Internet Engineering Task Force (IETF) S. Perreault
Request for Comments: 6351 Viagenie
Category: Standards Track August 2011
ISSN: 2070-1721
xCard: vCard XML Representation
Abstract
This document defines the XML schema of the vCard data format.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6351.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Example: Author's XML vCard . . . . . . . . . . . . . . . . . 3
5. Design Considerations . . . . . . . . . . . . . . . . . . . . 4
5.1. Extensibility . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Limitations . . . . . . . . . . . . . . . . . . . . . . . 7
6. Format Conversions . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8.1. Registration of the XML Namespace . . . . . . . . . . . . 11
8.2. Media Type . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Relax NG Schema . . . . . . . . . . . . . . . . . . . 14
1. Introduction
vCard [RFC6350] is a data format for representing and exchanging
information about individuals and other entities. It is a text-based
format (as opposed to a binary format). This document defines xCard,
an XML [W3C.REC-xml-20081126] representation for vCard. The
underlying data structure is exactly the same, enabling a 1-to-1
mapping between the original vCard format and the XML representation.
The XML formatting may be preferred in some contexts where an XML
engine is readily available and may be reused instead of writing a
standalone vCard parser.
Earlier work on an XML format for vCard was started in 1998 by Frank
Dawson [VCARD-DTD]. Sadly, it did not take over the world.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. The Schema
The schema is expressed in the RELAX NG language [ISO.19757-2.2008]
and is found in Appendix A.
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4. Example: Author's XML vCard
Simon Perreault
Perreault
Simon
ing. jr
M.Sc.
--0203
20090808T1430-0500
M
1 fr
2 en
work Viagenie
work
2875 boul. Laurier, suite D2-630
Quebec
QC
G1V 2M2
Canada
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work
voice
tel:+1-418-656-9254;ext=102
work
text
voice
cell
video
tel:+1-418-262-6501
work simon.perreault@viagenie.ca
work geo:46.766336,-71.28955
work http://www.viagenie.ca/simon.perreault/simon.asc
America/Montreal
home http://nomis80.org
5. Design Considerations
The general idea is to map vCard parameters, properties, and value
types to XML elements. For example, the "FN" property is mapped to
the "fn" element. In turn, that element contains a text element
whose content corresponds to the vCard property's value.
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vCard parameters are also mapped to XML elements. They are contained
in the element, which is contained in property elements.
For example, the "TYPE" parameter applied to the "TEL" property would
look like the following in XML:
voice
video
tel:+1-555-555-555
Parameters taking a list of values are simply repeated multiple
times, once for each value in the list.
Properties having structured values (e.g., the "N" property) are
expressed by XML element trees. Element names in that tree (e.g.,
"surname", "given", etc.) do not have a vCard equivalent since they
are identified by position in plain vCard.
Line folding is a non-issue in XML. Therefore, the mapping from
vCard to XML is done after the unfolding procedure is carried out.
Conversely, the mapping from XML to vCard is done before the folding
procedure is carried out.
A top-level element is used as root. It contains one or
more elements, each representing a complete vCard. The
element MUST be present even when only a single vCard is
present in an XML document.
The group construct (Section 3.2 in [RFC6350]) is represented with
the element. The "name" attribute contains the group's name.
For example:
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...
...
...
...
is equivalent to:
BEGIN:VCARD
VERSION:4.0
contact.FN=...
contact.EMAIL=...
media.PHOTO=...
CATEGORIES=...
END:VCARD
5.1. Extensibility
The original vCard format is extensible. New properties, parameters,
data types and values (collectively known as vCard elements, not to
be confused with XML elements) can be registered with IANA (see
[RFC6350], Section 10.2). It is expected that these vCard extensions
will also specify extensions to the XML format described in this
document.
New XML vCard property and parameter element names MUST be lower-
case. This is necessary to ensure that round-tripping between XML
and plain-text vCard works correctly.
