Gravity gradiometer system for Earth Exploration

We develop a gravity gradiometer (GG) for use on planetary missions to planets like Mars and Jupiter. With some modifications this development is extended to include (airborne) applications for the Dutch exploratory industry. We adapt key technology of the space based GG for the use in an environment with considerable acceleration noise. The major benefit is the considerable decrease in weight and size with the presently used gradiometer systems

Noise in (double) relaxation oscillation SQUIDs

We have modelled the effect of two intrinsic noise sources on the flux noise spectral density of (Double) Relaxation Oscillation SQUIDs ((D)ROSs) based on hysteretic Josephson tunnel junctions. An important noise source is the spread in the critical current of the SQUID due to thermal fluctuations. Critical current noise mainly determines the noise on the average output voltage of DROSs with high flux to voltage transfer. A second noise source is the spread in the relaxation frequency due to the random interaction between the Josephson oscillations and the relaxation oscillations during switching to the zero-voltage state. This effect can dominate the voltage noise of a ROS

The IMPRESS DDT: a database design toolbox based on a formal specification language

The Database Design Tool prototype is being developed in the IMPRESS project (Esprit project 6355). The IMPRESS project started in May 1992 and aims at creating a low-level storage manager tailored for multimedia applications, together with a library of efficient operators, a programming environment, high-level design tools and methodology. The DDT is part of this last effort.\ud \ud The project focuses on the field of Technical Information Systems, where there is a need for tools supporting modeling of complex objects. Designers in this field usually use incremental design or step by step prototyping, because this seems to be best suited for users coping with complexity and uncertainty about their own needs or requirements. The IMPRESS DDT aims at supporting the database design part of this process

MonetDB/XQuery - Consistent & Efficient Updates on the Pre/Post Plane

Relational XQuery processors aim at leveraging mature relational DBMS query processing technology to provide scalability and efficiency. To achieve this goal, various storage schemes have been proposed to encode the tree structure of XML documents in flat relational tables. Basically, two classes can be identified: (1) encodings using fixed-length surrogates, like the preorder ranks in the pre/post encoding [5] or the equivalent pre/size/level encoding [8], and (2) encodings using variable-length surrogates, like, e.g., ORDPATH [9] or P-PBiTree [12]. Recent research [1] showed a clear advantage of the former for efficient evaluation of XPath location steps, exploiting techniques like cheap node order tests, positional lookup, and node skipping in staircase join [7]. However, once updates are involved, variable-length surrogates are often considered the better choice, mainly as a straightforward implementation of structural XML updates using fixed-length surrogates faces two performance bottlenecks: (i) high physical cost (the preorder ranks of all nodes following the update position must be modified—on average 50% of the document), and (ii) low transaction concurrency (updating the size of all ancestor nodes causes lock contention on the document root)

Parallel Handling of Integrity Constraints

Integrity constraints form an important part of a data model. Therefore, a complete integrity constraint handling subsystem is considered an important part of any modern DBMS. In implementing an integrity constraint handling subsystem, there are two major problem areas: providing enough functionality and delivering good performance in constraint enforcement. In the PRISMA project, an integrity constraint handling subsystem for a relational DBMS is developed, that meets both requirements. Functionality is reached through a modular and extensible architecture of the subsystem. Performance is reached through extensive use of parallelism in various constraint enforcement algorithms.\ud The work reported in this document was conducted as part of the PRISMA project, a joint effort with Philips Research Laboratories Eindhoven, partially supported by the Dutch "Stimuleringsprojectteam Informaticaonderzoek (SPIN)

Incremental data uncertainty handling using evidence combination: a case study on maritime data reasoning

Semantic incompatibility is a conflict that occurs in the meanings of data. In this paper, we propose an approach for data cleaning by resolving semantic incompatibility. Our approach applies a dynamic and incremental enhancement of data quality. It checks the coherency/conflict of the newly recorded facts/relations against the existing ones. It reasons over the existing information and comes up with new discovered facts/relations. We choose maritime data cleaning as a validation scenario

Moa: extensibility and efficiency in querying nested data

Advanced non-traditional application domains such as geographic information systems and digital library systems demand advanced data management support. In an effort to cope with this demand, we present a novel multi-model DBMS architecture which provides efficient evaluation of queries on complexly structured data. A vital role in this architecture is played by the Moa language featuring a nested relational data model based on XNF2, in which we placed renewed interest. Furthermore, the architecture allows extensibility on all of its levels providing the means to better integrate domain-specific algorithms into the system. In addition to this, the extensibility of the Moa language is designed in a way that optimization obstacles due to blackbox treatment of ADTs is avoided. This combination of well-integrated domainspecific algorithms, extensibility open to optimization, and a mapping of queries on complexly structured data to an efficient physical algebra expression via a nested relational algebra, makes that the Moa system can efficiently handle complex queries from non-traditional application domains

//Rondje Zilverling: COMMIT/TimeTrails

Het TimeTrails-project3 gaat over data mining in grote hoeveelheden gegevens over gebeurtenissen in ruimte en tijd, d.w.z. met coördinaten en time-stamps. Dergelijke gegevens worden doorgaans vergaard door mensen, sensoren en wetenschappelijke observaties. Gegevensanalyse richt zich vaak op de vier W’s: Wie, Wat, Waar en Wanneer. Een belangrijke kwestie is het kunnen behappen van de grote hoeveelheden gegevens, d.w.z. "big data". Vanuit de UT werken we, d.w.z. de groepen EWI/DB en ITC/GIP, aan twee applicaties:\ud * Het in kaart brengen van de mening van het publiek bij grote infrastructuurproject zoals de aanleg van een nieuw stuk snelweg. Dit doen we met Twitter-analyse en data-visualisatie.\ud • Het vinden van goede vakantiebestemmingen. Hierbij spelen Social media, web harvesting en analyse van GPS-traces een rol

Parallel Evaluation of Multi-join Queries

A number of execution strategies for parallel evaluation of multi-join queries have been proposed in the literature. In this paper we give a comparative performance evaluation of four execution strategies by implementing all of them on the same parallel database system, PRISMA/DB. Experiments have been done up to 80 processors. These strategies, coming from the literature, are named: Sequential Parallel, Synchronous Execution, Segmented Right-Deep, and Full Parallel. Based on the experiments clear guidelines are given when to use which strategy. This is an extended abstract; the full paper appeared in Proc. ACM SIGMOD'94, Minneapolis, Minnesota, May 24–27, 199