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XML Schema: Datatypes is part 2 of a two-part draft of the specification for the
XML Schema definition language. This document proposes facilities for
defining datatypes to be used
in XML Schemas and other XML specifications.
The datatype language, which is itself represented in XML 1.0, provides a superset
of the capabilities found in XML 1.0 document type definitions (DTDs) for specifying
datatypes on elements and attributes.
This is a public working draft of XML Schema 1.0 for review by the
public and by members of the World Wide Web Consortium.
It has been reviewed by the XML Schema Working Group, and the Working
Group has agreed to its publication. The WG believes this draft to be
`feature-complete': the functionality included here is substantially
complete and is expected to be stable. We do not expect to add major
new functionality, or to make major changes to the functionality
described in this draft. Some sections of the draft (in particular
those on conformance), and some aspects of the design (in particular
details of the transfer syntax for schemas), on the other hand, are
still rough and are expected to be revised.
The WG expects to spend January, 2000, working out details, clarifying
points of uncertainty that arise in the review of this draft, cleaning
up inconsistencies, reviewing the design of the concrete transfer
syntax, and making editorial improvements.
Following that period of review and polishing, it is the WG's intent
to issue a Last Call for Review by other W3C working groups sometime
during February, 2000, and to submit this specification in March,
2000, for publication as a Candidate Recommendation. This schedule
may vary, depending on the comments of the public and of other W3C
working groups on this draft. Such comments are instrumental in the
WG's deliberations, and we encourage readers to review the draft and send comments to
www-xml-schema-comments@w3.org
(archive).
Although the Working Group does not anticipate further substantial
changes to the functionality described here, this is still a working
draft, subject to change based on experience and on comment by the
public and other W3C working groups. The present version should
be implemented only by those interested in providing a check on
its design or by those preparing for an implementation of the
Candidate Recommendation. The Schema WG will not
allow early implementation to constrain its ability to make changes to
this specification prior to final release.
A list of current W3C working drafts can be found at
http://www.w3.org/TR/. They may be updated,
replaced, or obsoleted by other documents at any time. It is inappropriate to use
W3C Working Drafts as reference material or to cite them as other than "work in progress".
Ed. Note:
Several "note types" are used throughout this draft:
-
issue [Issue (issue-name): ]
-
something on which the editors are seeking comment.
-
editorial note [Ed. Note: ]
-
something the editors wish to call to the attention of the
reader. To be removed prior to the recommendation becoming final.
-
note [Note: ]
-
something the editors wish to call to the attention of the reader.
To remain in the final recommendation.
1 Introduction
1.1 Purpose
1.2 Requirements
1.3 Scope
1.4 Terminology
2 Type System
2.1 Datatype
2.2 Value space
2.3 Lexical space
2.4 Datatype dichotomies
2.4.1 Atomic vs. aggregate datatypes
2.4.2 Primitive vs. generated datatypes
2.4.3 Built-in vs. user-generated datatypes
2.5 Facets
2.5.1 Fundamental facets
2.5.2 Constraining or Non-fundamental facets
3 Built-in datatypes
3.1 Namespace considerations
3.2 Primitive datatypes
3.2.1 string
3.2.2 boolean
3.2.3 float
3.2.4 double
3.2.5 decimal
3.2.6 timeInstant
3.2.7 timeDuration
3.2.8 recurringInstant
3.2.9 binary
3.2.10 uri
3.3 Generated datatypes
3.3.1 language
3.3.2 NMTOKEN
3.3.3 NMTOKENS
3.3.4 Name
3.3.5 QName
3.3.6 NCName
3.3.7 ID
3.3.8 IDREF
3.3.9 IDREFS
3.3.10 ENTITY
3.3.11 ENTITIES
3.3.12 NOTATION
3.3.13 integer
3.3.14 non-negative-integer
3.3.15 positive-integer
3.3.16 non-positive-integer
3.3.17 negative-integer
3.3.18 date
3.3.19 time
4 Defining Generated Datatypes
5 Conformance
Appendices
A Schema for Datatype Definitions (normative)
B DTD for Datatype Definitions (normative)
C Datatypes and Facets
C.1 Fundamental Facets
C.2 Constraining Facets
D ISO 8601 Date and Time Formats
D.1 ISO 8601 Conventions
D.2 Truncated Formats
D.3 Deviations from ISO 8601 Formats
D.3.1 Sign Allowed
D.3.2 More Than 9999 Years
E Regular Expressions
F References
F.1 Normative
F.2 Non-normative
G Acknowledgments (non-normative)
H Open Issues
I Revisions from Previous Draft
1 Introduction
1.1 Purpose
The [XML 1.0 Recommendation] specification defines limited
facilities for applying datatypes to document content in that documents
may contain or refer to DTDs that assign types to elements and attributes.
However, document authors, including authors of traditional
documents and those transporting data in XML,
often require a higher degree of type checking to ensure robustness in
document understanding and data interchange.
The table below offers two typical examples of XML instances
in which datatypes are implicit: the instance on the left
represents a billing invoice, the instance on the
right a memo or perhaps an email message in XML.
| Data oriented |
Document oriented |
<invoice>
<orderDate>1999-01-21</orderDate>
<shipDate>1999-01-25</shipDate>
<billingAddress>
<name>Ashok Malhotra</name>
<street>123 IBM Ave.</street>
<city>Hawthorne</city>
<state>NY</state>
<zip>10532-0000</zip>
</billingAddress>
<voice>555-1234</voice>
<fax>555-4321</fax>
</invoice>
|
|
<memo importance="high"
date="1999-03-23">
<from>Paul V. Biron</from>
<to>Ashok Malhotra</to>
<subject>Latest draft</subject>
<body>
We need to discuss the latest
draft <emph>immediately</emph>.
Either email me at <email>
mailto:paul.v.biron@kp.org</email>
or call <phone>555-9876</phone>
</body>
</memo>
|
|
The invoice contains several dates and telephone numbers, the postal
abbreviation for a state
(which comes from an enumerated list of sanctioned values), and a ZIP code
(which takes a definable regular form). The memo contains many
of the same types of information: a date, telephone number, email address
and an "importance" value (from an enumerated
list, such as "low", "medium" or "high"). Applications which process
invoices and memos need to raise exceptions if something that was
supposed to be a date or telephone number does not conform to the rules
for valid dates or telephone numbers.
In both cases, validity constraints exist on the content of the
instances that are not expressible in XML DTDs. The limited datatyping
facilities in XML have prevented validating XML processors from supplying
the rigorous type checking required in these situations. The result
has been that individual applications writers have had to implement type
checking in an ad hoc manner. This specification addresses
the need of both document authors and applications writers for a robust,
extensible datatype system for XML which could be incorporated into
XML processors. As discussed below, these datatypes could be used in other
XML-related standards as well.
1.2 Requirements
The [XML Schema Requirements] document spells out
concrete requirements to be fulfilled by this specification,
which state that the XML Schema Language must:
-
provide for primitive data typing, including byte, date,
integer, sequence, SQL & Java primitive data types, etc.;
-
define a type system that is adequate for import/export
from database systems (e.g., relational, object, OLAP);
-
distinguish requirements relating to lexical data representation
vs. those governing an underlying information set;
-
allow creation of user-defined datatypes, such as
datatypes that are derived from existing datatypes and which
may constrain certain of its properties (e.g., range,
precision, length, format).
1.3 Scope
This portion of the XML Schema Language discusses datatypes that can be
used in a XML Schema. These datatypes can be specified for element content
that would be specified as #PCDATA
and attribute values of various
types in a DTD. It is the intension of this specification that
it be usable outside of the context of XML Schemas for a wide range of other
XML-related activities such as [XSL] and [RDF Schema].
