RFC Dependency Graphs
---------------------

This script produces GraphViz files describing the "obsoletes" and
"updates" relationship between RFCs, by parsing the meta information
contained in the RFC Editor's XML version of the RFC index.

Requirements
------------

- "Dot" (graphviz renderer), with SVG output support
- Perl 5.x
- Perl libraries
  - Getopt::Long 
  - XML::Simple
  - Storable
- the RFC index XML file (see below)

Operation
---------

To describe a suite of documents a configuration file is required.  A sample
file for the SMTP suite is below:

  --8<--8<--
  T:SMTP
  RFC0822
  -RFC1349
  -RFC2181
  --8<--8<--

The first (optional) line starting "T:" sets the title of the GraphViz document.

The remaining lines specify which RFCs are to be explicitly included (or
excluded) from the dependency chain.  By default the script will look at
both "obsoletes" and "obsoleted-by" references (likewise for "updates"
and "updated-by") and build the dependency graph in both directions.
See the "--help" text for command line options to override this
behaviour.

The exclusions are particularly important when trying to build a
configuration file for any specific set of IETF protocols.  In some
cases RFCs affect multiple protocols, and left to its own devices the
dependency following logic would automatically extend into all of those
sets.

For example, in the SMTP example above, RFC 2181 is excluded from
following since it also updates various DNS protocol documents.  Without
this line, the resulting graph would include large portions of the DNS
document suite.  Similarly RFC 1349 (which updates RFC1123) would result
in the core IP protocol documents being included.

Some sample configuration files are included in the distribution
tarball, but note that may themselves already be obsolete, since more
RFCs are published all of the time.  If those RFCs "update" or
"obsolete" prior RFCs then the script will find them automatically, but
if they are standalone documents they will need to be added to the
configuration files manually.

The RFC Index File
------------------

You'll need a copy of the current "rfc-index.xml" file in the same
directory as the script - if you have "wget" then a call to "make fetch"
will download a copy.

The first time you run the script after each download of the XML index
the script will run more slowly as it parses the XML file.  It will then
save a more easily parseable version ("rfc-index.dump") which will be
used for subsequent runs.