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processors

·must·

support decimal numbers with a minimum of 18 decimal digits (i.e., with a

·totalDigits·

of 18). However,

processors

·may·

set an application-defined limit on the maximum number of decimal digits they are prepared to support, in which case that application-defined maximum number

·must·

be clearly documented.

3.2.3.1 Lexical representation

decimal has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39) separated by a period as a decimal indicator. An optional leading sign is allowed. If the sign is omitted, "+" is assumed. Leading and trailing zeroes are optional. If the fractional part is zero, the period and following zero(es) can be omitted. For example: -1.23, 12678967.543233, +100000.00, 210.

3.2.3.2 Canonical representation

The canonical representation for decimal is defined by prohibiting certain options from the Lexical representation (§3.2.3.1). Specifically, the preceding optional "+" sign is prohibited. The decimal point is required. Leading and trailing zeroes are prohibited subject to the following: there must be at least one digit to the right and to the left of the decimal point which may be a zero.

3.2.4 float

[Definition:] float is patterned after the IEEE single-precision 32-bit floating point type [IEEE 754-1985]. The basic ·value space· of float consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^24, and e is an integer between -149 and 104, inclusive. In addition to the basic ·value space· described above, the ·value space· of float also contains the following three special values: positive and negative infinity and not-a-number (NaN). The ·order-relation· on float is: x < y iff y - x is positive for x and y in the value space. Positive infinity is greater than all other non-NaN values. NaN equals itself but is ·incomparable· with (neither greater than nor less than) any other value in the ·value space·.

Note:

"Equality" in this Recommendation is defined to be "identity" (i.e., values that are identical in the

are equal and vice versa). Identity must be used for the few operations that are defined in this Recommendation. Applications using any of the datatypes defined in this Recommendation may use different definitions of equality for computational purposes;

-based computation systems are examples. Nothing in this Recommendation should be construed as requiring that such applications use identity as their equality relationship when computing.

Any value

·incomparable·

with the value used for the four bounding facets (

·minInclusive·

·maxInclusive·

·minExclusive·

, and

·maxExclusive·

) will be excluded from the resulting restricted

. In particular, when "NaN" is used as a facet value for a bounding facet, since no other

float

values are

·comparable·

with it, the result is a

either having NaN as its only member (the inclusive cases) or that is empty (the exclusive cases). If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted

; to add NaN back in requires union with the NaN-only space.

This datatype differs from that of

in that there is only one NaN and only one zero. This makes the equality and ordering of values in the data space differ from that of

only in that for schema purposes NaN = NaN.

A literal in the ·lexical space· representing a decimal number d maps to the normalized value in the ·value space· of float that is closest to d in the sense defined by [Clinger, WD (1990)]; if d is exactly halfway between two such values then the even value is chosen.

3.2.4.1 Lexical representation

float values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent. The exponent ·must· be an integer. The mantissa must be a decimal number. The representations for exponent and mantissa must follow the lexical rules for integer and decimal. If the "E" or "e" and the following exponent are omitted, an exponent value of 0 is assumed.

The special values positive and negative infinity and not-a-number have lexical representations INF, -INF and NaN, respectively. Lexical representations for zero may take a positive or negative sign.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 , -0, 0 and INF are all legal literals for float.

3.2.4.2 Canonical representation

The canonical representation for float is defined by prohibiting certain options from the Lexical representation (§3.2.4.1). Specifically, the exponent must be indicated by "E". Leading zeroes and the preceding optional "+" sign are prohibited in the exponent. If the exponent is zero, it must be indicated by "E0". For the mantissa, the preceding optional "+" sign is prohibited and the decimal point is required. Leading and trailing zeroes are prohibited subject to the following: number representations must be normalized such that there is a single digit which is non-zero to the left of the decimal point and at least a single digit to the right of the decimal point unless the value being represented is zero. The canonical representation for zero is 0.0E0.

3.2.5 double

[Definition:] The double datatype is patterned after the IEEE double-precision 64-bit floating point type [IEEE 754-1985]. The basic ·value space· of double consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^53, and e is an integer between -1075 and 970, inclusive. In addition to the basic ·value space· described above, the ·value space· of double also contains the following three special values: positive and negative infinity and not-a-number (NaN). The ·order-relation· on double is: x < y iff y - x is positive for x and y in the value space. Positive infinity is greater than all other non-NaN values. NaN equals itself but is ·incomparable· with (neither greater than nor less than) any other value in the ·value space·.

Note:

"Equality" in this Recommendation is defined to be "identity" (i.e., values that are identical in the

-based computation systems are examples. Nothing in this Recommendation should be construed as requiring that such applications use identity as their equality relationship when computing.

