Adam Bosworth article "Lessons Learned from the Web"

[Joseph Osako <scholr1@xxxxxxxxxxx>]

http://acmqueue.com/modules.php?name=Content&pa=showpage&pid=337&page=1

While he is primarily discussing conventional relational databases, I 
think that he makes several points which are relevant to the Xanadu 
Project as well. OTOH, some of the points also highlight important 
differences between Xanadu and conventional 'data management', and 
several of his criticisms of XML are in line with Xanalogical concepts, 
especially in regard to link metadata (self-describing links, 'time to 
live' markers, etc.)

His first 'lesson' (that text data formats are both more accessible and 
more scalable than binary data formats) is already a well-known 
principle among Unix programmers: outside of large database systems, 
binary data formats (as opposed to executables) are almost unknown in 
Unix, and for good reason. Note that human readability and editability 
is a key part of this: HTML works because anyone with a text editor and 
a little knowledge of the markup language can create a new web page; 
similarly, the fact that HTTP addresses are plain text and easily 
readable (at least for top-level addresses) has considerable impact on 
the accessibility of the web - to the extent that tools for shortening 
addresses, such as Snip URL (http://www.snurl.com), are quite popular as 
a way of making complex addresses more accessible. The implications of 
this for Xanadu are problematic, especially when taken in conjunction 
with lessons 6 and 7: because to is so fine-grained, Xanadu could not 
leverage these advantages even if a text format were used instead of a 
binary one. Given how Xanadu addresses work, reading a link would be a 
tedious exercise (how much useful information could a non-programmer get 
of out a tumbler address and a span of bytes?) and hand-editing out 
would be positively dangerous. Fine-grained chunking also presents 
scaling problems for distributed systems, and increases the coupling, 
both of which make the system both harder to use and more brittle. These 
are serious problems that are inherent in the Xanadu concept - without 
the ability to link to arbitrary data, it simply isn't Xanadu.

The point about staleness is an interesting one, with both positive and 
negative implications for Xanadu. The fact that Xanadu data is stored 
permanently, with only the data views  getting changed, Xanadu should 
have no problem with this; however, the fine-grained nature of Xanadu 
links again becomes a concern, as updating local caches (something that 
is supposed to be transparent in Xanadu, invisible to the user and 
automatically balanced) for impermanent data would require considerable 
overhead for consistency checking - something that the Web simply 
ignores. By requiring viewer updates to be done semi-manually, and 
requiring the data sources to have a custom-built solution for 'server' 
updates, it forces attention to the issue - which far from being a 
limitation, is a benefit, since (as Bosworth points out) no 
one-size-fits-all solution could cover every case.

Lesson five, however, is very encouraging: it vindicates the basic 
concept of hypertext, that non-linear presentation is not only possible 
but natural once the technology to support it exists. While the web only 
hints at the potential of a truly powerful hypertext system, it does 
show that Xanadu's overall direction is the right one.

Not surprisingly, some of his criticisms of both XML and relational 
databases do apply to Xanadu as well, but hardly all of them: if there 
is one thing Xanadu documents are not, it's monolithic, and ordering is 
of no consequence in Xanadu either. Still, his arguments do raise issues 
that any future hypertext system - Xanalogical or otherwise - will have 
to consider.