3.2 Primitive datatypes
The primitive datatypes defined by this specification
are described below. For each datatype, the
value space and lexical space
are defined, all constraining facets which apply
to the datatype are given and any datatypes derived
from this the datatype are specified.
primitive datatypes can only be added by revisions
to this specification.
3.2.1 string
[Definition:] The string datatype
represents character strings in XML. The value space
of string is the set of finite-length sequences of UCS
characters ([ISO 10646] and [Unicode]). A UCS
character (or just character, for short) is an atomic unit of
communication; it is not further specified except to note that every UCS
character has a corresponding UCS code point, which is an integer.
The order-relation of string is
the lexicographic ordering by [Unicode]
code point.
3.2.1.2 Derived datatypes
string has the
following built-in
derived datatypes:
3.2.2 boolean
[Definition:] boolean has the
value space required to support the mathematical
concept of binary-valued logic: {true, false}.
3.2.2.1 Lexical Representation
An instance of a datatype that is defined as boolean
can have the following legal lexical values {true, 1, false, 0}, with
'1' being the same as 'true' and '0' being the same as 'false'.
3.2.3 float
[Definition:] float corresponds
to 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 special values: positive and negative zero,
positive negative infinity and not-a-number.
The order-relation on float
is: x < y iff y - x is positive.
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; 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].
3.2.3.1 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 zero, positive
and negative infinity and not-a-number have 0,
-0, INF, -INF and
NaN, respectively.
For example, -1E4, 1267.43233E12, 12.78e-2, 12 and INF
are all legal literals for float.
3.2.4 double
[Definition:] The double
datatype corresponds to 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 special values: positive and negative zero,
positive negative infinity and not-a-number.
The order-relation on double
is: x < y iff y - x is positive.
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].
3.2.4.1 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.
The special values positive and negative zero, positive
and negative infinity and not-a-number have 0,
-0, INF, -INF and
NaN, respectively.
For example, -1E4, 1267.43233E12, 12.78e-2, 12 and INF
are all legal literals for double.
3.2.5 decimal
[Definition:] decimal
represents arbitrary precision decimal numbers.
The value space of decimal
consists of the values i × 10^n,
where i and n
are integers, with n being known
as the scale of the value space.
The order-relation on decimal
is: x < y iff y - x is positive.
NOTE:
The use of arbitrary precision decimal numbers, including all
datatypes derived from decimal (e.g., integer) in this
design impacts the implementation of schema processors in
a number of places: checking maxLength constraints on
strings, for example. It may impact interchange between
XML schemas and programming languages, databases, etc.
Our design discussions did not reveal convincing evidence of undue
burden because of arbitrary precision decimal numbers in this design,
but we welcome further input from implementors.
3.2.5.1 Lexical representation
decimal has a lexical representation
consisting of a finite-length sequence of decimal digits separated
by a period as a decimal indicator, in accordance with the scale and
precision facets, with an optional leading sign. 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.
3.2.5.3 Derived datatypes
decimal has the
following built-in
derived datatypes:
3.2.6 timeDuration
[Definition:]
timeDuration represents a duration of time.
The value space of timeDuration is the
space of time durations as defined in § 5.5.3.2 of
[ISO 8601].
The order-relation on timeDuration
is: x < y iff y - x is positive.
3.2.6.1 Lexical Representation
A single lexical representation, conforming to a subset of the
representations allowed by [ISO 8601], is allowed for
timeDuration. This lexical representation 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. 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.
Reduced precision and truncated representations of this format are allowed
provided they conform to the following:
-
The lowest order items may be omitted. If omitted their value is
assumed to be zero.
-
The lowest order item may have a decimal fraction.
-
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 designator 'T' shall be absent if all of the time items are absent.
The designator 'P' must always be present.
For example, P1347Y, P1347M are P1Y2MT2H are all allowed;
P0Y1347M and P0Y1347M0D are allowed. P-1347M is not allowed although
-P1347M is allowed. P1Y2MT is not allowed.
3.2.7 recurringDuration
[Definition:]
recurringDuration represents a
timeDuration that recurs with a specific
timeDuration starting from a specific origin.
The order-relation on timeDuration
is: x < y iff y - x is positive.
Recurring duration has two constraining facets
duration and period whose values
must be specified when the datatype is defined.
These facets specify the
length of the duration and after what duration it recurs. The lexical
format used to specify these facet values is the lexical format for
timeDuration. A value of 0 for the facet
period means that the duration does not recur i.e.
there is but a single ocurrence. A value of 0 for the facet
duration means that the duration is, in fact, a
single instant of time.