Any value

·incomparable·

with the value used for the four bounding facets (

·minInclusive·

·maxInclusive·

·minExclusive·

, and

·maxExclusive·

) will be excluded from the resulting restricted

. In particular, when "NaN" is used as a facet value for a bounding facet, since no other

double

values are

·comparable·

with it, the result is a

either having NaN as its only member (the inclusive cases) or that is empty (the exclusive cases). If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted

; to add NaN back in requires union with the NaN-only space.

This datatype differs from that of

in that there is only one NaN and only one zero. This makes the equality and ordering of values in the data space differ from that of

only in that for schema purposes NaN = NaN.

A literal in the ·lexical space· representing a decimal number d maps to the normalized value in the ·value space· of double that is closest to d; if d is exactly halfway between two such values then the even value is chosen. This is the best approximation of d ([Clinger, WD (1990)], [Gay, DM (1990)]), which is more accurate than the mapping required by [IEEE 754-1985].

3.2.5.1 Lexical representation

double values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent. The exponent ·must· be an integer. The mantissa must be a decimal number. The representations for exponent and mantissa must follow the lexical rules for integer and decimal. If the "E" or "e" and the following exponent are omitted, an exponent value of 0 is assumed.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 , -0, 0 and INF are all legal literals for double.

3.2.5.2 Canonical representation

The canonical representation for double is defined by prohibiting certain options from the Lexical representation (§3.2.5.1). Specifically, the exponent must be indicated by "E". Leading zeroes and the preceding optional "+" sign are prohibited in the exponent. If the exponent is zero, it must be indicated by "E0". For the mantissa, the preceding optional "+" sign is prohibited and the decimal point is required. Leading and trailing zeroes are prohibited subject to the following: number representations must be normalized such that there is a single digit which is non-zero to the left of the decimal point and at least a single digit to the right of the decimal point unless the value being represented is zero. The canonical representation for zero is 0.0E0.

3.2.6 duration

[Definition:] duration represents a duration of time. The ·value space· of duration is a six-dimensional space where the coordinates designate the Gregorian year, month, day, hour, minute, and second components defined in § 5.5.3.2 of [ISO 8601], respectively. These components are ordered in their significance by their order of appearance i.e. as year, month, day, hour, minute, and second.

Note:

All

processors

·must·

support year values with a minimum of 4 digits (i.e.,

YYYY

) and a minimum fractional second precision of milliseconds or three decimal digits (i.e.

s.sss

). However,

[ISO 8601:1998 Draft Revision]

processors

·may·

set an application-defined limit on the maximum number of digits they are prepared to support in these two cases, in which case that application-defined maximum number

·must·

be clearly documented.

3.2.6.1 Lexical representation

The lexical representation for duration is the [ISO 8601] extended format PnYn MnDTnH nMnS, where nY represents the number of years, nM the number of months, nD the number of days, 'T' is the date/time separator, nH the number of hours, nM the number of minutes and nS the number of seconds. The number of seconds can include decimal digits to arbitrary precision.

The values of the Year, Month, Day, Hour and Minutes components are not restricted but allow an arbitrary unsigned integer, i.e., an integer that conforms to the pattern [0-9]+.. Similarly, the value of the Seconds component allows an arbitrary unsigned decimal. Following [ISO 8601], at least one digit must follow the decimal point if it appears. That is, the value of the Seconds component must conform to the pattern [0-9]+(\.[0-9]+)?. Thus, the lexical representation of duration does not follow the alternative format of § 5.5.3.2.1 of [ISO 8601].

An optional preceding minus sign ('-') is allowed, to indicate a negative duration. If the sign is omitted a positive duration is indicated. See also ISO 8601 Date and Time Formats (§D).

For example, to indicate a duration of 1 year, 2 months, 3 days, 10 hours, and 30 minutes, one would write: P1Y2M3DT10H30M. One could also indicate a duration of minus 120 days as: -P120D.

Reduced precision and truncated representations of this format are allowed provided they conform to the following:

If the number of years, months, days, hours, minutes, or seconds in any expression equals zero, the number and its corresponding designator ·may· be omitted. However, at least one number and its designator ·must· be present.
The seconds part ·may· have a decimal fraction.
The designator 'T' must be absent if and only if all of the time items are absent. The designator 'P' must always be present.

For example, P1347Y, P1347M and P1Y2MT2H are all allowed; P0Y1347M and P0Y1347M0D are allowed. P-1347M is not allowed although -P1347M is allowed. P1Y2MT is not allowed.

