SAXON home page

SAXON: Change History

This file describes changes for versions 7.0 and later. For changes prior to version 7.0, see

Changes in version 7.1 (2002-04-30)


This version of Saxon has been modified and tested to work with JDOM beta 0.8 and with FOP 0.20.3. In both cases, code changes were needed to work with these versions, and I have not tested whether the code still works with earlier versions; the chances are that it doesn't.

Error clearance

In general, bugs that have been cleared in Saxon 6.5.1 or Saxon 6.5.2 have also been cleared in this release. For details of the clearance of specific bugs, see the bug tracker at Sourceforge. Remember that closed bugs are not listed unless you ask for them.

Multiple output documents

The href attribute of xsl:result-document is now interpreted as a relative URI, relative to the system ID of the principal result document. This works only where the system ID of the principal output is known, and uses the "file://" protocol. The result document is no longer created relative to the current working directory, for security reasons (it causes problems when executing an untrusted stylesheet in a servlet environment).

Note that when Saxon is invoked from the command line, the -o option should be used to specify the principal output destination. This will ensure that a suitable system ID is available. If the result document is sent to the standard output stream (even if this is redirected to a file), Saxon will not know the system identifier and will therefore be unable to create a secondary output destination using a relative URI. It is still possible, of course, to specify an absolute URI as the value of the href attribute - note that this must be a URL, not a filename, so it will typically start with file://.

It is now possible to specify an OutputURIResolver to be used to resolve the URI specified in the href attribute of the xsl:result-document element. This will be used in place of the standard output URI resolver. The OutputURIResolver is called when writing of the output document starts, at which point it must return a JAXP Result object to act as the output destination. It is called again when writing of an output document is complete. You can nominate an OutputURIResolver by calling ((Controller)transformer).setOutputURIResolver(new UserOutputResolver()), or by calling factory.setAttribute("", new UserOutputResolver()).

If the -t option is used, a message is written to the standard error output identifying the files written using using xsl:result-document.

It is now an error to use xsl:result-document when the current output destination is a temporary tree.

XSLT changes

The meaning of the ALLOW_EXTENSION_FUNCTIONS attribute in the TransformerFactory has been extended so that setting the value to false also disables extension elements and the creation of multiple output files. This is because all these operations carry similar risks when a servlet is allowed to execute untrusted stylesheets.

Added support for the separator attribute of <xsl:copy-of>.

The current() function may now be used in a pattern (specifically, within a predicate). Its value is the node being tested against the pattern. For example, match="*[*[name()=name(current())]" matches any element that contains another element with the same name.

A global variable or parameter may now be used in the match pattern of xsl:template, provided that it does not cause a circularity (that is, it must be possible to evaluate the variable without calling xsl:apply-templates)

A global variable or parameter may now be used in the match pattern or the use expression of xsl:key, provided that it does not cause a circularity (that is, it must be possible to evaluate the variable without using the key() function against the key being defined)

The key() function may now be used in the use or match attributes of xsl:key, provided the key definitions are not circular. (For example, key k1 can be defined in terms of key k2, provided that k2 is not defined in terms of k1.)

The group-ending-with attribute of xsl:for-each-group is implemented. It is especially useful where the last node in each group carries some kind of marker, for example continued="no".

Added attribute default="yes"|"no" to saxon:collation, to specify whether this collation should be used as the default collation. If more than one collation is specified as the default, the last one wins. If no default collation is specified, Unicode codepoint collation is used. The default collation is used by the compare() function if no third argument is supplied, by xsl:sort if no collation is specified (for data type text or string), and also by the comparison operators =, !=, <, >, etc.

The collation name is now a URI, not a QName.

Sorting and comparison according to Unicode codepoints can be achieved by setting up a collator as <saxon:collation name="unicode" class="net.sf.saxon.sort.CodepointCollator"/>

XPath changes

The implementation of the "and" and "or" operators has reverted to two-valued logic, since three-valued logic didn't make it into the published XPath 2.0 working draft. (Actually, it seems 3-valued logic wasn't working in Saxon 7.0 anyway).

Changed the "==" and "!==" operators to "is" and "isnot".

Changed string literals to allow the delimiting quote marks to be doubled. For example, <xsl:value-of select="'[He isn''t]'"/> displays the string [He isn't]

Changed the some and every expressions to allow multiple range variables, for example some $i in //I, $j in //J satisfies $i = $j

Implemented the singleton value-comparison operators (eq, ne, gt, lt, ge, le). These return an error if applied to a sequence containing more than one item, and return the empty sequence if either operand is an empty sequence; when applied to singletons, they return the same result as the XPath 1.0 operators (=, !=, etc).

Less-than and greater-than comparisons between nodes and/or strings now do a lexicographic comparison using the default collating sequence; at XPath 1.0 they did a numeric comparison. A warning is output in this situation (and one or two other situations, but not all) to advise of the backwards incompatibility.

