Green Computing - A Case for Data Caching and Flash Disks?
Green computing or energy saving when processing information is primarily considered a task of processor development. However, this position paper advocates that a holistic approach is necessary to reduce power consumption to a minimum. We discuss the potential of integrating NAND flash memory into DB-based architectures and its support by adjusted DBMS algorithms governing IO processing. The goal is to drastically improve energy efficiency while comparable performance as is disk-based systems is maintained.

title: Adaptive Resource Management in a Native XDBMS
abstract: A graphite reinforced glass composite is described comprising discontinuous graphite fibers in substantially planar orientation in a glass matrix with strength and fracture toughness greater than the unreinforced glass matrix. The resulting composite has superior strength, fluid impermeability, wear resistance, failure strain and fracture toughness. In fact, the stress-strain, curve for composites of the invention resembles that of metal making it particularly suitable for a variety of moldable shapes and machinable designs.

title: Usage-driven storage structures for native XML databases
abstract: There are numerous and influential parameters associated with the selection of suitable native storage structures for XML documents within an XML DBMS. The most important parameters are related to node labeling, path synopsis, document container layout, indexing, and text compression. While node labeling and the presence of a path synopsis greatly determine flexibility and efficiency of the entire DBMS-internal XML processing, the remaining issues primarily address I/O demand and space consumption. In particular, text compression---considered orthogonal to the design choices affected by the other parameters---implies additional algorithmic costs for encoding/decoding during document processing. Having the vision in mind that future storage managers can autonomously figure out optimal choices for all of these parameters, we discuss how various storage options favor different usage patterns and how they can be specified beforehand to influence native XML storage options by the anticipated usages.

title: Tailor-Made Native XML Storage Structures
abstract: Automatically choosing suitable native storage structures for XML doc- uments arriving at the XML DBMS is a challenging task for its storage manager. While some of the critical parameters require pre-specification, others can be deter- mined by pre-analysis or sampling of the incoming document or by just making ex- perience-driven "educated guesses". In this paper, we discuss approaches to achieve an adaptive behavior of the storage manager to provide tailor-made native XML stor- age structures to the extent possible. 1I ntroduction The XML data model allows for a great deal of modeling flexibility with which order, op- tional and multi-valued concepts, as well as deeply nested relationships can be captured. Therefore, the resulting tree structures of natively represented XML documents exhibit large variations in breadth and depth. Furthermore, XML documents may be data-centric having relatively little 'content' stored as short text values or they may be document-cen- tric where a single content node may contain huge portions of text, e.g., an entire book in a digital library. For these reasons, it is highly advisable to equip the storage manager with the ability to select reasonable or even optimal storage structures for documents. Furthermore, two cas- es have to be considered: a document sent by a client arrives at a time—the so-called block mode, i.e., the document can be pre-parsed and analyzed before a storage structure is cho- sen—or it arrives at the DBMS interface in stream mode where fragments present, due to their size, have to be allocated in a suitable storage structure on disk before the entire "streamed" document is available for the DBMS. In the latter case, the storage manager must decide—based on imprecise structural information—on the storage structure to be chosen and, at best, can make some educated guesses based on context or sampling infor- mation.

title: An Adaptive Storage Manager for XML Documents
abstract: 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.

title: Autonomous Management of Soft Indexes
abstract: 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.

title: Stubborn Sets for Standard Properties
abstract: Stubborn sets are a tool for state space reduction preserving certain system properties. We present stubborn set approaches for all popular Petri net standard properties. This extends the list of properties that can be analysed successfully (including boundedness, reversibility). For other properties, our approach can lead to larger reductions (reachability) than previous ones. Furthermore, shortest and chepest witness paths for several properties are now preserved.

title: 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.

title: Siphons, Traps and High-Level Nets with Infinite Color Domains
abstract: 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.

title: Distributed verification with LoLA
abstract: 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.

title: Using Petri net invariants in state space construction
abstract: The linear algebraic invariant calculus is a powerful technique for the verification of Petri nets. Traditionally it is used for structural verification, i.e. for avoiding the explicit construction of a state space. In this paper, we study the use of Petri net invariants for reducing the memory resources required during state space construction. While place invariants help to reduce the amount of memory needed for each single state (without reducing the number of states as such), transition invariants can be used to reduce the number of states to be stored. Interestingly, our approach does not require computing invariants in full, let alone storing them permanently. All information we need can be deduced from an upper triangular form of the Petri net's incidence matrix. Experiments prove that the place invariant technique leads to improvements in both memory and run time costs while transition invariants lead to a space/time tradeoff that can be controlled heuristically.