For the most part, this specification discusses what are sometimes referred
to as atomic datatypes in that they constrain the lexical representation
of a single literal. In some cases, as for example in IDREFS (§3.3.9),
ENTITIES (§3.3.11) and NMTOKENS (§3.3.3), the value may consist of a
list or set of literals separated by spaces. This is an example of what is
called an aggregate datatype. Future versions of this specification
may contain a more general mechanism for aggregate
(collection) datatypes
such as sets, bags and records.
Ed. Note:
The WG has voted to have a simple list aggregate construct. A list will be
whitespace separated list of some atomic datatype. There was not time to
incorporate that vote into this draft. This vote will affect the
IDREFS (§3.3.9), ENTITIES (§3.3.11), and NMTOKENS (§3.3.3)
types. The list generator will be available to all schema authors.
1.4 Terminology
The terminology used to describe XML Schema Datatypes is defined in the body of
this specification. The terms defined in the following list are used in building
those definitions and in describing the actions of a datatype processor:
-
For compatibility
-
A feature of this specification included solely to ensure that
schemas which use this feature remain compatible with
[XML 1.0 Recommendation]
2 Type System
This section describes the conceptual framework behind the type system
defined in this specification. The framework has been influenced by the
[ISO 11404] standard on language-independent datatypes
as well as the datatypes for [SQL] and for programming languages
such as Java.
The datatypes discussed in this specification are computer representations
of well known abstract concepts such as integer and date.
It is not the place of this specification to define these abstract concepts;
many other publications provide excellent definitions.
2.1 Datatype
[Definition:] In this specification,
a datatype is defined as a 3-tuple, consisting of
a) a set of distinct values, called its value space,
b) a set of lexical representations, called its lexical space,
and c) a set of facets that characterize properties of the
value space, individual values or lexical items.
2.2 Value space
[Definition:] A value
space is the set of permitted values for a given
datatype.
The value space of a given datatype can
be defined in one of the following ways:
-
enumerated outright (extensional definition)
-
defined axiomatically from fundamental notions (intensional definition)
-
defined as the subset of values from an already defined
value space with a given set of properties
-
defined as a combination of values from some already defined
value space(s) by a specific construction procedure
value spaces have certain properties. For example,
they always have the property of cardinality,
some definition of equality
and may be ordered by which individual
values within the value space can be compared to one another.
2.3 Lexical space
In addition to its value space, each datatype also has a lexical
space.
[Definition:] A
lexical space is a set of valid literals for a datatype.
Each value in the datatype's value space is denoted by one or
more literals in its lexical space.
For example, "100" and "1.0E2"
are two different literals from the lexical space of
float (§3.2.3) which both denote the same value.
The type system defined in this specification provides a mechanism for
schema designers to control the set of values and the corresponding set of
acceptable literals of those values for a datatype.
2.4 Datatype dichotomies
It is useful to categorize the datatypes defined in this specification
along various dimensions, forming a set of characterization dichotomies.
2.4.1 Atomic vs. aggregate datatypes
The first distinction to be made is that between atomic
and aggregate datatypes.
-
[Definition:] Atomic datatypes
are those having values which are intrinsically indivisible.
-
[Definition:] Aggregate
datatypes are those having values which can be decomposed into two
or more component values.
For example, a date that is represented as a single character
string could be the value of an atomic date datatype;
while
another date represented as separate "month", "day" and "year"
elements would be the value of an aggregate date
datatype.
Not surprisingly, the distinction is analogous to that between
an XML element whose content model is #PCDATA and one with element content.
As discussed above, this specification focuses mainly on atomic
datatypes.
Later versions of this specification may address aggregate
datatypes in more detail.
Note that
the legacy XML attribute types IDREFS (§3.3.9), ENTITIES (§3.3.11)
and NMTOKENS (§3.3.3) are conceptually aggregate
types (lists), although at present they are defined in this specification as
atomic.
A datatype which is atomic in this specification need not
be an "atomic" datatype in any programming language used to implement
this specification.
2.4.2 Primitive vs. generated datatypes
Next, we distinquish between primitive and
generated datatypes.
-
[Definition:] Primitive
datatypes are those that are not defined in terms of other datatypes;
they exist ab initio.
-
[Definition:] Generated
datatypes are those that are defined in terms of other datatypes.
For example, a float (§3.2.3) is a well defined mathematical
concept that cannot be defined in terms of other datatypes while
a date (§3.3.18) is a special case of the more general datatype
recurringInstant (§3.2.8).
The datatypes defined by this specification fall into both
the primitive and generated categories.
It is felt that a judiciously
chosen set of primitive datatypes will serve the widest
possible audience by providing a set of convenient datatypes that can be used as is,
as well as providing a rich enough base from which the variety of datatypes needed
by schema designers can be generated.
A datatype which is primitive in this specification need not
be a "primitive" datatype in any programming language used to implement
this specification.
Likewise, a datatype which is generated in this specification
need not be a "generated" datatype in any programming language used to implement
this specification.
[Definition:] Every generated
datatype is defined in terms of an existing datatype, referred to as
the basetype. basetypes may be either
primitive or generated.
[Definition:] If type a is the
basetype of type b, then b
is said to be a subtype of a.
The value space of a subtype
is a subset of the value space
of the basetype.
In the example above, date (§3.3.18)
is a subtype of the basetype
recurringInstant (§3.2.8).
2.4.3 Built-in vs. user-generated datatypes
Conceptually there is no difference between the built-in
generated
datatypes included in this specification and the user-generated
datatypes which will be created by individual schema designers.
The built-in generated datatypes are those
which are believed to
be so common that if they were not defined in this specification
many schema designers would end up "reinventing" them. Furthermore,
including these generated datatypes in this specification
serves to demonstrate the mechanics and utility of the datatype
generation facilities of this specification.
A datatype which is built-in in this specification need not
be a "built-in" datatype in any programming language used to implement
this specification.
Likewise, a datatype which is user-generated in this
specification need not
be a "user-generated" datatype in any programming language used to implement
this specification.
2.5 Facets
[Definition:] A facet is a
single defining aspect of a concept or an object. Generally speaking,
each facet characterizes a concept or object along independent aspects
or dimensions.
The facets of a datatype serve to distinguish those aspects of
one datatype which differ from other datatypes.
Rather than being defined solely in terms of a prose description
the datatypes in this specification are defined in terms of
the synthesis of facet values which together
determine the value space and properties of the datatype.
Facets are of two types: fundamental facets that define
the datatype and non-fundamental or constraining
facets that constrain the permitted values of a datatype.
2.5.1 Fundamental facets
Datatypes are characterized by properties of their value space.
Each of
these properties give rise to a facet that serves to characterize
the datatype.
These properties are discussed in this section.
2.5.1.1 Order
[Definition:] A value space, and hence
a datatype, is said to be ordered if there exists an
order relation
defined for that value space.
order relations
have the following
rules:
-
for every pair (a, b) from the value space,
either a < b or b <
a, or a = b;
-
for every triple (a, b, c) from the value space,
if a < b and
b < c, then a < c.
There may exist several possible order relations for a given
value space.
Additionally, there may exist multiple datatypes with the same
value space.
In such cases, each datatype will define a different order relation on the
value space.
Ed. Note:
Currently, no order relations are defined on the built-in
datatypes provided by this specification; additionally, there is no means
to specify an order relation on user-generated datatypes.
This will be addressed
in a future draft.
