D ISO 8601 Date and Time Formats
D.1 ISO 8601 Conventions
Three primitive datatypes described above,
timeInstant,
timeInstant, and recurringInstant, and two
derived dataypes, date and
time use
lexical formats inspired by [ISO 8601]. This appendix provides
more detail on the ISO formats and discusses some deviations from them for the datatypes we have defined.
[ISO 8601] "specifies the representation of dates in the Gregorian calendar and times and representations of periods of time". It should be pointed out that the datatypes described in this specification do not cover all the types of data covered by [ISO 8601], nor do they support all the lexical representations for those types of data. Specifically, we permit only a single lexical representation for each datatype.
[ISO 8601] lexical formats are described using "pictures" in
which characters are used in place of digits. These characters have the following
meanings:
- C -- represents a digit used in the thousands and hundreds components, the
"century" component, of the time element "year".
- Y -- represents a digit used in the tens and units components of the time
element "year".
- M -- represents a digit used in the time
element "month".
- D -- represents a digit used in the time
element "day".
- h -- represents a digit used in the time
element "hour".
- m -- represents a digit used in the time
element "minute".
- s -- represents a digit used in the time
element "second". In the formats described in this specification the whole number
of seconds may be followed by decimal seconds to an arbitrary level of precision.
This is represented in the picture by "ss.sss"
For all the information items indicated by the above characters, leading zeros
are required where indicated.
In addition to the above, certain characters are used as designators and appear
as themselves in lexical formats.
- T -- is used as time designator to indicate the start of the representation
of the time of day in timeInstant and recurringInstant.
It is also used to to indicate the start of the representation of the time-units for hour,
minutes, seconds and fractional seconds in timeInstant.
- Z -- is used as time-zone designator, immediately (without a space) following
a data element expressing the time of day in Coordinated Universal Time (UTC)
in timeInstant, recurringInstant, and time
D.2 Truncated Formats
[ISO 8601] supports a variety of "truncated" formats in which some of the characters on the left of specific formats, such as, for example, the century, can be omitted. Truncated formats are, in general, not permitted for the
datatypes defined in this specification with two exceptions. The
recurringInstant datatype uses a truncated format for
timeInstant to indicate recurring instants of time. In fact,
only recurring instants that can be represented truncated representations of
timeInstant are permitted.
Left truncated representations are also allowed for the date
datatype and can be used to represent recurring dates i.e. the same date every
century, every year or every month. Right truncated, or reduced precision,
representations are also allowed for date and can be used
to represent a specific month, a specific year, or a specific century.
D.3 Deviations from ISO 8601 Formats
D.3.1 Sign Allowed
An optional minus sign is allowed immediately preceding, without a space,
the lexical representations for timeInstant and
timeInstant.
E Regular Expressions
A regular expression R
is a sequence of characters that denotes a set of strings L(R).
When used to constrain the lexical space of a datatype, a regular expression R
asserts that only strings in L(R) are valid specifications for
values of that type.
[Definition:] A regular expression is composed from one or more branches, separated by | characters.
[Definition:] A branch consists of zero or more pieces, concatenated
together.
| For all pieces S, and for all branches T, valid
branches R are: |
Denoting the set of strings L(R) containing: |
| S |
all strings in L(S) |
| ST |
all strings st with s in L(S) and t in L(T) |
[Definition:] A piece is an
atom, possibly followed by a
quantifier.
| For all atoms S, valid
pieces R are: |
Denoting the set of strings L(R) containing: |
| S |
all strings in L(S) |
| S? |
the empty string, and all strings in L(S). |
| S* |
All strings st with s in L(S?) and t in L(S*). ( all concatenations of zero or more strings from L(S) ) |
| S+ |
All strings st with s in L(S) and t in L(S*). ( all concatenations of one or more strings from L(S) ) |
[Definition:] An atom is either a
normal character, a
character class, or
a parenthesized regular expression.
[Definition:] A quantifier
is is either
?,
*, or
+.
[Definition:] A metacharacter
is either
.,
\,
?,
*,
+,
(,
),
[, or
].
