TABLE OF CONTENTS
INTRODUCTION 2
1.0 Project Goals 2
1.1 Infrastructure 2
1.1.1 Internet 2
1.1.2 Wide Area Information Server 3
1.1.2 Archie File Information server 3
1.1.3 Gopher 4
1.1.4 World Wide Web 4
1.2 Reasons in choosing the WWW as the basis of the repository 6
OVERVIEW OF THE PROJECT 9
2.0 Features of the Repository 9
WORLD WIDE WEB CONCEPTS & TERMINOLOGY 12
3.0 World Wide Web project 12
3.1 WWW Clients and servers 13
3.2 HTML & URL 13
3.3 Popular Browsers and Servers 16
3.3.1 Text Based Browsers 16
3.3.2JGraphical WWW Browsers 17
3.4JJServers 20
GATEWAY TO THE TERADATA DATABASE COMPUTER 22
4.0 Gateway 22
4.1 Teradata DBC/1012 Architectural Overview 22
4.2 Teradata DBC/1012 Architectural Components 23
4.3 Programming on the Teradata DBC/1012 24
4.3.1 Call Level Interface (CLI) 24
4.3.2 BTEQ ( Batch Teradata Query facility ) Approach to programming
25
4.4 DBC/SQL 25
ON-LINE PROBLEM REPORT MECHANISM 26
5.0 Motivation 26
5.1 Existing problem reporting/review mechanisms 26
5.2 Mosaic based report mechanism with the Teradata Database computer
27
5.2.1 Implementation 27
5.3 Problem review mechanism 27
5.3.1 Implementation 28
5.4 Utility at our site 28
DYNAMIC HTML 31
6.1 Idea of Dynamic HTML 31
6.2 Implementation 31
6.3 Advantages to this approach 32
CGI & FORMS 34
7.1 Common Gateway Interface (CGI) 34
7.2 Forms 35
7.2.1 Using forms 35
7.3 Using Forms with CGI 39
7.4 Automatic mailin feature 40
CONCLUSION 42
8.0 Success of the Project 42
8.1 Limitations to the WWW 42
8.2 Future Work 42
APPENDIX A 44
CODE LISTINGS 44
APPENDIX B 72
MANAGING OUR WEB SITE 72
APPENDIX C 73
INTERESTING WEB SITES 73
APPENDIX D 75
WEB STATISTICS 75
APPENDIX E 80
EXAMPLE SQL STATEMENTS 80
APPENDIX F 82
SAMPLES OF FORMS USED IN THE PROJECT 82
References 87
CHAPTER 1
.c.INTRODUCTION
.c1.1.0 Project Goals
The goal of the project and report is to provide a basic framework for
Information Exchange using the World Wide Web . The developed framework
would be used to establish on on-line repository of information
pertaining to the Department of Computer Science . Existing
infrastructures will be examined . Useful tools would be developed using
a database as the back end of the Web. We will discuss various aspects
of the available browsers and concepts relating to the Web .Finally we
will draw some conclusions on the Web and determine future directions to
the repository .
.c1.1.1 Infrastructure
The purpose of any information system/repository is to provide users
with a seamless access to a variety of information . The repository
should provide the user community as well as the repository manage group
with simple and efficient means to ensure fast and reliable information
exchange . The infrastructure for the repository is based on the
services that the repository offers to its users . It is necessary to
explore the methods by which a repository can be practically implemented
. It is essential to first look at the available infrastructures and
then to select based on the resources available , adopt suitable
techniques that satisfy our requirements . A survey of the
infrastructure of information exchange resources is presented next and
analyzed for utility .
.c2.1.1.1 Internet
The true global information service currently existing is the massive
world wide network of computers called the Internet . In essence ,
Internet is composed of thousands of smaller regional networks scattered
throughout the globe . Having access to the Internet usually means
having access to a number of resources . A variety of tools are
available to assist users in finding and discovering information .These
resource and discovery tools aid the user in browsing and searching and
organizing information distributes across the internet , Browsing tools
allow the navigation of a user through the information space and
facilitate finding information .