2.5.1.3 Cardinality
[Definition:] Every value space
has associated
with it the concept of cardinality. Some value spaces
are finite,
some are countably infinite while still others are uncountably infinite. A
datatype is said to have the cardinality of its value space.
It
is sometimes useful to categorize value spaces
(and hence, datatypes) as
to their cardinality, there are three significant cases:
Every finite value space is necessarily exact. No computational
datatype has a value space that is is uncountably infinite.
2.5.1.4 Exact and Approximate
The computational representation of a datatype may limit the degree
to which values of the datatype can be distinguished.
[Definition:]
If every
value in the value space of the conceptual datatype is distinguishable
in the computational representation from every other value in the
value space,
then the datatype is said to be exact.
[Definition:]
If a datatype is not exact then it is approximate.
Certain mathematical datatypes with very large or infinite value
spaces have representations which are said to be approximate in that
multiple values in the conceptual value space map to single values
in the value space of the representation.
In this specification, all approximate datatypes have computational
models which specify, via parametric values, a degree of approximation,
that is, they require a certain minimum set of values of the mathematical
datatype to be distinguishable in the computational datatype.
Further, each value in the conceptual value space must be capable
of being represented in the representational value space
within a certain
distance i.e. the difference between the conceptual value and the
representational value must not exceed some agreed upon value.
2.5.1.5 Numeric
[Definition:] A datatype is said to be
numeric if its values are conceptually
quantities (in some mathematical number system).
[Definition:] A datatype
whose values are not numeric is said to be non-numeric
.
2.5.2 Constraining or Non-fundamental facets
[Definition:] Constraining
facets are optional properties that can be applied
to a datatype to constrain its value space.
Constraining
the value space consequently constrains the lexical space.
Adding constraining facets to a basetype is used in
Defining Generated Datatypes (§4).
In this section we define all constraining facets that
are available for use when generating subtypes.
2.5.2.1 length
[Definition:] length is
the number of units of length, where units of length
varies depending on the basetype.
The value of length must be a
positive-integer (§3.3.15).
For subtypes of string (§3.2.1),
length is measured in units of characters.
For subtypes of binary (§3.2.9), length
is measured in bits.
Ed. Note:
We need to ultimately reconcile the notion of string length with the resolution
of the i18n issues around character, indexing, etc. I18N recommends
that length and maxlength be a "character count" and do not indicate
storage requirements.
2.5.2.2 minlength
[Definition:] minlength is
the minimum number of units of length, where units of length
varies depending on the basetype.
The value of minlength must be a
positive-integer (§3.3.15).
For subtypes of string (§3.2.1),
minlength is measured in units of characters.
For subtypes of binary (§3.2.9), minlength
is measured in bits.
Constraint on Schemas: length and minlength
It is an error for both length
and minlength to be specified
for the same datatype.
2.5.2.3 maxlength
[Definition:] maxlength is
the maximum number of units of length, where units of length
varies depending on the basetype.
The value of maxlength must be a
positive-integer (§3.3.15).
For subtypes of string (§3.2.1),
maxlength is measured in units of characters.
For subtypes of binary (§3.2.9), maxlength
is measured in bits.
Constraint on Schemas: length and maxlength
It is an error for both length
and maxlength to be specified
for the same datatype.
2.5.2.7 maxExclusive
[Definition:]
maxExclusive is the upper bound
of the value space for a datatype with the
ordered
property. The value is exclusive in the sense that
the value is itself excluded from the value space.
The value of maxExclusive must be of the same type
as the basetype.
Constraint on Schemas: maxInclusive and maxExclusive
It is an error for both maxInclusive
and maxExclusive to be specified
for the same datatype.
2.5.2.9 minExclusive
[Definition:]
minExclusive is the lower bound
of the value space for a datatype with the
ordered
property. The value is exclusive in the sense that
the value is itself excluded from the value space
for the datatype.
The value of minExclusive must be of the same type
as the basetype.
Constraint on Schemas: minInclusive and minExclusive
It is an error for both minInclusive
and minExclusive to be specified
for the same datatype.
3 Built-in datatypes
3.2 Primitive datatypes
The primitive datatypes defined by this specification
are described below. For each datatype, the value space
and lexical space are specified, all
constraining facets which apply to the datatype are
enumerated and subtype, if any, defined by this specification
are listed.
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 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 ordered property of string is
the [Unicode] character number sequence.
Ed. Note:
We need to harmonize this definition with the I18N character model.
3.2.1.1 Constraining facets of string
string has the following constraining facets:
3.2.1.2 Subtypes of string
string has the following subtypes:
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 (§3.3.13)
whose absolute value is less than 2^24, and e is an
integer (§3.3.13) 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 mapping from a literal in the lexical space to a value
in the value space of
float follows IEEE round to nearest behavior
[IEEE 754-1985]. For further information on mapping literals to values in
the value space, see [Clinger, WD (1990)].
3.2.3.1 Lexical representation
float values have a single standard lexical representation consisting of
a mantissa followed, optionally, by the character "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 default
lexical rules for integer (§3.3.13) and decimal (§3.2.5).
If the "E" and the the following exponent are omitted, an exponent
value of 1 is assumed.
The specical 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 Constraining facets of float
float has the following constraining facets:
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 (§3.3.13)
whose absolute value is less than 2^53, and e is an
integer (§3.3.13) 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 mapping from a literal in the lexical space to a value in
the value space of double follows IEEE round
to nearest behavior [IEEE 754-1985]. For further information on
mapping literals to values in the value space, see
[Clinger, WD (1990)].
3.2.4.1 Lexical representation
double values have a single standard lexical representation consisting of
a mantissa followed, optionally, by the character "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 default
lexical rules for integer and decimal numbers discussed above.
If the "E" and the the following exponent are omitted, an exponent
value of 1 is assumed.
The specical 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 Constraining facets of double
double has the following constraining facets:
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 is an integer (§3.3.13)
and n is an integer (§3.3.13).
3.2.5.1 Lexical representation
decimal has a single standard lexical representation.
This consists of a finite 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.
For example: -1.23,
12678967.543233, +100000.00.
3.2.5.2 Constraining facets of decimal
decimal has the following constraining facets:
3.2.5.3 Subtypes of decimal
decimal has the following subtypes:
3.2.6 timeInstant
[Definition:] timeInstant
represents a combination of date and time values representing a single
instant in time.
The value space of timeInstant is the space of Gregorian dates
and legal time values as defined in § 5.4 of [ISO 8601].
3.2.6.1 Lexical Representation
A single lexical representation, which is a subset of the lexical
representations allowed by [ISO 8601], is allowed for timeInstant.
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 accomodate 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).
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.
3.2.6.2 Constraining facets of timeInstant
timeInstant has the following constraining facets:
3.2.7 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].
3.2.7.1 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 PnYnMnDTnHnMnnS, where Y represents the number
of years, M the number of months, D the number of
days, T is the date/time separator, H the number of hours, M the number of minutes and
S 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: 1Y2M3DT10H30M.
Right truncated forms of the above representation are allowed. For example,
P1347Y and P1347M are both allowed; P0Y1347M is also allowed.
P0Y1347M0D is not allowed and P-1347M is not allowed although -P1347M is
allowed.
Time periods, i.e. specific durations of time, can be represented by supplying
two items of information: a start instant and a duration or a start instant and
an end instant or an end instant and a duration.
3.2.7.2 Constraining facets of timeDuration
timeDuration also has the following constraining facets:
3.2.8 recurringInstant
[Definition:] recurringInstant
represents an instant of time that recurs with a specific
timeDuration (§3.2.7).