Although the primary purpose of this datatype is to serve as a basetype
from which the other date and time datatypes are generated, it can be
used as a datatype on its own by specifying the values for
duration and period when then
datatype is defined. The value that appears in an instance document is
the value of the origin when the recurrence begins.
| Constraint: duration and period required for recurringDuration |
It is an error for recurringDuration
to be used directly in a schema. Only datatypes that are
derived from recurringDuration by
specifying a value for duration and
period can be used in a schema.
|
3.2.7.1 Lexical Representation
A single lexical representation, which is a subset of the lexical
representations allowed by [ISO 8601], is allowed for
recurringDuration. This lexical representation is the
[ISO 8601] extended format CCYY-MM-DDThh:mm:ss.sss
where "CC" represents the century, "YY" the year, "MM" the month and
"DD" the day, preceded by an optional leading sign to indicate a
negative number. If the sign is omitted, "+" is assumed. The letter
"T" is the date/time separator and "hh", "mm", "ss.sss" represent hour,
minute and second respectively. Additional digits can be used to
increase the precision of fractional seconds if desired. To accommodate
year values greater than 9999 additional digits can be added to the
left of this representation.
This representation can be immediately followed by a "Z" to indicate
Coordinated Universal Time. To indicate the time zone, i.e. the
difference between the local time and Coordinated Universal Time,
the difference immediately follows the time and consists of a sign,
+ or -, followed by hh:mm. See also ISO 8601 Date and Time Formats (§D).
The derived datatype timeInstant uses the same lexical
representation. Other derived datatypes date,
time, timePeriod and
recurringDate use truncated versions of this lexical
representation.
3.2.7.3 Derived datatypes
recurringDuration has the
following built-in
derived datatypes:
3.2.8 binary
[Definition:] binary represents
arbitrary binary data. The value space of
binary is the set of finite-length sequences of binary
octets.
| Constraint: encoding required for binary |
It is an error for binary to be used
directly in a schema. Only datatypes that are derived
from binary by minimally specifying a value for
encoding can be used in a schema.
|
3.2.8.1 Constraining facets
binary has the
following constraining facets:
Ed. Note:
What does the pattern facet on binary really mean? Since pattern
operates on the lexical space, one would have to give a regex for the
base64 or hex that would result for a specific binary sequence that one
wanted to constrain...this is not too far fetched for hex, but almost
impossible for base64, isn't it?
3.2.9 uriReference
[Definition:]
uriReference represents a Uniform Resource Identifier (URI)
Reference as defined in Section 4 of [RFC 2396].
A uriReference may be absolute or relative, and may have
an optional fragment identifier.
[Definition:]
An absolute uriReference refers to a resource
in a manner which is independent of the context in which the
uriReference occurs.
[Definition:]
A relative uriReference refers to a resource
by describing the difference within a hierarchy of resources between the
context in which the relative uriReference occurs and
the absolute uriReference of the resource.
3.2.9.1 Lexical representation
The lexical space of uriReference is
the set of strings that match the URI-reference
production in Section 4 of [RFC 2396].
3.3 Derived datatypes
This section gives conceptual definitions for all
built-in derived datatypes
defined by this specification. The XML Representation used to define
derived datatypes (whether
built-in or user-derived) is
given in section XML representation of datatype definitions (§5.1) and the complete
definitions of the built-in
derived datatypes are provided in Appendix
Schema for Datatype Definitions (normative) (§A).
3.3.8 integer
[Definition:] integer is
derived from decimal by fixing the
value of scale to be 0. This results in the standard
mathematical concept of the integer numbers. The
value space of integer is the infinite
set {...,-2,-1,0,1,2,...}. The base type of
integer is decimal.
3.3.8.1 Lexical representation
integer has a lexical consisting of a finite-length sequence
of decimal digits with an optional leading sign. If the sign is omitted,
"+" is assumed. For example: -1, 0, 12678967543233, +100000.
3.3.8.3 Derived datatypes
integer has the
following built-in
derived datatypes:
3.3.9 nonPositiveInteger
[Definition:]
nonPositiveInteger is derived from
integer by fixing the value of
maxInclusive to be 0. This results in the
standard mathematical concept of the non-positive integers.
The value space of nonPositiveInteger
is the infinite set {...,-2,-1,0}. The base type
of nonPositiveInteger is integer.
3.3.9.1 Lexical representation
nonPositiveInteger has a lexical representation consisting
of a negative sign ("-") followed by a finite-length
sequence of decimal digits. If the sequence of digits consists of all
zeros then the sign is optional.
For example: -1, 0, -12678967543233, -100000.
3.3.9.3 Derived datatypes
nonPositiveInteger has the
following built-in
derived datatypes:
3.3.10 negativeInteger
[Definition:]
negativeInteger is derived from
nonPositiveInteger by fixing the value of
maxInclusive to be -1. This results in the
standard mathematical concept of the negative integers. The
value space of negativeInteger
is the infinite set {...,-2,-1}. The base type
of negativeInteger is nonPositiveInteger.
3.3.10.1 Lexical representation
negativeInteger has a lexical representation consisting
of a negative sign ("-") followed by a finite-length
sequence of decimal digits. For example: -1, -12678967543233, -100000.
3.3.11 long
[Definition:] long is
derived from integer by fixing the
values of maxInclusive to be 9223372036854775807
and minInclusive to be -9223372036854775808.
The base type of long is
integer.