3.2.6.2 Order relation on duration

In general, the ·order-relation· on duration is a partial order since there is no determinate relationship between certain durations such as one month (P1M) and 30 days (P30D). The ·order-relation· of two duration values x and y is x < y iff s+x < s+y for each qualified dateTime s in the list below. These values for s cause the greatest deviations in the addition of dateTimes and durations. Addition of durations to time instants is defined in Adding durations to dateTimes (§E).

1696-09-01T00:00:00Z
1697-02-01T00:00:00Z
1903-03-01T00:00:00Z
1903-07-01T00:00:00Z

The following table shows the strongest relationship that can be determined between example durations. The symbol <> means that the order relation is indeterminate. Note that because of leap-seconds, a seconds field can vary from 59 to 60. However, because of the way that addition is defined in Adding durations to dateTimes (§E), they are still totally ordered.

Relation P1Y > P364D <> P365D <> P366D < P367D P1M > P27D <> P28D <> P29D <> P30D <> P31D < P32D P5M > P149D <> P150D <> P151D <> P152D <> P153D < P154D

Implementations are free to optimize the computation of the ordering relationship. For example, the following table can be used to compare durations of a small number of months against days.

Months 1 2 3 4 5 6 7 8 9 10 11 12 13 ... Days Minimum 28 59 89 120 150 181 212 242 273 303 334 365 393 ... Maximum 31 62 92 123 153 184 215 245 276 306 337 366 397 ... 3.2.6.4 Totally ordered durations

Certain derived datatypes of durations can be guaranteed have a total order. For this, they must have fields from only one row in the list below and the time zone must either be required or prohibited.

year, month
day, hour, minute, second

For example, a datatype could be defined to correspond to the [SQL] datatype Year-Month interval that required a four digit year field and a two digit month field but required all other fields to be unspecified. This datatype could be defined as below and would have a total order.

<simpleType name='SQL-Year-Month-Interval'>
    <restriction base='duration'>
      <pattern value='P\p{Nd}{4}Y\p{Nd}{2}M'/>
    </restriction>
</simpleType>

3.2.7 dateTime

[Definition:] dateTime values may be viewed as objects with integer-valued year, month, day, hour and minute properties, a decimal-valued second property, and a boolean timezoned property. Each such object also has one decimal-valued method or computed property, timeOnTimeline, whose value is always a decimal number; the values are dimensioned in seconds, the integer 0 is 0001-01-01T00:00:00 and the value of timeOnTimeline for other dateTime values is computed using the Gregorian algorithm as modified for leap-seconds. The timeOnTimeline values form two related "timelines", one for timezoned values and one for non-timezoned values. Each timeline is a copy of the ·value space· of decimal, with integers given units of seconds.

The ·value space· of dateTime is closely related to the dates and times described in ISO 8601. For clarity, the text above specifies a particular origin point for the timeline. It should be noted, however, that schema processors need not expose the timeOnTimeline value to schema users, and there is no requirement that a timeline-based implementation use the particular origin described here in its internal representation. Other interpretations of the ·value space· which lead to the same results (i.e., are isomorphic) are of course acceptable.

All timezoned times are Coordinated Universal Time (UTC, sometimes called "Greenwich Mean Time"). Other timezones indicated in lexical representations are converted to UTC during conversion of literals to values. "Local" or untimezoned times are presumed to be the time in the timezone of some unspecified locality as prescribed by the appropriate legal authority; currently there are no legally prescribed timezones which are durations whose magnitude is greater than 14 hours. The value of each numeric-valued property (other than timeOnTimeline) is limited to the maximum value within the interval determined by the next-higher property. For example, the day value can never be 32, and cannot even be 29 for month 02 and year 2002 (February 2002).

Note:

The date and time datatypes described in this recommendation were inspired by

[ISO 8601]

. '0001' is the lexical representation of the year 1 of the Common Era (1 CE, sometimes written "AD 1" or "1 AD"). There is no year 0, and '0000' is not a valid lexical representation. '-0001' is the lexical representation of the year 1 Before Common Era (1 BCE, sometimes written "1 BC").

Those using this (1.0) version of this Recommendation to represent negative years should be aware that the interpretation of lexical representations beginning with a

'-'

is likely to change in subsequent versions.

[ISO 8601]

makes no mention of the year 0; in

the form '0000' was disallowed and this recommendation disallows it as well. However,

[ISO 8601:2000 Second Edition]

, which became available just as we were completing version 1.0, allows the form '0000', representing the year 1 BCE. A number of external commentators have also suggested that '0000' be allowed, as the lexical representation for 1 BCE, which is the normal usage in astronomical contexts. It is the intention of the XML Schema Working Group to allow '0000' as a lexical representation in the

dateTime

date

gYear

, and

gYearMonth

datatypes in a subsequent version of this Recommendation. '0000' will be the lexical representation of 1 BCE (which is a leap year), '-0001' will become the lexical representation of 2 BCE (not 1 BCE as in this (1.0) version), '-0002' of 3 BCE, etc.