.c2.1.1.2 Wide Area Information Server
The Wide Area Information Server (WAIS) is a full text information
retrieval architecture whose clients and servers communicate through the
Z39-50 protocol . A WAIS client translates user queries into the WAIS
protocol and submits them to the WAIS directory for recovery of relevant
information . WAIS servers execute full text searches on the subject .
In response to a query , a WAIS server returns a list of relevant object
descriptors which contain the words and phrases in the users query . A
yellow pages service that resides in a well known address is frequently
queried for information of participating WAIS servers . When new
information provider wants to join the WAIS , it must submit its
location , description and other relevant information to the discovery
server .
.c2.1.1.2 Archie File Information server
Archie specifically addresses the file discovery and retrieval problem
in large networks . Archie servers centralize indexing information on
file name data distributed throughout the Internet archive sites .
Currently , the Archie service makes available two types of databases .
In the first one the filenames database indexes names of files available
from hundreds of File transfer protocol (ftp sites ) . The entries in
the database are constantly updated . The user submits a query to the
database in the form of a regular expression for filenames that match
specific patterns , a complete list of FTP archive sites , or a list of
files available from specific sites . The second database is the whatis
database that contains the names and descriptions of software packages ,
documents, and other information available on the Internet . Entries in
the whatis database are text expressions consisting of key words and the
associated descriptions . Users can perform case insensitive text
searches to the keywords and corresponding descriptions . Currently the
whatis database is mainly updates from secondary data sources such as
Usenet postings , e-mail submissions , etc. . Archie developers have
described the utility as a low tech solution to the resource discovery
and information retrieval problem . However because of it's simplicity
in usage Archie has become a default information locator for many sites
.
.c2.1.1.3 Gopher
The Internet Gopher allows user to search and browse distributed
information . Gopher organizes information into a hierarchy where
intermediate nodes are directories or indices , and final nodes in the
tree are documents . The gopher architecture is composed of clients and
servers communicating through the Gopher protocol , which is implemented
upon TCP-IP . The root of the Gophers server hierarchy , located at the
University of Minnesota, is first invoked when Gopher is loaded . Links
are provided to lower level servers as the user navigates through the
network hierarchy . Users can navigate through the entire available
information base that contains full text document objects and directory
objects distributed across multiple servers . A full text search server
returns to the client handles to the documents that match the Boolean
regular expression provided by the user . Gopher objects can also
retrieve objects from WAIS , Archie, and FTP servers .
.c2.1.1.4 World Wide Web
The World Wide Web (WWW) merges the techniques of information discovery
and hypertext . The Web organizes data into distributed hypertext ,
where nodes are full text objects , directory objects called home pages
or indices . The Web also provides for full textual searches over
documents stored at a Web server . The WWW is also based on a client
server model . The client provides users with a hypertext like browsing
architecture . Besides its Hypertext Transfer protocol (HTTP) , WWW
clients can understand FTP and the Network news transfer protocol (NNTP)
. FTP in WWW clients access file archives on the Internet where the file
directories are browsed as hypertext objects . NNTP allows access to the
Internet news groups and news articles . News articles may also contain
references to other articles or news groups . These references are
represented as hyperlinks
HTTP allows document retrieval and full text search operations . HTTP
runs on top of TCP and maps each request to a TCP connection . HTTP
objects are identified by the HTTP protocol type , the corresponding
servers name and the path name to the file where the instance object
resides . The files are stored in the Hypertext Markup language(HTML)
which can be considered a subset of the Standard Generalized Markup
language(SGML) format .
The WWW discovery tree can access information across all kinds of
servers including WAIS , Gopher , NNTP , WWW servers and Archie servers
. Discovery of information involves the users starting on their home
page following a link to an index , executing a search and following the
resultant links . As users find interesting information they build their
personalized web by linking to nodes in the global web . Using the user
friendly browser interface , users can navigate through the different
classification trees to find and publish new information .The WWW exists
virtually . There is no standard way of viewing or navigating around it
. May software interfaces to the Web exist that have similar functions
and work in the same way no matter what computer or type of display is
used . A web browser is a software program on any computer with a
graphical or textual interface such as Macintosh, an X-Windows systems
or even and IBM-compatible with Windows . WWW clients or browsers are
available for the following platforms and environments . These are shown
in the tables Table 1 and Table 2 .Using the WWW as the basis of the
repository seems to be the direction necessary to be taken . Such an
implementation would provide the users seamless access to information .