Note that we do not attempt to support
general recurring instants of time, just those that needed to support
date (§3.3.18) and time (§3.3.19) and those
that arise from truncated and reduced lexical representations of
timeInstant (§3.2.6). See also ISO 8601 Date and Time Formats (§D).
3.2.8.1 Lexical Representation
The lexical representation for recurringInstant is the left truncated
[ISO 8601] representation for timeInstant (§3.2.6).
For example, if the century "CC" is omitted from the timeInstant
representation it means a timeInstant that recurs every hundred years.
Similarly, if "CCYY" is omitted it designates a time instant that recurs
every year.
Every two character "unit" of the representation that is omitted is indicated by
a single hyphen "-". For example, to indicate 1:20 pm on May the 31st
every year, one would write write: --05-31T13:20:00-05:00.
3.2.8.2 Constraining facets of recurringInstant
recurringInstant has the following constraining facets:
3.2.8.3 Subtypes of recurringInstant
recurringInstant has the following subtypes:
3.2.9 binary
[Definition:] binary
represents binary data. The value space of binary
is the set of finite sequences of binary bits.
3.2.9.1 Constraining facets of binary
binary has the following constraining facets:
3.2.10 uri
[Definition:] uri
represents a Uniform Resource Identifier (URI) Reference as defined
in [RFC 2396].
3.2.10.1 Constraining facets of uri
uri has the following constraining facets:
3.3 Generated datatypes
This section gives conceptual definitions for all built-in
generated
datatypes defined by this specification.
The abstract syntax
used to define generated datatypes (whether
built-in or user-generated) is
given in section Defining Generated Datatypes (§4) and the complete
definitions of the built-in generated
datatypes (written in the concrete syntax based on that
abstract syntax given in Appendix Schema for Datatype Definitions (normative) (§A)) are provided in Appendix
Schema for Datatype Definitions (normative) (§A).
3.3.13 integer
[Definition:] integer
is the standard mathematical concept of the integer numbers.
The value space of integer is the infinite set
{...,-2,-1,0,1,2,...}
The basetype of integer is decimal (§3.2.5).
3.3.13.1 Lexical representation
integer values have a single, standard lexical representation.
This consists of a string of digits with an optional leading sign.
If the sign is omitted, "+" is assumed. For example: -1, 0,
12678967543233, +100000.
3.3.13.2 Constraining facets of integer
integer has the following constraining facets:
3.3.13.3 Subtypes of integer
integer has the following subtypes:
3.3.14 non-negative-integer
[Definition:]
non-negative-integer
is the standard mathematical concept of the non-negative integers.
The value space of non-negative-integer
is the infinite set
{0,1,2,...}
.
The basetype of non-negative-integer
is integer (§3.3.13).
3.3.14.1 Lexical representation
non-negative-integer values have a single, standard lexical representation.
This consists of a string of digits with an optional leading "+" sign.
If the sign is omitted, "+" is assumed. For example: 1, 0,
12678967543233, +100000.
3.3.14.2 Constraining facets of non-negative-integer
non-negative-integer has the following constraining facets:
3.3.14.3 Subtypes of non-negative-integer
non-negative-integer has the following subtypes:
3.3.15 positive-integer
[Definition:]
positive-integer
is the standard mathematical concept of the positive integers.
The value space of positive-integer
is the infinite set
{1,2,...}.
The basetype
of positive-integer
is non-negative-integer (§3.3.14).
3.3.15.1 Lexical representation
positive-integer values have a single, standard lexical representation.
This consists of a string of digits with an optional leading "+" sign.
For example: 1, 12678967543233, +100000.
3.3.15.2 Constraining facets of positive-integer
positive-integer has the following constraining facets:
3.3.16 non-positive-integer
[Definition:]
non-positive-integer
is the standard mathematical concept of the non-positive integers.
The value space of non-positive-integer
is the infinite set {...,-2,-1,0}.
The basetype of non-positive-integer
is integer (§3.3.13).
3.3.16.1 Lexical representation
non-positive-integer values have a single, standard lexical representation.
This consists of a string of digits with a leading "-" sign.
For example: -1, 0, -12678967543233, -100000.
3.3.16.2 Constraining facets of non-positive-integer
non-positive-integer has the following constraining facets:
3.3.16.3 Subtypes of non-positive-integer
non-positive-integer has the following subtypes:
3.3.17 negative-integer
[Definition:]
negative-integer
is the standard mathematical concept of the negative integers.
The value space of negative-integer
is the infinite set
{...,-2,-1}.
The basetype
of negative-integer
is non-positive-integer (§3.3.16).
3.3.17.1 Lexical representation
negative-integer values have a single, standard lexical representation.
This consists of a string of digits with a leading "-" sign.
For example: -1, -12678967543233, -100000.
3.3.17.2 Constraining facets of negative integer
negative-integer has the following constraining facets:
3.3.18 date
[Definition:] date
represents a timeDuration (§3.2.7) that starts at midnight
of a specified day and lasts for 24 hours.
The value space of date is the set of
Gregorian calendar dates as defined in § 5.2.1 of [ISO 8601].
The basetype of date is
recurringInstant (§3.2.8).
3.3.18.1 Lexical Representation
The lexical representation for date is the reduced (right truncated)
lexical representation for recurringInstant (§3.2.8): CCYY-MM-DD.
To accomodate year values greater than 9999 additional digits can be added
to the left of this representation.
For example, to indicate May the 31st, 1999, one would write: 1999-05-31.
See also ISO 8601 Date and Time Formats (§D).
Left truncated
representations can be used to represent recurring dates. If the CC is
omitted it signifies a date that occurs every century. If the YY is also
omitted it signifies a date every year and so on. Every two character "unit" of
the representation that is omitted is indicated by a single hyphen "-".
For example, ---05 signifies the fifth day of every month.
Right truncated, or reduced precision, date representations can be used to
represent a specific month (CCYY-MM), a specific year (CCYY), or a specific
century (YY).
3.3.18.2 Constraining facets of date
date has the following constraining facets:
3.3.19 time
[Definition:] time
represents a recurring 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 basetype of time is
recurringInstant (§3.2.8).
time can be considered to be a shorthand to designate a
specific truncated representation for recurringInstant (§3.2.8).
3.3.19.1 Lexical Representation
The lexical representation for time is the left truncated lexical
representation for timeInstant (§3.2.6): hh:mm:ss.sss.
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).
3.3.19.2 Constraining facets of time
time has the following constraining facets:
4 Defining Generated Datatypes
A generated datatype can be defined from a
primitive datatype (or another
generated datatype)
by adding optional constraining facets. For example, it may be useful
to define a datatype called i4 (signed 4-byte integer) from the
built-in
datatype integer (§3.3.13) by supplying maxInclusive
and minInclusive facets. In this case, i4
is the name of the new user-generated datatype,
integer (§3.3.13) is its
basetype and maxInclusive and
minInclusive are the constraining facets.
| Example |
<datatype name="i4" source="integer">
<minInclusive value='-2147483648'/>
<maxInclusive value='2147483648'/>
</datatype>
|
|
|
This section defines the abstract syntax used for defining generated
datatypes.
This abstract syntax is used for defining both built-in
generated
and user-generated datatypes; the only difference between
the built-in
and user-generated
datatypes being that the datatype definitions for built-in
generated
datatypes are
included in the Schema for Datatype Definitions (normative) (§A) while the datatype definitions for
user-generated datatypes appear in schemas written by users.