Note:

See the conformance note in

which applies to this datatype as well.

3.2.7.1 Lexical representation

The ·lexical space· of dateTime consists of finite-length sequences of characters of the form: '-'? yyyy '-' mm '-' dd 'T' hh ':' mm ':' ss ('.' s+)? (zzzzzz)?, where

'-'? yyyy is a four-or-more digit optionally negative-signed numeral that represents the year; if more than four digits, leading zeros are prohibited, and '0000' is prohibited (see the Note above (§3.2.7); also note that a plus sign is not permitted);
the remaining '-'s are separators between parts of the date portion;
the first mm is a two-digit numeral that represents the month;
dd is a two-digit numeral that represents the day;
'T' is a separator indicating that time-of-day follows;
hh is a two-digit numeral that represents the hour; '24' is permitted if the minutes and seconds represented are zero, and the dateTime value so represented is the first instant of the following day (the hour property of a dateTime object in the ·value space· cannot have a value greater than 23);
':' is a separator between parts of the time-of-day portion;
the second mm is a two-digit numeral that represents the minute;
ss is a two-integer-digit numeral that represents the whole seconds;
'.' s+ (if present) represents the fractional seconds;
zzzzzz (if present) represents the timezone (as described below).

For example, 2002-10-10T12:00:00-05:00 (noon on 10 October 2002, Central Daylight Savings Time as well as Eastern Standard Time in the U.S.) is 2002-10-10T17:00:00Z, five hours later than 2002-10-10T12:00:00Z.

For further guidance on arithmetic with dateTimes and durations, see Adding durations to dateTimes (§E).

3.2.7.2 Canonical representation

Except for trailing fractional zero digits in the seconds representation, '24:00:00' time representations, and timezone (for timezoned values), the mapping from literals to values is one-to-one. Where there is more than one possible representation, the canonical representation is as follows:

The 2-digit numeral representing the hour must not be '24';
The fractional second string, if present, must not end in '0';
for timezoned values, the timezone must be represented with 'Z' (All timezoned dateTime values are UTC.).

3.2.7.3 Timezones

Timezones are durations with (integer-valued) hour and minute properties (with the hour magnitude limited to at most 14, and the minute magnitude limited to at most 59, except that if the hour magnitude is 14, the minute value must be 0); they may be both positive or both negative.

The lexical representation of a timezone is a string of the form: (('+' | '-') hh ':' mm) | 'Z', where

hh is a two-digit numeral (with leading zeros as required) that represents the hours,
mm is a two-digit numeral that represents the minutes,
'+' indicates a nonnegative duration,
'-' indicates a nonpositive duration.

The mapping so defined is one-to-one, except that '+00:00', '-00:00', and 'Z' all represent the same zero-length duration timezone, UTC; 'Z' is its canonical representation.

When a timezone is added to a UTC dateTime, the result is the date and time "in that timezone". For example, 2002-10-10T12:00:00+05:00 is 2002-10-10T07:00:00Z and 2002-10-10T00:00:00+05:00 is 2002-10-09T19:00:00Z.

3.2.7.4 Order relation on dateTime

dateTime value objects on either timeline are totally ordered by their timeOnTimeline values; between the two timelines, dateTime value objects are ordered by their timeOnTimeline values when their timeOnTimeline values differ by more than fourteen hours, with those whose difference is a duration of 14 hours or less being ·incomparable·.

In general, the ·order-relation· on dateTime is a partial order since there is no determinate relationship between certain instants. For example, there is no determinate ordering between (a) 2000-01-20T12:00:00 and (b) 2000-01-20T12:00:00Z. Based on timezones currently in use, (c) could vary from 2000-01-20T12:00:00+12:00 to 2000-01-20T12:00:00-13:00. It is, however, possible for this range to expand or contract in the future, based on local laws. Because of this, the following definition uses a somewhat broader range of indeterminate values: +14:00..-14:00.

The following definition uses the notation S[year] to represent the year field of S, S[month] to represent the month field, and so on. The notation (Q & "-14:00") means adding the timezone -14:00 to Q, where Q did not already have a timezone. This is a logical explanation of the process. Actual implementations are free to optimize as long as they produce the same results.

