The X Window System, Version 11, is the standard window system on Linux and UNIX systems. X11, designed in 1987, was “state of the art ” at that time. From its inception, X has been a network transparent window system in which X client applications can run on any machine in a network using an X server running on any display. While there have been some significant extensions to X over its history (e.g. OpenGL support), X’s design lay fallow over much of the 1990’s. With the increasing interest in open source systems, it was no longer sufficient for modern applications and a significant overhaul is now well underway. This paper describes revisions to the architecture of the window system used in a growing fraction of desktops and embedded systems 1

. We introduce an extension of -calculus, called label-selective - calculus, in which arguments of functions are selected by labels. The set of labels includes numeric positions as well as symbolic keywords. While the latter enjoy free commutation, the former must comply with relative precedence in order to preserve currying. This extension of -calculus is conservative in the sense that when the set of labels is the singleton f1g, it coincides with -calculus. The main result of this paper is that the label-selective -calculus is confluent. In other words, argument selection and reduction commute. Keywords. -Calculus, record calculus, concurrency, communication. 1 Synopsis Many modern programming languages allow specifying arguments of functions and procedures by symbolic keywords as well as using the traditional and natural numeric positions [16, 12, 4]. Symbolic keywords are usually handled as syntactic sugar and "compiled away" as numeric positions. This is made easy if the langua...

We introduce an extension of -calculus, called label-selective -calculus, in which arguments of functions are selected by labels. The set of labels includes numeric positions as well as symbolic keywords. While the latter enjoy free commutation, the former must comply with relative precedence in order to preserve currying. This extension of -calculus is conservative in the sense that when the set of labels is the singleton f1g, it coincides with -calculus. The main result of this paper is the proof that the label-selective -calculus is confluent. In other words, argument selection and reduction commute. R esum e Nous presentons une extension du -calcul, appelee -calcul label-selectif, dans laquelle les arguments des fonctions sont selectionnes par des etiquettes. L'ensemble des etiquettes comprend des positions numeriques aussi bien que des mot-clefs symboliques. Alors que ces derniers jouissent d'une commutativite libre, les premiers obeissent a une precedence relative pour preserver...