If a section of this specification has been updated since version 3.0, an overview of the changes is provided, along with links to navigate to the next or previous change.
See 1.2 What’s New in XSLT 4.0?
Sections with significant changes are marked with a ✭ symbol in the table of contents.
See 1.2 What’s New in XSLT 4.0?
PR 751 1386
The result type of a mode can be declared using an as attribute. The result type of all template rules in this mode must be consistent with this, as must the values returned by any built-in template rules for the mode.
See 6.7.5 Declaring the Result Type of a Mode
The xsl:for-each and xsl:apply-templates instructions acquire an attribute separator that can be used to insert content between adjacent items. [This change was in the editor's draft adopted as a baseline when the WG commenced work.]
See 7.1 The xsl:for-each instruction
PR 2015 2296
A variable-binding with no as or select attribute no longer attempts to create an implicit document node if the sequence constructor contains certain instructions (such as xsl:map, xsl:array, xsl:record, and xsl:select).
See 9.3 Values of Variables and Parameters
PR 2200 2236
Stylesheet functions may now be in no namespace, and may be invoked without use of a namespace prefix, provided they are private to a package.
See 10.3.1 Function Name and Arity
Functions that accept a lexical QName as an argument, such as key, function-available, element-available, type-available, system-property, accumulator-before, and accumulator-after, now have the option of supplying an xs:QName value instead. [This change was in the editor's draft accepted by the WG as its baseline when it started work.]
See 20 Additional Functions
Functions that accept a lexical QName as an argument, such as key, function-available, element-available, type-available, system-property, accumulator-before, and accumulator-after, now have the option of supplying an xs:QName value instead. [This change was in the editor's draft accepted by the WG as its baseline when it started work.]
See 24 Extensibility and Fallback
New in 4.0
See 26.4.1 fn:character-map
The xsl:for-each and xsl:apply-templates instructions acquire an attribute separator that can be used to insert content between adjacent items. [This change was in the editor's draft adopted as a baseline when the WG commenced work.]
See 6.4 Applying Template Rules
It is possible to invoke a named template using an extension instruction, specifically, an element whose name matches the name of the named template.
See 10.1.3 Invoking Named Templates using Extension Instructions
See 24.3 Extension Instructions
A new attribute xsl:map/@duplicates is available, allowing control over how duplicate keys are handled by the xsl:map instruction.
See 21.1.2 Handling of duplicate keys
PR 1497 1546
A new serialization parameter json-lines is available to enable output as one JSON value per line.
See 25.1 Creating Secondary Results
See 26.1 The xsl:output declaration
PR 159
Parameters on functions declared using xsl:function can now be defined as optional, with a default value supplied.
See 9.2.2 Default Values of Parameters
See 10.3 Stylesheet Functions
PR 237
The xsl:if instruction now allows then and else attributes.
See 8.1 Conditional Processing with xsl:if
In xsl:choose, the xsl:when and xsl:otherwise elements can take a select attribute in place of a sequence constructor.
See 8.2 Conditional Processing with xsl:choose
A new xsl:switch instruction is introduced.
See 8.3 Conditional Processing with xsl:switch
PR 326
The higher-order-function feature no longer exists; higher-order functions are now a core part of XSLT, no longer an optional extra.
See 27 Conformance
PR 353
A new attribute, main-module, is added to the xsl:stylesheet element. The attribute is provided for the benefit of development tools such as syntax-directed editors to provide information about all the components (variables, functions, etc) visible within a stylesheet module.
See 3.6 Stylesheet Element
A new element xsl:note is available for documentation and similar purposes: it can appear anywhere in the stylesheet and is ignored by the XSLT processor.
See 3.12.2 The xsl:note element
PR 401
Patterns (especially those used in template rules) can now be defined by reference to item types, so any item type can be used as a match pattern. For example match="~record(longitude, latitude, *)" matches any map that includes the key values "longitude" and "latitude".
