THE LITERARY PARADIGM  
      A piece of writing--say, a 
sheet of typed paper on the table-- 
looks  alone and independent.  This 
is quite misleading.  Solitary it may 
be, but it  is probably also part of 
a literature.  
      By "a literature" we do not 
mean anything to do with 
belles-lettres or  leather-bound 
books.  We mean it in the same broad 
sense of "the scientific  
literature", or that graduate-school 
question, "Have you looked at the  
literature?"  
      A literature is a system of 
interconnected writings.  We do not 
offer  this as our definition, but as 
a discovered fact.  And almost all 
writing is  part of a literature.  
      The way people write is based 
in large part on these 
interconnections.   A person reads an 
article.  He says to himself, "Where 
have I seen something  like that 
before? Oh yes--," and the previous 
connection is brought mentally  into 
play.  
      Consider how it works in 
science.  A genetic theorist, say, 
reads  current writings in the 
journals.  These refer back, 
explicitly, to other  writings; if he 
chooses to question the sources, or 
review their meaning, he  is 
following links as he gets the book 
and refers to it.  He may correspond  
with colleagues, mentioning in his 
letters what he has read, and 
receiving  replies suggesting that he 
read other things.  (Again, the 
letters are  implicitly connected to 
these other writings by implicit 
links.)  Seeking to  refresh his 
ideas, he goes back to Darwin and 
also derives inspiration from  other 
things he reads--the Bible, science 
fiction.  These are linked to his  
work in his mind.  
      In his own writing he quotes 
and cites the things he has read.  
(Again,  explicit links are being 
made.)  Other readers, taking 
interest in his  sources, read them 
(following the links).  
      In our Western cultural 
tradition, writings in principle 
remain  continuously available--both 
as recently quoted, and in their 
original  inviolable incarnations--in 
a great procession.  
      So far we have stressed some of 
the processes of referral and 
linkage.   But also of great 
importance are controversy and 
disagreement and  reevaluation.  
Everyone argues over the 
interpretation of former writing, 
even  our geneticists.  One author 
will cite (or link to) a passage in 
Darwin to  prove Darwin thought one 
thing, another will find another 
passage to try to  prove he thought 
another.  
      And views of a field, and the 
way a field's own past is viewed 
within  it, change.  A formerly 
forgotten researcher may come to 
light (like Mendel),  or a highly 
respected researcher may be 
discredited (Cyril Burt).  And so it  
goes, on and on.  The past is 
continually changing--or at least 
seems to be,  as we view it.  

      There is no predicting the use 
future people will make of what is  
written.  Any summary, any particular 
view, is exactly that: the 
perspective  of a particular 
individual (or school of thought) at 
a particular time.  We  cannot know 
how things will be seen in the 
future.  We can assume there will  
never be a final and definitive view 
of anything.  
      And yet this system functions.  

      In other words, even though in 
every field there is an ever-changing 
flux of emphasis and perspective and 
distortion, and an ever-changing 
fashion  in content and approach, the 
ongoing mechanism of written and 
published text  furnishes a flexible 
vehicle for this change, continually 
adapting.  Linkage  structure between 
documents forms a flux of invisible 
threads and rubber bands  that hold 
the thought together.  
      Linkage structure and its 
ramification are surprisingly similar 
in the  world of business.  
      A business letter will say, "In 
reply to your letter of the 13th..." 
or  a business form, another key 
communication, may say in effect, "In 
response to  your order of the 24th 
of last month, we can supply only 
half of what you have  asked for, but 
can fill the rest of the order with 
such-and-such item from our  
catalog."  All of these citations may 
be thought of as cross-linkages among 
documents.  
      The point is clear, whether in 
science or business or  belles 
lettres.   Within bodies of writing, 
everywhere, there are linkages we 
tend not to see.   The individual 
document, at hand, is what we deal 
with; we do not see the  total linked 
collection of them all at once.  But 
they are there, the  documents not 
present as well as those that are, 
and the grand cat's-cradle  among 
them all.  
      From this fundamental insight, 
we of Project Xanadu have endeavored 
to  create a system for text editing 
and retrieval that will receive, and 
handle,  and present documents with 
links between them.  We believe there 
is something  very right about the 
existing system of literature; indeed 
we suspect that  there are things 
about it that we don't even know, as 
with Nature. And so we  have tried to 
mirror, and replicate, and extend 
existing literary structure as  we 
have here described it.  
      But as we said earlier, the 
design of virtuality is a dialectic.  
First  we must study what there is; 
then we must venture a design in 
response to what  is.  And that 
design is not dictated by what we 
have seen, any more than the  design 
of a house is dictated by a hillside. 
There are only hints.  

  
 THE SYSTEM DESIGN  
      By the "design" of the system 
we mean its conceptual architecture: 
the  basic ideas of it.  But with 
many systems the general system of 
concepts is  filtered through 
innumerable complications and 
accidental features.  In this  system 
the basic ideas are the  only  ideas. 
      Our approach, then is to 
consider all documents as 
interconnected, or  potentially 
interconnected.  Not just documents, 
but linkages as well, are the  
fundamental elements of the system.  
(Links are actually parts of 
documents,  as will be seen later.)  
It is the different types of links 
that give both  power and 
complication to the system.  
      Our system, the Xanadu 
Hypertext System (tm), is intended to 
store a  body of writings as an 
interconnected whole, with linkages, 
and to provide  instantaneous access 
to any writings within that body.  
      For this system we have 
formulated a basic linkage structure 
that we  think meets all the needs of 
literature as we understand it, 
including  business literature.  
      Beyond this general idea there 
is little further to expound, except 
the  link structure and the document 
conventions, which are all the user 
really has  to learn.  
      Since the network is 
essentially invisible, all we have to 
discuss are  these links and links 
and documents.  
