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©Laboratory of
Advanced Information Technologies and Standards,
2001
George Mason University
TABLE
OF CONTENTS
Abstract
1 Introduction to
DIAL
2 Setting up a DIAL
Server
2.1 Download
DIAL executables and sample data
files
2.1.1
System Requirements for
Installation
2.2 Install DIAL
on UNIX platforms
2.3 Install DIAL on
Windows 95/NT platforms
2.4 Testing your
Installation
2.5 DIAL
Server’s Directory
Structures
3 DIAL data
Formats
3.1 HDF
3.2 HDF-EOS
4 Ingesting Data
into DIAL for distribution
4.1 Data
Preparation
4.2 Creation
of a Searchable Inventory Database
4.2.1
Insertion of Metadata into HDF
or HDF-EOS files
4.2.2
Extraction of Metadata to Form the
Inventory
5 Usage of
DIAL
5.1 Accessing
Files Through the Search
Interface
5.2 Accessing Files
Through the Quick View
interface
5.3 Using
dib_view Alone
5.4 Creating a Main
Page for Your Site
6 DIAL
Maintenance
7
References
This document contains information
about the downloading, installation,
utilization, and maintenance of the
Data and Information Access
Link (DIAL) server software on
Unix and Windows 95/Windows NT platforms.
The document also contains a brief
introduction to the DIAL functionality and
development history as well as the
DIAL-supported HDF and HDF-EOS data
formats. The target readers of this
document are the data producers and the
system administrators who want to set up a
DIAL server for distributing their data on
the World Wide Web (WWW).
The Earth Observing System (EOS) is a
very large, ambitious project funded by
NASA as a part of the Mission to Planet
Earth [1]. The EOS Data and
Information System (EOSDIS) is the portion
of the project that handles the vast
amounts of data gathered by EOS. Possibly
the most visible functions of EOSDIS will
be the archiving and distribution of the
enormous amounts of data. The current plan
calls for these functions to be carried
out by Distributed Active Archive Centers
(DAACs). Each of these DAACs will contain
a large, complex data system designed to
handle a large volume of data search and
order transactions.
Recent recommendations by the National
Research Council suggested that an EOSDIS
built from many small data systems working
loosely together, rather than a few
tightly coupled large data systems, may be
desirable. To that end, we have developed
the Data and Information Access Link
(DIAL, formerly known as DAAC-in-a-Box)
[2, 3]. DIAL is a portable suite
of software, specifications, and
documentation assembled primarily from
off-the-shelf public domain software and
easily customizable by the site
administrator. It is capable of
distributing data to a community of users
from a relatively small archive (by EOS
standards) via the WWW, which provides an
excellent model and many of the building
blocks for such a system.
The DIAL allows a data provider to:
- Set up a low-end workstation
(Windows 95/NT or UNIX) as a Web-based
scientific data server.
- Populate it with data.
- Establish Web pages to provide
search and selection of data.
- Provide browsing, subsetting,
subsampling, and downloading of data in
multiple formats.
- Provide client tools to be used
with Web browsers to further examine
and manipulate the data.
- Advertise the server to the EOSDIS
community.
Currently, this software has been
downloaded by over 300 sites and actively
used by about 25 sites. Examples of the
DIAL users include:
- EOS investigators
- NASA projects and data centers
- Advanced Composition Explorer
(ACE)
- National Oceanic and Atmospheric
Administration (NOAA) Pacific Marine
Laboratory
- International partners: DERA
(United Kingdom) and NASDA (Japan)
DIAL has been developed by the Data
Engineering Section of Raytheon
Information Technology and Scientific
Services (RITSS), in collaboration with
the National Center for Supercomputing
Applications (NCSA). The project was
funded by NASA/GSFC as one of Earth
Science Data and Information System
(ESDIS) prototype activities. Further
information and an online demonstration of
DIAL as well as how to download the DIAL
software and sample data can be obtained
from the DIAL home site at http://laits.gmu.edu.
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2
Setting up a DIAL
Server
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2.1
Download DIAL executables and sample data
files
Currently, DIAL is available for the
following platforms:
- IRIX 5.3/6.3
- Solaris 2.6
- Digital Alpha OSF/1
4.0
- Windows 95/NT
The UNIX version of the DIAL release
package is distributed in a compressed tar
file form, and the Windows 95/NT version
is distributed in self-extracting zip
files. The DIAL home site provides
instructions on how to download the latest
version of DIAL. Please check the DIAL
site periodically for the latest
release.