Figure 1 : WWW architecture
.c1.1.2 Reasons in choosing the WWW as the basis of the repository
The WWW has been chosen as the front end of the repository for many
reasons. Many Universities and Departments have set up WWW servers
that allow them to distribute hypermedia documents across the Internet
and local networks. The essential reasons for choosing the WWW are
listed below.
JFlexibility of Platforms for Browsers
The WWW is designed to convey information in a device independent
manner. Hypermedia documents can be shown on many different types of
computers. In other words, documents on the WWW are shown to users in a
way that is best suited to their display. Documents with graphics and
formatting may be shown in full color on an X-terminal, while only the
basic formatting and text will be shown on a text-only screen.
Choice in Platforms for Servers
WWW server software is also available for different types of hardware
platforms. This makes it easier to establish a WWW server without the
need for specific hardware requirements.
Information Navigation is Fast, Interactive and Highly Intuitive
Documents on the WWW contain hot-spots in the form of hyperlinks. Forms
and menus allow users to search quickly through archives and documents.
Multimedia presentations, on-line forms, and database interfaces can be
created so that users can interact and control information rather than
just view it.
The WWW Works on Standards and is Extensible
Most WWW clients and servers have been designed to communicate using
Transmission Control Protocol/Internet Protocol (TCP/IP). Many web
clients also speak the Gopher protocol, File Transfer Protocol (FTP),
and Network News Transfer Protocol (NNTP) so that hypermedia browsers
can also act as Gopher, FTP, and USENET client applications.
The Design of the WWW Provides for the Transfer of a Variety of Data
Formats
Audio, video, extended character sets, and interactive hot-spot graphics
are some of the fundamental types of data that can be transferred using
the WWW. There are actually no barriers to the types of data sent by
the server as long as the client or browser has an application
associated with the file data type to read it. This is essentially a
very important feature that can be taken advantage of for file data
types that are not a standard as of yet. As and when the formats become
pertinent, the clients can have the respective software to access up the
file.
World Wide web clients or browsers availability
Text only browsers Graphical Interface browsers
Dumb terminal , any Unix platform Sun4/Sun OS 4.1.x
Text only SunOs,IBM,AIX,DEC,Ultrix,VAX Silicon graphics IRIX 4.x
Macintosh Text only ,Mac SE's Sys7.x VMS
Perl Linux
emacs DEC MIPS Ultrix,DEC Alpha AXP
IBM RS/6000 , AIX 3.2
HP 9000/700 , HP/UX 9.x
NeXT,neXTStep 3.0
Commodore Amiga. Amiga OS 3.0
IBM Compatibles 386 and above with windows
Macintosh Computers System 7.x
Power Macintosh
Table 1
World Wide Web servers availability
Most flavors of UNIX
HP,SGI and SUN systems
DEC MIPS Ultrix and DEC Alpha AXP
Perl
Macintosh , 68020 or better, Power Macintosh and System 7.x
NeXTStep
VM, VM/CMS,VM/XA and VMS
Windows 3.1
Windows NT
Table 2
CHAPTER 2
.c.Overview of the project
.c1.2.0 Features of the Repository
The first step in establishing the repository was to set up and
configure a Hypretext transfer protocol server on the Departmental
machines . As is the convention adopted in the WWW community , the
machine was aliased to possess the name www.cs.wvu.edu . This is
primarily to isolate the user community from changes such as relocating
a server . Several versions of the server software is available. NCSA
httpd version 1.3 was used for our purpose .
The server provides a Home Page along with other tools and information
. The homepage document is in the HTML format and will contain
links/interfaces to other HTML documents .The Home page is shown in the
figure . It will consist of information pertinent to the Department of
Computer Science such as Course structure, faculty members , research
activities , technical reports , images of the college . In addition to
these basic documents features that are provided are
a) Gateway to the Teradata Database (SQL) computer ( Used as an on-line
problem report mechanism)
b) Support for system administrator to review problems submitted on-line
c) Ability for Students to add their Home page without intervention of
systems administrator ( An example of Dynamic HTML where files are
not used )
d) Automatic mail in feature through forms
e) Gateways to RFC 's
f) An on-line systems manual
g) For users unfamiliar with HTML an automatic tool to generate the Home
page
h) Interface to the Dept. Phone book database
i) A means of displaying the Web statistics
The virtual schema of the repository is shown in the Figure 2.
