Network Working Group M.T. Rose
Internet-Draft Invisible Worlds, Inc.
Category: Informational February 1999
Expires: August 02, 1999
Writing I-Ds and RFCs using XML
draft-mrose-writing-rfcs-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
To view the entire list of Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 02, 1999.
Abstract
This memo presents a technique for using XML as a source format for
documents in the Internet-Drafts and RFC series.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . 3
2. Using the DTD to Write I-Ds and RFCs . . . . . . . . . . 4
2.1 XML basics . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Front matter . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1 The title Element . . . . . . . . . . . . . . . . . . . 6
2.2.2 The author Element . . . . . . . . . . . . . . . . . . . 7
2.2.3 The date Element . . . . . . . . . . . . . . . . . . . . 8
2.2.4 Meta Data Elements . . . . . . . . . . . . . . . . . . . 8
2.2.5 The abstract Element . . . . . . . . . . . . . . . . . . 9
2.2.6 The note Element . . . . . . . . . . . . . . . . . . . . 9
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2.2.7 Status, Copyright Notice, Table of Contents . . . . . . 9
2.2.7.1 Conformance with RFC 2026 . . . . . . . . . . . . . . . 9
2.2.8 Everything in the Front . . . . . . . . . . . . . . . . 10
2.3 The Middle . . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1 The section Element . . . . . . . . . . . . . . . . . . 11
2.3.1.1 The t Element . . . . . . . . . . . . . . . . . . . . . 12
2.3.1.1.1 The list Element . . . . . . . . . . . . . . . . . . . . 12
2.3.1.2 The figure Element . . . . . . . . . . . . . . . . . . . 13
2.3.1.3 The xref Element . . . . . . . . . . . . . . . . . . . . 14
2.3.1.4 The eref Element . . . . . . . . . . . . . . . . . . . . 15
2.3.1.5 The vspace Element . . . . . . . . . . . . . . . . . . . 15
2.4 Back matter . . . . . . . . . . . . . . . . . . . . . . 16
2.4.1 The references Element . . . . . . . . . . . . . . . . . 16
2.4.2 Appendices . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.3 Copyright Status . . . . . . . . . . . . . . . . . . . . 17
3. Processing the XML Source File . . . . . . . . . . . . . 18
3.1 Editing . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.1 Checking . . . . . . . . . . . . . . . . . . . . . . . . 18
3.2 Converting to Text Format . . . . . . . . . . . . . . . 19
3.3 Converting to HTML Format . . . . . . . . . . . . . . . 19
3.4 Viewing . . . . . . . . . . . . . . . . . . . . . . . . 19
3.5 Searching . . . . . . . . . . . . . . . . . . . . . . . 19
4. Security Considerations . . . . . . . . . . . . . . . . 20
References . . . . . . . . . . . . . . . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . 21
A. The rfc Element . . . . . . . . . . . . . . . . . . . . 22
B. The RFC DTD . . . . . . . . . . . . . . . . . . . . . . 23
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1. Introduction
This memo describes how to write a document for the I-D and RFC
series using the Extensible Markup Language[1] (XML). This memo has
three goals:
1. To describe a simple XML Document Type Definition (DTD) that is
powerful enough to handle the simple formatting requirements of
RFC-like documents whilst allowing for meaningful markup of
descriptive qualities.
2. To describe software that processes XML source files, including
a tool that produces documents conforming to RFC 2223[2], HTML
format, and so on.
3. To provide the proof-of-concept for the first two goals (this
memo was written using this DTD and produced using that
software).
It is beyond the scope of this memo to discuss the political
ramifications of using XML as a source format for RFC-like
documents. Rather, it is simply noted that adding minimal markup to
plain text:
o allows the traditional production of textual RFC-like documents
using familiar editors;
o requires some, albeit minimal, additions to existing software
environments; and,
o permits information to be organized, searched, and retrieved
using both unstructured and structured mechanisms.
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2. Using the DTD to Write I-Ds and RFCs
We do not provide a formal or comprehensive description of XML.
Rather, this section discusses just enough XML to use a Document
Type Declaration (DTD) to write RFC-like documents.
If you're already familiar with XML, skip to Appendix B to look at
the DTD.
2.1 XML basics
There are very few rules when writing in XML, as the syntax is
simple. There are five terms you'll need to know:
1. An "element" usually refers to a start tag, an end tag, and all
the characters in between, e.g., "text and/or nested
elements"
2. An "empty element" combines the start tag and the end tag, e.g.,
"". You don't find these in HTML.
3. An "attribute" is part of an element. If present, they occur in
the start tag, e.g., "". Of course, they
can also appear in empty elements, e.g., "".
4. An "entity" is a textual macro that starts with "&". Don't worry
about these, you'll only use them whenever you want to put a "&"
or a "<" in your text.
5. A "token" is a string of characters. The first character is
either a letter or an underscore ("_"). Any characters that
follow are either letters, numbers, an underscore, or a period
(".").
First, start your source file with an XML declaration, a reference
to the DTD, and the "rfc" element:
...
Ignore the first two lines -- the declaration and the reference --
and simply treat them as opaque strings. Nothing else should be
present after the "" tag.
(NOTE TO READER: when this memo is published as an RFC, the "XXXX"
above will be replaced with the actual string to use in your source
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file.)
Second, make sure that all elements are properly matched and nested.
A properly matched element that starts with "" is
eventually followed with "". (Empty elements are always
matched.) Elements are properly nested when they don't overlap.
For example,
...
...
...
is properly nested.
However,
...
...
...
overlaps, so the elements aren't properly nested.
Third, never use "<" or "&" in your text. Instead, use either "<"
or "&", respectively.
Fourth, there are two quoting characters in XML, 'apostrophe' and
"quotation". Make sure that all attributes values are quoted, e.g.,
"", If the value contains one of the quoting
characters, then use the other to quote the value, e.g., "", If the value contains both quoting characters, then use
one of them to quote the value, and replace occurrances of that
character in the attribute value with either ''' (apostrophe)
or """ (quotation), e.g., "".
If you want to put a comment in your source file, here's the syntax:
Finally, XML is case sensitive.
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2.2 Front matter
Immediately following the "" tag is the "front" element:
...
(Note that in all examples, indentation is used only for expository
purposes.)
The "front" element consists of a "title" element, one or more
"author" elements, a "date" element, one or more optional "area"
elements, one or more optional "workgroup" elements, one or more
optional "keyword" elements, an optional "abstract" element. and,
one or more optional "note" elements.
2.2.1 The title Element
The "title" element identifies the title of the document. Because
the title will be used in the headers of the document when formatted
according to [2], if the title is more than 42 characters, then an
abbreviation should also be provided, e.g.,
The IETF's Discussion on "Source Format of RFC Documents"
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2.2.2 The author Element
Each "author" element identifies a document author. Since a document
may have more than one author, more than one "author" element may be
present. If the author is a person, then three attributes must be
present in the "" tag, "initials", "surname", and
"fullname", e.g.,
The "author" element itself consists of an "organization" element,
and, an optional "address" element.
The "organization" element is similar to the "title" element, in
that an abbreviation may be paired with a long organization name
using the "abbrev" attribute, e.g.,
USC/Information Sciences Institute
The "address" element consists of an optional "postal" element, an
optional "phone" element, an optional "facsimile" element, an
optional "email" element, and, an optional "uri" element.