2.1.1
System Requirements for
Installation
To install DIAL, you need an http
server installed on your machine. The PC
version of DIAL distribution package comes
with an Apache http server, which can be
installed automatically on your machine by
the DIAL auto-installation program if you
choose to install the Apache server too.
For UNIX machines, you also need to have a
rwx
(read-write-execute) permission to your
http server’s cgi-bin,
htdocs and icons
directories.
2.2
Install DIAL on UNIX
platforms
On Unix, after downloading the DIAL
distribution package, you have to
uncompress it (by using command gunzip for
*.gz files or uncompress for *.Z files).
After that, the tar file can be opened by
command tar xvf *.tar. The result of this
command is the creation of the DIAL
directory that has the following files and
sub-directories:
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File/Directory
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Description
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README
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The file contains instructions
on DIAL installation for a
specific platform.
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icons/
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This directory contains gif
files for icons on the DIAL
page.
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cgi-bin/
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cgi-bin/dib/
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This directory contains all
the DIAL cgi executables
(dial_search,
dial_view), palette files,
the palette configuration file,
and Java applet configuration
files.
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htdocs/
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htdocs/dib_home/
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This directory contains all
the DIAL's Java classes and
related files for the Java
interface.
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htdocs/hdf/
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This directory contains the
DIAL inventory file and sample
HDF data files.
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htdocs/trans/
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This directory contains HDF
and HDF-EOS sample data
files.
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tools/
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This directory contains
executables for creating your own
searchable metedata database
stored in a HDF file, and prepare
HDF or HDF-EOS data files for
DIAL.
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Move the contents of the cgi-bin,
htdocs and icons directories in the
distribution file to the corresponding
directories under the HTTP server root
directory.
If your server is an Apache server,
then make the following changes in the
srm.conf file:
- Uncomment ScriptAlias /cgi-bin/ to
point to the /cgi-bin/ directory under
the server root directory.
- set Alias /HDF/ to point to the
/htdocs/hdf/ directory under the server
root directory. (e.g. Alias /hdf/
"/usr/local/apache/htdocs/hdf/")
- set Alias /icons/ to point to the
/icons/ directory under the server root
directory.
For other types of HTTP servers,
please consult your Web administrator for
setting up the above aliases.
2.3
Install DIAL on Windows 95/NT
platforms
You can install DIAL on Windows 95/NT
from either a self-extracting zip file or
from a CD. If you are installing from the
self-extracting zip file, simply execute
the file. If you are installing DIAL from
the CD, launch winnt95\setup.exe by double
clicking on it. From here, the DIAL setup
program will step you through the
installation and configuration
process.
2.4
Testing your
Installation
- Restart your Web server.
- Bring up your favorite Web
browser.
- Enter the URL: "http://<your
machine internet name>/test.html" or
"http://localhost/test.html"
NOTE: If you are not running
your Web server on the standard port,
i.e., port 80, then you need to specify
the port number in your URL. (For example,
if you are running your Web server on port
8090, use the URL:
http://localhost:8090/test.html).
2.5
DIAL Server’s Directory
Structures
After your DIAL has been installed,
your DIAL server's directory structure
should look like the directory structure
shown in Figure 2.
Figure 2: The structure of all the
files and directories in DIAL’s
server
Although the data users of DIAL can
download data in multiple formats, the
data producers have to produce data in
DIAL-supported formats in order for DIAL
to distribute the data to the data users.
Two data formats, HDF and HDF-EOS, are
currently supported by DIAL. This section
provides an introduction to those two
formats.
3.1
HDF
The Hierarchical Data
Format, or HDF, is a
object-based file format for sharing
scientific data in a distributed
environment. HDF was developed by NCSA to
serve the needs of diverse groups of
scientists working on projects in various
fields with different computer
platforms[4]. HDF was designed to
address many requirements for storing
scientific data, including:
- Support for multiple types of data
and metadata commonly used by
scientists.
- Efficient storage of and access to
large data sets.
- Platform independence.
- Extensibility for future
enhancements and compatibility with
other standard formats.
HDF provides six data
models and their corresponding software
interface for storing and accessing
scientific data. The six data models,
as illustrated in figure 1a,
are raster image, palette, scientific
data set, annotation, vdata, and
vgroup.