Figure 2 : Virtual Schema of the Repository
Figure 3 Department Home Page
CHAPTER 3
.c.WORLD WIDE WEB CONCEPTS & TERMINOLOGY
.c1.3.0 World Wide Web project
The World Wide Web - a network of computers providing information and
resources on the Internet-grew out of a Hypertext project started out at
CERN , the European laboratory for Particle Physics . As a resource for
finding information and services the World Wide Web has become a
centrepiece of the information superhighway . The WWW is intuitive in
use and exists on many platforms, from simple text-based browsers to
full graphical implementations. It is an excellent way of cruising the
information space offered by the Internet resources. The WWW is
currently expanding at an estimated 4 times as fast as the Internet
explosion in the late 1980's.
The WWW is an attempt to unify the enormous amount of information
available from the global networks, with a very easy-to-use front end
interface and a server protocol. It may be thought of as a single tool
to combine individual network tools dispensing the need to run these
tools independently. Some of the more widely used tools are Anonymous
FTP, Archie, Wide Area Information Server (WAIS), and Gopher.
Anonymous FTP is one of the most useful of Internet facilities,
establishing the original archiving concept, making it possible to make
information available across the globe. The addition of a document
search engine, namely Archie, has made it possible to locate files in
the entire information space. However, Archie can give only a location.
It is still necessary to use an FTP client to retrieve the file. This
problem was partially addressed by Gopher by providing on line viewing
and retrieval facilities within a client package. The addition of
Veronica to Gopher filled the need for a search engine within the
abundance of Gopherspace. WAIS brought the power of full text searches
and questioning and of resources. Even though these tools and utilities
allowed the searching of the Internet and the retrieval of information
and resources found therein, searches and all finds continued to exist
generally independently of each other.The beauty of the WWW is the
ability to understand ad handle all these protoclos including NNTP ,
Gopher,Ftp etc.
.c1.3.1 WWW Clients and servers
The WWW software is designed around a distributed client-server
architecture. The WWW client (also called a WWW Browser) is a program
that can send requests for a document to any WWW server. A WWW server
is a program that, upon receipt of a request, sends the document back to
the requesting client. Using a distributed architecture means that a
client program may be running on a completely different and separate
machine from the server. The task of document storage is left to the
server and that of retrieval is local to the client. Therefore, each
program can concentrate on its individual duties and work independently
of each other. Because servers operate only when documents are
requested, they put a minimal amount of workload on the computers they
run on for each transaction. The WWW is composed of thousands of these
virtual transactions taking place per hour throughout the world,
creating a web of information flow.
.c1.3.2 HTML & URL
The language that WWW clients and servers use for communications is
called the HTTP. The standard language used for creating and
recognizing hypermedia documents is the HTML. It is loosely related to
the SGML. Start and end tags (markup) that precede and follow each
logical portion of a document are added to the standard text to
represent different attributes of the enclosed text. The entities are
defined by the HTML Document Type Definition (DTD). The HTML DTD
defines the elements and tags of the SGML subset. WWW documents are
written in HTML. HTML documents are nothing more than standard ASCII
files with formatting codes that contain information about layout (text
styles, document styles, paragraphs, lists) and, of course, hyperlinks.
A new version of HTML called HTML+ will be ready by the end of 1994 and
will support more interactive forms, hot-spots in images, more versatile
layout, and formatting options and formatted tables. Related to HTML is
HyTime, a proposed standard language for representing the structure of
multimedia, hypertext, hypermedia, and time and space based documents.
HyTime, Hypermedia/Time based Document Structuring Language is also
based on SGML as information content is packaged using standard markup.
HyTime was basically created for the digital information publishing
industry. HyTime can be used as a means of integrating the information
management of a multifaceted enterprise, facilitate concurrent
engineering and other forms of collaborative research.
The WWW uses Uniform Resource Locators (URL) to represent hypermedia
links and links to network services within HTML documents. It is
possible to represent any file or service on the Internet with a URL.
