In calculi for modelling communication protocols, internal and external choices play dual roles. Two external choices can be viewed naturally as dual too, as they represent an agreement between the communicating parties. If the interaction fails, the past agreements are good candidates as points where to roll back, in order to take a different agreement. We propose a variant of contracts with s...

Abstract This paper by reviewing the main examples of small to medium-scale retractable roof structures covering building courtyards is to present an innovative rigid retractable roof system employing spatial frames for a courtyard of an existing building in Tabriz Islamic Art University. The courtyard is currently used for temporary exhibitions and gatherings whenever permitted by environmenta...

Retractable type fall arresters are very effective personal equipment protecting against falls from a height. These devices are used under different atmospheric conditions and in the presence of various types of industrial pollution. For this reason appropriate locking after conditioning simulating extreme conditions of a worksite is one of the essential characteristics of retractable type fall...

j This paper presents a new concept for retractable roof structures. The new structures consist of a foldable lattice of beams connected by cylindrical joints, to which covering panels or membranes are attached. These structures fold towards their perimeter and there is practically no limit to their shape. Solutions to the key problems that have to be solved in the course of the kinematic desig...

In the setting of the π-calculus with binary sessions, we aim at relaxing the notion of duality of session types by the concept of retractable compliance developed in contract theory. This leads to extending session types with a new type operator of “speculative selection” including choices not necessarily offered by a compliant partner. We address the problem of selecting successful communicat...