The "postal" element contains one or more "street" elements,
followed by any combination of "city", "region" (state or province),
"code" (zipcode or postal code), and "country" elements, e.g.,
950 Charter StreetM/S 40Redwood CityCA94063US
This flexibility is provided to allow for different national formats
for postal addresses. Note however, that although the order of the
"city", "region", "code", and "country" elements isn't specified, at
most one of each may be present. Note that the value of the
"country" element should be a two-letter code from ISO 3166.
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The "phone", "facsimile", "email", and "uri" elements are simple,
e.g.,
+1 650 779 7081mrose@not.invisible.nethttp://invisible.net/
2.2.3 The date Element
The "date" element identifies the publication date of the document.
It consists of a month and a year, e.g.,
2.2.4 Meta Data Elements
The "front" element may contain meta data -- the content of these
elements does not appear in printed versions of the document.
A document has one or more optional "area", "workgroup" and
"keyword" elements, e.g.,
General
RFC Beautification Working GroupRFCRequest for CommentsI-DInternet-DraftXMLExtensible Markup Language
The "area" elements identify a general category for the document
(e.g., one of "Applications", "General", "Internet", "Management",
"Operations", "Routing", "Security", "Transport", or "User"), while
the "workgroup" elements identify the IETF working groups that
produced the document, and the "keyword" elements identify useful
search terms.
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2.2.5 The abstract Element
A document may have an "abstract" element, which contains one or
more "t" elements (Section 2.3.1.1). In general, only a single "t"
element is present, e.g.,
This memo presents a technique for using XML as a
source format for documents in the Internet-Drafts and RFC
series.
2.2.6 The note Element
A document may have one or more "note" elements, each of which
contains one or more "t" elements (Section 2.3.1.1). There is a
mandatory "title" attribute. In general, the "note" element contains
text from the IESG, e.g.,
The IESG has something to say.
2.2.7 Status, Copyright Notice, Table of Contents
Note that text relating to the memo's status, copyright notice, or
table of contents is not included in the document's markup -- this
is automatically inserted by an XML application when it produces
either a text or HTML version of the document.
2.2.7.1 Conformance with RFC 2026
If an Internet-Draft is being produced, then the "ipr2026" attribute
should be present in the "" tag at the beginning of the file.
The value of the attribute should be one of:
full: indicating that the document is in full conformance with all
the provisions of Section 10 of RFC 2026;
noDerivativeWorks: indicating that the document is in full
conformance with all the provisions of Section 10 of RFC 2026
except that the right to produce derivative works is not granted;
or,
none: indicating that the document is NOT offerred in accordance
with Section 10 of RFC 2026, and the author does not provide the
IETF with any rights other than to publish as an Internet-Draft.
In the latter case, a copyright notice will not be automatically
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inserted during processing by an XML application.
Consult [3] for further details.
2.2.8 Everything in the Front
So, putting it all together, we have, e.g.,
Writing I-Ds and RFCs using XMLInvisible Worlds, Inc.950 Charter StreetM/S 40Redwood CityCA94063US+1 650 779 7081mrose@not.invisible.nethttp://invisible.net/
General
RFC Beautification Working GroupRFCRequest for CommentsI-DInternet-DraftXMLExtensible Markup LanguageThis memo presents a technique for using XML as a
source format for documents in the Internet-Drafts and RFC
series.
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2.3 The Middle
The "middle" element contains all the sections of the document
except for the bibliography and appendices:
...
...
The "middle" element consists of one or more "section" elements.
2.3.1 The section Element
Each "section" element contains a section of the document. There is
a mandatory attribute, "title", that identifies the title of the
section. There is also an optional attribute, "anchor", that is used
for cross-referencing with the "xref" element (Section 2.3.1.3),
e.g.,
...
The "section" element is recursive -- each contains any number and
combination of "t", "figure", and "section" elements, e.g.,
...
...
...
............
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2.3.1.1 The t Element
The "t" element contains a paragraph, an item list, or a combination
of the two. Paragraphs are simply text. If a cross-reference is
needed to a section, figure, or reference, the "xref" element
(Section 2.3.1.3) is used; similarly, if an external-reference is
needed, the "eref" element (Section 2.3.1.4) is used.
2.3.1.1.1 The list Element
The "list" element contains one or more items. Each item is a "t"
element, allowing for recursion, e.g.,
The first item.The second item, which contains two bulleted sub-items:
The first sub-item.The second sub-item.
The "list" element has an optional attribute, "style", having the
value "numbers" (for numeric lists), "symbols" (for bulleted lists),
"hanging" (for hanging lists), or, "empty" (for indented text). If a
"list" element is nested, the default value is taken from its
closest parent; otherwise, the default value is "empty".
When nested within a "hanging list" element, the "t" element has an
optional attribute, "hangText" that specifies the text to be
inserted, e.g.,
indicating that the document is in full
conformance with all the provisions of Section 10 of RFC 2026;indicating that the document
is in full conformance with all the provisions of Section 10
of RFC 2026 except that the right to produce derivative works
is not granted;
or,indicating that the document is NOT offerred
in accordance with Section 10 of RFC 2026, and the author does
not provide the IETF with any rights other than to publish as
an Internet-Draft.
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2.3.1.2 The figure Element
The "figure" element groups an optional "preamble" element, an
"artwork" element, and an optional "postamble" element together. The
"figure" element also has an optional "anchor" attribute that is
used for cross-referencing with the "xref" element (Section
2.3.1.3). There is also an optional "title" attribute that
identifies the title of the figure.
The "preamble" and "postamble" elements, if present, are simply
text. If a cross-reference is needed to a section, figure, or
reference, the "xref" element (Section 2.3.1.3) is used; similarly,
if an external-reference is needed, the "eref" element (Section
2.3.1.4) is used.
The "artwork" element, which must be present, contains "ASCII
artwork". Unlike text contained in the "t", "preamble", or
"postamble" elements, both horizontal and vertical whitespace is
significant in the "artwork" element.
So, putting it all together, we have, e.g.,
which is a very simple example.
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If you have artwork with a lot of "<" characters, then there's an
XML trick you can use:
The "" construct is called a CDATA block --
everything between the innermost brackets is left alone by the XML
application.
Because the "figure" element represents a logical grouping of text
and artwork, an XML application producing a text version of the
document should attempt to keep these elements on the same page.
Because RFC 2223[2] allows no more than 69 characters by 49 lines of
content on each page, XML applications should be prepared to
prematurely introduce page breaks to allow for better visual
grouping.
2.3.1.3 The xref Element
The "xref" element is used to cross-reference sections, figures, and
references. The mandatory "target" attribute is used to link back to
the "anchor" attribute of the "section", "figure", and "reference"
elements. The value of the "anchor" and "target" attributes should
be formatted according to the token syntax in Section 2.1.
If used as an empty element, e.g.,
according to the token syntax in .
then the XML application inserts an appropriate phrase during
processing, such as "Section 2.1" or "XML
Basics".
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If used with content, e.g.,
conforming to RFC 2223.
then the XML application inserts an appropriate designation during
processing, such as "RFC 2223[2]" or "RFC
2223". Although the XML application decides what "an appropriate
designation" might be, its choice is consistent throughout the
processing of the document.
2.3.1.4 The eref Element
The "eref" element is used to reference external documents. The
mandatory "target" attribute is a URI[4], e.g.,
Cafe con Leche.
