120225250
Siphons, Traps and High-Level Nets with Infinite Color Domains
Commoner's Theorem establishes a relation between siphons, traps and liveness in free choice systems. Most proofs of this theorem do explicitly involve the finiteness of the net. Therefore we cannot apply the theorem directly to high level nets with infinite color domains.
119954332
How to calculate symmetries of Petri nets
Abstract. Symmetric net structure yields symmetric net behaviour. Thus, knowing the symmetries of a net, redundant calculations can be skipped. We present a framework for the calculation of symmetries for several net classes including place/transition nets, timed nets, stochastic nets, self–modifying nets, nets with inhibitor arcs, and many others. Our approach allows the specification of different symmetry groups. Additionally it provides facilities either to calculate symmetries on demand while running the actual analysis algorithm, or to calculate them in advance. For the latter case we define and calculate a ground set of symmetries. Such a set has polynomial size and is sufficient for an efficient implementation of the for all symmetries loop and the partition of net elements into equivalence classes. These two constructions are the usual way to integrate symmetries into an analysis algorithm.
195220837
Model-Checking with Coverability Graphs
We show that several formulas of a temporal logic can be verified using the coverability graph of the underlying system. Of course, the procedure is not capable of verifying all formulae, since already the reachability problem for (unbounded) Petri nets is computationally hard. Thus, the procedure returns true, false, or unknown for a query. The formulae that can be verified cover most of the well known standard properties which have been listed in the context of coverability graph analysis so far.
195610218
LoLA: a low level analyser
With LoLA, we put recently developed state space oriented algorithms to other tool developers disposal. Providing a simple interface was a major design goal such that it is as easy as possible to integrate LoLA into tools of different application domains. LoLA supports place/transition nets. Implemented verification techniques cover standard properties (liveness, reversibility, boundedness, reachability, dead transitions, deadlocks, home states) as well as satisfiability of state predicates and CTL model checking. For satisfiability, both exhaustive search and heuristically goal oriented system execution are supported. For state space reduction, LoLA features symmetries, stubborn sets, and coverability graphs.
118703657
Verification of Siphons and Traps for Algebraic Petri Nets
Siphons and traps are structures which allow for some implications on the net's behaviour and can be used in manual correctness proofs for concurrent systems. We introduce symbolic representations of siphons and traps which work quite well even in infinite cases and are still intuitively readable. The verification of symbolic siphons and traps is traced back to unification and structural induction on the terms. This approach is motivated by some additional considerations. For unification and other proposed structural reasoning mechanisms tool support is given by completeness proof tools studied in the theorem-proving community.
60532280
Distributed verification with LoLA
We report work in progress on a distributed version of explicit state space generation in the Petri net verification tool LoLA. We propose a data structure where all available memory of all involved workstations can be fully exploited, and load balancing actions are possible at any time while the verification is running. It is even possible to extend the set of involved workstations while a verification is running.
34666529
Fallstudie zur Modellierung von Software-Entwicklungsprozessen auf Basis von SPEM 2.0
The instant invention is directed to a method of producing a reaction mixture for forming solid or cellular materials from flowable reactants and, optionally, fillers, comprising premixing the components and, optionally, fillers in a first mixing zone and after-mixing in a second mixing zone, the improvement wherein said after-mixing is carried out in a slit-like annular zone which extends radially from the center, the surface boundaries of said annular zone are not parallel and one of said surface boundaries is rotated while the opposite facing surface boundary remains stationary. The instant invention is also directed to an apparatus for producing a reaction mixture for forming solid or cellular materials from flowable reactants and, optionally, fillers, comprising: (a) storage containers for reactants, from which (b) feed pipes lead via (c) metering pumps to a (d) premixing chamber which is arranged in a (e) housing, and on whose outlet opening an (f) after-mixing chamber is connected, the improvement wherein (g) said after-mixing chamber comprises a slit which is formed by (h) two baffle plates, one of which is provided with a (i) rotary drive.
18680044
Benchmarking Performance-Critical Components in a Native XML Database System
The rapidly increasing number of XML-related applications indicates a growing need for efficient, dynamic, and native XML support in database management systems (XDBMS). So far, both industry and academia primarily focus on benchmarking of high-level performance figures for a variety of applications, queries, or documents --- frequently executed in artificial workload scenarios --- and, therefore, may analyze and compare only specific or incidental behavior of the underlying systems. To cover the full XDBMS support, it is mandatory to benchmark performance-critical components bottom-up, thereby removing bottlenecks and optimizing component behavior. In this way, wrong conclusions are avoided when new techniques such as tailored XML operators, index types, or storage mappings with unfamiliar performance characteristics are used. As an experience report, we present what we have learned from benchmarking a native XDBMS and recommend certain setups to do it in a systematic and meaningful way.
11969863
Towards Flash Disk Use in Databases - Keeping Performance While Saving Energy?
Green computing or energy saving when processing information is primarily considered a task of processor development. We, however, advocate that a holistic approach is necessary to reduce power consumption to a minimum. We explore the potential of NAND flash memory in comparison to magnetic disks for DBMS-based architectures. For this reason, we attempt to identify the IO performance of both storage types at the device level and file system interface, before we approach the most important question how DBMS applications can take advantage of the flash performance characteristics. Furthermore, based on an analysis of storage structures and related benchmark runs in our XTC system, we discuss how IO-intensive DBMS algorithms have to be adjusted to take most out of the flash technology which is entering the server area with dramatic pace. The ultimate goal is to substantially improve energy efficiency while comparable performance as in disk-based DB servers is maintained.
14265278
An Adaptive Storage Manager for XML Documents
Effective and efficient management and manipulation of XML documents requires stable decisions at the time a document enters the XML DBMS to provide for storage structures which are adjusted to the document characteristics and which reflect the future processing needs. While some of the critical parameters require a kind of pre-specification, others can be determined by pre-analysis or sampling of the incoming document or by just making experience-driven “educated guesses”. Important parameters are related to node labeling, path synopsis, document container layout, and indexing. In this paper, we discuss approaches to achieve an adaptive behavior of the storage manager to provide tailor-made native XML storage structures to the extent possible.
2745798
Autonomous Management of Soft Indexes
In recent years the support for index tuning as pan of physical database design has gained focus in research and product development, which resulted in index and design advisors. Nevertheless, these tools provide a one-off solution for a continuous task and are not deeply integrated with the DBMS functionality by only applying the query optimizer for index recommendation and profit estimation and decoupling the decision about and execution of index configuration changes from the core system functionality. In this paper we propose an approach that continuously collects statistics for recommended indexes and based on this, repetitively solves the Index Selection Problem (lSP).A key novelty is the on-the-fly index generation during query processing implemented by new query plan operators In-dexBuildScan and SwitchPlan. Finally, we present the implementation and evaluation of the introduced concepts as part of the PostgreSQL system.