The rules for deciding when path expressions need to be sorted have been revised. As a result many cases now require no sort where previously a sort was done. Examples of such expressions include a/b/c, .//a, $x[1]/a, //@a. In addition, most path expressions that return results in reverse document order are now sorted by a simple reversal, which is much faster than a full sort.

There's a temporary bug in that path expressions returning namespace nodes don't always return them in document order. I'm awaiting resolution of the XPath 2.0 data model rules before fixing this.

Suppress lazy evaluation of assignable variables. (This was designed to prevent a stack overflow, it didn't succeed, but it seems a good idea anyway).

Added the ability for a Source object to be supplied as the value of a stylesheet parameter or as the value returned by an extension function.

Added dateTime and date data types. Initially the only operations supported are the currentDateTime function, the dateTime and date constructors, and conversion between strings, dates, and dateTimes in both directions. Conversion to string uses the timezone of the current locale.

Implemented comparisons (equals, less-than, etc) between dates and dateTimes. Also implemented sorting. The data-type of xsl:sort may take the two values "text" or "number" (which are treated as synonyms of xs:string and xs:double) or any XML Schema built-in data type for which sorting is supported. The values in the sequence to be sorted are converted to this data type (using the same rules as for cast as) and the rules for this data type determine the sort order.

Note that (as required by the XML Schema specification) dateTime values are normalized to UTC. The original timezone specified when the dateTime was constructed is not retained. If no timezone is present, this fact is remembered. Such a dateTime is compared with other dateTimes as if it were a UTC dateTime.

Implemented the instance of operator (including the instance of only variant): for example if ($x instance of xs:integer *) then x else y. The types that are currently supported are the 19 primitive schema types (the namespace may be either of the two namespaces permitted in XML Schema Part 2), the derived type xs:integer, the node types document, element, attribute, text, comment, processing-instruction, or namespace, and the abstract types node, and item. (There is no syntax currently for the general numeric type or for the general atomic type). The type name may be followed by one of the qualifiers "*", "+", or "?" to indicate the number of occurrences; if there is no qualifier, there must be exactly one occurrence. The more sophisticated forms of type-checking, using schema-defined complex types, are not yet supported.

Implemented the cast as data-type expression, for example cast as xs:boolean($x). The conversion rules are the same as those which apply implicitly when a value is supplied in a context where a different type is expected.

Implemented the treat as data-type expression. This doesn't actually have much use in an XSLT context, where type conversion is performed implicitly when required, and the semantics of the expression are probably not correctly implemented at this stage: the specification is still evolving.

New XPath API

A new API has been introduced for executing XPath expressions. This is simpler and safer than the API provided in previous releases, which was essentially improvised from implementation classes rather than being designed top-down as an interface suitable for application use. The API is loosely modelled on the proposed DOM Level 3 API for XPath.

The new API uses the class net.sf.saxon.xpath.XPathEvaluator. This class provides a few simple configuration interfaces to set the source document, the static context, and the context node, plus a number of methods for evaluating XPath expressions. The static context can be omitted if the expression does not use namespaces, external variables, or extension functions. If the expression uses namespaces, an instance of StandaloneContext can be supplied, allowing the required namespaces to be declared either explicitly, or by reference to the in-scope namespaces of some Node.

There are two methods for direct evaluation, evaluate() which returns a List containing the result of the expression (which in general is a sequence), and evaluateSingle() which returns the first item in the result (this is appropriate where it is known that the result will be single-valued). The results are returned as NodeInfo objects in the case of nodes, or as objects of the most appropriate Java class in the case of atomic values: for example, Boolean, Double, or String in the case of the traditional XPath 1.0 data types.

It is also possible to prepare an XPath expression for subsequent execution, using the createExpression() method on the XPathEvaluator class. This is worthwhile where the same expression is to be executed repeatedly. The compiled expression is represented by an instance of the class net.sf.saxon.xpath.XPathExpression, and it can be executed repeatedly, with different context nodes. However, the compiled expression is bound to one particular source document (this is to ensure that the same NamePool is used).

The design principle of this API is to minimize the number of Saxon classes that need to be used. Apart from the NodeInfo interface, which is needed when manipulating Saxon trees, only the four classes XPathProcessor, XPathExpression, StandaloneContext, and XPathException are needed. For convenience, XPathException and StandaloneContext have been moved to the net.sf.saxon.xpath package.

If you want to use extension functions or variables you will need to create your own implementation of StaticContext. Although this interface has been greatly simplified, this is still not to be attempted lightly.

The old APIs for executing expressions still exist for the time being, but they are likely to be less stable.