See 6.3.2.2 Type Patterns
PR 406
The new instruction xsl:array is introduced to allow construction of arrays.
See 22.1 Array Construction
PR 470
The xsl:stylesheet, xsl:transform, or xsl:package element may have a fixed-namespaces attribute making it easier to have the same namespace declarations in force throughout a stylesheet.
See 3.6.1 The fixed-namespaces Attribute
PR 489
The xsl:matching-substring and xsl:non-matching-substring elements within xsl:analyze-string may now take a select attribute in place of a contained sequence constructor.
See 17.1 The xsl:analyze-string Instruction
PR 534
A new serialization parameter escape-solidus is provided to control whether the character / is escaped as \/ by the JSON serialization method.
See 25.1 Creating Secondary Results
See 26.1 The xsl:output declaration
PR 542
A mode (called an enclosing mode) can be defined in which all the relevant template rules are children of the xsl:mode element. This is intended to allow a stylesheet design in which it is easier to determine which rules might apply to a given xsl:apply-templates call.
See 6.7.6 Enclosing Modes
PR 599
Simplified stylesheets no longer require an xsl:version attribute (which means they might not need a declaration of the XSLT namespace). Unless otherwise specified, a 4.0 simplified stylesheet defaults expand-text to true.
See 3.7 Simplified Stylesheet Modules
PR 635
The rules concerning the compatibility of schemas imported by different packages have been clarified. It is now explicitly stated that instructions that trigger validation must use the imported schema of the package in which validation is invoked. This differs from the current practice of some XSLT 3.0 processors, which may use (for example) a schema formed from the union of the imported schemas in all packages.
See 3.14 Importing Schema Components
See 25.4 Validation
PR 717
Capturing accumulators have been added; when streaming with a capturing accumulator, the accumulator-after has full access to a snapshot of the matched element node.
See 19.9 Capturing Accumulators
PR 718
To allow recursive-descent transformation on a tree of maps and arrays, a new set of built-in templates rules shallow-copy-all is introduced.
See 6.8 Built-in Template Rules
PR 740
A new attribute xsl:for-each-group/@split-when is available to give applications more complete control over how a sequence is partitioned
See 14 Grouping
PR 751
The xsl:mode declaration acquires an attribute as="sequence-type" which declares the return type of all template rules in that mode.
See 6.7.1 Declaring Modes
PR 1181
The [xsl:]xpath-default-namespace attribute can be set to the value ##any, which causes unprefixed element names to match in any namespace or none.
See 5.1.2 Unprefixed Lexical QNames in Expressions and Patterns
PR 1250
The strings used in the formatted number to represent a decimal separator, grouping separator, exponent separator, percent sign, per mille sign, or minus sign, are no longer constrained to be single characters.
See 5.5 Defining a Decimal Format
PR 1254
The rules concerning the interpretation of xsi:schemaLocation and xsi:noNamespaceSchemaLocation attributes have been tightened up.
See 25.4 Validation
See 25.4 Validation
PR 1306
An as attribute is available on the xsl:sequence instruction.
See 10.4.1 The xsl:sequence Instruction
PR 1361
The term atomic value has been replaced by atomic item.
See 2.1 Terminology
PR 1378
A function call at the outermost level can now be named using any valid EQName (for example fn:doc) provided it binds to one of the permitted functions fn:doc, fn:id, fn:element-with-id, fn:key, or fn:root. If two functions are called, for example doc('a.xml')/id('abc'), it is no longer necessary to put the second call in parentheses.
See 6.3.2.3 GNode Patterns
PR 1442
Default priorities are added for new forms of ElementTest and AttributeTest, for example element(p:*) and element(a|b).
See 6.3.3 Default Priority for Patterns
PR 1454
Duplicate xsl:include declarations within a stylesheet level are now ignored, preventing spurious errors caused by the presence of duplicate named components.
