XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (460 page)

BOOK: XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition
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  • When you want to indicate that an empty sequence is
    not
    allowed.
  • When the type name is defined in a schema with no target namespace (unless the default function namespace is the null namespace, which would be unusual, and cannot arise in XSLT). When your type names are unprefixed, you have to use the more verbose
    cast
    as
    syntax.

The sections that follow describe all the rules for converting a supplied value to a target type. We'll start by considering the rules for converting from a primitive type to another primitive type and then go on to consider how derived types are handled.

Converting between Primitive Types

The type conversions described in this section start with an atomic value that is labeled with a primitive type. For these purposes we consider a primitive type to be either one of the primitive types defined in Part 2 of the XML Schema specification, or the XPath-defined atomic type
xs:untypedAtomic
.. Although in XPath the types
xs:integer, xs:dayTimeDuration
and
xs:yearMonthDuration
are sometimes treated as primitive, in this chapter we will treat them as derived types, which is what they actually are.

For reasons of space, few examples of conversions are given in this chapter. However, in the download files for this book there is a stylesheet,
cast.xsl
, which exercises all the conversions between primitive types. It requires a schema-aware XSLT processor.

We couldn't get this stylesheet to run with our version of AltovaXML 2008.

The following table lists for each source type, the permitted destination types. The detailed rules for these conversions are then given in the subsequent sections, which for ease of reference are arranged alphabetically according to the type of the source value for the conversion.

Source Type
Permitted Result Types
anyURI
anyURI
,
string
,
untypedAtomic
base64Binary
base64Binary
,
hexBinary
,
string
,
untypedAtomic
boolean
boolean
,
decimal
,
double
,
float
,
string
,
untypedAtomic
date
date
,
dateTime
,
gDay
,
gMonth
,
gMonthDay
,
gYear
,
gYearMonth
,
string
,
untypedAtomic
dateTime
date
,
dateTime
,
gDay
,
gMonth
,
gMonthDay
,
gYear
,
gYearMonth
,
string
,
time
,
untypedAtomic
decimal
boolean
,
decimal
,
double
,
float
,
string
,
untypedAtomic
double
boolean
,
decimal
,
double
,
float
,
string
,
untypedAtomic
duration
duration
,
string
,
untypedAtomic
float
boolean
,
decimal
,
double
,
float
,
string
,
untypedAtomic
gDay
gDay
,
string
,
untypedAtomic
gMonth
gMonth
,
string
,
untypedAtomic
gMonthDay
gMonthDay
,
string
,
untypedAtomic
gYear
gYear
,
string
,
untypedAtomic
gYearMonth
gYearMonth
,
string
,
untypedAtomic
hexBinary
base64Binary
,
hexBinary
,
string
,
untypedAtomic
NOTATION
NOTATION
,
string
,
untypedAtomic
QName
QName
,
string
,
untypedAtomic
string
anyURI
,
base64Binary
,
boolean
,
date
,
dateTime
,
decimal, double
,
duration
,
float
,
gDay
,
gMonth
,
gMonthDay
,
gYear
,
gYearMonth
,
hexBinary
,
NOTATION
(note 1),
QName
(note 2),
string
,
time
,
untypedAtomic
time
time
,
string
,
untypedAtomic
untypedAtomic
anyURI
,
base64Binary
,
boolean
,
date
,
dateTime
,
decimal
,
double
,
duration
,
float
,
gDay
,
gMonth
,
gMonthDay
,
gYear
,
gYearMonth
,
hexBinary
,
string
,
time
,
untypedAtomic

Note 1: Casting from a string to
xs:NOTATION
itself is not allowed, because
xs:NOTATION
is an abstract type. Casting to a user-defined subtype of
xs:NOTATION
is permitted, but only if the string is written as a string literal.

Note 2: Casting from a string to
xs:QName
is allowed only if the string is written as a string literal. This means that the cast can always be done at compile time, which avoids problems in deciding the appropriate namespace context to use for the conversion.

Converting from anyURI

Destination Type
Rules
anyURI
The value is returned unchanged.
string
The value is returned as a string containing exactly the same characters as the supplied
anyURI
value. No percent-encoding or -decoding of special characters is performed.
untypedAtomic
Returns the same result as converting to a string, but the result is labeled as
untypedAtomic
.

Converting from base64Binary

Destination Type
Rules
base64Binary
The value is returned unchanged.
hexBinary
A
hexBinary
value is constructed containing the same octets as the original
base64Binary
value.
string
The canonical lexical representation of the
base64Binary
value is returned, as a string. This representation is defined in Part 2 of the XML Schema specification (be sure to read the latest version, the original has been corrected). It outputs the value with no whitespace.
untypedAtomic
Returns the same result as converting to a string, but the result is labeled as
untypedAtomic
.

Converting from boolean

Destination Type
Rules
boolean
The value is returned unchanged.
decimal
true
is converted to
1.0
,
false
to
0.0
.
double
true
is converted to
1.0e0
,
false
to
0.0e0
.
float
true
is converted to
xs:float(1.0e0)
,
false
to
xs:float(0.0e0)
.
string
Returns the string
“true”
or
“false”
.
untypedAtomic
Returns the same result as converting to a string, but the result is labeled as
untypedAtomic
.

Converting from date

Destination Type
Rules
date
The value is returned unchanged.
dateTime
Returns the
dateTime
representing the instant in time at which the relevant date starts. The timezone (or the absence of a timezone) is retained unchanged. For example, the date
2008-04-04
becomes the
dateTime
2008-04-04 T00:00:00
.
gDay
Returns a
gDay
value containing the same day component and timezone (or absence of a timezone) as the original date.
gMonth
Returns a
gMonth
value containing the same month component and timezone (or absence of a timezone) as the original date.
gMonthDay
Returns a
gMonthDay
value containing the same month and day components and timezone (or absence of a timezone) as the original date.
gYear
Returns a
gYear
value containing the same year component and timezone (or absence of a timezone) as the original date.
gYearMonth
Returns a
gYearMonth
value containing the same year and month components and timezone (or absence of a timezone) as the original date.
string
Returns the canonical lexical representation of the date, retaining the original timezone. For example, a date with no timezone might be converted to the string
2008-06-19
, while a date in the Pacific timezone might become
2008-06-19-08:00
. The timezone is represented as
±hh:mm
, except for UTC which is represented by the single letter
Z
.
untypedAtomic
Returns the same result as converting to a string, but the result is labeled as
untypedAtomic
.

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