Unregistered extensions (i.e., those starting with "X-" and
"VND-...-") are expressed in XML by using elements starting with "x-"
and "vnd-...-". Usage of XML namespaces [W3C.REC-xml-names-20091208]
for extensibility is RECOMMENDED for extensions that have no
equivalent in plain-text vCard. Refer to Section 6 for the
implications when converting between plain-text vCard and XML.
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Examples:
1
value goes here
1
value goes here
Note that extension elements do not need the "X-" or "VND-" prefix in
XML. The XML namespace mechanism is sufficient.
A vCard XML parser MUST ignore XML elements and attributes for which
it doesn't recognize the expanded name. The normal behavior of
ignoring XML processing instructions whose target is not recognized
MUST also be followed.
In the original vCard format, the "VERSION" property was mandatory
and played a role in extensibility. In XML, this property is absent.
Its role is played by the vCard core namespace identifier, which
includes the version number. vCard revisions will use a different
namespace.
Parameters containing a list of values are expressed using a list of
elements in XML (e.g., the element).
5.2. Limitations
The schema does not validate the cardinality of properties. This is
a limitation of the schema definition language. Cardinalities of the
original vCard format [RFC6350] MUST still be respected.
Some constructs (e.g., value enumerations in type parameters) have
additional ordering constraints in XML. This is a result of
limitations of the schema definition language, and the order is
arbitrary. The order MUST be respected in XML for the vCard to be
valid. However, reordering as part of conversion to or from plain
vCard MAY happen.
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6. Format Conversions
When new properties or "X-" properties are used, a vCard<->xCard
converter might not recognize them or know what the appropriate
default value types are, yet they need to be able to preserve the
values. A similar issue arises for unrecognized property parameters.
As a result, the following rules are applied when dealing with
unrecognized properties and property parameters:
o When converting from vCard to xCard:
* Any property that does not include a "VALUE" parameter and
whose default value type is not known MUST be converted using
the value type XML element . The content of that
element is the unprocessed value text.
* Any unrecognized property parameter MUST be converted using the
value type XML element , with its content set to the
parameter value text, treated as if it were a text value, or
list of text values.
* The content of "XML" properties is copied as is to XML.
* Property and parameter XML element names are converted to
lower-case.
* Property value escaping is undone. For example, "\n" becomes a
NEWLINE character (ASCII decimal 10).
* Double-quoting of parameter values, as well as backslash
escaping in parameter values, is undone. For example,
PARAM="\"foo\",\"bar\"" becomes "foo","bar".
o When converting xCard to vCard:
* Properties in the vCard 4 namespace:
+ If the converter knows of a specific plain-text
representation for this property, it uses it. For example,
the element corresponds to the "ADR" property, which
is encoded using comma-separated lists separated by
semicolons.
+ Otherwise, the property name is taken from the element name,
property parameters are taken from the element,
and the content of the property is taken from the content of
the value element. If the property element has attributes
or contains other XML elements, they are dropped.
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+ If a standard property's XML element contains XML elements
and attributes for which the converter doesn't recognize the
expanded name, they are dropped. Therefore, it is
RECOMMENDED to limit extensions to the property level to
ensure that all data is preserved intact in round-trip
conversions.
* Properties in other namespaces are wrapped as is inside an
"XML" property.
* Any property value XML elements are converted
directly into vCard values. The containing property MUST NOT
have a "VALUE" parameter.
* Any parameter value XML elements are converted as if
they were value type XML elements.
* Property and parameter names are converted to upper-case.
* Property value escaping (Section 3.3 of [RFC6350]) is carried
out. For example, a NEWLINE character (ASCII decimal 10)
becomes "\n".
* Double-quoting of parameter values, as well as backslash
escaping in parameter values, is carried out. For example,
"foo","bar" becomes PARAM="\"foo\",\"bar\"".
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For example, these two vCards are equivalent:
J. Doe
Doe
J.
image/jpeg
alien.jpg
My web page!
BEGIN:VCARD
VERSION:4.0
FN:J. Doe
N:Doe;J.;;
X-FILE;MEDIATYPE=image/jpeg:alien.jpg
XML:My web page!
END:VCARD
7. Security Considerations
All the security considerations applicable to plain vCard [RFC6350]
are applicable to this document as well.
