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, constraining facets which apply
to the datatype are listed and any datatypes derived
from this 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.
NOTE:
As noted in Order (§2.5.1.2), the fact that this specification does
not specify an order-relation for string
does not preclude other applications from treating strings as being ordered.
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, 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.
3.2.3.2 Canonical representation
The canonical representation for float is defined by
prohibiting certain options from the
Lexical representation (§3.2.3.1). Specifically, the preceding optional "+" sign is prohibited from the
mantissa. The exponent must be indicated by "E" ande number representations must be normalized such that for non-zero numbers there is a single non-zero
digit to the left of the decimal point. Leading and trailing zeroes are
disallowed in the mantissa and leading zeroes are disallowed in the exponent.
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.
3.2.4.2 Canonical representation
The canonical representation for double is defined by
prohibiting certain options from the
Lexical representation (§3.2.4.1). Specifically, the preceding optional "+" sign is prohibited from the
mantissa. The exponent must be indicated by "E" ande number representations must be normalized such that for non-zero numbers there is a single non-zero
digit to the left of the decimal point. Leading and trailing zeroes are
disallowed in the mantissa and leading zeroes are disallowed in the exponent.
3.2.5 decimal
[Definition:] decimal
represents arbitrary precision decimal numbers.
The value space of decimal
is the set of the values i × 10^-n,
where i and n are integers
such that n >= 0.
The order-relation on decimal
is: x < y iff y - x is positive.
[Definition:]
The value space of types derived from decimal
with a value for precision of p
is the set of values i × 10^-n, where
n and i are integers such that
p >= n >= 0 and the number of significant decimal digits
in i is less than or equal to p.
[Definition:]
The value space of types derived from decimal
with a value for scale of s
is the set of values i × 10^-n, where
i and n are integers such
that 0 <= n <= s.
Ed. Note: Priority Feedback Request
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.
3.2.5.2 Canonical representation
The canonical representation for decimal is defined by
prohibiting certain options from the
Lexical representation (§3.2.5.1). Specifically, the preceding optional "+" sign is prohibited. Leading zeroes are prohibited. Trailing
zeroes to the right of the decimal point are also prohibited.
3.2.5.4 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
a six-dimensional space where the coordinates
designate the 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.
The order-relation on timeDuration is stated as follows: for instances
x and y of timeDuration, x-y is defined as component-wise subtraction.
x > y iff all the components of x-y are non-negative and at least one
component is positive. x < y iff all the components of x-y are
non-positive and at least one component is negative. x = y iff all
components of x-y are zero.
3.2.6.1 Lexical representation
A single lexical representation, similar to 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.
The values of the
Year, Month, Day, Hour and Minutes components are not restricted but
allow an arbitrary integer. Similarly, the value of the Seconds component
allows an arbitrary decimal, that is they do 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:
-
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 recurringDuration
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 occurrence. A value of 0 for the facet
duration means that the duration is, in fact, a
single instant of time.
recurringDuration is a conceptual datatype which serves as a
basetype
from which the other date and time datatypes are generated. It can also be
used as a basetype for user-derived datatypes. A user-derived datatype
can be generated from recurringDuration by specifying the values
for
duration and period. 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. The year 0000 is prohibited.
This representation can be immediately followed by a "Z" to indicate
Coordinated Universal Time (UTC). 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.
3.2.7.2 Canonical representation
The canonical representation for recurringDuration is defined
by prohibiting certain options from the
Lexical representation (§3.2.7.1). Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal
Time (UTC) and be indicated by a "Z".
3.2.7.4 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-inderived 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-inderived 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 representation 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.
3.3.8.2 Canonical representation
The canonical representation for integer is defined
by prohibiting certain options from the
Lexical representation (§3.3.8.1). Specifically, the preceding optional "+" sign is prohibited and leading zeroes are prohibited.
3.3.8.4 Derived datatypes
integer has the
following built-in derived datatypes:
3.3.9 nonPositiveInteger
[Definition:] nonPositiveInteger is derived from
integer by setting 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.
3.3.9.2 Canonical representation
The canonical representation for nonPositiveInteger is defined
by prohibiting certain options from the
Lexical representation (§3.3.9.1). Specifically, the
negative sign ("-") is required with the token "0" and leading zeroes are prohibited.
3.3.9.4 Derived datatypes
nonPositiveInteger has the
following built-in derived datatypes:
3.3.10 negativeInteger
[Definition:] negativeInteger is derived from
nonPositiveInteger by setting 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.
3.3.10.2 Canonical representation
The canonical representation for negativeInteger is defined
by prohibiting certain options from the
Lexical representation (§3.3.10.1). Specifically, leading zeroes are prohibited.
3.3.11 long
[Definition:] long is
derived from integer by setting the
value 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.
3.3.11.2 Canonical representation
The canonical representation for long is defined
by prohibiting certain options from the
Lexical representation (§3.3.11.1). Specifically, the
the optional "+" sign is prohibited and leading zeroes are prohibited.
3.3.11.4 Derived datatypes
long has the
following built-in derived datatypes:
3.3.12 int
[Definition:] int
is derived from long by setting the
value 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.
3.3.12.2 Canonical representation
The canonical representation for int is defined
by prohibiting certain options from the
Lexical representation (§3.3.12.1). Specifically, the
the optional "+" sign is prohibited and leading zeroes are prohibited.
3.3.12.4 Derived datatypes
int has the
following built-in derived datatypes:
3.3.13 short
[Definition:] short is
derived from int by setting the
value 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.
3.3.13.2 Canonical representation
The canonical representation for short is defined
by prohibiting certain options from the
Lexical representation (§3.3.13.1). Specifically, the
the optional "+" sign is prohibited and leading zeroes are prohibited.
3.3.13.4 Derived datatypes
short has the
following built-in derived datatypes:
3.3.14 byte
[Definition:] byte
is derived from short
by setting the value 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.
3.3.14.2 Canonical representation
The canonical representation for byte is defined
by prohibiting certain options from the
Lexical representation (§3.3.14.1). Specifically, the
the optional "+" sign is prohibited and leading zeroes are prohibited.
3.3.15 nonNegativeInteger
[Definition:] nonNegativeInteger is derived from
integer by setting the value of
minInclusive to be 0. This results in 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, 1267896