[Definition:] An abstract
syntax provides a formal specification of the information
provided for each generated datatype definition.
The abstract syntax is presented using a simplified BNF. Defined terms are to
the left. Their components are to the right, with a small amount of
meta-syntax: ()s for grouping, | to separate alternatives, ? for optionality, *
and + for iteration.
[Definition:] The concrete
syntax for generated datatype definitions is the exact
element and attribute names used in definitions..
The concrete syntax is a key feature of its proposed design.
The concrete syntax is the form in which the schema
language is used by datatype designers. Though its elements
and attributes are often different from the terms of the abstract
syntax bnf, the features and expressive power of the two are congruent.
We include a preliminary concrete syntax in this draft, via examples, as well as
in Schema for Datatype Definitions (normative) (§A) (defined using the schema language of
[XML Schema Part 1: Structures]) and DTD for Datatype Definitions (normative) (§B).
The emphasis in this version has been to stay quite close to the abstract syntax.
Ed. Note:
The abstract syntax proposed here (and hence, the concrete syntax) are
preliminary, as they allow datatype definitions which are logically inconsistent
(e.g., they allow numeric facets on
non-numeric datatypes). This will be corrected
in future drafts, as the XML Schema language comes to allow the specification
of tighter constraints.
Ed. Note:
This section needs more explanatory text describing the productions and
their relationship to the conceptual framework described in sections
Type System (§2) and Built-in datatypes (§3).
The following is the definition for a possible built-in
generated datatype "currency". This datatype definition
would appear in the schema which defines datatypes for XML Schemas
and shows that a generated datatype can have the same
value space as its basetype,
which might mean that
it is just an "alias" or "renaming" of basetype. In this case,
the specification would probably also define some
"semantics" for currency which went beyond those of decimal.
| Example |
<datatype name="currency" source="decimal"/>
|
|
|
Constraint on Schemas: Unique datatype definitions
The name of the datatype being defined must be unique among the datatypes
defined in the containing schema.
| Datatype names |
[4] | datatypename | ::= |
builtinname |
usergenname
| |
[5] | builtinname | ::= | Name | QName | NCName | | |
| | | ID | IDREF |IDREFS | | |
| | | NMTOKEN | NMTOKENS | | |
| | | ENTITY | ENTITIES | | |
| | | string | uri | | |
| | | timeInstant | timeDuration | recurringInstant | |
| | | binary | | |
| | | float | double | decimal |integer | | |
| | | non-negative-integer | positive-integer | | |
| | | non-positive-integer | negative-integer | | |
| | | date | time | language | |
[6] | usergenname | ::= |
datatypeRef
| |
|
NOTE:
The datatypename production
above is not to be confused with that labeled
datatypeName in
[XML Schema Part 1: Structures].
Constraint on Schemas: Literal type
The literal value give must be of the same type as the datatype
as the basetype given in the datatype definition in which this facet
appears.
| Example |
|
The following is the definition of a user-generated datatype
which could be used to represent monetary amounts, such as in a financial
management application which does not have figures above $1M
and only allow whole cents. This definition would appear in a schema
authored by an "end-user" and shows how to define a datatype by specifying
facet values which constrain the range of the basetype in a manner
specific to the basetype
(different than specifying max/min values as before)
|
<datatype name="amount" source="decimal">
<precision value='8'/>
<scale value='2'/>
</datatype>
|
|
|
This type could just as well have been defined with the
potential built-in generated
type "currency" (defined above) as its basetype.
|
|
| Example |
|
The following example is a datatype definition for a
user-generated
datatype which limits the values of dates to the three
US holidays enumerated. This datatype definition would appear in a schema
authored by an "end-user" and shows how to define a datatype by enumerating
the values in its value space. The enumerated values must be
type-valid literals for the basetype.
|
<datatype name="holidays" source="date">
<annotation>
<info>some US holidays</info>
</annotation>
<enumeration value='--01-01'>
<annotation>
<info>New Year's day</info>
</annotation>
</enumeration>
<enumeration value='--07-04'/>
<annotation>
<info>4th of July</info>
</annotation>
</enumeration>
<enumeration value='--12-25'/>
<annotation>
<info>Christmas</info>
</annotation>
</enumeration>
</datatype>
|
|
|
Issue (definition-overriding):
In some cases it may be desirable to specify datatype constraints in
instance documents rather than in a schema. Should this be allowed?
If the document does not have a schema then, clearly, the only
possibility of adding datatype constraints is in the document instance.
Even if the document has a schema the document instance may want to
further restrict the content. For example, the schema may specify a value
to be a string but the instance may want to impose a particular
regex constraint on it.
If we decide to allow datatype specification or specialization in
instance document what syntax should be used?
This needs to be coordinated with
the structural schema editorial team.
Issue (non-positive-integer-literal):
Do we need productions for the literals of non-negative-integer,
positive-integer, non-positive-integer and negative-integer?
5 Conformance
Ed. Note:
This section (both its abstract content and its concrete wording)
has not yet garnered consensus among WG members.
The XML specification [XML 1.0 Recommendation] defines two levels of conformance.
Well-formed documents conform to valid XML syntax but may or may not obey
the constraints defined by a DTD. Valid XML documents conform to the structure
laid down in a DTD. Thus, if a DTD defines an attribute as an ID (§3.3.7),
instances
of XML documents conforming to the DTD can only be valid if the values of
such attributes are valid XML names and are unique in the document. By
introducing
additional datatypes to XML, this specification extends the notion of validity
in the sense that values defined to have a certain datatype in the schema
must conform to the lexical representations allowed for that datatype.
Values that do not conform to the datatype defined for them in the schema
raise a conformance error. As, for example, the appearance of a
letter in a value defined as integer (§3.3.13). Similarly, for a value
defined as a subtype of string (§3.2.1)
with length equal to 5, a value of "ABC" would
raise an error -- length too short -- as would a value of "abcdefgh" -- length
too long.
For conformance it is not enough that the representation conform to a legal
literal in the lexical space of the datatype;
it must also represent a legal value in the
value space. For example, the
timeInstant (§3.2.6), timeDuration (§3.2.7),
recurringInstant (§3.2.8),
date (§3.3.18) and time (§3.3.19) values
must conform to legal Gregorian
dates and legal time values as specified in the descriptions of these datatypes.
user-generated datatypes are defined by giving values to
certain constraining facets. For example, a subtype
of integer (§3.3.13) within a certain range could be defined by
giving values to maxInclusive and minInclusive
facets. A switch on the
datatypes processor could be used to turn validation off for these facets.
This could be used by a processor that used the datatypes processor to eliminate
validation of user-generated datatypes.
It also needs to be said that there are no expressions on
datatypes; neither are there operations on datatypes.
If we decide to allow datatype specification or specialization in instance
documents (see issue "definition-overriding" above) then
validating XML processors should be able to validate the format
of values in XML documents in these cases as well by using the
datatypes processor.