Most WWW browsers allow the user to specify a URL and connect to that
document or service. When a hyperlink is selected within a document,
the user is actually sending a request to open a URL. In this way,
hyperlinks can be made not only to other texts and media but also to
other network services. WWW browsers are typically not just WWW clients
but are also full featured FTP, Gopher, and Telnet clients. HTML+ will
allow the use of URL's to perform E-mail functions automatically.
SGML grew out of a decade of work addressing the need for capturing the
logical elements of documents as opposed to the processing functions to
be performed on those elements. SGML is essentially an extensible
document description language, based on a notation for embedding tags
into the body of a document's text. It is defined by the international
standard International Organization for Standardization (ISO)J8879. The
markup structure permitted for each class of documents is defined by an
SGML Document Type Definition (DTD). It is impractical to design a DTD
to meet the needs of all possible users. Instead, the markup has been
tailored to the needs of a specific community.
In HTML, the need to support a wide range of display types and to keep
browser software as simple as possible limits the complexity that can be
handled. Text is tagged with marks that pass information to a software
reader. The readers use the tag information to format the text and
other media for the viewer. As mentioned earlier, HTML is soon to be
superseded by HTML+ which contains additional features and enhancements.
HTML+ has grown out of several years of experience with the HTML
document format of the WWW community. Browser writers are experimenting
with extensions to HTML and it is appropriate to draw these ideas
together into a revised document format. The new format is designed to
allow a gradual roll over from HTML, adding features like tables,
captioned figures, and fill-out forms for querying remote databases or
mailing questionnaires.
Basically, HTML uses tags to tell the WWW browser how to layout the text
and also how to make links to other parts of the same document or
documents. The location of the document is specified by a Uniform
Resource Locator. The URL is a system of identifying where a resource
resides anywhere on the Internet. In the same way that a local computer
needs to know where a file is stored in order to open it, the URL
locates a file as long as the entire path of the file is specified. The
data types that the URL can address are not limited to files alone.
Databases, images, news groups, Gopher and Archie servers, and many
other services are capable of being addressed via URLs.
The URL is a simple concept and can be grasped quite easily. The most
straightforward use of URLs is to point at other WWW documents on HTTP
servers. If the URL of a document is known, a browser can be pointed
there. Generally, however, the navigation of the WWW is through other
WWW documents; and the URLs of these documents need not be known. Most
browsers inform the user of the URL to which a certain link will take
them.
The WWW is based on the concept of links. The underlying language is
powerful and yet extremely simple. Within any WWW HTML document, there
can be links to other documents, links to marks within the same
document, and links to other resources such as FTP sites, Gopher
servers, WAIS servers, news groups, and finally to the fast growing list
of experimental services being developed.
The WWW relates to existing resources in a simple manner:JJpointers can
be easily built into text documents to specify the location of the
target. The target can be a text file, an image, a specific location in
a text file, a Gopher server, FTP site, or various other types of
information. The work of locating and displaying the target information
is done within the local application browser. The information is
transferred across the Internet and is displayed as per the rules of the
local client browser application. All formatting and layout information
is constructed locally. For this reason, WWW browsers return different
results depending on their sophistication. WWW browsers will also
interpret information from FTP and Gopher sites easily. The format of
data transfer used in the WWW is called the HTTP. All the WWW servers
have to do is honor this communications protocol when information is
transferred.
The explosive growth of the WWW brings close to realizations the concept
of everyone having access to any document, sound recording, or video
image on a computer screen. The underlying principle of the WWW is a
simple concept:JJthe combination of a HTML and the URL. The HTML file
can be created with any standard word processor adding special HTML
pointers, markers, and style tags. The encoded information is used by
the user's WWW software to interpret the layout and style and to make
internal and external hyperlinks. The URL addresses enable the HTML to
link to any available resource around the Internet.
HTTP/WWW works by making the embedded hyperlinks manifest. These
hyperlinks are inserted into the documents using the HTML. The
hyperlinks are not seen directly by the user, but the effects are shown
in the browsers. Browsers vary depending upon the sophistication and
power of the platform, from simple line mode browsers to a full
Graphical User Interface (GUI). However, all browsers have a common
purpose which is to allow a user to navigate around the WWW from link to
link, with as little trouble as possible. The software makes these
connections in the background. Text based browsers show a number next
to each hyperlink which can be chosen to activate that link and initiate
information transfer. A browser such as Lynx highlights links and
allows the user to move to different points on the screen using arrows.
