Conversations
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<html xmlns="http://www.w3.org/1999/xhtml">
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<title>
Conversations - Ideaas about web architecture
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<address>
Tim Berners-Lee<br />
Date: 1998, last change: $Date: 2009/08/27 21:38:06 $<br />
Status: personal view only. Editing status: first draft.
</address>
<p>
<a href="./">Up to Design Issues</a>
</p>
<hr />
<h1>
Conversations and state
</h1>
<p>
See also: <a href="PaperTrail">Paper Trail</a> - presented as
a a student project
</p>
<p>
The basic model of the web is a world of information.
Theoretically, a mapping between URIs and representations of
the resources they identify, and experientially fro a person
a space one can navigate.
</p>
<p>
Interestingingly, trends at the leading edge of user
interface development, and at the semantic web development
both point to a world which uses a different model. Human
interfaces are moving from screens to conversational mode.
The semantic web, while very exciting when viewed as a
</p>
<p>
Human user interfaces use more and more devices such as
speech, gestures and so on, which are not screens. What is
special about a screen? A screen with a window system
presents a large amount of informatoin at the same time to a
person. In practice, more or less everything which a person
is concentrting on at one time can be presented in its
current state. When the number of pixels on a screen broke
through a certain threshold (roughly the 640x320 VGA limit)
this led to the development of direct manipulation interface
metaphors: folders one could open, and drag and drop. The
essential things about this is that the computer is at every
instant presenting the current state, whether it or the human
is manipulating it. The communication betwen personand
machine is in terms of the mutual manipulation of a shared
state. The web was intended to extend that form of
communication by mutual manipulation of a shared state to
remote human-human interaction. While the tools and protocols
have their limitations (see UI) much of its effectiveness
derived from this model. Because fundamental thing is a
shared space of information, one can talk about navigation
around within the space, and use all the primaval facilities
that the human memory has for navigation.
</p>
<p>
This is all very well, but it was not always so. When
computer terminals had only 24 rows of 80 characters, even
when they were addressable, there was a tendency for most
jobs to use command line interafaces, for example when
manipulating files and directories. The interface was
conversational, in that the exchanges were small commands and
responses. There was a shared abstract state, but it was
imagined in the abstract by the person, and held in some
unvisualized form by the computer. This too has itas
advantages, in that the imagination of a person can well
exceed (on a good day) the capacity of a screen in its
ability to hold complex interrelated structures. The
interesting thing is that now there is a tednedncy to use
many devices which do not have the large screen. The screens
on cellphones are currently so small that, while one can
scale a web page down and adapt it to a small screen, this
might be chosing simply the wrong interface metaphor. When
the audio phone only is used, then the shared state becomes
zero and the interface is completely conversational again.
</p>
<p>
The characteristic of a conversation is the state is the set
of utterances, or messages, which have been conveyed. This is
differenet from a shared expression of a commonly agreed
state. The <a href="PaperTrail.html">Paper Trail concept</a>
links these two modesl in the Semantic Wee Semantic Web, by
formally defining the overal agreed state as a function of
messages to date. A service which allows a phone user to
browse the web converts the other way: it conveys part of the
the space of information by means of a conversation. It is is
important for a number of reasons.
</p>
<ul>
<li>It allows us to formalize the models of human-machine
interface which are in fact conversational for many
non-screen devices;
</li>
<li>It allows us to formalize social, for example commercial,
transactions for which the paper trail is in fact th emost
accurate model anyway;
</li>
<li>It provides us with tools we can use for formally
analysing the infrastructure protocols such as HTTP which
with which the information world is actually implemented in
practice.
</li>
<li>The standardization of XML protocols has, with XML (and
RDF), a richness in terms of marshalling data formats to
build on, and, with xml-schemas xforms and rdfs, a richness
to draw on in terms of languages for defining valid
documents, but has no basis yet for defining with equivalent
power the validity (and semantics) of a sequence of
interrlated messages which are a protocol.
</li>
</ul>
<p>
It is not as though the web today itself perfectly matches
the stateless model at all. The moment it was created as a
basically stateles system, many web site designers took it as
their challenge to get around this model in order to create a
conversational interface -- and many still do Our concerns
about privacy stem largel;y from the knowledge that our
"reading" of documents is in fact done by a series of
protocols which leave a trace. The P3P project involves
quantifying the information transfer which actually takes
place. Our handling of HTML forms is getting more complex,
and a form itself, becomes, on many sites, the definition os
a protocol - a set of valid sequences of information
actions..
</p>
<p>
This was written as a note to accompany a talk to the W3C
Advisory Committee of November 2000. At such times, we
discuss the status of existing work and look ahead to feel
the direction in which we will need to move in the future.
Often, we notice that Web technology is now entering a field
new to the Web but old of itself. In these cases, we can view
the process we need to go through either has extending web
technology into this field, or of <em>Webizing</em> the
field. This has happened, more or less, to hypertext to SGML,
and is heppending to knowledge representation. Now an
interesting field is teh formal specification of protocols.
There is much out there to build on, but is has not been
applied yet to the exchange of XML documents conveying RDF
graphs. However, it seems to be a relevant direction in which
to look when predicting where the leading edge, and therefore
the Consortium, should be in a few year's time.
</p>
<p>
@@ - already web privacy concerns come from in fact it being
a conversation -- there is implict state. A
</p>
<p>
@@ Reasons for formalizaing protcols a la Paper Trail.: uses
concepts of validation and will be able to resuse tools -
extends semnatics of documnets to semnatics of conversaions.
- Creates a formal basis for defining conversaionsal systems
of all kinds, including indirctly human language oriented
systems.
</p>
<p>
@@ Machine-machines and human-human convergence
</p>
<p>
Originally written 2000/11
</p>
<hr />
<p>
<a href="Overview.html">Up to Design Issues</a>
</p>
<p>
<a href="../People/Berners-Lee">Tim BL</a>
</p>
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