The ordering between two dateTimes P and Q is defined by the following algorithm:

A.Normalize P and Q. That is, if there is a timezone present, but it is not Z, convert it to Z using the addition operation defined in Adding durations to dateTimes (§E)

Thus 2000-03-04T23:00:00+03:00 normalizes to 2000-03-04T20:00:00Z

B. If P and Q either both have a time zone or both do not have a time zone, compare P and Q field by field from the year field down to the second field, and return a result as soon as it can be determined. That is:

For each i in {year, month, day, hour, minute, second}
1. If P[i] and Q[i] are both not specified, continue to the next i
2. If P[i] is not specified and Q[i] is, or vice versa, stop and return P <> Q
3. If P[i] < Q[i], stop and return P < Q
4. If P[i] > Q[i], stop and return P > Q
Stop and return P = Q

C.Otherwise, if P contains a time zone and Q does not, compare as follows:

P < Q if P < (Q with time zone +14:00)
P > Q if P > (Q with time zone -14:00)
P <> Q otherwise, that is, if (Q with time zone +14:00) < P < (Q with time zone -14:00)

D. Otherwise, if P does not contain a time zone and Q does, compare as follows:

P < Q if (P with time zone -14:00) < Q.
P > Q if (P with time zone +14:00) > Q.
P <> Q otherwise, that is, if (P with time zone +14:00) < Q < (P with time zone -14:00)

Examples:

Determinate Indeterminate 2000-01-15T00:00:00 < 2000-02-15T00:00:00 2000-01-01T12:00:00 <> 1999-12-31T23:00:00Z 2000-01-15T12:00:00 < 2000-01-16T12:00:00Z 2000-01-16T12:00:00 <> 2000-01-16T12:00:00Z 2000-01-16T00:00:00 <> 2000-01-16T12:00:00Z 3.2.7.5 Totally ordered dateTimes

Certain derived types from dateTime can be guaranteed have a total order. To do so, they must require that a specific set of fields are always specified, and that remaining fields (if any) are always unspecified. For example, the date datatype without time zone is defined to contain exactly year, month, and day. Thus dates without time zone have a total order among themselves.

3.2.8 time

[Definition:] time represents an instant of time that recurs every day. The ·value space· of time is the space of time of day values as defined in § 5.3 of [ISO 8601]. Specifically, it is a set of zero-duration daily time instances.

Since the lexical representation allows an optional time zone indicator, time values are partially ordered because it may not be able to determine the order of two values one of which has a time zone and the other does not. The order relation on time values is the Order relation on dateTime (§3.2.7.4) using an arbitrary date. See also Adding durations to dateTimes (§E). Pairs of time values with or without time zone indicators are totally ordered.

Note:

See the conformance note in

which applies to the seconds part of this datatype as well.

3.2.8.1 Lexical representation

The lexical representation for time is the left truncated lexical representation for dateTime: hh:mm:ss.sss with optional following time zone indicator. For example, to indicate 1:20 pm for Eastern Standard Time which is 5 hours behind Coordinated Universal Time (UTC), one would write: 13:20:00-05:00. See also ISO 8601 Date and Time Formats (§D).

3.2.8.2 Canonical representation

The canonical representation for time is defined by prohibiting certain options from the Lexical representation (§3.2.8.1). Specifically, either the time zone must be omitted or, if present, the time zone must be Coordinated Universal Time (UTC) indicated by a "Z". Additionally, the canonical representation for midnight is 00:00:00.

3.2.9 date

[Definition:] The ·value space· of date consists of top-open intervals of exactly one day in length on the timelines of dateTime, beginning on the beginning moment of each day (in each timezone), i.e. '00:00:00', up to but not including '24:00:00' (which is identical with '00:00:00' of the next day). For nontimezoned values, the top-open intervals disjointly cover the nontimezoned timeline, one per day. For timezoned values, the intervals begin at every minute and therefore overlap.

A "date object" is an object with year, month, and day properties just like those of dateTime objects, plus an optional timezone-valued timezone property. (As with values of dateTime timezones are a special case of durations.) Just as a dateTime object corresponds to a point on one of the timelines, a date object corresponds to an interval on one of the two timelines as just described.

Timezoned date values track the starting moment of their day, as determined by their timezone; said timezone is generally recoverable for canonical representations. [Definition:] The recoverable timezone is that duration which is the result of subtracting the first moment (or any moment) of the timezoned date from the first moment (or the corresponding moment) UTC on the same date. ·recoverable timezone·s are always durations between '+12:00' and '-11:59'. This "timezone normalization" (which follows automatically from the definition of the date ·value space·) is explained more in Lexical representation (§3.2.9.1).

