In this paper we study a large query log of more than twenty million queries with the goal of extracting the semantic relations that are implicitly captured in the actions of users submitting queries and clicking answers. Previous query log analyses were mostly done with just the queries and not the actions that followed after them. We first propose a novel… (More)
Finding near(est) neighbors is a classic, difficult problem in data management and retrieval, with applications in text and image search,in finding similar objects and matching patterns. Here we study <i>cluster pruning</i>, an extremely simple randomized technique. During preprocessing we randomly choose a subset of data points to be <i>leaders</i> the… (More)
We investigate synchronized hyperedge replacement (SHR) as general framework for distributed programming and system design. We propose a slender version of SHR which dramaticaly reduces the mathematical overhead of the original proposal  and use it to interpret the distributed CCS  and the calculus of Mobile Ambients  in a uniform semantic… (More)
We present a case study where Synchronising Graphs, a system of parallel graph transformation, are used to solve the syntactic unification problem for first order rational terms (with possibly infinite unifier). The solution we offer is efficient, that is quasi-linear, and simple: a program of 28 characters.
Synchronising Graphs is a system of parallel graph transformation designed for modeling process interaction in a network environment. Although notions of observational equivalence are abundant in the literature for process calculi, not so for graph rewriting, where system behaviour is typically context dependent. We propose a theory of context-free… (More)
(versione 4) We introduce the Synchronised Hyperedge Environment, SHE, a tool for developing, analysing and automatically verifying distributed and concurrent systems. SHE supports a visual, declarative style of programming based on a graph rewrite system called Synchronising Graphs (SG) [3, 4], a general semantical framework which has been used for… (More)