Note that while the "target" attribute is always present, the "eref"
element may be empty, e.g.,
and the XML application inserts an appropriate designation during
processing such as "[9]" or "http://invisible.net/".
2.3.1.5 The vspace Element
The "vspace" element, which may occur only inside the "t" element,
is used by the author to provide formatting guidance to the XML
application. There is an attribute, "blankLines", that indicates the
number of blank lines that should be inserted. A physical linebreak
is specified by using the default value, "0".
In addition, the "vspace" element can be used to force a new
physical paragraph within a list item, e.g.,
This is list item.
This is part of the same list item,
although when displayed, it appears
as a separate physical paragraph.
An XML application producing a text version of the document should
exercise care when encountering a value for "blankLines" that causes
a pagebreak -- in particular, if a "vspace" element causes a
pagebreak, then no further blank lines should be inserted. This
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allows authors to "force" a pagebreak by using an arbitrarily large
value, e.g., "blankLines='100'".
Finally, note that the "vspace" element is always empty -- it never
contains any text.
2.4 Back matter
Finally, the "back" element is used for references and appendices:
...
The "back" element consists of an optional "references" element,
and, one or more optional "section" elements. The "back" element
itself is optional, if your document doesn't have any references or
appendices, you don't have to include it.
2.4.1 The references Element
The "references" element contains the document's bibliography. It
contains one or more "reference" elements.
Each "reference" element contains a "front" element and one or more
optional "seriesInfo" elements.
We've already discussed the "front" element back in Section 2.2.
The "seriesInfo" element identifies the document series and number
of the reference, e.g., "RFC 2200", "STD 1", and so on.
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The "reference" element has an optional "anchor" attribute that is
used for cross-referencing with the "xref" element (Section
2.3.1.3), e.g.,
Internet Official Protocol Standards
USC/Information Sciences Institute
RFC 2200STD 1
The "reference" element also has an optional "target" attribute that
is used for external references (c.f., Section 2.3.1.4). The XML
application, if producing an HTML version of the document will use
the "target" attribute accordingly; however, if the "seriesInfo"
element starts with the string "RFC " (e.g., "RFC 2223") the XML
application should automatically provide an appropriate default for
the "target" attribute (e.g., "http://example.com/rfcs/rfc2223.txt").
2.4.2 Appendices
To include appendices after the bibliography, simply add more
"section" elements. (For an example, look at the example at the
beginning of Section 2.4.)
2.4.3 Copyright Status
The copyright status for the document is not included in the
document's markup -- this is automatically inserted by an XML
application that produces either a text or HTML version of the
document.
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3. Processing the XML Source File
This section concerns itself with applications that operate on an
XML source file. A lot of XML tools are available, as are many lists
of XML resources, e.g., Cafe con Leche[5].
There are two kinds of XML tools: validating and non-validating.
Both check that the source file conforms to the rules given in
Section 2.1. However, in addition to making sure that the source
file is well-formed, a validating tool also reads the DTD referenced
by the source file to make sure that they match. There are a number
of both validating and non-validating tools available.
3.1 Editing
There are several XML editors available. Ideally, you want an editor
that validates. This has two advantages:
o the editor provides guidance in fleshing-out the document
structure; and,
o the editor validates that the source file matches the rules in
the DTD.
There are two major modes in Emacs that support XML: sgml-mode and
psgml[6]. The latter mode allows you to validate the source file (by
calling an external program). If you visit the source file in Emacs
and the major mode isn't "SGML" or "XML", then usually all it takes
is adding these lines to your ".emacs" file:
(setq auto-mode-alist
(cons (cons "\\.xml$" 'sgml-mode) auto-mode-alist))
and then restarting Emacs.
The author uses both sgml-mode in Emacs, and a commercial validating
editor, Clip! version 1.5[7], when editing source files.
3.1.1 Checking
If your editor doesn't validate, then you should run a program to
validate the source file.
The author uses the AlphaWorks XML parser[8] for this purpose. It
requires that your system have a Java virtual machine. In addition
to Java, there are validating parsers written in C, Perl, Python,
and Tcl.
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3.2 Converting to Text Format
The author has written the xml2rfc tool[9], which reads the source
file and produces both a text and HTML version of the document.
(This memo was produced using the xml2rfc tool.) Note that xml2rfc
isn't a validating tool, so it's a good idea to use either a
validating editor or run a stand-alone validating parser prior to
using the tool.
3.3 Converting to HTML Format
The XML Style Language (XSL) is used to describe transformations
from the source file into some other structured file. So, ideally
you should use an XSL-capable formatter to convert an XML source
file to HTML.
However, as of this writing XSL is still in considerable flux.
(Hence, no reference was included in this memo, as by the time you
read this section, the reference would be outdated.) So, in the
interim, the author uses the xml2rfc tool for this purpose, even
though this tool doesn't provide much flexibility in its HTML layout.
3.4 Viewing
Browsers that support either XSL or Cascading Style Sheets (CSS) are
able to view the source file directly.
At present, the author doesn't use any of these browsers, instead
converting source files to either text or HTML.
3.5 Searching
As with text editors, any text-oriented search tool (e.g., grep) can
be used on the source file. However, there are search tools
available that understand structured source.
The author uses sgrep version 1.9[10] for this purpose, e.g.
sgrep -g xml 'ELEMENTS("title") not in ELEMENTS("back")' \
writing-rfcs.xml
which extracts the title element from the source file.
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4. Security Considerations
This memo raises no security issues; however, according to [2], your
document should contain a section near the end that discusses the
security considerations of the protocol or procedures that are the
main topic of your document, e.g.,
...
This memo raises no security issues;
however,
according to ,
your document should contain a section near the end that
discusses the security considerations of the protocol or
procedures that are the main topic of your document.
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References
[1] World Wide Web Consortium, "Extensible Markup Language (XML)
1.0", February 1998.
[2] Postel, J., Reynolds, J., "Instructions to RFC Authors", RFC
2223, October 1997.
[3] Bradner, S.O., "The Internet Standards Process -- Revision 3",
RFC 2026, BCP 9, October 1996.
[4] Berners-Lee, T., Fielding, R.T., Masinter, L., "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August
1998.
[5] http://metalab.unc.edu/xml/
[6] http://www.inria.fr/koala/plh/sxml.html
[7] http://www.t2000-usa.com/
[8] http://www.alphaworks.ibm.com/formula/xml/
[9] http://memory.palace.org/authoring/
[10] http://www.cs.helsinki.fi/~jjaakkol/sgrep.html
Author's Address
Marshall T. Rose
Invisible Worlds, Inc.
950 Charter Street
North 40
Redwood City, CA 94063
US
Phone: +1 650 779 7081
EMail: mrose@not.invisible.net
URI: http://invisible.net/
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Appendix A. The rfc Element
The "" tag at the beginning of the file, with only an "ipr2026"
attribute (Section 2.2.7.1), produces an Internet-Draft. However,
when other attributes are added to this tag by the RFC editor, an
RFC is produced, e.g.,
At a minimum, the "number" attribute should be present.
