22,942 research outputs found
CEDAR: tools for event generator tuning
I describe the work of the CEDAR collaboration in developing tools for tuning
and validating Monte Carlo event generator programs. The core CEDAR task is to
interface the Durham HepData database of experimental measurements to event
generator validation tools such as the UCL JetWeb system - this has
necessitated the migration of HepData to a new relational database system and a
Java-based interaction model. The "number crunching" part of JetWeb is also
being upgraded, from the Fortran HZTool library to the new C++ Rivet system and
a generator interfacing layer named RivetGun. Finally, I describe how Rivet is
already being used as a central part of a new generator tuning system, and
summarise two other CEDAR activities, HepML and HepForge.Comment: 13 pages, prepared for XI International Workshop on Advanced
Computing and Analysis Techniques in Physics Research, Amsterdam, April 23-27
200
Towards a Holistic Integration of Spreadsheets with Databases: A Scalable Storage Engine for Presentational Data Management
Spreadsheet software is the tool of choice for interactive ad-hoc data
management, with adoption by billions of users. However, spreadsheets are not
scalable, unlike database systems. On the other hand, database systems, while
highly scalable, do not support interactivity as a first-class primitive. We
are developing DataSpread, to holistically integrate spreadsheets as a
front-end interface with databases as a back-end datastore, providing
scalability to spreadsheets, and interactivity to databases, an integration we
term presentational data management (PDM). In this paper, we make a first step
towards this vision: developing a storage engine for PDM, studying how to
flexibly represent spreadsheet data within a database and how to support and
maintain access by position. We first conduct an extensive survey of
spreadsheet use to motivate our functional requirements for a storage engine
for PDM. We develop a natural set of mechanisms for flexibly representing
spreadsheet data and demonstrate that identifying the optimal representation is
NP-Hard; however, we develop an efficient approach to identify the optimal
representation from an important and intuitive subclass of representations. We
extend our mechanisms with positional access mechanisms that don't suffer from
cascading update issues, leading to constant time access and modification
performance. We evaluate these representations on a workload of typical
spreadsheets and spreadsheet operations, providing up to 20% reduction in
storage, and up to 50% reduction in formula evaluation time
Database independent Migration of Objects into an Object-Relational Database
This paper reports on the CERN-based WISDOM project which is studying the
serialisation and deserialisation of data to/from an object database
(objectivity) and ORACLE 9i.Comment: 26 pages, 18 figures; CMS CERN Conference Report cr02_01
HepData and JetWeb: HEP data archiving and model validation
The CEDAR collaboration is extending and combining the JetWeb and HepData
systems to provide a single service for tuning and validating models of
high-energy physics processes. The centrepiece of this activity is the fitting
by JetWeb of observables computed from Monte Carlo event generator events
against their experimentally determined distributions, as stored in HepData.
Caching the results of the JetWeb simulation and comparison stages provides a
single cumulative database of event generator tunings, fitted against a wide
range of experimental quantities. An important feature of this integration is a
family of XML data formats, called HepML.Comment: 4 pages, 0 figures. To be published in proceedings of CHEP0
Facets and Typed Relations as Tools for Reasoning Processes in Information Retrieval
Faceted arrangement of entities and typed relations for representing
different associations between the entities are established tools in knowledge
representation. In this paper, a proposal is being discussed combining both
tools to draw inferences along relational paths. This approach may yield new
benefit for information retrieval processes, especially when modeled for
heterogeneous environments in the Semantic Web. Faceted arrangement can be used
as a se-lection tool for the semantic knowledge modeled within the knowledge
repre-sentation. Typed relations between the entities of different facets can
be used as restrictions for selecting them across the facets
Functorial Data Migration
In this paper we present a simple database definition language: that of
categories and functors. A database schema is a small category and an instance
is a set-valued functor on it. We show that morphisms of schemas induce three
"data migration functors", which translate instances from one schema to the
other in canonical ways. These functors parameterize projections, unions, and
joins over all tables simultaneously and can be used in place of conjunctive
and disjunctive queries. We also show how to connect a database and a
functional programming language by introducing a functorial connection between
the schema and the category of types for that language. We begin the paper with
a multitude of examples to motivate the definitions, and near the end we
provide a dictionary whereby one can translate database concepts into
category-theoretic concepts and vice-versa.Comment: 30 page
HepData reloaded: reinventing the HEP data archive
We describe the status of the HepData database system, following a major
re-development in time for the advent of LHC data. The new HepData system
benefits from use of modern database and programming language technologies, as
well as a variety of high-quality tools for interfacing the data sources and
their presentation, primarily via the Web. The new back-end provides much more
flexible and semantic data representations than before, on which new external
applications can be built to respond to the data demands of the LHC
experimental era. The HepData re-development was largely motivated by a desire
to have a single source of reference data for Monte Carlo validation and tuning
tools, whose status and connection to HepData we also briefly review.Comment: 7 pages, 3 figures, Presented at 13th International Workshop on
Advanced Computing and Analysis Techniques in Physics Research (ACAT 2010),
February 22-27, 2010, Jaipur, Indi
Testing a global city hypothesis : an assessment of polarization across US cities
Social polarization is perhaps most evident within the world's large cities where we can easily observe stark contrasts between wealth and poverty. A world city theoretical perspective has emerged that associates large cities importance in a global network of cities to the degree of internal polarization within these cities. The research reported here locates 57 large US cities within this world city hierarchy and then empirically examines the hypothesized positive association between global centrality and social polarization using a multivariate, cross-city analysis. The findings are mixed, with some evidence that global centrality increases income polarization, but only in the context of higher levels of immigration. There is no evidence that a city's centrality affects occupational polarization. We conclude by suggesting implications for the world city literature and future research
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