Volume 9, Issue 1
January 2000
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INTRODUCTION
At this month's AAS meeting in Atlanta, Georgia, the ADC featured its work
with eXtensible Markup Language (XML) technologies at an exhibit booth and in
display papers. This reflects the current emphasis within the ADC to
understand how to apply XML to improve the data center's services and data
acquisition activities.
- James E. Gass (Raytheon ITSS), Editor
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An XML-Based Prototype ADC Search Service
James E. Gass and Brian M. Holmes (Raytheon ITSS)
Our on-going efforts to improve data discovery have resulted in a prototype
search service based on eXtensible Markup Language (XML) technologies. This
experimental service gives ADC's users greater control when searching the ADC's
collection of published data than is available through the established ADC
search facility. This prototype uses off-the-shelf Java class libraries and
object-oriented programming techniques to implement a powerful content-based
search capability.
ADC's XML research project, begun in early 1999, has already produced XML
documents that describe some 2,400 separate ADC data sets (roughly 85% of the
ADC's holdings). This body of dataset descriptions is an excellent testbed for
prototyping improved ADC data location services.
XML uses customized HTML-like tags to markup information. Unlike HTML, the tag
names identify the information content, rather than the structure or display
of the information. The set of tags and their attributes are defined as
needed, or specified in a Document Type Definition (DTD) selected to suit the
information at hand. The result is self-describing documents. The rich
content tagging of these descriptions will make it possible to perform
highly focussed searches for ADC data sets that meet users needs.
The Document Object Model (DOM) is a standard way for programs to access and
manipulate XML documents. It specifies how XML documents can be represented as
objects during the execution of a program. The German National Research
Center for Information Technology's Integrated Publication and Information
Systems Institute (GMD-IPSI) provides a package that saves this run-time
representation of an XML document to a binary file as a "Persistent DOM" or
PDOM. While the PDOM does not create an inverted index of the words in the
document, it does index the location of each element tag. This provides very
fast access to all of the tags, for example, even if the XML
document is very large.
For our demo, we created a single large (22MB) XML document by concatenating
the 2,400 XML data set descriptions of ADC's holdings, and used the PDOM
facility to create a binary file representation of the large XML document's
hierarchy. The resulting 29MB file is our "database" of data set documents,
and is accessed with GMD-IPSI's XQL query package. Initially, we've given the
user the choice of a simple HTML form-based interface or a more comprehensive
Java applet interface. The form parameters (form-based interface) or the XQL
query (applet-based interface) are included on the URL to the web server.
The web server recognizes that the URL represents a servlet request, and
passes it on to the Apache JServ servlet engine. JServ dispatches the request
for execution by the QueryServlet. The Java servlet constructs an XQL query
from the form parameters or uses the applet's XQL query directly, calling the
GMD-IPSI's XQL query engine to find the matching data sets in the PDOM.
The results of the query are in XML format, so they are transformed with an
eXtensible Stylesheet Language Transform (XSLT) script into HTML for display
in the user's browser. Java classes from IBM's XML4J parser and LotusXSL
processor packages are used to perform the transformation.
The prototype ADC search service, with its two user interfaces, can be found
at http://xml.gsfc.nasa.gov/search_demo/intro.html
This application of XML technologies to the ADC's holdings does allow for much
more precise searches than are possible with the established search service
(see http://adc.astro.umd.edu/adc/sciencedata.html#search). For example, one
can now easily find ADC tables published since 1998 with information about the
Ca II line.
This project has shown that useful XML applications can largely be implemented
with free tools and code packages. Even though XML technologies and tools
are rapidly changing, they are already useful, and their adherence to various
W3C standards makes it easy to combine tools from different sources into a
working application.
The prototype XML search application has provided good feedback for our
efforts to design a generally useful DTD for astronomical data. Future work
will include applying XML markup to data tables to permit record level search
and retrieval, refined user interfaces, development of help files and
tutorials, and expanding the XML data set descriptions to include all ADC data
sets.
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XDF, the eXtensible Data Format for Scientific Data
Ed Shaya (Raytheon ITSS)
Work is ongoing at the ADC to define an XML mark-up language that allows the
major classes of scientific data to be represented in a consistent manner
independent of the scientific specialty involved, and that makes use of object
models encompassed by modern programming languages. Such data representations
would benefit from the widespread acceptance that XML has, and could bring
about greater interdisciplinary information transfer. It is reasonable to
expect that this approach would lead to improved public dissemination of
scientific and technical explorations.
A large fraction of scientific numeric data in existence can be classified
into the following three categories:
1) A simple parameter set to a single value, possibly
infinite, or a range of values, possibly of infinite extent
(e.g. x=3.1 or 0 < y < 180).
2) Gridded samples of scalar or vector fields embedded in
a continuous N-dimensional space. We shall refer to this
class as fields.
3) Lists of items and values for a selection of their
properties. Commonly, this class of data is called tables.