The other attributes are:
o "obsoletes", having a comma-separated list of RFC numbers, that
the document obsoletes;
o "updates", having a comma-separated list of RFC numbers, that the
document updates;
o "category", having one of these values:
1. "std", for a Standards-Track document;
2. "bcp", "for a Best Current Practices document;
3. "exp", for an Experimental Protocol document;
4. "historic", for a historic document; or,
5. "info", the default, for an Informational document.
o "seriesNo", having the corresponding number in the STD (std), BCP
(bcp), or FYI (info) series.
Finally, a special entity, "&rfc.number;", is available. Authors
preparing an RFC should use this entity whenever they want to
reference the number of the RFC within the document itself. In
printed versions of the document, the appropriate substitution (or
"XXXX") will occur.
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Internet-Draft Writing I-Ds and RFCs using XML February 1999
Appendix B. The RFC DTD
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Internet-Draft Writing I-Ds and RFCs using XML February 1999
Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Writing I-Ds and RFCs using XML
This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups.
Note that other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any time.
It is inappropriate to use Internet-Drafts as reference material or to cite
them other than as "work in progress."
1.
Introduction 2.
Using the DTD to Write I-Ds and RFCs 2.1
XML basics 2.2
Front matter 2.2.1
The title Element 2.2.2
The author Element 2.2.3
The date Element 2.2.4
Meta Data Elements 2.2.5
The abstract Element 2.2.6
The note Element 2.2.7
Status, Copyright Notice, Table of Contents 2.2.7.1
Conformance with RFC 2026 2.2.8
Everything in the Front 2.3
The Middle 2.3.1
The section Element 2.3.1.1
The t Element 2.3.1.1.1
The list Element 2.3.1.2
The figure Element 2.3.1.3
The xref Element 2.3.1.4
The eref Element 2.3.1.5
The vspace Element 2.4
Back matter 2.4.1
The references Element 2.4.2
Appendices 2.4.3
Copyright Status 3.
Processing the XML Source File 3.1
Editing 3.1.1
Checking 3.2
Converting to Text Format 3.3
Converting to HTML Format 3.4
Viewing 3.5
Searching 4.
Security Considerations §
References §
Author's Address A.
The rfc Element B.
The RFC DTD
This memo describes how to write a document for the I-D and RFC series
using the Extensible Markup Language[1] (XML).
This memo has three goals:
To describe a simple XML Document Type Definition (DTD) that is
powerful enough to handle the simple formatting requirements of RFC-like
documents whilst allowing for meaningful markup of descriptive
qualities.
To describe software that processes XML source files,
including a tool that produces documents
conforming to RFC 2223[2],
HTML format, and so on.
To provide the proof-of-concept for the first two goals
(this memo was written using this DTD and produced using that
software).
It is beyond the scope of this memo to discuss the political
ramifications of using XML as a source format for RFC-like documents.
Rather,
it is simply noted that adding minimal markup to plain text:
allows the traditional production of textual RFC-like documents using
familiar editors;
requires some, albeit minimal, additions to existing software
environments; and,
permits information to be organized, searched, and retrieved
using both unstructured and structured mechanisms.
We do not provide a formal or comprehensive description of XML.
Rather,
this section discusses just enough XML to use a Document Type
Declaration (DTD) to write RFC-like documents.
If you're already familiar with XML,
skip to The RFC DTD to look at the DTD.
There are very few rules when writing in XML,
as the syntax is simple.
There are five terms you'll need to know:
An "element" usually refers to a start tag, an end tag, and all the
characters in between,
e.g.,
"<example>text and/or nested elements</example>"
An "empty element" combines the start tag and the end tag,
e.g.,
"<empty/>".
You don't find these in HTML.
An "attribute" is part of an element.
If present, they occur in the start tag, e.g.,
"<example name='value'>".
Of course,
they can also appear in empty elements, e.g.,
"<empty name='value'/>".
An "entity" is a textual macro that starts with "&".
Don't worry about these,
you'll only use them whenever you want to put a "&" or a "<" in
your text.
A "token" is a string of characters.
The first character is either a letter or an underscore ("_").
Any characters that follow are either letters, numbers, an
underscore, or a period (".").
First,
start your source file with an XML declaration,
a reference to the DTD,
and the "rfc" element:
<?xml version="1.0"?>
<!DOCTYPE rfc SYSTEM "rfcXXXX.dtd">
<rfc>
...
</rfc>
Ignore the first two lines
-- the declaration and the reference --
and simply treat them as opaque strings.
Nothing else should be present after the "</rfc>" tag.
(NOTE TO READER:
when this memo is published as an RFC,
the "&rfc.number;" above will be replaced with the actual string to
use in your source file.)
Second,
make sure that all elements are properly matched and nested.
A properly matched element that starts with
"<example>" is eventually followed with "</example>".
(Empty elements are always matched.)
Elements are properly nested when they don't overlap.
For example,
<outer>
...
<inner>
...
</inner>
...
</outer>
is properly nested.
However,
<outer>
...
<inner>
...
</outer>
...
</inner>
overlaps, so the elements aren't properly nested.
Third,
never use "<" or "&" in your text.
Instead, use either "<" or "&", respectively.
Fourth,
there are two quoting characters in XML, 'apostrophe' and "quotation".
Make sure that all attributes values are quoted,
e.g., "<example name='value'>",
If the value contains one of the quoting characters,
then use the other to quote the value,
e.g., "<example name='"'>",
If the value contains both quoting characters,
then use one of them to quote the value,
and replace occurrances of that character in the attribute value with
either ''' (apostrophe) or """ (quotation),
e.g., "<example name='"'"'>".
If you want to put a comment in your source file,
here's the syntax:
(Note that in all examples,
indentation is used only for expository purposes.)
The "front" element consists of a "title" element,
one or more "author" elements,
a "date" element,
one or more optional "area" elements,
one or more optional "workgroup" elements,
one or more optional "keyword" elements,
an optional "abstract" element.
and,
one or more optional "note" elements.
The "title" element identifies the title of the document.
Because the title will be used in the headers of the document when formatted
according to [2],
if the title is more than 42 characters,
then an abbreviation should also be provided,
e.g.,
<title abbrev="Much Ado about Nothing">
The IETF's Discussion on "Source Format of RFC Documents"
</title>
Each "author" element identifies a document author.
Since a document may have more than one author,
more than one "author" element may be present.
If the author is a person,
then three attributes must be present in the "<author>" tag,
"initials", "surname", and "fullname",
e.g.,
<author initials="M.T." surname="Rose"
fullname="Marshall T. Rose">
The "author" element itself consists of an "organization" element,
and,
an optional "address" element.
The "organization" element is similar to the "title"
element,
in that an abbreviation may be paired with a long organization name
using the "abbrev" attribute, e.g.,
<organization abbrev="ISI">
USC/Information Sciences Institute
</organization>
The "address" element consists of an optional "postal" element,
an optional "phone" element,
an optional "facsimile" element,
an optional "email" element,
and,
an optional "uri" element.
The "postal" element contains one or more "street" elements,
followed by any combination of "city", "region" (state or province),
"code" (zipcode or postal code), and "country" elements, e.g.,
This flexibility is provided to allow for different national
formats for postal addresses.
Note however,
that although the order of the "city", "region", "code", and "country"
elements isn't specified,
at most one of each may be present.
Note that the value of the "country" element should be a two-letter
code from ISO 3166.
The "phone", "facsimile", "email", and "uri" elements are
simple, e.g.,
The "front" element may contain meta data --
the content of these elements does not appear in printed versions of
the document.
