propositional sequent calculus S (within a standard class of right-sided calculi) is complete if and only if S contains Mp (that is, each rule of Mp is derivable in S). Thus one can view M as a minimal complete core of Gentzen's LK.

math.LO↗
arXiv2008

Hypergames and full completeness for system F (rough draft)

This paper reviews the fully complete hypergames model of system $F$, presented a decade ago in the author's thesis. Instantiating type variables is modelled by allowing ``games as moves''. The uniformity of a quantified type variable $\forall X$ is modelled by copycat expansion: $X$ represents an unknown game, a kind of black box, so all the player can do is copy moves between a positive occurrence and a negative occurrence of $X$. This presentation is based on slides for a talk entitled ``Hypergame semantics: ten years later'' given at `Games for Logic and Programming Languages', Seattle, August 2006.

math.LO↗
arXiv2006

Proofs Without Syntax

"[M]athematicians care no more for logic than logicians for mathematics." Augustus de Morgan, 1868. Proofs are traditionally syntactic, inductively generated objects. This paper presents an abstract mathematical formulation of propositional calculus (propositional logic) in which proofs are combinatorial (graph-theoretic), rather than syntactic. It defines a *combinatorial proof* of a proposition P as a graph homomorphism h : C -> G(P), where G(P) is a graph associated with P and C is a coloured graph. The main theorem is soundness and completeness: P is true iff there exists a combinatorial proof h : C -> G(P).

math.LO↗
arXiv2005

Simple multiplicative proof nets with units

This paper presents a simple notion of proof net for multiplicative linear logic with units. Cut elimination is direct and strongly normalising, in contrast to previous approaches which resorted to moving jumps (attachments) of par units during normalisation. Composition in the resulting category of proof nets is simply path composition: all of the dynamics happens in GoI(Setp), the geometry-of-interaction construction applied to the category of sets and partial functions.

math.LO↗
arXiv2005

Logic Without Syntax

This paper presents an abstract, mathematical formulation of classical propositional logic. It proceeds layer by layer: (1) abstract, syntax-free propositions; (2) abstract, syntax-free contraction-weakening proofs; (3) distribution; (4) axioms (p OR NOT p). Abstract propositions correspond to objects of the category G(Rel^L) where G is the Hyland-Tan double glueing construction, Rel is the standard category of sets and relations, and L is a set of literals. Abstract proofs are morphisms of a tight orthogonality subcategory of Gl(Rel^L), where we define Gl as a lax variant of G. We prove that the free binary product-sum category (contraction-weakening logic) over L is a full subcategory of Gl(Rel^L), and the free distributive lattice category (contraction-weakening-distribution logic) is a full subcategory of Gl(Rel^L). We explore general constructions for adding axioms, which are not Rel-specific or (p OR NOT p)-specific.

math.LO↗
arXiv2005

Classical Logic = Fibred MLL

This paper represents classical propositional proofs as *combinatorial proofs*, which are more abstract than proof nets: superposition (contraction/weakening) is modelled mathematically, as a lax form of fibration, rather than syntactically (as in proof nets, which involve contraction and weakening nodes). A combinatorial proof is a `fibred' multiplicative linear proof net, hence the slogan in the title. Cut elimination retains its richness from sequent calculus: its non-determinism does not collapse to become confluent. [Note: this is merely a 2-page synopsis, accepted for a short presentation at Logic in Computer Science '05.]

math.LO↗