An important complication is that the values of properties
in tables may be fields (e.g. an atlas).
Examples of N-dimensional spaces include physical space, projected space,
time, wavelength, frequency, energy scales or some other parameter space. The
fields include tightly sampled grids such as spectra, images, animations, or
time-series measurements. It also includes sparsely sampled data such as
event detection or pointed single aperture measurements. The embedded space
is almost always continuous, the sampling is often not.
Because fields always has some finite resolution, it is always gridded
(sometimes variably) and both fields and tables are therefore represented
similarly as ordered lists of values. Software can take advantage of this
similarity by sharing input/output methods between the two. In fact much of
the data handling can be similar: subsetting, taking cross-sectioning, etc.
However, the fundamental difference between the tables and fields is the fact
that tabled properties rarely form a continuous space and therefore
interpolation and analyses depending on interpolation are not sensible.
For XDF, the fields and tables are considered to be a single class of
N-dimensional objects, that can contain any combination of four distinct types
of dimensions; continuous coordinates, discontinuous item and property spaces,
and discontinuous vector components that usually refer to continuous
coordinates.
A point of departure for the XDF format is a standardized format for
associating the embedded space with the data and for keeping data associated
with the same space together in a consistent and organized manner. This has
been a failing of most of the existing scientific data formats probably
because they are too loose with associated scales and axes descriptions. It
is often difficult to create an application that can display axes along with
all of the data without some user intervention. And too often the axes
information is simply not present in the data file.
For more on this format development check out our XML web pages at
http://tarantella.gsfc.nasa.gov/xml.
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Newly Acquired and Updated Catalogs/Journal Tables
Gail L. Schneider (Raytheon ITSS)
The following catalogs and journal tables are currently available from the
ADC repository. The ADC gratefully acknowledges the CDS, AAS, and individual
authors who have recently contributed to our repository.
See http://adc.astro.umd.edu/adc/acq_new_updated.html#new_list for a hypertext
version of this article containing direct links to each catalog and journal
table listed.
NEW CATALOGS AND JOURNAL TABLES
ID# Abbreviated Title (First Author, Year)
Photometric Data
2227 The Asiago Supernova Catalogue 1999 (Barbon+, 1999)
Combined & Derived Data
5103 NPG G5-M stars RV, DDO and BV photometry (Yoss+, 1997)
Miscellaneous Data
6062A Photoelectric Absorption Cross Sect (Balucinska-Church, McCammon 1992)
6082 Stark broadening of H lines (Stehle 1995)
6098 Stark broadening of H lines (Stehle+, 1999)
Radio Sources
8059 The FIRST Survey, version 1999Jul (White+ 1999)
High-Energy Data
9010A ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
9028 ROSAT HRI Pointed Observations (1RXH) (ROSAT Team, 1999)
Astronomy and Astrophysics
J/A+A/351/212 V1794 UBVR time series (Jetsu+, 1999)
J/A+A/352/39 Great Attractor region redshifts (Woudt+, 1999)
J/A+A/352/117 Galactic lithium evolution revisited (Romano+, 1999)
J/A+A/352/297 The dust content of planetary nebulae (Stasinska+, 1999)
J/A+A/352/555 Fundamental parameters of stars (Allende Prieto+, 1999)
J/A+A/352/600 O & B stars Hbeta photometry. I. (Kaltcheva+, 1999)
J/A+A/352/605 O & B stars Hbeta photometry. II. (Kaltcheva+, 1999)
Astronomy and Astrophysics Supplement Series
J/A+AS/52/63 H I Survey of the Galactic Center Region (Burton+, 1983)
J/A+AS/65/267 A 5-GHz Survey of Radio Sources (Altschuler 1986)
J/A+AS/139/1 HI in Byurakan blue compact galaxies (Thuan+, 1999)
J/A+AS/139/25New proper-motion stars -30<DE<-5, 13h30m<RA<<4 (Wroblewski+ 1999)
J/A+AS/139/29 Empirical calibration of the 4000 A break (Gorgas+, 1999)