A document has one or more optional "area",
"workgroup" and "keyword" elements, e.g.,
<area>General</area>
<workgroup>RFC Beautification Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
The "area" elements identify a general category for the
document
(e.g., one of "Applications", "General", "Internet", "Management",
"Operations", "Routing", "Security", "Transport", or "User"),
while the "workgroup" elements identify the IETF working groups that
produced the document,
and the "keyword" elements identify useful search terms.
A document may have one or more "note" elements,
each of which contains one or more "t" elements.
There is a mandatory "title" attribute.
In general,
the "note" element contains text from the IESG,
e.g.,
<note title="IESG Note">
<t>The IESG has something to say.</t>
</note>
Note that text relating to the memo's status, copyright notice, or
table of contents is not included in the document's markup -- this is
automatically inserted by an XML application when it produces either
a text or HTML version of the document.
If an Internet-Draft is being produced,
then the "ipr2026" attribute should be present in the "<rfc>"
tag at the beginning of the file.
The value of the attribute should be one of:
full:
indicating that the document is in full conformance with all
the provisions of Section 10 of RFC 2026;
noDerivativeWorks:
indicating that the document is in full
conformance with all the provisions of Section 10 of RFC 2026 except that the
right to produce derivative works is not granted; or,
none:
indicating that the document is NOT offerred in accordance with
Section 10 of RFC 2026, and the author does not provide the IETF with any rights
other than to publish as an Internet-Draft.
In the latter case,
a copyright notice will not be automatically inserted during
processing by an XML application.
<front>
<title>Writing I-Ds and RFCs using XML</title>
<author initials="M.T." surname="Rose"
fullname="Marshall T. Rose">
<organization>Invisible Worlds, Inc.</organization>
<address>
<postal>
<street>950 Charter Street</street>
<street>M/S 40</street>
<city>Redwood City</city> <region>CA</region>
<code>94063</code>
<country>US</country>
</postal>
<phone>+1 650 779 7081</phone>
<email>mrose@not.invisible.net</email>
<uri>http://invisible.net/</uri>
</address>
</author>
<date month="February" year="1999"/>
<area>General</area>
<workgroup>RFC Beautification Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
<abstract>
<t>This memo presents a technique for using XML as a
source format for documents in the Internet-Drafts and RFC
series.</t>
</abstract>
</front>
Each "section" element contains a section of the document.
There is a mandatory attribute,
"title",
that identifies the title of the section.
There is also an optional attribute,
"anchor",
that is used for cross-referencing with
the "xref" element,
e.g.,
The "t" element contains a paragraph, an item list, or a combination of the two.
Paragraphs are simply text.
If a cross-reference is needed to a section, figure, or reference,
the "xref" element is used;
similarly,
if an external-reference is needed,
the "eref" element is used.
The "list" element contains one or more items.
Each item is a "t" element,
allowing for recursion, e.g.,
<list style="numbers">
<t>The first item.</t>
<t>The second item, which contains two bulleted sub-items:
<list style="symbols">
<t>The first sub-item.</t>
<t>The second sub-item.</t>
</list>
</t>
</list>
The "list" element has an optional attribute,
"style",
having the value "numbers" (for numeric lists),
"symbols" (for bulleted lists),
"hanging" (for hanging lists),
or,
"empty" (for indented text).
If a "list" element is nested,
the default value is taken from its closest parent;
otherwise,
the default value is "empty".
When nested within a "hanging list" element,
the "t" element has an optional attribute,
"hangText" that specifies the text to be inserted, e.g.,
<list>
<t hangText="full:">indicating that the document is in full
conformance with all the provisions of Section 10 of RFC 2026;</t>
<t hangText="noDerivativeWorks:">indicating that the document
is in full conformance with all the provisions of Section 10
of RFC 2026 except that the right to produce derivative works
is not granted;
or,</t>
<t hangText="none:">indicating that the document is NOT offerred
in accordance with Section 10 of RFC 2026, and the author does
not provide the IETF with any rights other than to publish as
an Internet-Draft.</t>
</list>
The "figure" element groups an optional "preamble" element,
an "artwork" element,
and an optional "postamble" element together.
The "figure" element also has an optional "anchor" attribute that is
used for cross-referencing with
the "xref" element.
There is also an optional "title" attribute that identifies the title
of the figure.
The "preamble" and "postamble" elements,
if present,
are simply text.
If a cross-reference is needed to a section, figure, or reference,
the "xref" element is used;
similarly,
if an external-reference is needed,
the "eref" element is used.
The "artwork" element,
which must be present,
contains "ASCII artwork".
Unlike text contained in the "t", "preamble", or "postamble" elements,
both horizontal and vertical whitespace is significant in the "artwork"
element.
So,
putting it all together, we have, e.g.,
<figure anchor="figure_example">
<preamble>So,
putting it all together, we have, e.g.,</preamble>
<artwork>
ascii artwork goes here...
be sure to use "<" or "&" instead of "<" and "&",
respectively!
</artwork>
<postamble>which is a very simple example.</postamble>
</figure>
which is a very simple example.
If you have artwork with a lot of "<" characters,
then there's an XML trick you can use:
<figure>
<preamble>If you have artwork with a lot of "<"
characters, then there's an XML trick you can use:</preamble>
<artwork><![CDATA[
ascii artwork goes here...
just don't use "]]" in your artwork!
]]></artwork>
<postamble>The "<![CDATA[ ... ]]>" construct is called
a CDATA block -- everything between the innermost brackets is
left alone by the XML application.</postamble>
</figure>
The "<![CDATA[ ... ]]>" construct is called a CDATA
block -- everything between the innermost brackets is left alone by
the XML application.
Because the "figure" element represents a logical grouping of text
and artwork,
an XML application producing a text version of the document should
attempt to keep these elements on the same page.
Because RFC 2223[2] allows no more than 69
characters by 49 lines of content on each page,
XML applications should be prepared to prematurely introduce page
breaks to allow for better visual grouping.
The "xref" element is used to cross-reference sections, figures, and
references.
The mandatory "target" attribute is used to link back to the "anchor"
attribute of the "section", "figure", and "reference" elements.
The value of the "anchor" and "target" attributes should be formatted
according to the token syntax in XML basics.
If used as an empty element,
e.g.,
according to the token syntax in <xref target="xml_basics"/>.
then the XML application inserts an appropriate phrase
during processing,
such as "Section 2.1" or
"<a href="#xml_basics">XML Basics</a>".
If used with content, e.g.,
conforming to <xref target="refs.RFC2223">RFC 2223</xref>.
then the XML application inserts an appropriate
designation during processing,
such as "RFC 2223[2]" or
"<a href="#refs.RFC2223">RFC 2223</a>".
Although the XML application decides what "an appropriate designation"
might be,
its choice is consistent throughout the processing of the document.
The "eref" element is used to reference external documents.
The mandatory "target" attribute is a
URI[4], e.g.,
<eref target="http://metalab.unc.edu/xml/">Cafe con Leche</eref>.
Note that while the "target" attribute is always present,
the "eref" element may be empty, e.g.,
<eref target="http://invisible.net/"/>
and the XML application inserts an appropriate designation during
processing such as "[9]" or
"<a href="http://invisible.net/">http://invisible.net/</a>".
The "vspace" element,
which may occur only inside the "t" element,
is used by the author to provide formatting guidance to the XML
application.
