513 research outputs found
Partitioned storage for temporal databases
Efficiently maintaining history data on line together with current data is difficult. This paper discusses one promising approach, the temporally partitioned store. The current store contains current data and possibly some history data, while the history store holds the rest of the data. The two stores can utilize different storage formats, and even different storage media, depending on the individual data characteristics. We discuss various issues on the temporally partitioned store, investigate several formats for the history store, and evaluate their performance on a set of sample queries
On the Semantics of "Now" in Databases
While "now" is expressed in SQL as CURRENT-TIMESTAMP within queries, this value cannot be
stored in the database. However, this notion of an ever-increasing current-time value has been
reflected in some temporal data models by inclusion of database-resident variables, such as
"now," "until-changed," "â," "@" and "-." Time variables are very desirable, but their use
also leads to a new type of database, consisting of tuples with variables, termed a variable
database.
This paper proposes a framework for defining the semantics of the variable databases of temporal
relational data models. A framework is presented because several reasonable meanings
may be given to databases that use some of the specific temporal variables that have appeared
in the literature. Using the framework, the paper defines a useful semantics for such databases.
Because situations occur where the existing time variables are inadequate, two new types of
modeling entities that address these shortcomings, timestamps which we call now-relative and
now-relative indeterminate, are introduced and defined within the framework. Moreover, the paper
provides a foundation, using algebraic bind operators, for the querying of variable databases
via existing query languages. This transition to variable databases presented here requires minimal
change to the query processor. Finally, to underline the practical feasibility of variable
databases, we show that database variables can be precisely specified and efficiently implemented
in conventional query languages, such as SQL, and in temporal query languages, such
as TSQL2.Information Systems Working Papers Serie
Focus Stacking Images of Morphological Character States for Differentiating the Adults of \u3ci\u3eIxodes affinis\u3c/i\u3e and \u3ci\u3eIxodes scapularis\u3c/i\u3e (Acari: Ixodidae) in Areas of Sympatry
Adult females and males of Ixodes affinis and Ixodes scapularis are illustrated by focus stacking image photography, and morphological character states are described that reliably differentiate the two species. In conjunction with other environmental cues, such as the questing phenology of adults, these characteristics will enable the rapid identification of adults of either sex along the southern Coastal Plain of the United States, where these species are sympatric
ANTARES: Progress towards building a `Broker' of time-domain alerts
The Arizona-NOAO Temporal Analysis and Response to Events System (ANTARES) is
a joint effort of NOAO and the Department of Computer Science at the University
of Arizona to build prototype software to process alerts from time-domain
surveys, especially LSST, to identify those alerts that must be followed up
immediately. Value is added by annotating incoming alerts with existing
information from previous surveys and compilations across the electromagnetic
spectrum and from the history of past alerts. Comparison against a knowledge
repository of properties and features of known or predicted kinds of variable
phenomena is used for categorization. The architecture and algorithms being
employed are described
Observational and Dynamical Characterization of Main-Belt Comet P/2010 R2 (La Sagra)
We present observations of comet-like main-belt object P/2010 R2 (La Sagra)
obtained by Pan-STARRS 1 and the Faulkes Telescope-North on Haleakala in
Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on
Mauna Kea, the Danish 1.54 m telescope at La Silla, and the Isaac Newton
Telescope on La Palma. An antisolar dust tail is observed from August 2010
through February 2011, while a dust trail aligned with the object's orbit plane
is also observed from December 2010 through August 2011. Assuming typical phase
darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag
between August 2010 and December 2010, suggesting that dust production is
ongoing over this period. These results strongly suggest that the observed
activity is cometary in nature (i.e., driven by the sublimation of volatile
material), and that P/La Sagra is therefore the most recent main-belt comet to
be discovered. We find an approximate absolute magnitude for the nucleus of
H_R=17.9+/-0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an
albedo of p=0.05. Using optical spectroscopy, we find no evidence of
sublimation products (i.e., gas emission), finding an upper limit CN production
rate of Q_CN<6x10^23 mol/s, from which we infer an H2O production rate of
Q_H2O<10^26 mol/s. Numerical simulations indicate that P/La Sagra is
dynamically stable for >100 Myr, suggesting that it is likely native to its
current location and that its composition is likely representative of other
objects in the same region of the main belt, though the relatively close
proximity of the 13:6 mean-motion resonance with Jupiter and the (3,-2,-1)
three-body mean-motion resonance with Jupiter and Saturn mean that dynamical
instability on larger timescales cannot be ruled out.Comment: 23 pages, 13 figures, accepted for publication in A
The ANTARES Astronomical Time-Domain Event Broker
We describe the Arizona-NOIRLab Temporal Analysis and Response to Events
System (ANTARES), a software instrument designed to process large-scale streams
of astronomical time-domain alerts. With the advent of large-format CCDs on
wide-field imaging telescopes, time-domain surveys now routinely discover tens
of thousands of new events each night, more than can be evaluated by
astronomers alone. The ANTARES event broker will process alerts, annotating
them with catalog associations and filtering them to distinguish customizable
subsets of events. We describe the data model of the system, the overall
architecture, annotation, implementation of filters, system outputs, provenance
tracking, system performance, and the user interface.Comment: 24 Pages, 8 figures, Accepted by A
A Three-Dimensional Atlas of the Honeybee Neck
Three-dimensional digital atlases are rapidly becoming indispensible in modern biology. We used serial sectioning combined with manual registration and segmentation of images to develop a comprehensive and detailed three-dimensional atlas of the honeybee head-neck system. This interactive atlas includes skeletal structures of the head and prothorax, the neck musculature, and the nervous system. The scope and resolution of the model exceeds atlases previously developed on similar sized animals, and the interactive nature of the model provides a far more accessible means of interpreting and comprehending insect anatomy and neuroanatomy
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