What follows is the direct dump of the Documentation/FAQ file, at the date given below in the Id: thingy.
<:# line 0 "../gzigzag/Documentation/FAQ":>
Frequently Asked Questions about GZigZag, with answers.
$Id: FAQ,v 1.7 2001/02/09 05:59:36 ajk Exp $

All trademarks are the trademarks of their respective owners.

Note that the 'I' in this document is Tuomas Lukka.

Section I: General questions

1. Where to get the latest version of this FAQ?

The source code for all versions of this FAQ is kept as a part of the
GZigZag CVS repository. See the GZigZag sourceforge page at 

for accessing the source. The FAQ is in the directory Documentation/

2. What is ZigZag?

ZigZag, an invention of Ted Nelson, is a new type of data structure.

For mathematicians, the key words would be

 	- discrete
	- multidimensional
	- locally euclidean
	- with global directions (coordinate axes)

and for non-mathematicians, these are explained below:

		the information is stored in cells, kind of like a 

		instead of two dimensions, X and Y, that a spreadsheet 
		has, a ZigZag space can have any number of dimensions
		which are distinguished by strings.

	Locally Euclidean:
		a spreadsheet is globally euclidean, i.e. it is a lattice.
		ZigZag is only locally euclidean, so the neighborhood of
		(i.e. the cells next to) a given cell looks euclidean:
		if you go up and come down, you are back where you were before.

		But if you start from location 1, and go up, left, down and
		right, you might not get back to where you were, let's
		say you are at location 2. But if you then go left, up, down
		and right from location 2, you get back to location 1.

		The connections in ZigZag are user-alterable so you can
		connect any two cells along any given dimension, but
		because of the local euclidean constraint, each cell
		can be connected to only one cell in the positive and one
		cell in the negative direction on each dimension.

Computer scientists might note that ZigZag is an interesting special
case of graphs.

3. What is GZigZag?

GZigZag is an implementation of ZigZag developed by a research group led
by Tuomas Lukka at the university of Jyvaskyla.

It is licensed under the LGPL (and XPL, the Xanadu Public License which
is still under works).

4. Who is the maintainer of GZigZag?

Tuomas Lukka, <lukka@iki.fi>. He has written most of the code in GZigZag (and
most of it while traveling on trains).

This maintainership is by proxy from Ted Nelson, who has the official
maintainership but who does not program.

5. How complete/stable is GZigZag?

It's pre-alpha. It is already usable for many things but it is nowhere
near feature complete yet. 

As for stability, crashes are quite rare but the development speed is high.

6. What are some planned features?

See Java/TODO in the distribution.

7. Are there any mailing lists associated with ZigZag/GZigZag?

See http://www.xanadu.com/zigzag

8. How can I help?

Email Tuomas Lukka <lukka@iki.fi> and ask.

Section II: Using (G)ZigZag

1. How can I learn to create my own structures so that they work well?

There are some ideas in the document "A Gentle Introduction to ZigZag",
available under the 


directory on the CVS, or as a postscript file from the web page.

Section III: Questions specific to the Java version

1. Why Java?

Portability, garbage collection, SPEED (with JIT: for linux, IBM's
JDK-1.1.8 is GREAT), portable graphics, easy C interface, available APIs
(e.g. JMF), etc.

You will note that I did not mention the language itself above:
I don't like the language itself that much: I'd prefer to work in
Perl. Unfortunately it does not provide all of these other features and
the ones it does it does not provide as easily and conveniently as Java.

1.1 Where do I get Java sources for GZigZag?

If you know CVS, you can checkout module GZigZag in
:pserver:anonymous@cvs.gzigzag.sourceforge.net:/cvsroot/gzigzag .
Otherwise, you can use our nightly-generated source snapshots
available at ftp://gzigzag.sourceforge.net/pub/gzigzag/snapshots/ .
They are packaged in GNU-Zipped tar archives and in ZIP archives,
choose whichever is best for you.

The Java sources are located in the Java/ subdirectory of the full
source tree.

1.2 Where do I get precompiled class files for GZigZag?

We have a build daemon that builds the current CVS version nighly and
puts two JAR archives of it in
ftp://gzigzag.sourceforge.net/pub/gzigzag/snapshots/ .  The
-without-modules version contains the core GZigZag.  The -with-modules
version is much larger and contains some additional functionality.

1.5. It's WAY too slow! Are you out of your mind?

No. For me, it's quite comfortable on my 233MHz Pentium 80Mb laptop.
There are several possible reasons for this: 

* You are using a Java interpreter without a JIT (Just-In-Time)
  compiler. As mentioned in the answer to the previous question, for
  Linux, I recommend IBM's JDK 1.1.8. Do NOT ask me about proprietary
  operating systems - GZigZag works there but over there you're on
  your own for platform-specific questions.  Another quite fast JVM is
  Kaffe, but unfortunately at least some versions of Kaffe have a
  nasty bug that makes using GigZag on it quite unpleasant.

* Your Java interpreter is not using enough memory. By default, some Java
  interpreters only use 16Megs at maximum. Try starting with

	java -mx30m -ms30m foo.Main

  to set it to allocate 30Megs at startup (or more if you have enough memory).
  That way it won't be garbage collecting constantly and you may get quite a 
  significant performance improvement.

1.5.1. I can't use IBM's JDK: it doesn't have the Swing classes

You are using an old version of GZigZag.  Current CVS versions and
snapshots do not require Swing.

1.9. I want to report a bug; how do I do that?

There are instructions about this in http://www.gzigzag.org/bugs.html .

2. How is the Java code structured?

ZZCell and ZZSpace are the center of it all. Start from there and
also ZZDimension, ZZDimSpace, ZZLocalDimension, ZZPersistentDimension,
ZZPersistentDimSpace ...
These latter ones are still a bit new and finding their places.

3. Why is the ZZEventQueue not called / what is ZZObs / ... ?

Legacy. It's currently supplanted by the ZZUpdateManager for view updates
but may be revived later.

4. What is the saved file format?

See the Java/storage/ and Java/media subdirectories of the source
tree, especially storage/Recs.java, storage/ZZPersistentDimSpace.java
and media/StringScroll.java.

5. Will my files be upwards compatible?

No: the format will change soon. However, you can dump the space into XML
(will be explained later) and restore it to the new file type.

6. Are there any coding standards?

See the file CODING in CVS.

7. Do you accept patches?

Yes, we do, but it helps if you consult with us first to make sure your
intended change is in a reasonable direction. Much functionality should go
into the Modules/ as well.

diff -u (unified diff) is preferred.

8. What are the advantages of the new Java version over the old Perl version?

- Graphics. You just need to see the vanishing view to see why it's important.
And that's just the beginning.

- Active development.

9. What are the disadvantages of the new Java version over the old Perl version?

- Ted's own keystrokes do not yet work (to be fixed soon)

Section III: Questions specific to the Perl version

1. Wasn't there a Perl version or something?

Yes, written by Andrew Pam and others.

2. Are the files from the Perl version compatible with the new Java version?


3. Is it possible to import files from the Perl version to the new Java version?

Not yet, but soon. Only needs a short Perl script to read the DB_File from
the Perl version and write the corresponding XML code and then you can import
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