For example: the first moment of 2002-10-10+13:00 is 2002-10-10T00:00:00+13, which is 2002-10-09T11:00:00Z, which is also the first moment of 2002-10-09-11:00. Therefore 2002-10-10+13:00 is 2002-10-09-11:00; they are the same interval.

Note:

For most timezones, either the first moment or last moment of the day (a

dateTime

value, always UTC) will have a

date

portion different from that of the

date

itself! However, noon of that

date

(the midpoint of the interval) in that (normalized) timezone will always have the same

date

portion as the

date

itself, even when that noon point in time is normalized to UTC. For example, 2002-10-10-05:00 begins during 2002-10-09Z and 2002-10-10+05:00 ends during 2002-10-11Z, but noon of both 2002-10-10-05:00 and 2002-10-10+05:00 falls in the interval which is 2002-10-10Z.

Note:

See the conformance note in

which applies to the year part of this datatype as well.

3.2.9.1 Lexical representation

For the following discussion, let the "date portion" of a dateTime or date object be an object similar to a dateTime or date object, with similar year, month, and day properties, but no others, having the same value for these properties as the original dateTime or date object.

The ·lexical space· of date consists of finite-length sequences of characters of the form: '-'? yyyy '-' mm '-' dd zzzzzz? where the date and optional timezone are represented exactly the same way as they are for dateTime. The first moment of the interval is that represented by: '-' yyyy '-' mm '-' dd 'T00:00:00' zzzzzz? and the least upper bound of the interval is the timeline point represented (noncanonically) by: '-' yyyy '-' mm '-' dd 'T24:00:00' zzzzzz?.

Note:

The

·recoverable timezone·

of a

date

will always be a duration between '+12:00' and '11:59'. Timezone lexical representations, as explained for

dateTime

, can range from '+14:00' to '-14:00'. The result is that literals of

date

s with very large or very negative timezones will map to a "normalized"

date

value with a

·recoverable timezone·

different from that represented in the original representation, and a matching difference of +/- 1 day in the

date

itself.

3.2.9.2 Canonical representation

Given a member of the date ·value space·, the date portion of the canonical representation (the entire representation for nontimezoned values, and all but the timezone representation for timezoned values) is always the date portion of the dateTime canonical representation of the interval midpoint (the dateTime representation, truncated on the right to eliminate 'T' and all following characters). For timezoned values, append the canonical representation of the ·recoverable timezone·.

3.2.10 gYearMonth

[Definition:] gYearMonth represents a specific gregorian month in a specific gregorian year. The ·value space· of gYearMonth is the set of Gregorian calendar months as defined in § 5.2.1 of [ISO 8601]. Specifically, it is a set of one-month long, non-periodic instances e.g. 1999-10 to represent the whole month of 1999-10, independent of how many days this month has.

Since the lexical representation allows an optional time zone indicator, gYearMonth values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gYearMonth values are considered as periods of time, the order relation on gYearMonth values is the order relation on their starting instants. This is discussed in Order relation on dateTime (§3.2.7.4). See also Adding durations to dateTimes (§E). Pairs of gYearMonth values with or without time zone indicators are totally ordered.

Note: Because month/year combinations in one calendar only rarely correspond to month/year combinations in other calendars, values of this type are not, in general, convertible to simple values corresponding to month/year combinations in other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.

Note:

See the conformance note in

which applies to the year part of this datatype as well.

3.2.10.1 Lexical representation

The lexical representation for gYearMonth is the reduced (right truncated) lexical representation for dateTime: CCYY-MM. No left truncation is allowed. An optional following time zone qualifier is allowed. To accommodate year values outside the range from 0001 to 9999, additional digits can be added to the left of this representation and a preceding "-" sign is allowed.

For example, to indicate the month of May 1999, one would write: 1999-05. See also ISO 8601 Date and Time Formats (§D).

3.2.11 gYear

[Definition:] gYear represents a gregorian calendar year. The ·value space· of gYear is the set of Gregorian calendar years as defined in § 5.2.1 of [ISO 8601]. Specifically, it is a set of one-year long, non-periodic instances e.g. lexical 1999 to represent the whole year 1999, independent of how many months and days this year has.

Since the lexical representation allows an optional time zone indicator, gYear values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gYear values are considered as periods of time, the order relation on gYear values is the order relation on their starting instants. This is discussed in Order relation on dateTime (§3.2.7.4). See also Adding durations to dateTimes (§E). Pairs of gYear values with or without time zone indicators are totally ordered.

Note: Because years in one calendar only rarely correspond to years in other calendars, values of this type are not, in general, convertible to simple values corresponding to years in other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.

Note:

See the conformance note in

which applies to the year part of this datatype as well.