Full graphical interface browsers use colors or underlining to show the
hyperlinks and mark text. Backtracking to previously accessed
locations, going back to a home page starting point, or hot listing
(collecting favorite places to return in later sessions), keeping track
of places visited in current session, and searching by keyword are some
of the features that make using such browsers productive tools.
.c1.3.3 Popular Browsers and Servers
A closer look is taken into some of the more popular browser and server
software available currently. The browsers are mainly divided into two
categories:JJtext based and graphical based browser systems.
.c2.3.3.1 Text Based Browsers
Line Mode Browser
This is the most basic program for WWW access. It is a general purpose
information retrieval tool that gives WWW readership to anyone with a
dumb terminal. Although it may not be as flashy as a window
implementation, it covers a wide class of users who still do not have
window facilities. It is important to realize that a user is still
viewing the exact same document as would a user with full graphical
(minus images) interface. There are no cut-down versions for text-based
systems. Links are marked by a number in a square bracket; pressing the
number on the keypad will initiate the link. The line mode browser will
run on a variety of systems including UNIX systems, VMS with any flavor
of TCP/IP, VM/CMS, DOS-PC, MVS, and the Macintosh.
Lynx Full Screen Browser
This is a hypertext browser for vt100 monitors using full screen, arrow
keys, and highlighting. It is similar to the Line Mode Browser, but it
uses highlighting to mark hypertext rather than numbers. These are
navigated through by using the cursor and the arrow keys. Up and down
arrow keys move the user back and forth sequentially through the links.
The right and left arrow keys allow the user to jump back through links.
In a situation where searching is allowed, pressing the forward slash
key lets the user search for a text string.
DosLynx
A text-based browser.
PerlWWW
A tty-based browser written in perl.
VMS WWW
A full screen client based on VMS's SMG screen management routines.
W3 browse mode for emacs.
Uses multiple fonts when used with Lemacs or Epoch.
.c2.3.3.2JGraphical WWW Browsers
Mosaic
Mosaic is to the World Wide Web what X windows was to UNIX .
Mosaic was developed by the Software Design Group of the NCSA to
interface with the WWW. Initial versions of Mosaic have been developed
for X-Windows, Microsoft Windows, and Apple Macintosh. This is freely
available, simple to use and has contributed greatly to the explosive
use of the WWW. It has a great level of consistency across the
different platforms and handles services such as FTP, Usenet, Gopher,
and WAIS excellently. The Mosaic project defined the ideal set of
features, with the aim of consistency across platforms. Mosaic has the
ability to display:JJ
% Hypertext and Hypermedia documents.
% Electronic text in a variety of forms.
% Text in bold and Italic.
% Layout elements such as paragraphs, bulleted lists, and quoted
paragraphs.
The capability to support hypermediaJ Jaudio, video, graphics, extended
character sets, and interactive hot-spot graphics is fundamental to
Mosaic. These processes are accomplished using external software that
is linked to Mosaic. When a special hypermedia link is initiated, the
external software is called, and the file needing to use the application
is submitted for execution. Mosaic has the capability to support and
make hypermedia links to FTP, Gopher, Telnet, NNTP, and WAIS servers.
Mosaic will also keep track of where a user has been, offering a list of
visits which enables quick backtracking, useful when a dead end appears
at the end of a long line of link traversals. Mosaic allows the user to
add sites to hot lists of URLs, perfect for those must visit sites.
Mosaic also offers the capability to cache copy of pages the user
visits, so during backtracking, downloads are not necessary.
Due to its consistency across different platforms, using Mosaic varies
very little from one variety to another. It is quite straightforward
and intuitive in nature. Shown next is a comprehensive list of
available browsers. It is important to note that browsers are available
for all the important host platforms available.
Mosaic Netscape
Mosaic Netscape is the latest browser , developed at Mosaic
Communications Corporation . The present release is a Beta version . It
is much more sophisticated than NCSA mosaic and is seems to be faster
than NCSA mosaic in document retrieval . Mnay features such as the mail
to feature and the ability to read and post news that were not present
in Mosaic have been incorporated into this version of Netscape .
