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.
59701825
Controllability of Open Workflow Nets.
An open workflow net is basically a workflow net extended with a message passing interface. Open workflow nets are adequate models for services or parts of inter-organizational business processes. We investigate the problem of controllability, a natural counterpart of soundness in classical workflow nets (as studied by van der Aalst). We distinguish centralized, distributed, and local controllability and provide solutions to all problems.
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.
117881226
Narrowing Petri Net State Spaces Using the State Equation
Given a (possibly partially defined) state, all count vectors of transition sequences reaching that state are solutions to a corresponding Petri net state equation. We propose a search strategy where sequences corresponding to a minimal solution of the state equation are explored first. Then step by step the search space is relaxed to arbitrary count vectors. This heuristics relies on the observation that in many (though provably not in all) cases, minimal solutions of the state equation can be realized as a firing sequence. If no target state is reachable, either the state equation does not have solutions, or our search method would yield the full state space. We study the impact of the state equation on reachability, present an algorithm that exploits information from the state equation and discuss its application in stateless search as well as its combination with stubborn set reduction.
172504304
LoLA wird Pfadfinder.
LoLA ist ein erreichbarkeitsgraphbasiertes Werkzeug f ur Stellen/Transitions{Netze. Hier geht es um LoLAs Fahigkeit, erreichbare Zustande mit vorgegebenen Eigenschaften zu suchen und im Erfolgsfall einen solchen Zustand mit einem Weg von der Anfangsmarkierung dorthin anzugeben. Die Besonderheit besteht darin, da wahrend der Suche nur zwei Zustande gespeichert werden: der Anfangszustand und der aktuelle Zustand. Anstatt also den Zustandsraum systematisch zu durchmustern (und dabei meist am Speicherende zu scheitern), navigiert LoLA ohne Kenntnis der schon betretenen Zustande durch den Erreichbarkeitsgraph. Da sie trotzdem ihre Aufgabe erfolgreich lost, liegt an ihren spezi schen Fahigkeiten: Schnelligkeit, Bescheidenheit, Zielstrebigkeit, Neugier und Ausdauer.
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.
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.
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.
5829856
The promise of solid state disks: increasing efficiency and reducing cost of DBMS processing
Most database systems (DBMSs) today are operating on servers equipped with magnetic disks. In our contribution, we want to motivate the use of two emerging and striking technologies, namely native XML DBMSs (XDBMSs for short) and solid state disks. In this context, the traditional read/write model optimized by a sophisticated cache hierarchy and the IO cost model for databases needs adjustment. Such new devices together with optimized storage mapping of XML documents provide a number of challenging characteristics. We discuss howtheir optimization potential ca be exploited to enhance transactional DB performance under reduced energy consumption to match increasing application demands and, at the same time, to guarantee economic energy use in data centers.
15429796
Essential Performance Drivers in Native XML DBMSs
As a multi-layered XML database management system, we have designed, implemented, and optimized over the recent five years our prototype system XTC, a native XDBMS providing multi-lingual query interfaces (XQuery, XPath, DOM). In particular in higher system layers, we have compared competing concepts and iteratively found salient solutions which drastically improved the overall XDBMS performance. XML query processing is critically affected by the smooth interplay of concepts and methods on all architectural layers: node labeling and mapping options for storage structures; availability of suitable index mechanisms; provision of a spectrum of path processing operators; query language compilation and optimization. Furthermore, effective and efficient locking protocols must be present to guarantee the ACID properties for XML processing and to achieve high transaction throughput. 
 
In this survey, we outline our experiences gained during the implementation and optimization of XTC. We figure out the "key drivers" to maximize throughput while keeping the response times at an acceptable level. Because we have implemented all options and alternatives in XTC, dedicated benchmark runs allow for comparisons in identical environments and illustrate the benefit of all implementation decisions.
17363995

 Storing and indexing XML documents upside down

AbstractXML documents contain substantial redundancy in their structure part, because each path from the root
 node to a leaf node is explicitly represented and typically large sets of such path instances belong to
 a path class, i.e., the nodes of the path instances are labeled by the same sequence of element (or attribute)
 names. To save storage space and I/O cost, we want to get rid of this structural redundancy to the extent
 possible. While all known methods for the physical representation (storage) of XML documents proceed from
 the root via the element/attribute hierarchy (internal nodes) down to the leaves (values), we follow an
 upside-down approach which explicitly stores the values and only reconstructs
 the internal nodes, if needed. The cornerstones for such a solution are suitable node labels and a path
 synopsis which efficiently represents all path classes of an XML document. As a solution, we propose a compact
 internal storage format for native XML database systems where the inner structure of the stored documents
 is virtualized. Because this elementless storage format provides an efficient reconstruction of a document
 using its path synopsis, all processing properties are preserved and the semantics of navigational and declarative
 operations of XML languages remains unchanged. Adjusted indexes support the full spectrum of so-called
 content-and-structure single path queries. Apart from greatly reduced storage consumption, our approach
 demonstrates its superiority, compared to competing methods, not only for a substantial fraction of those
 queries, but also for storing, reconstructing, and navigating XML documents.