There is an attribute,
"blankLines",
that indicates the number of blank lines that should be inserted.
A physical linebreak is specified by using the default value, "0".
In addition,
the "vspace" element can be used to force a new physical paragraph
within a list item, e.g.,
<list style="numbers">
<t>This is list item.
<vspace blankLines="1"/>
This is part of the same list item,
although when displayed, it appears
as a separate physical paragraph.</t>
</list>
An XML application producing a text version of the document should
exercise care when encountering a value for "blankLines" that causes a
pagebreak --
in particular,
if a "vspace" element causes a pagebreak,
then no further blank lines should be inserted.
This allows authors to "force" a pagebreak by using an arbitrarily
large value, e.g., "blankLines='100'".
Finally, note that the "vspace" element is always empty -- it never
contains any text.
The "back" element consists of an optional "references" element,
and,
one or more optional "section" elements.
The "back" element itself is optional,
if your document doesn't have any references or appendices,
you don't have to include it.
The "reference" element also has an optional "target"
attribute that is used for external references
(c.f., The eref Element).
The XML application,
if producing an HTML version of the document will use the "target"
attribute accordingly;
however, if the "seriesInfo" element starts with the string "RFC "
(e.g., "RFC 2223")
the XML application should automatically provide an appropriate
default for the "target" attribute
(e.g., "http://example.com/rfcs/rfc2223.txt").
To include appendices after the bibliography,
simply add more "section" elements.
(For an example,
look at the example at the beginning of Back matter.)
The copyright status for the document is not included in the
document's markup -- this is automatically inserted by an XML
application that produces either a text or HTML version of the document.
This section concerns itself with applications that operate on
an XML source file.
A lot of XML tools are available,
as are many lists of XML resources,
e.g.,
Cafe con Leche.
There are two kinds of XML tools: validating and non-validating.
Both check that the source file conforms to the rules given in
XML basics.
However,
in addition to making sure that the source file is well-formed,
a validating tool also reads the DTD referenced by the source file
to make sure that they match.
There are a number of both validating and non-validating tools available.
There are several XML editors available.
Ideally,
you want an editor that validates.
This has two advantages:
the editor provides guidance in fleshing-out the document structure;
and,
the editor validates that the source file matches the rules in the DTD.
There are two major modes in Emacs that support XML:
sgml-mode and
psgml.
The latter mode allows you to validate the source file
(by calling an external program).
If you visit the source file in Emacs and the major mode isn't
"SGML" or "XML",
then usually all it takes is adding these lines to your ".emacs"
file:
If your editor doesn't validate,
then you should run a program to validate the source file.
The author uses
the
AlphaWorks XML parser for this purpose.
It requires that your system have a Java virtual machine.
In addition to Java,
there are validating parsers written in C, Perl, Python, and Tcl.
The author has written
the xml2rfc tool,
which reads the source file and produces both a text and HTML version
of the document.
(This memo was produced using the xml2rfc tool.)
Note that xml2rfc isn't a validating tool,
so it's a good idea to use either a validating editor or run a stand-alone
validating parser prior to using the tool.
The XML Style Language (XSL) is used to describe transformations
from the source file into some other structured file.
So,
ideally you should use an XSL-capable formatter to convert an XML source
file to HTML.
However,
as of this writing XSL is still in considerable flux.
(Hence,
no reference was included in this memo,
as by the time you read this section,
the reference would be outdated.)
So,
in the interim,
the author uses the xml2rfc tool for this purpose,
even though this tool doesn't provide much flexibility in its HTML layout.
As with text editors,
any text-oriented search tool (e.g., grep) can be used on the source file.
However,
there are search tools available that understand structured source.
This memo raises no security issues;
however,
according to [2],
your document should contain a section near the end that discusses the
security considerations of the protocol or procedures that are the
main topic of your document, e.g.,
<middle>
...
<section title="Security Considerations">
<t>This memo raises no security issues;
however,
according to <xref target="refs.RFC2223"/>,
your document should contain a section near the end that
discusses the security considerations of the protocol or
procedures that are the main topic of your document.</t>
</section>
</middle>
The "<rfc>" tag at the beginning of the file,
with only an "ipr2026" attribute,
produces an Internet-Draft.
However,
when other attributes are added to this tag by the RFC editor,
an RFC is produced, e.g.,
At a minimum,
the "number" attribute should be present.
The other attributes are:
"obsoletes",
having a comma-separated list of RFC numbers,
that the document obsoletes;
"updates",
having a comma-separated list of RFC numbers,
that the document updates;
"category",
having one of these values:
"std", for a Standards-Track document;
"bcp", "for a Best Current Practices document;
"exp", for an Experimental Protocol document;
"historic", for a historic document; or,
"info", the default, for an Informational document.
"seriesNo",
having the corresponding number in the STD (std), BCP (bcp), or FYI (info)
series.
Finally,
a special entity, "&rfc.number;", is available.
Authors preparing an RFC should use this entity whenever they want to
reference the number of the RFC within the document itself.
In printed versions of the document,
the appropriate substitution (or "XXXX") will occur.
<!--
DTD for the RFC document series, draft of 99-01-30
-->
<!--
Contents
DTD data types
The top-level
Front matter
The Body
Back matter
-->
<!--
DTD data types:
entity description
====== ===============================================
NUMBER [0-9]+
NUMBERS a comma-separated list of NUMBER
MONTH the month of the year, e.g., "January"
YEAR a four-digit year, e.g., "1999"
URI e.g., "http://invisible.net/"
ATEXT/CTEXT printable ASCII text (no line-terminators)
TEXT character data
-->
<!ENTITY % NUMBER "CDATA">
<!ENTITY % NUMBERS "CDATA">
<!ENTITY % MONTH "CDATA">
<!ENTITY % YEAR "CDATA">
<!ENTITY % URI "CDATA">
<!ENTITY % ATEXT "CDATA">
<!ENTITY % CTEXT "#PCDATA">
<!ENTITY % TEXT "#PCDATA">
<!ENTITY rfc.number "XXXX">
<!--
The top-level
-->
<!--
attributes for the "rfc" element are supplied by the RFC
editor. when preparing drafts, authors should leave them blank.
the "seriesNo" attribute is used if the category is, e.g., BCP.