These characters have special meanings in regular expressions,
but can be escaped to form atoms that denote
the sets of strings containing only themselves, i.e., an escaped
metacharacter behaves like a normal character.
[Definition:] A normal character is
any XML character that is not a metacharacter. In regular expressions, a normal
character is an atom that denotes
the singleton set of strings containing only itself.
E.1 Character Classes
[Definition:] A character class is an
atom R that identifies a set of characters
C(R). The set of strings
L(R) denoted by a character class
R
contains one single-character string "c" for each character c in
C(R).
A character class is either a character class escape or a character class expression.
[Definition:] A
character class expression is a character group surrounded
by [ and ] characters. For all character groups G, [G]
is a valid character class expression, identifying the set of characters
C([G]) = C(G).
[Definition:] A character group is
either positive character group, a negative character group, or
a character class subtraction.
[Definition:] A positive character group
consists of one or more character ranges or character class escapes, concatenated together. A positive
character group identifies the set of characters containing all of the characters in all of the
sets identified by its constituent ranges or escapes.
[Definition:] A negative character group
is a positive character group preceded by the ^ character. For all
positive character groups P, ^P is a valid negative character
group, and C(^P) contains all XML characters that are not
in C(P).
[Definition:] A
character class subtraction is a character class expression subtracted
from a positive or negative character group, using the - character.
For any positive or negative character group G, and any character class expression C,
G-C is a valid character class subtraction, identifying the set of all characters in
C(G) that are not also in C(C).
[Definition:] A character range
R identifies a set of characters C(R) containing all XML characters
with Unicode code points in a specified range.
A single XML character is a character range that identifies the set of characters containing
only itself. All XML chacters are valid character ranges, except as follows:
A character range may also be written in the form s-e, identifying the set
that contains all XML characters with Unicode code points greater than or equal to the code point
of s, but not greater than the code point of e.
s-e is a valid character range iff:
NOTE: The code point of a single character escape is the code point of the single character in
the set of characters that it identifies.
E.1.1 Character Class Escapes
[Definition:] A character class escape is a
short sequence of characters that identifies predefined character class. The valid character
class escapes include the single character escapes, the multi-character escapes, and the
category escapes.
[Definition:] A single character escape identifies
a set containing a only one character -- usually because that
character is difficult or impossible to write directly into a regular expression.
| The valid single character escapes are: |
Identifying the set of characters C(R) containing: |
\n |
the newline character (
) |
\r |
the return character (
) |
\t |
the tab character (	) |
\\ |
\ |
\. |
. |
\- |
- |
\^ |
^ |
\? |
? |
\* |
* |
\+ |
+ |
\( |
( |
\) |
) |
\[ |
[ |
\] |
] |
[Definition:] The
Unicode Standard [Unicode] defines a number of character properties
and provides mappings from code points to specific character properties. The
set containing of all characters that have property
X, may be identified with a category escape \p{X}.
The compliment of this set may be specified with the category escape \P{X}.
([\P{X}] = [^\p{X}]).
The following table specifies the main character properties (for more information, see
Chapter 4 of [Unicode]).