3.3.11.1 Lexical representation
long has a lexical representation consisting
of an optional sign followed by a finite-length
sequence of decimal digits. If the sign is omitted, "+" is assumed.
For example: -1, 0,
12678967543233, +100000.
3.3.11.3 Derived datatypes
long has the
following built-in
derived datatypes:
3.3.12 int
[Definition:] int
is derived from long by fixing the
values of maxInclusive to be 2147483647 and
minInclusive to be -2147483648. The
base type of int is long.
3.3.12.1 Lexical representation
int has a lexical representation consisting
of an optional sign followed by a finite-length
sequence of decimal digits. If the sign is omitted, "+" is assumed.
For example: -1, 0,
126789675, +100000.
3.3.12.3 Derived datatypes
int has the
following built-in
derived datatypes:
3.3.13 short
[Definition:] short is
derived from int by fixing the
values of maxInclusive to be 32767 and
minInclusive to be -32768. The
base type of short is
int.
3.3.13.1 Lexical representation
short has a lexical representation consisting
of an optional sign followed by a finite-length sequence of decimal
digits. If the sign is omitted, "+" is assumed.
For example: -1, 0, 12678, +10000.
3.3.13.3 Derived datatypes
short has the
following built-in
derived datatypes:
3.3.14 byte
[Definition:] byte
is derived from short
by fixing the values of maxInclusive to be 127
and minInclusive to be -128.
The base type of byte is
short.
3.3.14.1 Lexical representation
byte has a lexical representation consisting
of an optional sign followed by a finite-length
sequence of decimal digits. If the sign is omitted, "+" is assumed.
For example: -1, 0,
126, +100.
3.3.15 nonNegativeInteger
[Definition:]
nonNegativeInteger is derived from
integer by fixing the value of
minInclusive to be 0. This results in is the
standard mathematical concept of the non-negative integers. The
value space of nonNegativeInteger
is the infinite set {0,1,2,...}. The base type of
nonNegativeInteger is integer.
3.3.15.1 Lexical representation
nonNegativeInteger has a lexical representation consisting
of an optional sign followed by a finite-length
sequence of decimal digits. If the sign is omitted, "+" is assumed.
For example:
1, 0, 12678967543233, +100000.
3.3.15.3 Derived datatypes
nonNegativeInteger has the
following built-in
derived datatypes:
3.3.17 unsignedInt
[Definition:]
unsignedInt is derived from
unsignedLong by fixing the values of
maxInclusive to be 4294967295. The
base type of unsignedInt is
unsignedLong.
3.3.17.1 Lexical representation
unsignedInt has a lexical representation consisting
of a finite-length
sequence of decimal digits. For example: 0,
1267896754, 100000.
3.3.17.3 Derived datatypes
unsignedInt has the
following built-in
derived datatypes:
3.3.18 unsignedShort
[Definition:]
unsignedShort is derived from
unsignedInt by fixing the value
maxInclusive to be 65535. The
base type of unsignedShort is
unsignedInt.
3.3.18.1 Lexical representation
unsignedShort has a lexical representation consisting
of a finite-length
sequence of decimal digits.
For example: 0,
12678, 10000.
3.3.18.3 Derived datatypes
unsignedShort has the
following built-in
derived datatypes:
3.3.20 positiveInteger
[Definition:]
positiveInteger is derived from
nonNegativeInteger by fixing the value of
minInclusive to be 1. This results in the standard
mathematical concept of the positive integer numbers.
The value space of positiveInteger
is the infinite set {1,2,...}. The base type of
positiveInteger is nonNegativeInteger.
3.3.20.1 Lexical representation
positiveInteger has a lexical representation consisting
of an optional positive sign ("+") followed by a finite-length
sequence of decimal digits.
For example: 1, 12678967543233, +100000.
3.3.21 timeInstant
[Definition:]
timeInstant represents a specific instant of time. The
value space of timeInstant is the space
of Combinations of date and time of day values as defined
in § 5.4 of [ISO 8601]. The base type
of timeInstant is recurringDuration.
timeInstant is generated from
recurringDuration by setting the value of the
duration facet equal to "P0Y" and the value of the
period facet equal to "P0Y" (no recurrence).
3.3.21.1 Lexical Representation
A single lexical representation, which is a subset of the lexical
representations allowed by [ISO 8601], and is the same
lexical representation as its basetype recurringDuration
is allowed for timeInstant.
For example, to indicate 1:20 pm on May the 31st, 1999 for Eastern
Standard Time which is 5 hours behind Coordinated Universal Time, one
would write: 1999-05-31T13:20:00-05:00.
3.3.22 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]. The base type of
time is recurringDuration.
date is generated from recurringDuration
by setting the value of the duration facet equal
to "P0Y" and the value of the period facet equal to
"PY24H" (24 hours).
3.3.22.1 Lexical Representation
The lexical representation for time is the left
truncated lexical representation for timeInstant:
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, one would write: 13:20:00-05:00. See also
ISO 8601 Date and Time Formats (§D).