A Schema for Datatype Definitions (normative)
<?xml version='1.0'?>
<!-- XML Schema schema for XML Schemas: Part 2: Datatypes -->
<!DOCTYPE schema PUBLIC "-//W3C//DTD XMLSCHEMA 19991216//EN" "../WD-xmlschema-1-19991217/structures.dtd" >
<schema xmlns="<http://www.w3.org/1999/XMLSchema" targetNamespace="<http://www.w3.org/1999/XMLSchema" version="Id: datatypes.xsd,v 1.19 1999/12/17 10:33:15 ht Exp ">
<type name="datatype" source="annotated" derivedBy="extension"
abstract="true">
<element ref="facet" minOccurs="0" maxOccurs="*"/>
<attribute name="name" type="NCName" minOccurs="0">
<annotation>
<info>Will be restricted to required or forbidden</info>
</annotation>
</attribute>
<attribute name="source" type="QName" minOccurs="1"/>
<attribute name="final" type="derivationSet"/>
<attribute name="abstract" type="boolean"/>
</type>
<type name="namedDatatype" source="datatype">
<annotation>
<info>This is for the top-level datatype element,
as ref'ed in <schema</info>
</annotation>
<attribute name="name" minOccurs="1">
<annotation><info>Required at the top level</info></annotation>
</attribute>
</type>
<type name="anonDatatype" source="datatype">
<annotation>
<info>This is for the nested datatype element,
as used in <element</info>
</annotation>
<attribute name="name" maxOccurs="0">
<annotation><info>Forbidden when nested</info></annotation>
</attribute>
</type>
<element name="datatype" equivClass="schemaTop" type="namedDatatype"/>
<key name="datatype">
<selector>schema/datatype</selector>
<field>@name</field>
</key>
<type name="facet" source="annotated" derivedBy="extension">
<attribute name="value" minOccurs="1"/>
</type>
<element name="facet" type="facet" abstract="true"/>
<element name="minBound" abstract="true" equivClass="facet"/>
<element name="minExclusive" equivClass="minBound"/>
<element name="minInclusive" equivClass="minBound"/>
<element name="maxBound" abstract="true" equivClass="facet"/>
<element name="maxExclusive" equivClass="maxBound"/>
<element name="maxInclusive" equivClass="maxBound"/>
<type name="numFacet" source="facet" derivedBy="restriction">
<attribute name="value" type="non-negative-integer"/>
</type>
<element name="precision" type="numFacet" equivClass="facet"/>
<element name="scale" type="numFacet" equivClass="facet"/>
<element name="length" type="numFacet" equivClass="facet"/>
<element name="minlength" type="numFacet" equivClass="facet"/>
<element name="maxlength" type="numFacet" equivClass="facet"/>
<!-- the following datatype is used to limit the
possible values for the encoding facet on
the binary datatype -->
<datatype name="encodings" source="NMTOKEN">
<enumeration value="hex">
<annotation>
<info>each (8-bit) byte is encoded as a sequence
of 2 hexidecimal digits</info>
</annotation>
</enumeration>
<enumeration value="base64">
<annotation>
<info>value is encoded in Base64 as defined in the MIME RFC</info>
</annotation>
</enumeration>
</datatype>
<element name="encoding" equivClass="facet">
<type source="facet" derivedBy="restriction">
<attribute name="value" type="encodings"/>
</type>
</element>
<element name="period" equivClass="facet">
<type source="facet" derivedBy="restriction">
<attribute name="value" type="timeDuration"/>
</type>
</element>
<element name="enumeration" equivClass="facet"/>
<element name="pattern" equivClass="facet"/>
<!-- built-in generated datatypes -->
<!-- only has a few for now, eventually needs to have all of them -->
<datatype name="integer" source="decimal">
<scale value="0"/>
</datatype>
<datatype name="non-negative-integer" source="integer">
<minInclusive value="0"/>
</datatype>
<datatype name="positive-integer" source="non-negative-integer">
<minInclusive value="1"/>
</datatype>
<datatype name="non-positive-integer" source="integer">
<maxInclusive value="0"/>
</datatype>
<datatype name="negative-integer" source="non-positive-integer">
<maxInclusive value="-1"/>
</datatype>
<datatype name="date" source="recurringInstant">
<period value="000000T2400"/>
</datatype>
<datatype name="time" source="recurringInstant">
<period value="000000T2400"/>
</datatype>
<datatype name="NMTOKENS" source="string">
<pattern value="\c+(\s\c+)*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#NT-Nmtokens">
pattern matches production 8 from the XML spec
</info>
</annotation>
</pattern>
</datatype>
<datatype name="NMTOKEN" source="NMTOKENS">
<pattern value="\c+">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#NT-Nmtoken">
pattern matches production 7 from the XML spec
</info>
</annotation>
</pattern>
</datatype>
<datatype name="Name" source="NMTOKEN">
<pattern value="\i\c*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#NT-Name">
pattern matches production 5 from the XML spec
</info>
</annotation>
</pattern>
</datatype>
<datatype name="ID" source="NCName">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#id">
values of this datatype must be unique within
a document
</info>
</annotation>
</datatype>
<datatype name="IDREFS" source="string">
<pattern value="[\i-[:]][\c-[:]]*(\s[\i-[:]][\c-[:]]*)*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#NT-Names">
pattern matches production 6 from the XML spec
(modified as required by the
Conformance section in
Namespaces in XML
(http://www.w3.org/TR/REC-xml-names#conformance))
</info>
<info source="http://www.w3.org/TR/REC-xml#idref">
values of this datatype must have occured within
a document as the value of some component
of type ID
</info>
</annotation>
</pattern>
</datatype>
<datatype name="IDREF" source="IDREFS">
<pattern value="[\i-[:]][\c-[:]]*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml-names#NT-NCName">
pattern matches production 4 from the Namespaces in XML spec
</info>
<info source="http://www.w3.org/TR/REC-xml#idref">
values of this datatype must have occured within
a document as the value of some component
of type ID
</info>
</annotation>
</pattern>
</datatype>
<datatype name="ENTITIES" source="string">
<pattern value="[\i-[:]][\c-[:]]*(\s[\i-[:]][\c-[:]]*)*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml#NT-Names">
pattern matches production 6 from the XML spec
(modified as required by the
Conformance section in
Namespaces in XML
(http://www.w3.org/TR/REC-xml-names#conformance))
</info>
<info source="http://www.w3.org/TR/REC-xml#entname">
values of this datatype must match the name of
an unparsed entity declared in the schema
</info>
</annotation>
</pattern>
</datatype>
<datatype name="ENTITY" source="ENTITIES">
<pattern value="[\i-[:]][\c-[:]]*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml-names#NT-NCName">
pattern matches production 4 from the Namespaces in XML spec
</info>
<info source="http://www.w3.org/TR/REC-xml#entname">
values of this datatype must match the name of
an unparsed entity declared in the schema
</info>
</annotation>
</pattern>
</datatype>
<datatype name="NCName" source="Name">
<pattern value="[\i-[:]][\c-[:]]*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml-names/#NT-NCName">
pattern matches production 4 from the
Namespaces in XML spec
</info>
</annotation>
</pattern>
</datatype>
<datatype name="QName" source="Name">
<pattern value="([\i-[:]][\c-[:]]*:)?[\i-[:]][\c-[:]]*">
<annotation>
<info source="http://www.w3.org/TR/REC-xml-names/#NT-QName">
pattern matches production 6 from the
Namespaces in XML spec
</info>
</annotation>
</pattern>
</datatype>
</schema>
|
B DTD for Datatype Definitions (normative)
<!-- DTD for XML Schemas: Part 2: Datatypes -->
<!-- Id: datatypes.dtd,v 1.16 1999/12/10 17:48:39 ht Exp -->
<!ENTITY % p ''> <!-- can be overriden in the internal subset of a
schema document to establish a namespace prefix -->
<!-- Define all the element names, with optional prefix -->
<!ENTITY % datatype "%p;datatype">
<!ENTITY % maxExclusive "%p;maxExclusive">
<!ENTITY % minExclusive "%p;minExclusive">
<!ENTITY % maxInclusive "%p;maxInclusive">
<!ENTITY % minInclusive "%p;minInclusive">
<!ENTITY % precision "%p;precision">
<!ENTITY % scale "%p;scale">
<!ENTITY % length "%p;length">
<!ENTITY % minlength "%p;minlength">
<!ENTITY % maxlength "%p;maxlength">
<!ENTITY % enumeration "%p;enumeration">
<!ENTITY % pattern "%p;pattern">
<!ENTITY % encoding "%p;encoding">
<!ENTITY % period "%p;period">
<!-- annotation elements -->
<!ENTITY % annotation "%p;annotation">
<!ENTITY % appinfo "%p;appinfo">
<!ENTITY % info "%p;info">
<!-- Define some entities for informative use as attribute types -->
<!ENTITY % URI "CDATA">
<!ENTITY % URIList "CDATA">
<!ENTITY % QName "CDATA">
<!ENTITY % NCName "NMTOKEN">
<!ENTITY % non-negative-integer "NMTOKEN">
<!ENTITY % boolean "(true|false)">
<!ENTITY % derivationChoice "(restriction|extension)">
<!ENTITY % derivationSet "CDATA">
<!-- #all or space-separated list drawn from derivationChoice -->
<!ENTITY % exactSet "CDATA">
<!-- #all or space-separated list drawn from
derivationChoice + 'equivClass' -->
<!-- Note that the use of 'facet' below is less restrictive than is
really intended: There should in fact be no more than one of each of
minInclusive, minExclusive, maxInclusive, maxExclusive,
precision, scale,
length, maxlength, minlength, encoding, period within datatype,
and the min- and max- variants of Inclusive and Exclusive are
mutually exclusive.