HDF files are
self-describing. The term
"self-description" means that, for each
HDF data object (structure) in a file,
there is comprehensive information about
the data. This information is often
referred to as metadata.
Also, different types of data can be
included within a single HDF file. For
example, it is possible to store symbolic,
numerical and graphical data within an HDF
file by using appropriate HDF data
models.
HDF can be viewed as several levels. At
its lowest level, HDF is a physical file
format for storing scientific data. At its
highest level, HDF is a collection of
utilities and applications for
manipulating, viewing, and analyzing data
stored in HDF files. Between these levels,
HDF is a software library that provides
high-level and low-level programming
interfaces to its data models. It also
includes supporting software that make it
easy to store, retrieve, visualize,
analyze, and manage data in HDF files. The
basic interface layer, or the
low-level API, is reserved
for software developers. It was designed
for direct file I/O of data streams, error
handling, memory management, and physical
storage. It is a software toolkit for
experienced HDF programmers who wish to
make HDF do something more than what is
currently available through the
higher-level interfaces. Low-level
routines are available only in C.
FIGURE 1a – HDF Data
Structures
The HDF application programming
interfaces, or APIs,
include several independent sets of
routines, with each set specifically
designed to simplify the process of
storing and accessing one type of data.
These interfaces are represented in Figure
1b as the second layer from the top.
Although each interface requires
programming, all the low-level details can
be ignored. In most cases, all one must do
is make the correct function call at the
correct time, and the interface will take
care of the rest. Most HDF interface
routines are available in both FORTRAN-77
and C.
At the highest level, general
applications, HDF includes various
command-line utilities for
managing and viewing HDF files, several
NCSA applications that
support data visualization and analysis,
and a variety of third-party
applications. The HDF utilities
are included in the NCSA HDF distribution
package.
Source code and documentation for the
HDF libraries, as well as binaries for
supported platforms, are freely available
but subject to the restrictions listed in
the copyright notice. Those materials are
available via NCSA's anonymous FTP server
ftp.ncsa.uiuc.edu, in the
directory /HDF/. (The HDF FTP
server at http://hdf.ncsa.uiuc.edu mirrors
this material in the directory
/pub/dist/HDF/.) Applications
supported by NCSA, as well as applications
contributed by members of the worldwide
HDF user community, are also available on
these servers.
FIGURE 1b – Three levels of
Interaction with the HDF
File
3.2
HDF-EOS
HDF-EOS is the standard format for
EOSDIS data production and archive. The
EOSDIS Core System (ECS), the
infrastructure of EOSDIS, will provide
scientists and other users a broad range
of desktop services from a number of
science data centers and through the World
Wide Web. The HDF-EOS data format is
standard HDF with ECS conventions, data
models, and metadata added.
There are three HDF-EOS specific data
models, point, grid, and swath, for
storing geospatial data. These data models
allow the file contents to be queried by
geographic coordinates and time. An
HDF-EOS file also contains ECS metadata
which are essential for ECS search and
other user services. An HDF-EOS file can
be read by any tool that accepts standard
HDF files, although HDF-EOS geolocation or
temporal information generally is not
accessible using standard HDF calls. A
data product does not need to fit any of
the grid, point or swath models to be
considered HDF-EOS. If ECS metadata are
included, it is a valid HDF-EOS file.
HDF-EOS is implemented as a C library
extension of the standard HDF library
(with FORTRAN bindings). HDF-EOS
ordinarily is based on the latest release
of HDF.
What is the
swath data model?
The swath data model is used to
represent time sequences of scan lines,
profiles, or other array data. A swath has
an "along-track" direction that is
monotonic with time and usually a
"cross-track" direction associated with
each time instance. The cross-track
direction need not be a straight line; a
circular scanning instrument can utilize
this data model by specifying its
coordinates as a function of time. This
data type will be most useful for products
at EOS processing levels 1 or 2.
What is the
grid data model?
The grid data model is used to store
data located on a regular grid, based upon
one of several map projections. This data
model will be most useful for products at
EOS processing levels 3 or 4. The
ECS-supported map projections include
Space Oblique Mercator, Universal
Transverse Mercator (UTM), Interrupted
Goode, Polar Steroegraphic, Lambert
Azimuthal Equal Area, Lambert Conformal
Conic, Polyconic, Transverse Mercator,
Hotine Oblique Mercator, and Integerized
Sinusoidal.