3.2.11.1 Lexical representation

The lexical representation for gYear is the reduced (right truncated) lexical representation for dateTime: CCYY. No left truncation is allowed. An optional following time zone qualifier is allowed as for dateTime. To accommodate year values outside the range from 0001 to 9999, additional digits can be added to the left of this representation and a preceding "-" sign is allowed.

For example, to indicate 1999, one would write: 1999. See also ISO 8601 Date and Time Formats (§D).

3.2.12 gMonthDay

[Definition:] gMonthDay is a gregorian date that recurs, specifically a day of the year such as the third of May. Arbitrary recurring dates are not supported by this datatype. The ·value space· of gMonthDay is the set of calendar dates, as defined in § 3 of [ISO 8601]. Specifically, it is a set of one-day long, annually periodic instances.

Since the lexical representation allows an optional time zone indicator, gMonthDay values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gMonthDay values are considered as periods of time, in an arbitrary leap year, the order relation on gMonthDay values is the order relation on their starting instants. This is discussed in Order relation on dateTime (§3.2.7.4). See also Adding durations to dateTimes (§E). Pairs of gMonthDay values with or without time zone indicators are totally ordered.

Note: Because day/month combinations in one calendar only rarely correspond to day/month combinations in other calendars, values of this type do not, in general, have any straightforward or intuitive representation in terms of most other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.

3.2.12.1 Lexical representation

The lexical representation for gMonthDay is the left truncated lexical representation for date: --MM-DD. An optional following time zone qualifier is allowed as for date. No preceding sign is allowed. No other formats are allowed. See also ISO 8601 Date and Time Formats (§D).

This datatype can be used to represent a specific day in a month. To say, for example, that my birthday occurs on the 14th of September ever year.

3.2.13 gDay

[Definition:] gDay is a gregorian day that recurs, specifically a day of the month such as the 5th of the month. Arbitrary recurring days are not supported by this datatype. The ·value space· of gDay is the space of a set of calendar dates as defined in § 3 of [ISO 8601]. Specifically, it is a set of one-day long, monthly periodic instances.

This datatype can be used to represent a specific day of the month. To say, for example, that I get my paycheck on the 15th of each month.

Since the lexical representation allows an optional time zone indicator, gDay values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gDay values are considered as periods of time, in an arbitrary month that has 31 days, the order relation on gDay values is the order relation on their starting instants. This is discussed in Order relation on dateTime (§3.2.7.4). See also Adding durations to dateTimes (§E). Pairs of gDay values with or without time zone indicators are totally ordered.

Note: Because days in one calendar only rarely correspond to days in other calendars, values of this type do not, in general, have any straightforward or intuitive representation in terms of most other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.

3.2.13.1 Lexical representation

The lexical representation for gDay is the left truncated lexical representation for date: ---DD . An optional following time zone qualifier is allowed as for date. No preceding sign is allowed. No other formats are allowed. See also ISO 8601 Date and Time Formats (§D).

3.2.14 gMonth

[Definition:] gMonth is a gregorian month that recurs every year. The ·value space· of gMonth is the space of a set of calendar months as defined in § 3 of [ISO 8601]. Specifically, it is a set of one-month long, yearly periodic instances.

This datatype can be used to represent a specific month. To say, for example, that Thanksgiving falls in the month of November.

Since the lexical representation allows an optional time zone indicator, gMonth values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gMonth values are considered as periods of time, the order relation on gMonth is the order relation on their starting instants. This is discussed in Order relation on dateTime (§3.2.7.4). See also Adding durations to dateTimes (§E). Pairs of gMonth values with or without time zone indicators are totally ordered.

Note: Because months in one calendar only rarely correspond to months in other calendars, values of this type do not, in general, have any straightforward or intuitive representation in terms of most other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.

3.2.14.1 Lexical representation

The lexical representation for gMonth is the left and right truncated lexical representation for date: --MM. An optional following time zone qualifier is allowed as for date. No preceding sign is allowed. No other formats are allowed. See also ISO 8601 Date and Time Formats (§D).

3.2.15 hexBinary

[Definition:] hexBinary represents arbitrary hex-encoded binary data. The ·value space· of hexBinary is the set of finite-length sequences of binary octets.

3.2.15.1 Lexical Representation

hexBinary has a lexical representation where each binary octet is encoded as a character tuple, consisting of two hexadecimal digits ([0-9a-fA-F]) representing the octet code. For example, "0FB7" is a hex encoding for the 16-bit integer 4023 (whose binary representation is 111110110111).

3.2.15.2 Canonical Representation

The canonical representation for hexBinary is defined by prohibiting certain options from the Lexical Representation (§3.2.15.1). Specifically, the lower case hexadecimal digits ([a-f]) are not allowed.