Cello
Cello is a multi-purpose MS Windows Internet browser which permits a
user to access information from many sources in different types of
formats. Cello can access data from the WWW, Gopher, FTP, CSO, X.500
directory servers, WAIS servers, Hytelnet, techInfo, and others through
external gateways. Cello can be used with the WWW HTML hypertext markup
standard to build local hypertext systems on Local Area Networks (LANs)
or on single machines. Cello also permits the post processing of any
file to a Windows application through the file manager.
Amiga browsers
A Mosaic Browser for AmigaOS, based on NCSA's Mosaic. Supports older
Amigas as well as the newer machines in the latest versions.
NeXT Step browsers
OmniWeb A WWW browser for NeXTStep.
WWW
CERN's NeXT Browser-Editor. A browser/editor for NeXTStep.
tk UNIX WWW
Browser/Editor for X11 (Beta test version).
MidasWWW Browser
A UNIX/X browser from Tony Johnson (Betaversion ).
Viola for X (Beta)
Viola has two versions for UNIX/X:JJone using Motif, one using Xlib (no
Motif). Handles HTML+ forms and tables.
Chimera
UNIX/X Browser using Athena (does not require Motif). Supports forms,
in-line images, etc.; closest to Mosaic in feel of the non-Motif X11
browsers.
.c1.3.4JJServers
Servers are available for UNIX, Macintosh, MS Windows, and VMS systems.
UNIX Servers
NCSA httpd
NCSA has released a server, known as the NCSA httpd.
CERN httpd
Deveoped at CERN .
GN Gopher/HTTP server
The GN server is unique in that it can serve both WWW and Gopher clients
(in their native modes). This is a good server for those migrating from
Gopher to WWW, although it does not have the server-side-script
capabilities of the NCSA and CERN servers.
Perl server
There is also a server written in the Perl scripting language, called
Plexus.
Macintosh Servers
MacHTTP
This is a server for the Macintosh family.
MS Windows and Windows NT Servers
HTTPS (Windows NT)
HTTPS is a server for Windows NT systems, both Intel and Alpha-based.
NCSA httpd for Windows
The NCSA httpd for Windows has most of the features of the UNIX version,
including scripts.
SerWeb
A simple, effective server for Windows. There is also a Windows NT
version of SerWeb.
WEB4HAM
Another Windows-based server.
VMS Servers
CERN HTTP for VMS
A port of the CERN server to VMS.
Threaded HTTP Server
A native VMS server which uses DECthreads(tm). This is a potentially
major performance advantage because VMS has a high overhead for each
process.
CHAPTER 4
.c.Gateway to the Teradata database computer
.c1.4.0 Gateway
Gateways are programs which handle information requests and return the
appropriate results . We have implemented a Mosaic gateway to the
database computer ie Mosaic presents the user interface while the
database is the back end . Forms are the mechansim used to obtain user
input . The forms contents are interpreted and submitted to the database
and the results of the opreation whether it be a query or a submission
are carried out and an appropriate error message or success message is
displayed accordingly . The mechanism by which this is accomplished is
by means of a common gateway interface (CGI) script . The interface was
written in the C language with embedded SQL statements to perform the
database operation . The gateway was written to acomplish specific
operations like a system problem report mechanism , student information
database , phone numbers of faculty students etc . With minimal effort
the gateway can be customized to perform other tasks as well .
.c1.4.1 Teradata DBC/1012 Architectural Overview
The DBC/1012 Teradata Data Base Computer is a complete database
management system that integrates hardware and software, relieving the
attached hosts of the software DBMS burden. The DBC/1012 attaches
directly to the high-speed I/O channels of mainframe computers, as well
as to minicomputers and intelligent workstations via local area
networks.
The DBC/1012 employs a unique architecture of multiple processors ,
software, and direct-access storage devices. The DBC/1012 breaks he
central processing unit bottleneck by harnessing the cost-efficient
power of multiple microprocessors operating in parallel. Data is spread
across a number of processors and disk storage units. This design
enables the system to sustain concurrent access to the relational data
base from end-user interactive sessions, on-line transaction systems,
and high-volume batch jobs.