See 3.10.2 Stylesheet Inclusion
PR 1505
New variables err:stack-trace, err:additional, and err:map are available within an xsl:catch clause.
See 8.4 Try/Catch
PR 1530
The contents of a character map declared using xsl:character-map are now available dynamically via a new character-map function.
See 26.4 The character-map function
PR 1544
It is no longer an intrinsic error for a global variable to refer to itself; this is now permitted, for example in cases where the value of the global variable is a recursive inline function. Cases where self-reference would not make sense are covered by the existing rules on circularities: see 9.11 Circular Definitions.
See 9.5 Global Variables and Parameters
PR 1549
The input to the serializer can be defined using the select attribute of xsl:result-document as an alternative to using a sequence constructor.
See 25.1 Creating Secondary Results
PR 1560
The default value for the indent parameter is now defined to be no for all output methods other than html and xhtml.
See 26.2 Serialization parameters
PR 1617
Named item types can be declared using the new xsl:item-type element. This is designed to avoid repeating lengthy type definitions (for example function types) every time they are used.
See 5.4.1 Named Item Types
PR 1622
The rules for equality comparison have changed to bring keys into line with maps.
See 20.2.2 fn:key
New in 4.0.
See 20.2.3 fn:map-for-key
PR 1674
Composite sort keys are allowed in xsl:sort.
See 13.1.2 Comparing Sort Key Values
PR 1689
Composite merge keys are now allowed.
See 15 Merging
New in 4.0
See 15.5.2 fn:current-merge-key-array
PR 1694
The xsl:map instruction allows a select attribute as an alternative to the contained sequence constructor.
See 21.1 Map Instructions
The xsl:map-entry instruction, in common with other instructions, now raises error XTSE3185 (rather than XTSE3280) if both a select attribute and a sequence constructor are present.
See 21.1 Map Instructions
PR 1703
Ordered maps are introduced.
See 21.1 Map Instructions
PR 1708
Named record types are introduced.
See 5.4.2 Named Record Types
PR 1772
The default priority for a template rule using a union pattern has changed. This change may cause incompatible behavior.
See 6.3.3 Default Priority for Patterns
PR 1819
Different parts of a stylesheet may now use different imported schemas.
See 2.10 Stylesheets and XML Schemas
The standard attribute [xsl:]schema-role is introduced, to allow different parts of a stylesheet to use different schemas.
See 3.3 Standard Attributes
Different parts of a stylesheet may now use different imported schemas.
See 3.14 Importing Schema Components
A stylesheet can import multiple schemas with different schema role names.
See 3.14.1 Multiple Schemas
PR 1856
The rules for xsl:analyze-string have been adjusted to allow for new capabilities in regular expressions, such as zero-width assertions.
See 17.1 The xsl:analyze-string Instruction
PR 1858
The xsl:record instruction is introduced to make construction of record maps simpler.
See 21.1.1 Record Instruction
Attribute xsl:record/@xsl:duplicates is added to control duplicate keys handling in the xsl:record instruction.
See 21.1.2 Handling of duplicate keys
PR 1875
The xsl:apply-imports and xsl:next-match instructions automatically pass supplied parameters to the overridden template rule.
See 6.9 Overriding Template Rules
PR 1888
A new XSLT element, xsl:package-location is provide to indicate to the processor where the required package is to be found.
See 3.4.3 Locating Packages
PR 1929
The xsl:mode declaration acquires an attribute copy-namespaces which determines whether or not the built-in template rule copies unused namespace bindings.
See 6.7.1 Declaring Modes
PR 2006
A new function fn:apply-templates is introduced.
See 6.7.3 The apply-templates Function
New in 4.0
See 6.7.3.1 fn:apply-templates
PR 2008
The xsl:select instruction is new in 4.0.
See 10.4.2 The xsl:select Instruction
PR 2030
In order to reduce duplication between the XSLT and XQuery specifications, description of the validation process has been moved to the Functions and Operators specification.