XML Signature [W3C.CR-xmldsig-core1-20110303] and XML Encryption
[W3C.CR-xmlenc-core1-20110303] can be used with xCard to provide
authentication and confidentiality.
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8. IANA Considerations
8.1. Registration of the XML Namespace
URI: urn:ietf:params:xml:ns:vcard-4.0
Registrant Contact: The IESG
XML: None. Namespace URIs do not represent an XML specification.
8.2. Media Type
This section defines the MIME media type [RFC4288] for use with
vCard-in-XML data.
To: ietf-types@iana.org
Subject: Registration of media type application/vcard+xml
Type name: application
Subtype name: vcard+xml
Required parameters: none
Optional parameters: charset as defined for application/xml in
[RFC3023]; per [RFC3023], use of the charset parameter with the
value "utf-8" is "STRONGLY RECOMMENDED".
Encoding considerations: Same as encoding considerations of
application/xml as specified in [RFC3023].
Security considerations: This media type has all of the security
considerations described in [RFC3023], plus those listed in
Section 7.
Interoperability considerations: This media type provides an
alternative syntax to vCard data [RFC6350] based on XML.
Published specification: This specification.
Applications that use this media type: Applications that currently
make use of the text/vcard media type can use this as an
alternative. In general, applications that maintain or process
contact information can use this media type.
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Additional information:
Magic number(s): none
File extension(s): XML data should use ".xml" as the file
extension.
Macintosh file type code(s): none
Person & email address to contact for further information: Simon
Perreault
Intended usage: COMMON
Restrictions on usage: none
Author: Simon Perreault
Change controller: IETF
9. Acknowledgments
Thanks to the following people for their input:
Alexey Melnikov, Barry Leiba, Bjorn Hoehrmann, Cyrus Daboo, Joe
Hildebrand, Joseph Smarr, Marc Blanchet, Mike Douglass, Peter Saint-
Andre, Robins George, Zahhar Kirillov, Zoltan Ordogh.
10. References
10.1. Normative References
[ISO.19757-2.2008]
International Organization for Standardization,
"Information technology -- Document Schema Definition
Language (DSDL) -- Part 2: Regular-grammar-based
validation -- RELAX NG", ISO International
Standard 19757-2, October 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC6350] Perreault, S., "vCard Format Specification", RFC 6350,
August 2011.
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[W3C.REC-xml-20081126]
Paoli, J., Yergeau, F., Maler, E., Bray, T., and C.
Sperberg-McQueen, "Extensible Markup Language (XML) 1.0
(Fifth Edition)", World Wide Web Consortium
Recommendation REC-xml-20081126, November 2008,
.
[W3C.REC-xml-names-20091208]
Bray, T., Hollander, D., Layman, A., Tobin, R., and H.
Thompson, "Namespaces in XML 1.0 (Third Edition)", World
Wide Web Consortium Recommendation REC-xml-names-20091208,
December 2009,
.
10.2. Informative References
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[VCARD-DTD]
Dawson, F., "The vCard v3.0 XML DTD", Work in Progress,
June 1998.
[W3C.CR-xmldsig-core1-20110303]
Roessler, T., Solo, D., Yiu, K., Reagle, J., Hirsch, F.,
Eastlake, D., and M. Nystroem, "XML Signature Syntax and
Processing Version 1.1", World Wide Web Consortium CR CR-
xmldsig-core1-20110303, March 2011,
.
[W3C.CR-xmlenc-core1-20110303]
Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch,
"XML Encryption Syntax and Processing Version 1.1", World
Wide Web Consortium CR CR-xmlenc-core1-20110303,
March 2011,
.
