Rebol - A Messaging Language

Kieron Lawson (
Mon, 6 Sep 1999 12:44:50 +1200

September 3, 1999

REBOL, the Relative Expression-Based Object Language, is a
fascinating new scripting language developed at REBOL Technologies by
Carl Sassenrath, the architect of the Amiga operating system. REBOL
is intended to be used for Internet programming and, among its many
features, it contains very easy-to-use networking capabilities. An
example is this tiny line of REBOL code which retrieves a web page
and emails it to a (fictitious) email address: "send
read" As anyone with experience in other
programming languages knows, this simple task would require more code
in almost any other language. The simplicity of some tasks in the
language comes at the expense of the apparently extensive task of
learning the entire language. For users more comfortable with
traditional, imperative programming languages, this task may seem
daunting at first, but ultimately REBOL may provide a far faster and
easier way to implement useful network-centric programs. REBOL, while
not open source, is freely available in binary form for use on
numerous platforms including Win95/98/NT, MacOS, Linux, and many
others. [CL]
What is a Messaging Language?

"There is great power here. Enormous productivity and leverage await

--Carl Sassenrath
Creator of the REBOL Language

REBOL (pronounced "REB-ul") introduces the concept of a messaging

Our definition of a messaging language is one that provides highly-
integrated connectivity (networking) along with context sensitivity
(what we call "dialecting"). English and other natural languages are
messaging languages. Unlike most computer languages which command or
compute, messaging languages communicate or describe. They are a
superset of the former. After all, if you can communicate, you can
always command, but not the other way around.

When you consider natural (human) languages, you find one enduring
element: their ability to adapt to change. For instance, we constantly
add new words to English and from time to time even alter its grammar.
This leaves the language free to evolve as we evolve.

When we apply human languages to domains such as medicine, fishing, law,
dancing, engineering, photography, and nearly every other discipline, we
create specialized "sub-languages" to improve the efficiency of our
expression. In messaging language terms, we call this dialecting. It is
the ability to create variations, or sub-languages, for domain-specific

Dialecting provides us with greater expressive economy. When a lawyer
uses the word "contract" it has the full implication of years of
experience behind the simple expression. When a movie director calls out
"pan left" or "zoom slowly to a close up", she depends on the economy of
the words to produce quick results. The message is carried, but few
words are required. That is the power of context sensitivity.

As a messaging language, REBOL provides seamless network connectivity to
the Internet protocols such as HTTP, FTP, SMTP, POP, NNTP, Finger, and
others. It can be applied not only to scripting, but to any domain that
would benefit from greater expressive leverage and productivity. Its
power is broad. With context sensitivity, REBOL is capable of an endless
evolution. It can express concepts, data, and actions never before

REBOL is truly one of the most flexible and powerful computer languages
ever created. It has tremendous depth, yet through its use of
connectivity and dialecting, it keeps simple things simple to do. It
provides great leverage and productivity and takes that bold step
necessary to propel computing technology into the next century.

For examples of using REBOL, the Messaging Language, see..... here.