What is the
point data model?
The point data model is used to store
data from a network of locations that are
irregularly spaced. The user may define
hierarchical "levels" that are similar to
linked tables in a relational database.
The point data model is most suitable for
data obtained from point measurements,
such as weather station data, buoy data,
ship-measured oceanographic data.
How are
metadata inserted, viewed, and extracted
from HDF-EOS files?
The SDP Toolkit (http://newsroom.hitc.com/sdptoolkit/toolkit.html)
provides the easiest method for handling
metadata. This library contains calls for
writing, manipulating and accessing
metadata in HDF-EOS files. EOSView can be
used to view metadata. For more
information on how to set your metadata,
write to pgstlkit@eos.hitc.com.
What types of
metadata are embedded in an HDF-EOS file
and what are the added storage
requirements?
An HDF-EOS file must contain ECS "core"
metadata which is essential for ECS search
services. Core metadata are populated
using the SDP Toolkit, rather than through
HDF-EOS calls. "Archive" metadata
(supplementary information included by the
data provider) may also be present. If
grid, point, or swath data types have been
used, there also will be structural
metadata describing how these data types
have been translated into standard HDF
data types. Metadata resides in
human-readable form in the Object
Descriptor Language (ODL). Structural
metadata uses 32K of storage, regardless
of the amount actually required. The sizes
of the core and archive metadata vary
depending on what has been entered by the
user.
What are the
options for adding ECS metadata to
standard HDF files?
For data products that will be accessed
by ECS but which remain in native HDF,
there is a choice of 1) adding no ECS
metadata in the HDF file, 2) inserting ECS
metadata into the HDF file, or 3)
"appending" ECS metadata to the HDF file.
"Append" means updating the HDF location
table so that the appended metadata
becomes known to the HDF
libraries/tools.
How do I
obtain HDF-EOS? Who maintains the
libraries?
HDF-EOS was developed and is maintained
by Raytheon Information Technology Systems
(RITS) under contract to EOSDIS Core
System (ECS). Information on downloading
can be obtained by sending e-mail to
pgstlkit@eos.hitc.com.
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4
Ingesting Data into DIAL for
distribution
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4.1
Data Preparation
If data to be distributed are already
in HDF or HDF-EOS format, DIAL can work
directly with these data. However, if the
data are not in DIAL-supported formats,
conversion of data into DIAL-supported
formats is required. Currently, data
translators for converting ARC/INFO
exchange format into HDF-EOS are available
freely for SGI, SUN, and Windows 95/NT
platforms at http://heineken.gsfc.nasa.gov/eosgis/eghome.html.
The GeoTIFF and ArcView Shape translators
will be available in 1999 at the same
site. More data translators and some
generic data description tools are planned
to be developed. In addition, data
providers can develop data translators to
translate their specific data into HDF or
HDF-EOS. Both HDF and HDF libraries are
freely available for building the
customized data translators. See Section
3.1 and 3.2 for how to obtain the HDF and
HDF-EOS libraries.
4.2
Creation of a Searchable Inventory
Database
Once the data are in HDF or HDF-EOS
format, DIAL’s dib_view CGI program
can directly work with those files to
provide data users with the capabilities
of data access and manipulation on
individual files. However, if the data
provider wants to provide the data search
capability to users for searching
individual data files in the DIAL site, a
searchable inventory database has to be
created to work with DIAL’s
dib_search CGI program. The current
procedure for creating the searchable
inventory database involves two steps:
The first step is to prepare the
metadata in PVL or ODL form. If the data
files already contain the metadata in PVL
or ODL format, this step is not required.
There are two ways to create the inventory
database from PVL or ODL formatted
metadata. One way is to insert the
metadata into the HDF or HDF-EOS files as
a global attribute called 'coremetadata'.
The second way is to create metadata files
and not change the data files.
The second step is to run "crinv" to
extract the metadata items from the data
files or the metadata files to form the
searchable inventory database.
The following two sections give
detailed instructions on how to create the
inventory database.
4.2.1
Insertion of Metadata into HDF or HDF-EOS
files
- Change the directory to
DIAL/tools
(where DIAL is the directory containing
the current DIAL distribution). The
following files are in this directory:
- crinv:
A binary executable program for
creating your own inventory.
- meta:
A binary executable program for
preparing HDF files for DIAL.
