The Underground War: Military Mining Operations in Support of the Attack on Vimy Ridge, 9 April 1917

This article aims briefly to describe the significance and evolution of military mining as a battlefield tactic during the Great War, with special reference to the role these underground operations played in the greatest success of Canadian arms—the capture of Vimy Ridge. No military historian’s visit to Vimy Ridge, this country’s most symbolic and emotion-laden battlefield, would be complete without a stop at the Grange Tunnel, an infantry subway dug during the winter and spring of 1916–1917 by the soldier-miners of the 172 Tunnelling Company, Royal Engineers. They were ably assisted by work parties from all four veteran battalions of 3rd Canadian Infantry Division’s 7th Brigade: The Black Watch (42 Battalion), The Royal Canadian Regiment, Princess Patricia’s Canadian Light Infantry and the Edmonton Regiment (49 Battalion). Tunnel guides explain how this cool, humid, subterranean passage, hurriedly burrowed into the compacted flint and chalk of an Artois hill, was part of a 13-tunnel underground labyrinth. It protected the assaulting infantry battalions of the Canadian Corps from the terrible and ever-present dangers of German bombardment as they made their final move from their reserve trenches in the rear, forward to their assembly trenches in the very front of the Canadian line

The Last Mile of The Way: Soul Music and the Civil Rights Movement

In the summer of 1960, a group of Soul performers was scheduled to perform at a segregated dance in Little Rock, Arkansas. Jesse Belvin, Jackie Wil-son and Arthur Prysock were to play two shows that evening—one for a black audience and a second show for a white audience. These segregated shows were essentially the norm in the majority of the country. However, that night, Jackie Wilson decided he was not going to perform the second show for a white audi-ence and encouraged the others to follow suit. They were all subsequently run out of town at gun point and somewhere outside of Little Rock, Belvin’s tires on his 59’ Cadillac blew and he lost control of the vehicle, resulting in the death of him and his wife. Arkansas investigators attributed the accident to “disgruntled white” audience members who slashed the tires of the Cadillac. Meanwhile at lo-cal Soul concerts the “K-9 dogs [were] patrolling the aisles to prevent race mixing or over demonstrativeness on part of the colored population” in Birmingham

The Computer Misuse Act 1990: lessons from its past and predictions for its future

The age of the internet has thrown down some real challenges to the Computer Misuse Act 1990. Recently, the Government made changes to this piece of legislation, in an attempt to meet two of those challenges--the proliferation of “ Denial of Service” (DoS) attacks, and the creation and dissemination of “ Hackers' tools” --and to fulfil international commitments on cybercrime. Yet some of these new measures invite criticisms of policy, form and content, and bring doubts about how easy to interpret, and how enforceable, they will be

Partial-order reduction for parity games with an application on parameterised Boolean Equation Systems (Technical Report)

Partial-order reduction (POR) is a well-established technique to combat the problem of state-space explosion. Most approaches in literature focus on Kripke structures or labelled transition systems and preserve a form of stutter/weak trace equivalence or weak bisimulation. Therefore, they are at best applicable when checking weak modal mucalculus. We propose to apply POR on parity games, which can encode the combination of a transition system and a temporal property. Our technique allows one to apply POR in the setting of mu-calculus model checking. We show with an example that the reduction achieved on parity games can be significantly larger. Furthermore, we identify and repair an issue where stubborn sets do not preserve stutter equivalence

Trace Spaces: an Efficient New Technique for State-Space Reduction

State-space reduction techniques, used primarily in model-checkers, all rely on the idea that some actions are independent, hence could be taken in any (respective) order while put in parallel, without changing the semantics. It is thus not necessary to consider all execution paths in the interleaving semantics of a concurrent program, but rather some equivalence classes. The purpose of this paper is to describe a new algorithm to compute such equivalence classes, and a representative per class, which is based on ideas originating in algebraic topology. We introduce a geometric semantics of concurrent languages, where programs are interpreted as directed topological spaces, and study its properties in order to devise an algorithm for computing dihomotopy classes of execution paths. In particular, our algorithm is able to compute a control-flow graph for concurrent programs, possibly containing loops, which is "as reduced as possible" in the sense that it generates traces modulo equivalence. A preliminary implementation was achieved, showing promising results towards efficient methods to analyze concurrent programs, with very promising results compared to partial-order reduction techniques