-->
<!ELEMENT rfc (front,middle,back?)>
<!ATTLIST rfc
number %NUMBER; #IMPLIED
obsoletes %NUMBERS; ""
updates %NUMBERS; ""
category (std|bcp|info|exp|historic)
"info"
seriesNo %NUMBER; #IMPLIED
ipr2026 (full|noDerivativeWorks|none)
#IMPLIED>
<!--
Front matter
-->
<!ELEMENT front (title,author+,date,area*,workgroup*,keyword*,
abstract?,note?)>
<!-- the "abbrev" attribute is used for headers, etc. -->
<!ELEMENT title (%CTEXT;)>
<!ATTLIST title
abbrev %ATEXT; #IMPLIED>
<!ELEMENT author (organization,address?)>
<!ATTLIST author
initials %ATEXT; #IMPLIED
surname %ATEXT; #IMPLIED
fullname %ATEXT; #IMPLIED>
<!ELEMENT organization
(%CTEXT;)>
<!ATTLIST organization
abbrev %ATEXT; #IMPLIED>
<!ELEMENT address (postal?,phone?,facsimile?,email?,uri?)>
<!-- at most one of each the city, region, code, and country
elements may be present -->
<!ELEMENT postal (street+,(city|region|code|country)*)>
<!ELEMENT street (%CTEXT;)>
<!ELEMENT city (%CTEXT;)>
<!ELEMENT region (%CTEXT;)>
<!ELEMENT code (%CTEXT;)>
<!ELEMENT country (%CTEXT;)>
<!ELEMENT phone (%CTEXT;)>
<!ELEMENT facsimile (%CTEXT;)>
<!ELEMENT email (%CTEXT;)>
<!ELEMENT uri (%CTEXT;)>
<!ELEMENT date EMPTY>
<!ATTLIST date
month %MONTH; #REQUIRED
year %YEAR; #REQUIRED>
<!-- meta-data... -->
<!ELEMENT area (%CTEXT;)>
<!ELEMENT workgroup (%CTEXT;)>
<!ELEMENT keyword (%CTEXT;)>
<!ELEMENT abstract (t)+>
<!ELEMENT note (t)+>
<!ATTLIST note
title %ATEXT; #REQUIRED>
<!--
The body
-->
<!ELEMENT middle (section)+>
<!ELEMENT section (t|figure|section)*>
<!ATTLIST section
anchor ID #IMPLIED
title %ATEXT; #REQUIRED>
<!ELEMENT t (%TEXT;|xref|eref|list|vspace)*>
<!ATTLIST t
hangText %ATEXT; #IMPLIED>
<!-- the value of the style attribute is inherited from the closest
parent -->
<!ELEMENT list (t+)>
<!ATTLIST list
style (numbers|symbols|hanging|empty)
"empty">
<!ELEMENT xref (%CTEXT;)>
<!ATTLIST xref
target IDREF #REQUIRED
pageno (true|false) "false">
<!ELEMENT eref (%CTEXT;)>
<!ATTLIST eref
target %URI; #REQUIRED>
<!ELEMENT vspace EMPTY>
<!ATTLIST vspace
startBlank %NUMBER; "0">
<!ELEMENT figure (preamble?,artwork,postamble?)>
<!ATTLIST figure
anchor ID #IMPLIED
title %ATEXT; "">
<!ELEMENT preamble (%TEXT;|xref|eref)*>
<!ELEMENT artwork (%TEXT;)*>
<!ATTLIST artwork
xml:space (default|preserve) "preserve">
<!ELEMENT postamble (%TEXT;|xref|eref)*>
<!--
Back matter
-->
<!-- sections, if present, are appendices -->
<!ELEMENT back (references?,section*)>
<!ELEMENT references (reference+)>
<!ELEMENT reference (front,seriesInfo*)>
<!ATTLIST reference
anchor ID #IMPLIED
target %URI; #IMPLIED>
<!ELEMENT seriesInfo (%CTEXT;)>
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
------- =_aaaaaaaaaa0
Content-Type: text/xml; charset="us-ascii"
Content-ID: <20685.919210993.4@dbc.fv.com>
Content-Description: draft-mrose-writing-rfcs-00.xml
Writing I-Ds and RFCs using XMLInvisible Worlds, Inc.950 Charter StreetNorth 40Redwood CityCA94063US+1 650 779 7081mrose@not.invisible.nethttp://invisible.net/
General
RFCRequest for CommentsI-DInternet-DraftXMLExtensible Markup LanguageThis memo presents a technique for using XML as a source
format for documents in the Internet-Drafts and RFC series.This memo describes how to write a document for the I-D and RFC series
using the Extensible Markup Language (XML).
This memo has three goals:
To describe a simple XML Document Type Definition (DTD) that is
powerful enough to handle the simple formatting requirements of RFC-like
documents whilst allowing for meaningful markup of descriptive
qualities.To describe software that processes XML source files,
including a tool that produces documents
conforming to RFC 2223,
HTML format, and so on.To provide the proof-of-concept for the first two goals
(this memo was written using this DTD and produced using that
software).It is beyond the scope of this memo to discuss the political
ramifications of using XML as a source format for RFC-like documents.
Rather,
it is simply noted that adding minimal markup to plain text:
allows the traditional production of textual RFC-like documents using
familiar editors;requires some, albeit minimal, additions to existing software
environments; and,permits information to be organized, searched, and retrieved
using both unstructured and structured mechanisms.We do not provide a formal or comprehensive description of XML.
Rather,
this section discusses just enough XML to use a Document Type
Declaration (DTD) to write RFC-like documents.If you're already familiar with XML,
skip to to look at the DTD.There are very few rules when writing in XML,
as the syntax is simple.
There are five terms you'll need to know:
An "element" usually refers to a start tag, an end tag, and all the
characters in between,
e.g.,
"<example>text and/or nested elements</example>"An "empty element" combines the start tag and the end tag,
e.g.,
"<empty/>".
You don't find these in HTML.An "attribute" is part of an element.
If present, they occur in the start tag, e.g.,
"<example name='value'>".
Of course,
they can also appear in empty elements, e.g.,
"<empty name='value'/>".An "entity" is a textual macro that starts with "&".
Don't worry about these,
you'll only use them whenever you want to put a "&" or a "<" in
your text.A "token" is a string of characters.
The first character is either a letter or an underscore ("_").
Any characters that follow are either letters, numbers, an
underscore, or a period (".").(NOTE TO READER:
when this memo is published as an RFC,
the "&rfc.number;" above will be replaced with the actual string to
use in your source file.)Second,
make sure that all elements are properly matched and nested.
A properly matched element that starts with
"<example>" is eventually followed with "</example>".
(Empty elements are always matched.)
Elements are properly nested when they don't overlap.Third,
never use "<" or "&" in your text.
Instead, use either "<" or "&", respectively.Fourth,
there are two quoting characters in XML, 'apostrophe' and "quotation".
Make sure that all attributes values are quoted,
e.g., "<example name='value'>",
If the value contains one of the quoting characters,
then use the other to quote the value,
e.g., "<example name='"'>",
If the value contains both quoting characters,
then use one of them to quote the value,
and replace occurrances of that character in the attribute value with
either ''' (apostrophe) or """ (quotation),
e.g., "<example name='"'"'>".Finally,
XML is case sensitive.The "front" element consists of a "title" element,
one or more "author" elements,
a "date" element,
one or more optional "area" elements,
one or more optional "workgroup" elements,
one or more optional "keyword" elements,
an optional "abstract" element.
and,
one or more optional "note" elements.The "author" element itself consists of an "organization" element,
and,
an optional "address" element.The "address" element consists of an optional "postal" element,
an optional "phone" element,
an optional "facsimile" element,
an optional "email" element,
and,
an optional "uri" element.The "front" element may contain meta data --
the content of these elements does not appear in printed versions of
the document.Note that text relating to the memo's status, copyright notice, or
table of contents is not included in the document's markup -- this is
automatically inserted by an XML application when it produces either
a text or HTML version of the document.If an Internet-Draft is being produced,
then the "ipr2026" attribute should be present in the "<rfc>"
tag at the beginning of the file.
The value of the attribute should be one of:
indicating that the document is in full conformance with all
the provisions of Section 10 of RFC 2026;indicating that the document is in full
conformance with all the provisions of Section 10 of RFC 2026 except that the
right to produce derivative works is not granted; or,indicating that the document is NOT offerred in accordance with
Section 10 of RFC 2026, and the author does not provide the IETF with any rights
other than to publish as an Internet-Draft.