On the other hand, pattern and enumeration may repeat -->
<!ENTITY % minBound '(%minInclusive; | %minExclusive;)'>
<!ENTITY % maxBound '(%maxInclusive; | %maxExclusive;)'>
<!ENTITY % bounds '%minBound; | %maxBound;'>
<!ENTITY % numeric '%precision; | %scale;'>
<!ENTITY % ordered '%bounds; | %numeric;'>
<!ENTITY % unordered
'%pattern; | %enumeration; | %length; | %maxlength; | %minlength;
| %encoding; | %period;'>
<!ENTITY % facet '%ordered; | %unordered;'>
<!ENTITY % facetAttr 'value CDATA #REQUIRED'>
<!ENTITY % facetModel '(%annotation;)?'>
<!ELEMENT %datatype; ((%annotation;)?,(%facet;)*)>
<!ATTLIST %datatype;
name %NCName; #IMPLIED
source %QName; #REQUIRED
final %derivationSet; ''
abstract %boolean; 'false'>
<!-- name is required at top level -->
<!ELEMENT %maxExclusive; %facetModel;>
<!ATTLIST %maxExclusive; %facetAttr;>
<!ELEMENT %minExclusive; %facetModel;>
<!ATTLIST %minExclusive; %facetAttr;>
<!ELEMENT %maxInclusive; %facetModel;>
<!ATTLIST %maxInclusive; %facetAttr;>
<!ELEMENT %minInclusive; %facetModel;>
<!ATTLIST %minInclusive; %facetAttr;>
<!ELEMENT %precision; %facetModel;>
<!ATTLIST %precision; %facetAttr;>
<!ELEMENT %scale; %facetModel;>
<!ATTLIST %scale; %facetAttr;>
<!ELEMENT %length; %facetModel;>
<!ATTLIST %length; %facetAttr;>
<!ELEMENT %minlength; %facetModel;>
<!ATTLIST %minlength; %facetAttr;>
<!ELEMENT %maxlength; %facetModel;>
<!ATTLIST %maxlength; %facetAttr;>
<!-- This one can be repeated -->
<!ELEMENT %enumeration; %facetModel;>
<!ATTLIST %enumeration; %facetAttr;>
<!-- This one can be repeated -->
<!ELEMENT %pattern; %facetModel;>
<!ATTLIST %pattern; %facetAttr;>
<!ELEMENT %encoding; %facetModel;>
<!ATTLIST %encoding; %facetAttr;>
<!ELEMENT %period; %facetModel;>
<!ATTLIST %period; %facetAttr;>
<!-- Annotation is either application information or documentation -->
<!-- By having these here they are available for datatypes as well
as all the structures elements -->
<!ELEMENT %annotation; (%appinfo; | %info;)*>
<!-- User must define annotation elements in internal subset for this
to work -->
<!ELEMENT %appinfo; ANY> <!-- too restrictive -->
<!ATTLIST %appinfo;
source %URI; #IMPLIED>
<!ELEMENT %info; ANY> <!-- too restrictive -->
<!ATTLIST %info;
source %URI; #IMPLIED
xml:lang CDATA #IMPLIED>
|
C Datatypes and Facets
Ed. Note:
This section (both its abstract content and its concrete wording)
has not yet garnered consensus among WG members.
C.1 Fundamental Facets
The following table shows the values of the fundamental facets
for each built-in datatype.
Ed. Note:
(PVB
1999-07-09)
Some entries in this table might
conflict with what it says elsewhere in this draft, as creating
this table pointed out to me some problems with the way some
of the fundamental facets are defined (not to mention any
transcription errors on my part in creating the table).
We obviously need more introductory text here explaining this
table to the reader
C.2 Constraining Facets
The constraining facets are listed below with all the primitive
and
genrated datatypes that they apply to.
Ed. Note:
Some entries in this table might
conflict with what it says elsewhere in this draft, as creating
this table pointed out to me some problems with the way some
of the constraining facets and datatypes are defined (not to
mention any transcription errors on my part in creating the table).
The constraining facet length applies to:
The constraining facet minlength applies to:
The constraining facet maxlength applies to:
The constraining facet pattern applies to:
The constraining facet enumeration applies to:
The constraining facet maxInclusive applies to:
The constraining facet maxExclusive applies to:
The constraining facet minInclusive applies to:
The constraining facet minExclusive applies to:
The constraining facet precision applies to:
The constraining facet scale applies to:
The constraining facet encoding applies to:
The constraining facet period applies to:
D ISO 8601 Date and Time Formats
Ed. Note:
This section (both its abstract content and its concrete wording)
has not yet garnered consensus among WG members.
D.1 ISO 8601 Conventions
Three primitive datatypes described above,
timeInstant (§3.2.6),
timeDuration (§3.2.7), and recurringInstant (§3.2.8), and two
generated dataypes, date (§3.3.18) and
time (§3.3.19) 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.
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 (§3.2.8) datatype uses a truncated format for
timeInstant (§3.2.6) to indicate recurring instants of time. In fact,
only recurring instants that can be represented truncated representations of
timeInstant (§3.2.6) are permitted.
Left truncated representations are also allowed for the date (§3.3.18)
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 (§3.3.18) and can be used
to represent a specific month, a specific year, or a specific century.
D.3 Deviations from ISO 8601 Formats
E Regular Expressions
Ed. Note:
This section (both its abstract content and its concrete wording)
has not yet garnered consensus among WG members.
The following represents a summary of the Unicode regular expression
support which has been proposed for pattern. The next
draft of this specification will contain a full description of the proposal.
-
patterns match against the value space and not against
the lexical space of string (more below)
-
Unicode support between Level 1 and Level 2 as defined in
[Unicode Regular Expression Guidelines]. This support covers all of
Section 2 as well as Sections 3.1 and 3.2 of [Unicode Regular Expression Guidelines].
-
patterns match against the entire string value.
This means there are no "^" or "$" metacharacters as in
[Perl]. To get "substring" matching behavior, simply
use a pattern such as ".*[a-z].*".
