What can you verify and Enforce at Runtime?

International audienceThe underlying property, its definition and representation play a major role when monitoring a system. Having a suitable and convenient framework to express properties is thus a concern for runtime analysis. It is desirable to delineate in this framework the sets of properties for which runtime analysis approaches can be applied to. This paper presents a unified view of runtime verification and enforcement of properties in the Safety-Progress classification. Firstly, we extend the Safety-Progress classification of properties in a runtime context. Secondly, we characterize the set of properties which can be verified (monitorable properties) and enforced (enforceable properties) at runtime. We propose in particular an alternative definition of ''property monitoring'' to the one classically used in this context. Finally, for the delineated sets of properties, we define specialized verification and enforcement monitors

Activation of p34cdc2 protein kinase by microinjection of human cdc25C into mammalian cells. Requirement for prior phosphorylation of cdc25C by p34cdc2 on sites phosphorylated at mitosis.

International audienceHuman cdc25C protein, a specific tyrosine phosphatase that activates the p34cdc2 protein kinase at mitosis, is itself a phosphoprotein that shows increased phosphorylation during the G2-M transition. In vitro, cdc25C protein is substantially phosphorylated by purified p34cdc2-cyclin B protein kinase. Of seven putative phosphorylation sites for p34cdc2 protein kinase present in human cdc25C, five are phosphorylated by p34cdc2 protein kinase in vitro, as assessed by tryptic phosphopeptide mapping and peptide sequencing. These same sites are also phosphorylated in vivo during the G2-M transition in normal mammalian fibroblasts and have been precisely mapped. The cdc25C phosphorylated in vitro by p34cdc2 protein kinase exhibits a 2-3-fold higher activity than the nonphosphorylated cdc25C, as assayed by activation of inactive cdc2 prokinase. Microinjection of purified cdc25C proteins into living fibroblasts reveals that only the phosphorylated form of cdc25 is highly effective in activating G2 cells into premature prophase in a manner similar to microinjection of purified active p34cdc2 protein kinase. Together these data show that multisite phosphorylation of cdc25C by p34cdc2-cyclin B protein kinase occurs at the G2-M transition and is sufficient to induce the autoamplification of cdc2/M-phase promoting factor necessary to drive somatic mammalian cells into mitosis

Symbolic quality control for multimedia applications

We present a fine grain quality control method for multimedia applications. The method takes as input an application software composed of actions. The execution times of actions are unknown increasing functions of quality level parameters. The method allows the construction of a Controller which computes adequate action schedules and corresponding quality levels, so as to meet QoS requirements for a given platform. These include requirements for safety (action deadlines are met) as well optimality (maximization and smoothness of quality levels). The Controller consists of a Quality Manager and a Scheduler. For each action, the Controller uses a quality management policy for choosing a schedule and quality levels meeting the QoS requirements. The schedule is selected amongst a set of optimal schedules computed by the Scheduler. We extend and improve results of previous papers providing a solid theoretical basis for designing and implementing the Controller. We propose a symbolic quality management method using speed diagrams, a representation of the controlled system's dynamics. Instead of numerically computing a quality level for each action, the Quality Manager changes action quality levels based on the knowledge of constraints characterizing control relaxation regions. These are sets of states in which quality management for a given number of computation steps can be relaxed without degrading quality. We study techniques for efficient computation of optimal schedules. We present experimental results including the implementation of the method and benchmarks for an MPEG4 video encoder. The benchmarks show drastic performance improvement for controlled quality with respect to constant quality. They also show that symbolic quality management allows significant reduction of the overhead with respect to numeric quality management. Finally, using optimal schedules can lead to considerable performance gains. © 2008 Springer Science+Business Media, LLC