WASD VMS Hypertext Services -Technical Overview
1 - Introduction
[next] [previous] [contents] [full-page]
This document provides an basic overview of the WASD VMS Hypertext Services.
All programs were designed only to specifically comply with the requirements of
DEC-C, within a Compaq TCP/IP Services for VMS environment, or compatible.
The document assumes a basic understanding of the
hypertext technologies and uses terms without explaining them (e.g. HTTP,
HTML, URL, CGI, SSI, etc.) The reader is refered to documents specifically
on these topics.
Also see
WASD Hypertext Services - Environment Overview
containing a description of WASD Web author facilities, and the
WASD Hypertext Services - Scripting Overview
for information on CGI, CGIplus, ISAPI, OSU, etc., scripting.
It is strongly suggested those using printed versions of this document
also access the Hypertext version. It provides online demonstrations of some
concepts.
Objectives
The primary impetus for an internal Web environment was a 1993 decision by
Wide Area Surveillance Division (WASD) management (then High Frequency Radar
Division, HFRD) to make as much information as possible, both administrative
and research, available online (to use the current term ... an
intranet). Early experimentation with a Gopher
implementation soon made way for the obvious advantages of the emerging Web
technology.
It then became the objective of this author to make all of our
systems' VMS-related resources available via HTTP and HTML, regardless of the
underlying data or storage format. An examination of the WASD package will
show that this objective is substantially achieved.
Reasons For Yet Another Web Package
Reasons for developing a local HTTP server were few but compelling:
- The WASD (then HFRD) Web implementation began mid-1994.
- It was prefered to support the hypertext environment on a VMS platform.
At the time this the most widely used and accessible environment within WASD.
- At that time servers (and even at that time there were quite a few
variations) were largely Unix based, although it was being supported (to a
greater or lesses extent) across a wide range of platforms. Ports to VMS, if
they existed, were often in progress or half-baked, employing
Unixisms that don't translate elegantly to the VMS environment.
- The VMS version of the CERN server (3.0-6) was evaluated during mid-1994:
- It was (still is) not multi-threaded under VMS (i.e. cannot support
concurrent clients). For example, a lengthy search may delay other clients
for unacceptable periods.
- The performance was good with document transfers, but became poor when
running a script.
- It is acknowleged in the release notes that it cannot handle a client
cancelling a data transfer (a not-uncommon action). This was confirmed
experimentally.
- An early version of the OSU (DECthreads) server was evaluated via
documentation mid-1994. The author considered that the DECthreads of the time
to have limitations (including frequent, show-stopping bugs) and OSU had a
number of implementation idiosyncracies (e.g. DECnet based scripting).
- HyperText Transport Protocol, in the then standard implementation
(HTTP/1.0, RFC1945), was relatively simple to implement to the level required
to support intra-Divisional requirements.
- As of December 1995 the server has worked extremely
well and has a number of facilities tailored for the VMS environment. It can
continue to be utilized until there are overwhelming reasons for implementing
something else.
- As of June 1997 the server and associated software
continues to evolve and provide a stable and effective VMS Web environment,
even with the advent of a small number of commercial VMS Web products.
- As of October 1999 the package is beginning to mature as
an HTTP/1.0 solution, providing not only a fast and stable server but an
increasingly extensive collection of applications and tools.
- As of July 2002 it continues to be refined and extended.
A greater emphasis on "commercial" functionality has occured over the
past couple of years.
- As of December 2004 it now complies with the HTTP/1.1
specification (RFC2616) and provides a very respectable range of functionality
and the fastest and most efficient serving environment for VMS.
[next] [previous] [contents] [full-page]