- dial.cfg:
This is the configuration file for
the DIAL server. The parameter
values given in this file are for
the DIAL server installed at
http://laits.gmu.edu.
These values have to be
appropriately modified based on your
metadata.
- Define your search attributes by
modifying the dial.cfg
configuration file. A sample
dial.cfg
configuration file is:
Attribute Datatype Search Conversion Equivalent
-------------------------------------------------------------------------------
LongName char8(80) YES NONE NONE
EastBoundingCoordinate float32 YES LONG MAXLONG
NorthBoundingCoordinate float32 YES LAT MAXLAT
SouthBoundingCoordinate float32 YES LAT MINLAT
WestBoundingCoordinate float32 YES LONG MINLONG
RangeBeginningDate uint32 YES DATE MINDATE
RangeEndingDate uint32 YES DATE MAXDATE
RangeBeginningTime uint32 YES TIME MINTIME
RangeEndingTime uint32 YES TIME MAXTIME
ArchiveCenter char8(20) YES NONE NONE
ParameterName char8(30) YES NONE NONE
PlatformShortName char8(20) YES NONE NONE
SensorShortName char8(20) YES NONE NONE
- For each of your HDF data files,
create a file to contain the metadata
that will be searched by DIAL. For
example, here is a PVL formatted
metadata file.
STARTCOREMETADATA
LongName =
ERS-1 Ice Motion Vectors;
EastBoundingCoordinate
= -115.8717;
NorthBoundingCoordinate
= 82.1543;
SouthBoundingCoordinate
= 80.3253;
WestBoundingCoordinate
= -127.5484;
RangeBeginningDate
= 1993-01-04;
RangeEndingDate
= 1993-01-07;
RangeBeginningTime
= 21:21:35;
RangeEndingTime
= 21:27:18;
ArchiveCenter
= ASF;
ParameterName
= ICE MOTION;
ParameterName
= ICE VELOCITY;
PlatformShortName
= ERS-1;
SensorShortName
= SAR;
ENDCOREMETADATA
- Execute meta program to add the
metadata block defined between the
STARTCOREMETADATA and ENDCOREMETADATA
lines. (STARTCOREMETADATA and
ENDCOREMETADATA lines are used by the
meta program to recognize the start and
end of the metadata to be written to
the data file.) For example, meta
./hdf/ice.hdf ice.meta to create a
coremeta attribute for the ice.hdf file
that will be searched for by DIAL.
- Move your modified data files to
the htdocs/hdf directory under the
server root directory.
4.2.2
Extraction of Metadata to Form the
Inventory
The DIAL inventory can exist in two
forms. One form is an HDF file. The other
form is a database table.
The crinv program, an executable in the
DIAL/tools directory standing for "create
inventory", is used to create a searchable
inventory stored in an HDF file or a
Database table.
Creating an
HDF Inventory File
The crinv program needs at least three
parameters to create an HDF inventory
file. The first parameter is the name of
the new inventory file, the second is the
name of the configuration file followed by
one or more input HDF files or metadata
files. For example, "crinv
my-inventory.hdf dial.cfg
/htdocs/hdf/*.hdf". If crinv is run on the
command line with less than three
parameters, a usage message will show
up.
Creating a
Database Inventory Table
The crinv program needs the "-d" option
and at least four parameters to create the
database inventory table. The first
parameter is the name of the configuration
file, the second is the URL for the
database (JDBC driver, database server
hostname, database server port number, and
database name), the third is the inventory
table name, followed by one or more input
HDF or metadata files. For example,
crinv –d dial.cfg
jdbc:msql://hostname:port/mydatabase
mytable *.hdf.
NOTE: Make sure that you
set environment variable CLASSPATH
to include the path of the JDBC driver
and LD_LIBRARY_PATH to include the
path of the library libdialhdf.so
if they are not in the current
directory.
Inventory
Creation Steps:
- Edit filetable.temp to replace the
file path for the leapsec.dat (is also
located in your tools directory.
- Set environment variable
"FILETABLE_PATH" to point to your DIAL
tools directory.
- Execute crinv on your HDF or
metadata files.
- Move your "inventory.hdf" and the
data files to the htdocs/hdf directory
under the server root directory.
