Open-source XLink library (was Re: XLink - where are we?)

[Simon St.Laurent]

After spending the last few months talking and talking about how amazingly
cool XLink _could_ be, I've taken a few steps toward _doing_ things with
XLink.  The steps aren't lovely or stupendous (yet), but I hope that they
might represent a step forward.  The code is not yet ready for prime time,
but the discussion on this list makes it fairly clear that there is a need
for this kind of project.

Working from the 3/3/98 Working Draft, I've put together a few small Java
examples that use XLink and am at work on a library based on John Cowan's
ParserFilter class that extracts the linking information from a document,
allowing the application to process the document without having to deal
with the issues involved in creating and managing links.  Right now the
library supports simple and extended links, but not hub groups or attribute
remapping.  I'm planning on adding legacy support for HTML's A element at
some point in the future as well.

The examples are from Building XML Applications, and were small, simple,
one-off applets.  They can be found at the bottom of
http://www.simonstl.com/buildxml/.  They use image maps (my handling of
text link proved disastrous) and are unfortunately a bit slow as a result.
They pretty much just show what some _very_ simple XLink applications might
look like.  The source code for these examples will be in the book, and (if
I can get the necessary permissions from my editor) may appear online as well.

The library is and will be open source, though at this point I haven't
firmly decided on a license. (GPL is likely, in some slightly modified
form.) I should emphasize that the library is in (fairly ugly) alpha form;
the feature set is not yet nearly complete, especially the LinkSet class.
The basic XLinkFilter has worked on the samples on which I've tested it,
transforming multi-directional links into more workable sets of single
direction links.  The LinkSet is an extended Vector, but will probably
change to something more flexible when Java 1.2 comes along.  (I will try
to keep a 1.1 version, however.)  Information on the XLinkFilter and
supporting code is at http://www.simonstl.com/projects/xlinkfilter/.

This filter only handles XLink; XPointer is a necessary complement, but
another large piece to deal with.  Support for a DOM model in addition to
SAX is another necessary piece, but one that I haven't yet begun.

Documentation at present is weak, and the comments in the code aren't
enough.  They will improve, and I will add real JavaDoc comments as well.
(Promise!)

All contributions/modifications/suggestions on functionality, code,
licensing, etc. are welcome.  I'll be in and out for the next few days, but
will be returning to more focused work on this library over the weekend.



Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer
Cookies / Sharing Bandwidth (November)
Building XML Applications (December)
http://www.simonstl.com

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