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Appendix A. Relax NG Schema
default namespace = "urn:ietf:params:xml:ns:vcard-4.0"
### Section 3.3: vCard Format Specification
#
# 3.3
iana-token = xsd:string { pattern = "[a-zA-Z0-9-]+" }
x-name = xsd:string { pattern = "x-[a-zA-Z0-9-]+" }
### Section 4: Value types
#
# 4.1
value-text = element text { text }
value-text-list = value-text+
# 4.2
value-uri = element uri { xsd:anyURI }
# 4.3.1
value-date = element date {
xsd:string { pattern = "\d{8}|\d{4}-\d\d|--\d\d(\d\d)?|---\d\d" }
}
# 4.3.2
value-time = element time {
xsd:string { pattern = "(\d\d(\d\d(\d\d)?)?|-\d\d(\d\d?)|--\d\d)"
~ "(Z|[+\-]\d\d(\d\d)?)?" }
}
# 4.3.3
value-date-time = element date-time {
xsd:string { pattern = "(\d{8}|--\d{4}|---\d\d)T\d\d(\d\d(\d\d)?)?"
~ "(Z|[+\-]\d\d(\d\d)?)?" }
}
# 4.3.4
value-date-and-or-time = value-date | value-date-time | value-time
# 4.3.5
value-timestamp = element timestamp {
xsd:string { pattern = "\d{8}T\d{6}(Z|[+\-]\d\d(\d\d)?)?" }
}
# 4.4
value-boolean = element boolean { xsd:boolean }
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# 4.5
value-integer = element integer { xsd:integer }
# 4.6
value-float = element float { xsd:float }
# 4.7
value-utc-offset = element utc-offset {
xsd:string { pattern = "[+\-]\d\d(\d\d)?" }
}
# 4.8
value-language-tag = element language-tag {
xsd:string { pattern = "([a-z]{2,3}((-[a-z]{3}){0,3})?|[a-z]{4,8})"
~ "(-[a-z]{4})?(-([a-z]{2}|\d{3}))?"
~ "(-([0-9a-z]{5,8}|\d[0-9a-z]{3}))*"
~ "(-[0-9a-wyz](-[0-9a-z]{2,8})+)*"
~ "(-x(-[0-9a-z]{1,8})+)?|x(-[0-9a-z]{1,8})+|"
~ "[a-z]{1,3}(-[0-9a-z]{2,8}){1,2}" }
}
### Section 5: Parameters
#
# 5.1
param-language = element language { value-language-tag }?
# 5.2
param-pref = element pref {
element integer {
xsd:integer { minInclusive = "1" maxInclusive = "100" }
}
}?
# 5.4
param-altid = element altid { value-text }?
# 5.5
param-pid = element pid {
element text { xsd:string { pattern = "\d+(\.\d+)?" } }+
}?
# 5.6
param-type = element type { element text { "work" | "home" }+ }?
# 5.7
param-mediatype = element mediatype { value-text }?
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# 5.8
param-calscale = element calscale { element text { "gregorian" } }?
# 5.9
param-sort-as = element sort-as { value-text+ }?
# 5.10
param-geo = element geo { value-uri }?
# 5.11
param-tz = element tz { value-text | value-uri }?
### Section 6: Properties
#
# 6.1.3
property-source = element source {
element parameters { param-altid, param-pid, param-pref,
param-mediatype },
value-uri
}
# 6.1.4
property-kind = element kind {
element text { "individual" | "group" | "org" | "location" |
x-name | iana-token }*
}
# 6.2.1
property-fn = element fn {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type }?,
value-text
}
# 6.2.2
property-n = element n {
element parameters { param-language, param-sort-as, param-altid }?,
element surname { text }+,
element given { text }+,
element additional { text }+,
element prefix { text }+,
element suffix { text }+
}
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# 6.2.3
property-nickname = element nickname {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type }?,
value-text-list
}
# 6.2.4
property-photo = element photo {
element parameters { param-altid, param-pid, param-pref, param-type,
param-mediatype }?,
value-uri
}
# 6.2.5
property-bday = element bday {
element parameters { param-altid, param-calscale }?,
(value-date-and-or-time | value-text)
}
# 6.2.6
property-anniversary = element anniversary {
element parameters { param-altid, param-calscale }?,
(value-date-and-or-time | value-text)
}
# 6.2.7
property-gender = element gender {
element sex { "" | "M" | "F" | "O" | "N" | "U" },
element identity { text }?