DIAL provides three main CGI programs
that work with an HTTP server to provide
the data access services to users. The
three CGI programs are dib_search,
dib_view, and transient.
dib_search searches the inventory
database based on users' queries. The
search results are the individual files
that meet the users' search criteria. The
results are sent back to the users as an
HTML pages with embedded URLs linking to
dib_view for each file.
dib_view handles all data browsing,
subsetting, subsampling, reformatting, and
downloading requests from data users.
transient creates an HTML page that
lists all files in a directory with
embedded URLs linking dib_view to
each file. Thus, both dib_search
and transient have to work with
dib_view to fulfil the data
distribution tasks. However,
dib_view can also work alone in
DIAL. Therefore, DIAL can be used in three
ways for data distributions:
dib_search/dib_view pair,
transien/ dib_view pair, and
dib_view alone. For all three ways,
a URL entry point for starting DIAL has to
be provided in an HTML page (e.g., in the
main page of your site). The following
sections will discuss the pros and cons of
each way of using DIAL.
5.1
Accessing Files Through the Search
Interface
This is the most common way to use
DIAL. By using DIAL in this way, both DIAL
search and data access capabilities are
provided to the data users. Therefore,
most of DIAL's functions will be
exploited. However, this method requires
the creation of a searchable inventory
database, which will take some time if the
metadata are not already in the data
files. But if the number of data files to
be distributed is hundreds, thousands, or
even more, this method provides the best
way for users to find the data they
need.
Since dib_view will be
automatically linked by search results,
only a URL entry point to
dib_search is needed. To invoke
DIAL in this way, you have to place a DIAL
URL in an HTML page in the following
way:
http:/hostname/cgi_dir/dib_search/hdf_dir?inventory_db&
{html | java}
where:
hostname is the name of the machine
on which DIAL is installed. cgi_dir
is the CGI directory where all the dib CGI
programs are located. hdf_dir is a
directory under the document root
directory where the data files and the
inventory database are located.
inventory_db is the inventory
database name. The last option in the URL
is the selection of the HTML or JAVA users
interface. If JAVA is selected, the JAVA
version of the DIAL user interface will be
shown to data users.
An example URL for using DIAL in this
way on the DIAL home site is:
http://laits.gmu.edu/cgi-bin/dib/dib_search/hdf?inventry.hdf&html
5.2
Accessing Files Through the Quick View
interface
If the number of data files that you
want to distribute is small (less than
about 100 HDF files), and those files do
not contain the metadata readable by
crinv, DIAL provides an alternative
and fast way for distributing the data by
using the Quick View interface provided by
the transient program. In
this way, you don't have to create a
searchable inventory database. What you
need to do is just move the data files to
a directory under your document root
directory, and provide an URL link to
start the transient CGI program. The
advantage of using DIAL in this way is
that you can move data files into the
transient directory at any time and they
will be immediately become visible and
accessible to the data users. The
disadvantage is that the data users will
not be able to do a catalog search.
The URL to use DIAL in this way
is:
http://hostname/cgi_dir/transient/trans_dir?
where :
hostname is the name of the machine
on which DIAL is installed. cgi_dir
is the CGI directory where all the dib CGI
programs are located. trans_dir is
the directory where all the data files are
located. This directory must be under the
HTTP document root directory.
An example URL for using DIAL in this
way on the DIAL home site is:
http://laits.gmu.edu/cgi-bin/dib/transient/trans?
5.3
Using dib_view
Alone
You can directly embed the
dib_view URL into your HTML pages.
By presenting data to the users in this
way, you can combine a detailed
description of a data file with direct
access to data. No inventory database is
needed for this method of data
distribution. This method is suitable for
data providers to distribute a small
number of static data files to data users.
The URL for using DIAL in this way is:
http://hostname/cgi_dir/dib_view/hdf_dir?file_name[&java|html]
Where:
hostname is the name of the machine
on which DIAL is installed. cgi_dir
is the CGI directory where all the dib CGI
programs are located. file_name is
the name of data file to be accessed. The
file must reside in the hdf_dir
directory. The default user interface will
be JAVA also you can select html
interface.
An example URL for using DIAL in this
way on the DIAL home site is:
http://laits.gmu.edu/cgi-bin/dib/dib_view/trans?17766010.hdf
5.4
Creating a Main Page for Your
Site
- Regardless of the access method(s)
you choose to make available to your
users, you will need to create a
main page for your DIAL
installation. This is the initial page
users will see when they enter your
site for the first time. It should
probably include some introductory
material about your site or your
project, in addition to the URLs that
you construct from the guidelines in
sections 5.1 – 5.3.