J/A+AS/139/47 1995 Saturnian satellites mutual events (Emelianov+, 1999)
J/A+AS/139/69 UBV Astrometry and Photometry of doubles (Shatsky+, 1999)
J/A+AS/139/97 HI properties of nearby galaxies (Karachentsev+, 1999)
J/A+AS/139/135 The Optical Spectrum of RR Tel (Crawford+ 1999)
J/A+AS/139/141 Galaxies in the Perseus Cluster (Brunzendorf+, 1999)
J/A+AS/139/425 CCD Photometry and Astrometry of Double Stars (Cuypers+, 1999)
J/A+AS/139/433 RV and vsini of evolved stars (de Medeiros+ 1999)
J/A+AS/139/483 Early-type gal. kinematics in compact groups (Bonfanti+, 1999)
J/A+AS/139/491 BVI photometry of nearby galaxies (Makarova+, 1999)
J/A+AS/139/513 1975-1995 V1794 Cyg UBVRI photometry (Jetsu+, 1999)
J/A+AS/139/545 1-22 GHz spectra survey (Kovalev+, 1999)
J/A+AS/139/525 Abell 496 heliocentric velocities (Durret+, 1999)
J/A+AS/139/559 Abell 496 photometric catalogue (Slezak+, 1999)
J/A+AS/140/29 Photometric monitoring of 47 late-type stars (Strassmeier+, 1999)
J/A+AS/140/55 Pulsation of galactic long-period variables (Barthes+, 1999)
J/A+AS/140/79 Radii of 22 galactic Cepheids (Imbert, 1999)
J/A+AS/140/89 Galaxy coordinates. II (Paturel, 1999)
J/A+AS/140/351 UBV photometry of SGP AGNs (La Franca+, 1999)
Monthly Notices of the Royal Astronomical Society
J/MNRAS/229/589 Interplanetary Scintillation Survey at 81.5 MHz (Purvis+ 1987)
EXTERNAL DATA SET LINKS
Combined & Derived Data External Databases
E5003 Multiband Astronomical Imaging Service ON-line (NAOJ/ADAC 1999)
Nonstellar and Extended Objects External Databases
E7006 Hypercat Extragalactic Database (Prugniel+ 1999)
UPDATED CATALOGS AND JOURNAL TABLES
Data corrected:
Astrometric and Positional Data
1006 Cape 20554 Faint Stars, -40 to -52, 1900.0 (Spencer Jones+ 1939)
Spectroscopic Data
3070 Luyten's White Dwarf Catalogues (Luyten, 1970-77)
3200A Catalogue of [Fe/H] (Cayrel de Strobel+, 1997)
Miscellaneous Data
6042 Identification of a Constellation From Position (Roman 1987)
Radio Sources
8053 The Green Bank Survey (Maslowski+ 1972-87)
Astronomy and Astrophysics
J/A+A/341/751 ROSAT HRI observations of the Pleiades (Micela+ 1999)
Astronomy and Astrophysics Supplement Series
J/A+AS/49/715 New variable stars (Terzan+, 1982)
J/A+AS/126/1 Double stars measurements (Gili+ 1997)
J/A+AS/131/73 Catalogue of HI maps of galaxies. I. (Martin 1998)
J/A+AS/137/299 Hamburg/SAO Survey for ELGs. II. (Pustilnik+ 1999)
J/A+AS/137/451 Radial velocities. IX. (Duflot+, 1999)
Astronomical Journal
J/AJ/77/405 Intense radio sources at 1400MHz (BDFL sample) (Bridle+, 1972)
J/AJ/90/1437 Active Extragalactic Objects III (Coleman+ 1985)
J/AJ/92/787 Outer galaxy VLA survey (Fich 1986)
J/AJ/105/427 IRAS fluxes of UCM galaxies (Rego+ 1993)
J/AJ/108/405 Montreal Blue Galaxy Survey. II. (Coziol+, 1994)
J/AJ/115/635 Cepheid radial velocities (Metzger+ 1998)
Astrophysical Journal
J/ApJ/434/54 Spectral properties of X-ray-selected AGNs (Thompson+ 1994)
J/ApJ/441/307 Proper motions and brightness of Cas A (Anderson+ 1995)
J/ApJ/471/694 Abell 2390 Gunn photometry and equivalent widths (Abraham+ 1996)
Astrophysical Journal Supplement Series
J/ApJS/95/457 IRAS images of nearby dark clouds (Wood+ 1994)
J/ApJS/112/245 Redshift survey for IRAS galaxies (Nakanishi+ 1997)
Publications of the Beijing Astronomical Observatory
J/other/PBeiO/24.71 CPASJ2 catalogue (Lu+, 1994)
Publications of the Kinematika Fizika Nebesnykh Tel. (kiev)
J/other/KFNT/12.20 Nearby stars metallicities (Zakhozhaj+ 1996)
Additional data files added:
Astronomy and Astrophysics
J/A+A/280/581 Chemical abundances of PNe (Pasquali+, 1993)
ReadMe file revisited:
Astrometric and Positional Data
1090 Positions of 502 Stars in Pleiades Region (Eichhorn+ 1970)
Photometric Data
2146 Observations of the Ap Star HR 1217 from 1980-86 (Kurtz+ 1989)
Spectroscopic Data
3084B Galactic O Stars (Cruz-Gonzalez+ 1974)
Nonstellar and Extended Object
7110A Rich Clusters of Galaxies (Abell, Corwin, Olowin 1989)
7158 Revised and Updated Cat of QSOs (Hewitt, Burbidge 1993)
Astronomy and Astrophysics
J/A+A/323/739 ROSAT detected quasars. II. (Brinkmann+ 1997)
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