-
patterns may contain the follow character class escape
sequences (CCES)
- CCES Name Meaning
- \t tab (	)
- \n newline ( )
- \r return ( )
- \w word char (XML prods. 84 | 88)
- \s white space (XML prod. 3)
- \d digit (XML prod. 88)
- \c name char (XML prod. 4)
- \i initial NMTOKEN char (XML prod. 5)
Furthermore, \W, \S, \D, \C and \I are allowed, and mean the
compliment of their lower case form (as in Perl)
-
patterns may also contain any CCES of the form: \p{x},
where x is one of the 1 or 2 letter properties defined in
the Unicode Character Database [Unicode Database]. The \p{x} syntax
is as in [Perl 5.6].
Furthermore, \P{x} is allowed and means the
compliment of its lower case form (as in Perl)
Examples of properties are:
-
Lu Letter, Uppercase
- Nd Number, Decimal Digit
- Pc Punctuation, Connector
- Sm Symbol, Math
patterns may also contain CCES of the form:
\p{Isx},
where x is one of the block names defined in
the Unicode Character Database [Unicode Database] and Chapter 15
of the Unicode Specification [Unicode]. The \p{x} syntax
is as in [Perl 5.6].
Furthermore, \P{x} is allowed and means the
compliment of its lower case form (as in Perl)
Examples of blocks are:
-
BasicLatin (�-)
- Latin-1Supplement (€-ÿ)
- Greek (Ͱ-Ͽ)
- HangulSyllables (&xAC00;-힣)
Thus, to match any Greek character one would use:
\p{IsGreek}
-
patterns may NOT contain octal or hexidecimal escape
sequences such as:
\033 or \x1B,
XML Character References
should be used instead.
-
within character classes, ranges (e.g. [a-z]) refer
to code point ranges
-
character class subtraction is allowed using the following
syntax:
[a-z-[mn]]
-
character class complimentation is allowed using the
following syntax:
[^a-z]
-
case dependant and case independant matching will be supported
-
the usual grouping and repetition operators are allowed:
(), |, +, ?, *, {n}, {n,m}, {n,}
-
notably NOT allowed are:
the various "zero-width" assertions from Perl:
\b, \B, lookahead or lookbehind (e.g., (?=...) (?<=...),
backreferences (e.g., /(a-z).*\1)
Concerning point #1: patterns match against the value space
and not against
the lexical space of string (§3.2.1)...
We (or maybe it's just me, I can't remember how extensively the PTF
discussed this issue) are proposing that the value space
of string (§3.2.1)
be a normalized form of the lexical space, where normalization
occurs as per the CharModel WD [8] (which amounts to Unicode Normalization
Form C [9]).
Any comments appreciated. We are especially requesting input on alternate
syntax for specifying character class subtraction (point #9 above). The
sytnax proposed here is from [2] but its not ideal in our opinion.
F References
Ed. Note:
This section (both its abstract content and its concrete wording)
has not yet garnered consensus among WG members.
G Acknowledgments (non-normative)
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 Lotu
Development Corp. and IBM for providing teleconferencing facilities.
The current members of the XML Schema Working Group are:
Paula Angerstein, Vignette Corporation;
David Beech, Oracle Corp.;
Paul V. Biron, Health Level Seven;
Allen Brown, Microsoft;
Greg Bumgardner, Rogue Wave Software;
Lee Buck, Extensibility;
Dean Burson, Lotus Development Corporation;
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;
Setrag Khoshafian, Technology Deployment International (TDI);
Janet Koenig, Sun Microsystems;
Ara Kullukian, Technology Deployment International (TDI);
Andrew Layman, Microsoft;
Dmitry Lenkov, Hewlett Packard Company;
Eve Maler, ArborText, Inc.;
Ashok Malhotra, IBM;
Murray Maloney, Commerce One;
John McCarthy, Lawrence Berkeley National Laboratory;
Noah Mendelsohn, Lotus Development Corporation;
Don Mullen, Extensibility;
Murata Makoto, Xerox;
Frank Olken, Lawrence Berkeley National Laboratory;
Dave Peterson, Graphic Communications Association;
Mark Reinhold, Sun Microsystems;
Shriram Revankar, Xerox;
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;
Priscilla Walmsley, XMLSolutions;
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.
Gabe Beged-Dov, Rogue Wave Software;
George Feinberg, Object Design;
Charles Frankston, Microsoft;
Ernesto Guerrieri, Inso;
Michael Hyman, Microsoft;
Chris Olds, Wall Data;
William Shea, Merrill Lynch;
Ralph Swick, W3C;
Tony Stewart, Rivcom
I Revisions from Previous Draft
-
1999-11-08: PVB: removed real datatype and all references to it
-
1999-11-08: PVB: added inital definitions for float and double datatypes.
This initial definition is not intended to be complete, we need a more
complete description of the round-to-nearest behavior of mapping literals
into the value space (i.e., a more readable description of "best approximation"
from the Clinger paper in the non-normative references section).
-
1999-11-08: PVB: corrected typos in the definitions of datatypes generated
from integer to corrected identify the generated type
-
1999-11-08: PVB: added specref elements to all mentions of constraining facets
-
1999-11-08: PVB: added term elements to all mentions of a datatype name in
the definition of that datatype
-
1999-11-12: PVB: changed lexical space of timeDuration to be more consistent
with ISO 8601, nYnMnDTnHnMnS (minus the 'P' designator).
-
1999-11-12: PVB fixed productions for decimalLiteral to allow forms such as
-.12 and -23.
-
19991122: AM: Added some more explanation to timeDuration format. Fixed
Appendix D to reflect changes.
-
19991122: AM: Added "uncountable infinite and exact" value space to 2.4.1.3
-
19991122: AM: Removed issue "Better Reference Mechanisms".
-
19991122: AM: Added "collation sequence for strings is Unicode characater number".
-
19991122: AM: Added min/max facets to date/time dataypes.
-
19991122: AM: Removed issues on URI and binary datatypes.
-
19991122: AM: Added value space validation to conformance section.
-
19991122: AM: Added values space definitions to date/time datatypes.
-
1999-12-08: pvb: Added QName datatype
-
1999-12-08: pvb: changed language to be a subtype of string
-
1999-12-10: pvb: many small editorial changes for consistency
-
1999-12-10: pvb: Added pattern facet to all date/time types (should
have been there all along)
-
1999-12-10: pvb: Added full list of facets and subtypes to each type
definition
-
1999-12-10: pvb: replaced regex appendix with a brief summary of proposed
Unicode support, complete proposal coming shortly
-
1999-12-10: pvb: moved some references from normative to non-normative
-
1999-12-10: pvb: changed concrete syntax for datatype defns to more closely
match the structures draft: in particular, to allow annotations on the
datatype element and all facet elements.
-
1999-12-15: pvb: added normaitive reference to RTC 2045 for def of base64
-
1999-12-15: pvb: many more small editorial changes, for consistency in
style and presentation
-
1999-12-15: pvb: corrected small errors in table in appendix C.1, Fundamental
facets
-
1999-12-15: pvb: filled out list of datatypes for each facet in appendix C.2,
Constraining facets
-
1999-12-15: expanded abstract
-
1999-12-15: pvb: updated description of lexical space for float/double to
include literals for +- inf, +- 0, nan.
-
1999-12-16: pvb: modified defns of ID, IDREF, IDREFS, ENTITY, ENTITIES
and NOTATION to match NCName instead of Name as required by the Namespaces
in XML spec
-
1999-12-16: pvb: fully specified value space for decimal