The DBC/1012 relieves the host of its heavy software DBMS burden . When
attached to LAN, the DBC/1012 can operate as a data base server in a
networking environment. Shareability permits the user to simultaneously
access data from a heterogeneous group of hosts.
It provides major improvements over conventional software approaches in
such areas as price/performance, modularity and data integrity. The
architecture provides modularity in disk storage capacity and processing
power. As the size of a data base grows, additional processing power
may be added. The fully redundant hardware, software, power and
data storage (if desired) of the system ensure availability and
reliability, providing continuous operation of the system.
.c1.4.2 Teradata DBC/1012 Architectural Components
The DBC/1012 consists of seven basic subsystems
Host System Communications Interface (HSCI) (Software)
This software resides in the host computer and enables users to conduct
sessions with the DBC/1012.
Interface Processor(IFP)
IFPs manage channel traffic between a host computer directly connected
to the DBC/1012. An IFP translates requests from a host into internal
commands, forwards the requests, and coordinates the responses as they
return from the multiprocessors. Communications
traffic is balanced over the IFPs
Communications Processor(COP)
COPs perform the same function as IFPs, only for hosts that are
connected to the DBC/1012 over a local area network.
Ynet (Interprocessor Bus)
The Ynet is a bus that interconnects all IFPs, COPs, and AMPs. It
performs many of the tasks--in hardware--associated with multiprocessor
system management.
Access Module Processor(AMP)
AMPs receive requests forwarded over the Ynet by IFPs and COPs, and
perform the required data manipulations. Data is distributed evenly
across all AMPs. When AMPs are added to a DBC/1012 to increase storage
capacity (or performance), the data is automatically redistributed.
Disk Storage Unit (DSU)
The DSUs serve as the storage medium for the system. Each AMP can
support as many as four 500 MB DSUs, for a total of 2 GB of storage
capacity per AMP.
Systems Console
The system console is an IBM-compatible microcomputer that allows the
system operator to get reports of the DBC/1012 status, current
configuration, and performance.
.c1.4.3 Programming on the Teradata DBC/1012
.c2.4.3.1 Call Level Interface (CLI)
The CLI library is an intermediate level interface between the DBC/1012
system and an application program. CLI service routines are link edited
with an application program or are dynamically loaded at runtime to:
Provide a set of common functions for managing communications with the
DBC/1012 database computer.
Provide a convenient interface for applications that do not use the
COBOL preprocessor.
Allow application programs written in languages that accept a call
statement (e.g. Assembly Language) to access data on the DBC/1012
database computer.
There are essentially three routines for operations related to the call
level interface. The first routine, DBCHINI, initializes a data
structure called DBCAREA that is shared between
the application program and most of the CLI routines. DBCHINI also does
internal initialization for the CLI itself. (Before calling DBCHINI,
the application must allocate space for the DBCAREA.) The second
routine, DBCHL, is used to interact with the Teradata, i.e., to log in,
issue a query, do an update, create a table,
log off, etc.
The third routine , DBCHLN, performs cleanup when the application
program is finished.
.c2.4.3.2 BTEQ ( Batch Teradata Query facility ) Approach to
programming
The BTEQ approach to programming involves having the user to execute in
batch mode a series of DBC/SQL statements . BTEQ features include
% Use of more than one DBC/SQL statement per request
% Ability to read data from and write data to files maintained on the
host computer
% Ability to repeat a request
% Flexibility in defining report format features
.c1.4.4 DBC/SQL
A single language, DBC/SQL, is used for data definition, manipulation,
and control. DBC/SQL is compatible with the IBM/SQL. DBC/SQL statements
may be used interactively by users or may be embedded into application
programs.
DBC/SQL can be used for the formulation of basic queries needed for
information retrieval from a table, modification of a table and the
display of statistical data related to numeric fields in the database.
The syntax of DBC/SQL statements is very similar to SQL. Utility Program
Control statements, Echo statement and the Using modifier are SQL
statements that are not supported in DBC/SQL. Also, several of the
options associated with a few of the statements contained in SQL are not
supported in DBC/SQL . An example would be the having clause associated
with the Select statement.