| Category | Property | Meaning |
| Letters | L | All Letters |
| Lu | Uppercase |
| Ll | Lowercase |
| Lt | Titlecase |
| Lm | Modifier |
| Lo | Other |
| |
| Marks | M | All Marks |
| Mn | Non-Spacing |
| Mc | Spacing Combining |
| Me | Enclosing |
| |
| Numbers | N | All Numbers |
| Nd | Decimal Digit |
| Nl | Letter |
| No | Other |
| |
| Punctuation | P | All Punctuation |
| Pc | Connector |
| Pd | Dash |
| Ps | Open |
| Pe | Close |
| Pi | Initial quote
(may behave like Ps or Pe depending on usage) |
| Pf | Final quote
(may behave like Ps or Pe depending on usage) |
| Po | Other |
| |
| Separators | Z | All Separators |
| Zs | Space |
| Zl | Line |
| Zp | Paragraph |
| |
| Symbols | S | All Symbols |
| Sm | Math |
| Sc | Currency |
| Sk | Modifier |
| So | Other |
| |
| Other | C | All Others |
| Cc | Control |
| Cf | Format |
| Cs | Surrogate |
| Co | Private Use |
| Cn | Not Assigned |
[Definition:] A
multi-character escape
provides a simple way to identify a commonly used set of characters:
| Character Sequence |
Equivalent character class |
| . | [^\n\r] |
| \s | [ \t\n\r] |
| \S | [^\s] |
| \i | [\p{L}\p{Nl}:_] |
| \I | [^\i] |
| \c | [\p{?}\p{?}] |
| \C | [^\c] |
| \d | \p{Nd} |
| \D | [^\d] |
| \w | [\p{?}\p{?}] |
| \W | [^\w] |
G Acknowledgments (non-normative)
The following have contributed material to this draft:
- Matt Timmermans
- Mark Reinhold
The editors acknowledge the members of the XML Schema Working Group, the members of other W3C Working Groups, and industry experts in other
forums who have contributed directly or indirectly to the process or content of
creating this document. The Working Group is particularly grateful to Lotus
Development Corp. and IBM for providing teleconferencing facilities.
The current members of the XML Schema Working Group are:
David Beech, Oracle Corp.; Paul V. Biron, Health Level Seven; Don Box, DevelopMentor; Allen Brown, Microsoft; Greg Bumgardner, Rogue Wave Software; Lee Buck, Extensibility; Charles Campbell, Informix; Peter Chen, Bootstrap Alliance and LSU; David Cleary, Progress Software; Dan Connolly, W3C (staff contact); Andrew Eisenberg, Progress Software; Rob Ellman, Calico Commerce; David Ezell, Hewlett Packard Company; David Fallside, IBM; Matthew Fuchs, Commerce One; Paul Grosso, ArborText, Inc.; Dave Hollander, CommerceNet (co-chair); Mary Holstege, Calico Commerce; Jane Hunter, Distributed Systems Technology Centre (DSTC Pty Ltd); Renato Iannella, Distributed Systems Technology Centre (DSTC Pty Ltd); Rick Jelliffe, Academia Sinica; Dianne Kennedy, Graphic Communications Association; Andrew Layman, Microsoft; Dmitry Lenkov, Hewlett Packard Company; Eve Maler, Sun Microsystems; Ashok Malhotra, IBM; Murray Maloney, Commerce One; John McCarthy, Lawrence Berkeley National Laboratory; Noah Mendelsohn, Lotus Development Corporation; Don Mullen, Extensibility; Frank Olken, Lawrence Berkeley National Laboratory; Dave Peterson, Graphic Communications Association; Mark Reinhold, Sun Microsystems; Jonathan Robie, Software AG; Lew Shannon, NCR; C. M. Sperberg-McQueen, W3C (co-chair); Henry S. Thompson, University of Edinburgh; Matt Timmermans, Microstar; Jim Trezzo, Oracle Corp.; Steph Tryphonas, Microstar; Mark Tucker, Health Level Seven; Asir Vedamuthu, webMethods; Priscilla Walmsley, XMLSolutions; Norm Walsh, ArborText, Inc.; Aki Yoshida, SAP AG
The XML Schema Working Group has benefited in its work from the
participation and contributions of a number of people not currently
members of the Working Group, including
in particular those named below. Affiliations given are those current at
the time of their work with the WG.
Paula Angerstein, Vignette Corporation; Gabe Beged-Dov, Rogue Wave Software; Dean Burson, Lotus Development Corporation; George Feinberg, Object Design; Charles Frankston, Microsoft; Ernesto Guerrieri, Inso; Michael Hyman, Microsoft; Setrag Khoshafian, Technology Deployment International (TDI); Janet Koenig, Sun Microsystems; Ara Kullukian, Technology Deployment International (TDI); Murata Makoto, Xerox; Chris Olds, Wall Data; Shriram Revankar, Xerox; William Shea, Merrill Lynch; Ralph Swick, W3C; Tony Stewart, Rivcom