In the latter case,
a copyright notice will not be automatically inserted during
processing by an XML application.Consult for further details.
]]>
]]>
The "t" element contains a paragraph, an item list, or a combination of the two.
Paragraphs are simply text.
If a cross-reference is needed to a section, figure, or reference,
the "xref" element is used;
similarly,
if an external-reference is needed,
the "eref" element is used.The "figure" element groups an optional "preamble" element,
an "artwork" element,
and an optional "postamble" element together.
The "figure" element also has an optional "anchor" attribute that is
used for cross-referencing with
the "xref" element.
There is also an optional "title" attribute that identifies the title
of the figure.
The "preamble" and "postamble" elements,
if present,
are simply text.
If a cross-reference is needed to a section, figure, or reference,
the "xref" element is used;
similarly,
if an external-reference is needed,
the "eref" element is used.The "artwork" element,
which must be present,
contains "ASCII artwork".
Unlike text contained in the "t", "preamble", or "postamble" elements,
both horizontal and vertical whitespace is significant in the "artwork"
element.
]]>
which is a very simple example.Because the "figure" element represents a logical grouping of text
and artwork,
an XML application producing a text version of the document should
attempt to keep these elements on the same page.
Because RFC 2223 allows no more than 69
characters by 49 lines of content on each page,
XML applications should be prepared to prematurely introduce page
breaks to allow for better visual grouping.The "xref" element is used to cross-reference sections, figures, and
references.
The mandatory "target" attribute is used to link back to the "anchor"
attribute of the "section", "figure", and "reference" elements.
The value of the "anchor" and "target" attributes should be formatted
according to the token syntax in .The "vspace" element,
which may occur only inside the "t" element,
is used by the author to provide formatting guidance to the XML
application.
There is an attribute,
"blankLines",
that indicates the number of blank lines that should be inserted.
A physical linebreak is specified by using the default value, "0".An XML application producing a text version of the document should
exercise care when encountering a value for "blankLines" that causes a
pagebreak --
in particular,
if a "vspace" element causes a pagebreak,
then no further blank lines should be inserted.
This allows authors to "force" a pagebreak by using an arbitrarily
large value, e.g., "blankLines='100'".Finally, note that the "vspace" element is always empty -- it never
contains any text.
]]>
The "back" element consists of an optional "references" element,
and,
one or more optional "section" elements.
The "back" element itself is optional,
if your document doesn't have any references or appendices,
you don't have to include it.The "references" element contains the document's bibliography.
It contains one or more "reference" elements.Each "reference" element contains a "front" element and one or more
optional "seriesInfo" elements.We've already discussed the "front" element back in
.The "seriesInfo" element identifies the document series and number of
the reference,
e.g., "RFC 2200", "STD 1", and so on.The "reference" element also has an optional "target"
attribute that is used for external references
(c.f., ).
The XML application,
if producing an HTML version of the document will use the "target"
attribute accordingly;
however, if the "seriesInfo" element starts with the string "RFC "
(e.g., "RFC 2223")
the XML application should automatically provide an appropriate
default for the "target" attribute
(e.g., ).To include appendices after the bibliography,
simply add more "section" elements.
(For an example,
look at the example at the beginning of .)The copyright status for the document is not included in the
document's markup -- this is automatically inserted by an XML
application that produces either a text or HTML version of the document.This section concerns itself with applications that operate on
an XML source file.
A lot of XML tools are available,
as are many lists of XML resources,
e.g.,
Cafe con Leche.There are two kinds of XML tools: validating and non-validating.
Both check that the source file conforms to the rules given in
.
However,
in addition to making sure that the source file is well-formed,
a validating tool also reads the DTD referenced by the source file
to make sure that they match.
There are a number of both validating and non-validating tools available.There are several XML editors available.
Ideally,
you want an editor that validates.
This has two advantages:
the editor provides guidance in fleshing-out the document structure;
and,the editor validates that the source file matches the rules in the DTD.The author uses both sgml-mode in Emacs,
and a commercial validating editor,
Clip! version 1.5,
when editing source
files.If your editor doesn't validate,
then you should run a program to validate the source file.The author uses
the
AlphaWorks XML parser for this purpose.
It requires that your system have a Java virtual machine.
In addition to Java,
there are validating parsers written in C, Perl, Python, and Tcl.The author has written
the xml2rfc tool,
which reads the source file and produces both a text and HTML version
of the document.
(This memo was produced using the xml2rfc tool.)
Note that xml2rfc isn't a validating tool,
so it's a good idea to use either a validating editor or run a stand-alone
validating parser prior to using the tool.The XML Style Language (XSL) is used to describe transformations
from the source file into some other structured file.
So,
ideally you should use an XSL-capable formatter to convert an XML source
file to HTML.However,
as of this writing XSL is still in considerable flux.
(Hence,
no reference was included in this memo,
as by the time you read this section,
the reference would be outdated.)
So,
in the interim,
the author uses the xml2rfc tool for this purpose,
even though this tool doesn't provide much flexibility in its HTML layout.Browsers that support either XSL or Cascading Style Sheets (CSS)
are able to view the source file directly.At present,
the author doesn't use any of these browsers,
instead converting source files to either text or HTML.As with text editors,
any text-oriented search tool (e.g., grep) can be used on the source file.
However,
there are search tools available that understand structured source.Extensible Markup Language (XML) 1.0World Wide Web ConsortiumMIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+ 1 617 253 2613+ 1 617 258 5999timbl@w3.orghttp://www.w3c.orgInstructions to RFC AuthorsUSC/Information Sciences Institute4676 Admiralty WayMarina del ReyCA90292US+1 310 822 1511+1 310 823 6714Postel@ISI.EDUUSC/Information Sciences Institute4676 Admiralty WayMarina del ReyCA90292US+1 310 822 1511+1 310 823 6714jkrey@isi.eduRFC 2223The Internet Standards Process -- Revision 3Harvard UniversityHolyoke Center, Room 8131350 Massachusettes AvenueCambridgeMA02138US+1 617 495 3864sob@harvard.eduRFC 2026BCP 9Uniform Resource Identifiers (URI): Generic SyntaxWorld Wide Web ConsortiumMIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+1 617 253 5702+1 617 258 8682timbl@w3.orgUniversity of California, IrvineDepartment of Information and Computer ScienceUniversity of California, IrvineIrvineCA92697-3425US+1 949 824 7403+1 949 824 1715fielding@ics.uci.eduXerox PARC3333 Coyote Hill RoadPalo AltoCA94304US+1 650 812 4365+1 650 812 4333masinter@parc.xerox.comRFC 2396The other attributes are:
"obsoletes",
having a comma-separated list of RFC numbers,
that the document obsoletes;"updates",
having a comma-separated list of RFC numbers,
that the document updates;"category",
having one of these values:
"std", for a Standards-Track document;"bcp", "for a Best Current Practices document;"exp", for an Experimental Protocol document;"historic", for a historic document; or,"info", the default, for an Informational document."seriesNo",
having the corresponding number in the STD (std), BCP (bcp), or FYI (info)
series.Finally,
a special entity, "&rfc.number;", is available.
Authors preparing an RFC should use this entity whenever they want to
reference the number of the RFC within the document itself.
In printed versions of the document,
the appropriate substitution (or "XXXX") will occur.