See 25.4 Validation
PR 2123
A new attribute xsl:for-each-group/@merge-when is available to give applications control to create groups based on clustering, overlap, and networks.
See 14 Grouping
PR 2200
User-defined functions can now have names that are in no namespace. An unprefixed name appearing in a function call is resolved to a no-namespace function with matching local name in preference to a function in the standard fn namespace.
See 10.3 Stylesheet Functions
PR 2213
A new attribute trusted=yes|no is added to xsl:evaluate to indicate whether the XPath expression to be evaluated is trusted to access external resources. The default value is no, which may cause backwards incompatibility. Dynamic evaluation using xsl:evaluate is no longer an optional feature of the XSLT language.
See 10.5 Dynamic XPath Evaluation
The dynamic evaluation feature no longer exists; processor are now required to support the xsl:evaluate instruction.
See 27 Conformance
PR 2218
Numeric values of type xs:decimal are compared as decimals, without first converting to xs:double.
See 13.1.2 Comparing Sort Key Values
PR 2246
New in 4.0
See 17.2.1 fn:regex-groups
PR 2246
New in 4.0
See 17.2.1 fn:regex-groups
PR 2251
The xsl:text instruction can now have a select attribute, and it can take a sequence constructor as its content. The only remaining distinction between the xsl:text and xsl:value-of instructions is that whitespace text node children of xsl:text are treated as significant, rather than being stripped during stylesheet preprocessing.
See 11.4 Creating Text Nodes
The rules for xsl:text and xsl:value-of are integrated, allowing xsl:text to be used to construct all text nodes, whether the content is fixed or variable.
See 11.4.2 The xsl:text and xsl:value-of instructions
PR 2259
A new serialization parameter canonical is available to give control over serialization of XML, XHTML, and JSON.
See 25.1 Creating Secondary Results
See 26.1 The xsl:output declaration
PR 2274
XSLT-specific components of the dynamic context can now be retained in the captured context of a function item, in the same way as XPath-defined components of the dynamic context.
See 5.3.4 Additional Dynamic Context Components used by XSLT
In XSLT 4.0, the function item current-group#0 retains the value of the current group within its captured context.
See 14.2.1 fn:current-group
In XSLT 4.0, the function item current-grouping-key#0 retains the value of the current grouping key within its captured context.
See 14.2.2 fn:current-grouping-key
In XSLT 4.0, the function item current-merge-group retains the value of the current merge-key within its captured context.
See 15.5.1 fn:current-merge-group
In XSLT 4.0, the function item current-merge-key#0 retains the value of the current group within its captured context.
See 15.5.3 fn:current-merge-key
In XSLT 4.0, the function item regex-group#1 retains the value of the current captured substrings within its captured context.
See 17.2.2 fn:regex-group
In XSLT 4.0, the function item current#0 retains the value of the current item within its captured context.
See 20.5.1 fn:current
In XSLT 4.0, the function item current-output-uri#0 retains the value of the current output URI within its captured context.
See 25.3.1 fn:current-output-uri
PR 2283
The conformance requirements for extension attributes have been relaxed: the requirement to maintain strict conformance to the specification in the presence of extension attributes is now a should rather than a must, and extension attributes are allowed to modify the form of serialized output without limitation.
See 24.1 Extension Attributes
PR 2301
The attribute cdata is added to xsl:text and xsl:value-of to request serialization of a text node as a CDATA section.
See 11.4.2 The xsl:text and xsl:value-of instructions
See 11.4.3 Generating CDATA Sections
PR 2323
The outermost element of a simplified stylesheet need no longer be a literal result element, it can now be any instruction (including xsl:result-document). This allows a simplified stylesheet to produce JSON output as well as XML or HTML.
See 3.7 Simplified Stylesheet Modules
PR 2736
The xsl:mode/@typed attribute has been clarified and expanded to provide better control over the handling of items other than XNodes.
See 6.7.4 Declaring the Type of Values Processed by a Mode