}
# 6.3.1
param-label = element label { value-text }?
property-adr = element adr {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type, param-geo, param-tz,
param-label }?,
element pobox { text }+,
element ext { text }+,
element street { text }+,
element locality { text }+,
element region { text }+,
element code { text }+,
element country { text }+
}
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# 6.4.1
property-tel = element tel {
element parameters {
param-altid,
param-pid,
param-pref,
element type {
element text { "work" | "home" | "text" | "voice"
| "fax" | "cell" | "video" | "pager"
| "textphone" }+
}?,
param-mediatype
}?,
(value-text | value-uri)
}
# 6.4.2
property-email = element email {
element parameters { param-altid, param-pid, param-pref,
param-type }?,
value-text
}
# 6.4.3
property-impp = element impp {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
# 6.4.4
property-lang = element lang {
element parameters { param-altid, param-pid, param-pref,
param-type }?,
value-language-tag
}
# 6.5.1
property-tz = element tz {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
(value-text | value-uri | value-utc-offset)
}
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# 6.5.2
property-geo = element geo {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
# 6.6.1
property-title = element title {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type }?,
value-text
}
# 6.6.2
property-role = element role {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type }?,
value-text
}
# 6.6.3
property-logo = element logo {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type, param-mediatype }?,
value-uri
}
# 6.6.4
property-org = element org {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type, param-sort-as }?,
value-text-list
}
# 6.6.5
property-member = element member {
element parameters { param-altid, param-pid, param-pref,
param-mediatype }?,
value-uri
}
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# 6.6.6
property-related = element related {
element parameters {
param-altid,
param-pid,
param-pref,
element type {
element text {
"work" | "home" | "contact" | "acquaintance" |
"friend" | "met" | "co-worker" | "colleague" | "co-resident" |
"neighbor" | "child" | "parent" | "sibling" | "spouse" |
"kin" | "muse" | "crush" | "date" | "sweetheart" | "me" |
"agent" | "emergency"
}+
}?,
param-mediatype
}?,
(value-uri | value-text)
}
# 6.7.1
property-categories = element categories {
element parameters { param-altid, param-pid, param-pref,
param-type }?,
value-text-list
}
# 6.7.2
property-note = element note {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type }?,
value-text
}
# 6.7.3
property-prodid = element prodid { value-text }
# 6.7.4
property-rev = element rev { value-timestamp }
# 6.7.5
property-sound = element sound {
element parameters { param-language, param-altid, param-pid,
param-pref, param-type, param-mediatype }?,
value-uri
}
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# 6.7.6
property-uid = element uid { value-uri }
# 6.7.7
property-clientpidmap = element clientpidmap {
element sourceid { xsd:positiveInteger },
value-uri
}
# 6.7.8
property-url = element url {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
# 6.8.1
property-key = element key {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
(value-uri | value-text)
}
# 6.9.1
property-fburl = element fburl {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
# 6.9.2
property-caladruri = element caladruri {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
# 6.9.3
property-caluri = element caluri {
element parameters { param-altid, param-pid, param-pref,
param-type, param-mediatype }?,
value-uri
}
Perreault Standards Track [Page 21]
RFC 6351 xCard August 2011
# Top-level grammar
property = property-adr | property-anniversary | property-bday
| property-caladruri | property-caluri | property-categories
| property-clientpidmap | property-email | property-fburl
| property-fn | property-geo | property-impp | property-key
| property-kind | property-lang | property-logo
| property-member | property-n | property-nickname
| property-note | property-org | property-photo
| property-prodid | property-related | property-rev
| property-role | property-gender | property-sound
| property-source | property-tel | property-title
| property-tz | property-uid | property-url
start = element vcards {
element vcard {
(property
| element group {
attribute name { text },
property*
})+
}+
}
Author's Address
Simon Perreault
Viagenie
2600 boul. Laurier, Suite 625
Quebec, QC G1V 4W1
Canada
Phone: +1 418 656 9254
EMail: simon.perreault@viagenie.ca
URI: http://www.viagenie.ca
Perreault Standards Track [Page 22]
RFC, FYI, BCP