3.2.16 base64Binary

[Definition:] base64Binary represents Base64-encoded arbitrary binary data. The ·value space· of base64Binary is the set of finite-length sequences of binary octets. For base64Binary data the entire binary stream is encoded using the Base64 Alphabet in [RFC 2045].

The lexical forms of base64Binary values are limited to the 65 characters of the Base64 Alphabet defined in [RFC 2045], i.e., a-z, A-Z, 0-9, the plus sign (+), the forward slash (/) and the equal sign (=), together with the characters defined in [XML 1.0 (Second Edition)] as white space. No other characters are allowed.

For compatibility with older mail gateways, [RFC 2045] suggests that base64 data should have lines limited to at most 76 characters in length. This line-length limitation is not mandated in the lexical forms of base64Binary data and must not be enforced by XML Schema processors.

The lexical space of base64Binary is given by the following grammar (the notation is that used in [XML 1.0 (Second Edition)]); legal lexical forms must match the Base64Binary production.

Base64Binary ::= ((B64S B64S B64S B64S)* ((B64S B64S B64S B64) | (B64S B64S B16S '=') | (B64S B04S '=' #x20? '=')))?

B64S ::= B64 #x20?


 B16S         ::= B16 #x20?
 B04S         ::= B04 #x20?


 B04         ::=  [AQgw]


  B16         ::=  [AEIMQUYcgkosw048]

  B64         ::=  [A-Za-z0-9+/]

Note that this grammar requires the number of non-whitespace characters in the lexical form to be a multiple of four, and for equals signs to appear only at the end of the lexical form; strings which do not meet these constraints are not legal lexical forms of base64Binary because they cannot successfully be decoded by base64 decoders.

Note:

The above definition of the lexical space is more restrictive than that given in

[RFC 2045]

as regards whitespace -- this is not an issue in practice. Any string compatible with the RFC can occur in an element or attribute validated by this type, because the

·whiteSpace·

facet of this type is fixed to

collapse

, which means that all leading and trailing whitespace will be stripped, and all internal whitespace collapsed to single space characters,

before

the above grammar is enforced.

The canonical lexical form of a base64Binary data value is the base64 encoding of the value which matches the Canonical-base64Binary production in the following grammar:

Canonical-base64Binary ::= (B64 B64 B64 B64)* ((B64 B64 B16 '=') | (B64 B04 '=='))?

Note:

For some values the canonical form defined above does not conform to

[RFC 2045]

, which requires breaking with linefeeds at appropriate intervals.

The length of a base64Binary value is the number of octets it contains. This may be calculated from the lexical form by removing whitespace and padding characters and performing the calculation shown in the pseudo-code below:

lex2 := killwhitespace(lexform) -- remove whitespace characters lex3 := strip_equals(lex2) -- strip padding characters at end length := floor (length(lex3) * 3 / 4) -- calculate length

Note on encoding: [RFC 2045] explicitly references US-ASCII encoding. However, decoding of base64Binary data in an XML entity is to be performed on the Unicode characters obtained after character encoding processing as specified by [XML 1.0 (Second Edition)]

3.2.17 anyURI

[Definition:] anyURI represents a Uniform Resource Identifier Reference (URI). An anyURI value can be absolute or relative, and may have an optional fragment identifier (i.e., it may be a URI Reference). This type should be used to specify the intention that the value fulfills the role of a URI as defined by [RFC 2396], as amended by [RFC 2732].

The mapping from anyURI values to URIs is as defined by the URI reference escaping procedure defined in Section 5.4 Locator Attribute of [XML Linking Language] (see also Section 8 Character Encoding in URI References of [Character Model]). This means that a wide range of internationalized resource identifiers can be specified when an anyURI is called for, and still be understood as URIs per [RFC 2396], as amended by [RFC 2732], where appropriate to identify resources.

Note:

Section 5.4

Locator Attribute

[XML Linking Language]

requires that relative URI references be absolutized as defined in

[XML Base]

before use. This is an XLink-specific requirement and is not appropriate for XML Schema, since neither the

·lexical space·

nor the

of the

anyURI

type are restricted to absolute URIs. Accordingly absolutization must not be performed by schema processors as part of schema validation.

Note:

Each URI scheme imposes specialized syntax rules for URIs in that scheme, including restrictions on the syntax of allowed fragment identifiers. Because it is impractical for processors to check that a value is a context-appropriate URI reference, this specification follows the lead of

[RFC 2396]

(as amended by

[RFC 2732]

) in this matter: such rules and restrictions are not part of type validity and are not checked by

processors. Thus in practice the above definition imposes only very modest obligations on