For examples of how to construct a
main page for your DIAL installation,
you may look at the file test.html in
the htdocs/ directory of your
web server or at the main page of the
DIAL home site at http://laits.gmu.edu.
If you choose to work from one of these
files to create your main page,
don’t forget to change all of the
machine names to the name of the
machine on which you have installed
DIAL. For example, if you install DIAL
on a machine called
mydial.company.com, you would
need to change all references to
localhost or
laits.gmu.edu to
mydial.company.com.
It is customary to name your main
page "index.html" and put it in the
htdocs/ directory of your web
server. Using this convention
simplifies the URL that users must type
to gain initial access to your site.
For instance, using the example site
from above, users would only need to
enter the URL http://mydial.company.com.
DIAL does not require frequent
maintenance. The following paragraphs list
common DIAL management activities.
1. Add new data files:
If there are new data files to be
ingested into DIAL, the searchable
metadata database (i.e. the inventory
file inventory.hdf) has to be updated
by following the instructions in
section 4.
2. Remove data files: If a
data file is removed from the DIAL
server, the searchable metadata
database (i.e. the inventory file
inventory.hdf) has to be updated. In
the future versions of DIAL, a new tool
program which supports the removal of
data files from the DIAL server, will
be included.
3. Update metadata of data
files: If a DIAL data file requires
updates that include its metadata, the
"CoreMeta" attribute of the DIAL data
file and the inventory.hdf also need
updates. A new tool program which
supports the update of the data
files’ metadata from the DIAL
server, will also be included in a
future release of DIAL server.
4. Add new palettes: DIAL
presents palettes for data users to
select while browsing the array type of
data. The palettes are from two
sources: 1) the internal palettes in
the HDF or HDF-EOS data files; and 2)
DIAL system palettes distributed with
the DIAL distribution package. For
inserting palettes into HDF or HDF-EOS
files, please use the HDF palette
interface. While it is somewhat
difficult to add palettes into an HDF
or HDF-EOS file, adding new palettes
into the DIAL system is very easy by
just following the steps listed
below:
Create an ASCII palette
file by using any text editor. The
file name should have a .pal
extension. The ASCII palette file
contains four columns. The first
column is the palette entry. All
browse images created by DIAL are
8-bit images. Therefore, the maximum
number of entries is 256, the
largest entry is 255, and the
smallest entry is 0. You can create
a palette with less than 256
entries. The second column is the
red value, the third column is green
value, and the fourth column is blue
value. The range for these color
values is from 0 to 255.
Copy the newly created ASCII
palette file into the directory
where the dib_view program is
located (e.g., cgi-bin/dib). In that
directory, there is a file named
dib_pal.lst. This ASCII file
contains the names of all DIAL
system palettes. You should insert
the palette file name without the
extension into this list file by
using any text editor. After doing
this step, the newly created palette
is inserted into DIAL.
- 5. Delete temporary files:
DIAL will create some temporary
files during the execution. The names
of those temporary files begin with
html, gif, bin,
hdf, and asc. On UNIX
machines, those files are located in
the /var/tmp or /tmp directory; and in
Windows 95/NT machines, the files are
located in the directory where dib_view
and dib_search programs are located
(e.g., cgi-bin/dib). Those files are
normally deleted by the DIAL CGI
programs which create them. However, if
the execution of a CGI program is
aborted due to some circumstances
(e.g., when users click the stop button
in their Web browsers), those temporary
files will be left undeleted. Sometimes
those temporary files are quite large,
therefore it is necessary to delete
those files periodically by using
operating system commands.
- MTPE EOS Reference Handbook,
1995. EOS Project Science Office, NASA
Goddard Space Flight Center.
- R. Suresh., D. Ilg, T. Meyer and
M., Folk A Web Based Science
Data Server http://spsosun.gsfc.nasa.gov//DaacinaBox.html
- Liping Di, R. Suresh, K. Doan, Doug
Ilg, Ken McDonald, 1999. "DIAL-an
Interoperable Web-based Scientific Data
Server". In M. Goodchild, M. Egenhofer,
R. Fegeas, and C. Kottman edit,
Interoperating Geographic
Information Systems, Section 4.
System Experiences. Kluwer Academic
Publishers, Norwell, MA.
- The NCSA HDF Home Page
http://hdf.ncsa.uiuc.edu.
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