Internal changes

Changed ContentEmitter to check in startElement() that qname and local-name are both supplied; this checks against parser configuration errors. This change could (should?) be retrofitted to the 6.5 branch. The change also uses a stack of namecodes so that endElement() doesn't need to look up the names in the name pool. In implementing this change, I discovered that Saxon depends on the XML parser passing the QName argument to the startElement() call, something which according to the SAX2 specification is optional. However, all known parsers supply this argument, and the code changes to cope with its absence would damage performance, so I have simply documented this as a dependency on the parser.

Implemented infrastructure for data type support:

I have changed the implementation of temporary trees (result tree fragments). The FragmentValue class has disapeared. This delayed the construction of an actual tree until it the tree was actually used as a node-set: the effect was to optimize simple uses of temporary trees but at considerable cost to the more general usage which is now permitted in XSLT 2.0. Also, the introduction of tinytrees has reduced the value of this optimization. Therefore, a temporary tree is now constructed immediately as a real tree.

A side-effect of this change is that when disable-output-escaping is used while writing nodes to a tree, the instructions to switch escaping on and off are recorded in the tree in the form of the processing instructions defined by JAXP 1.1. Previously, these instructions were recorded in a form that kept the information through an xsl:copy-of instruction, but lost the information if the tree was processed in any other way. Note that the behavior of "sticky d-o-e" (that is, the effect of disabling output escaping when writing to a temporary tree) is currently an open issue in XSLT 2.0.

The indexes associated with keys are no longer referenced from each document instance, they are handled externally. This makes it easier to share the same index implementation across all the different document implementations. The indexes are now held by the KeyManager. It uses a WeakHashMap to ensure that when a document is removed from memory by the garbage collector, its indexes are removed too.

The mechanism for keeping stylesheet signatures in the namepool has been removed. It caused a creeping "memory leak" in continuously running services, and is not really needed. It was invented to allow namepools to be copied, but this facility has never been properly documented or tested. Instead, there is now a simple check that the source document and stylesheet are using the same namepool. (This change, or a simplified version of it, has also been made to 6.5.2).

The StaticContext interface has been greatly simplified, reducing duplication and making it easier to create a new implementation of this interface. This has been achieved partly by doing some work in the XPath ExpressionParser that was previously done in the StaticContext, and partly by changing those functions such as format-number() and sort() that only work in an XSLT context to check that the context is indeed XSLT before accessing the context information.

SQL extension

At the suggestion of Claudio Thomas [], I have extended the sql:query instruction to allow the attribute disable-output-escaping="yes|no". This is useful where the database content being retrieved contains XML or HTML markup that is to be preserved in the output. Use this with care; it disables escaping for all the rows and columns retrieved, some of which may contain special characters such as "<" and "&" that do need to be escaped.

This change has not been tested.

Extension functions

Added extension functions: saxon:parse() and saxon:serialize(). These allow conversion of a string containing well-formed XML to a tree structure, and vice-versa.

Added extension functions: saxon:string-to-unicode() and saxon:unicode-to-string(). These allow conversion between a string and a sequence of integers representing the Unicode values of the characters in the string.

Added extension functions saxon:pause-tracing() and saxon:resume-tracing().

The return value from an extension function may now be an implementation of java.util.List, representing a sequence. The members of the List must all implement

An argument to an extension function may now be the class, or a subclass. If the supplied value is a sequence, the first node in the sequence is passed to the function; it is an error if there is no node in the supplied sequence, or if the node is of the wrong type.

The rules for calling extension functions with a sequence-valued argument have been clarified, and some new options are permitted, e.g. declaring the argument as java.util.List. The possibilities have not been extensively tested.

Implemented memo functions (thanks to Robert Brotherus for the suggestion). If you specify the attribute saxon:memo-function="yes" on xsl:function, Saxon will keep a cache that maps the supplied argument values to the result of the function, and if the function is called twice with the same arguments, the original result will be returned without re-evaluating the function. Don't use this option on a function that depends on the context, or on a function that creates a new temporary tree and is required to create a new instance each time. Also note that there are cases where it may be faster to re-evaluate the function than to do the lookup; this is especially true if the argument is a large node-set.

Changes in version 7.0 (2001-12-20)

This version introduces initial support of features defined in working drafts of XSLT 2.0 and XPath 2.0.

Version 7.0 should be regarded as an experimental alpha release. For production use, please continue to use Saxon 6.5

The Saxon package name has changed from com.icl.saxon to net.sf.saxon. Any applications that use Saxon java classes directly (rather than relying on the JAXP interface) will need to be modified. Note that this also affects the settings of the system properties javax.xml.parsers.SAXParserFactory and javax.xml.transform.TransformerFactory.

The entry point from the command line has changed from com.icl.saxon.StyleSheet to net.sf.saxon.Transform.

The namespace URI for saxon extensions has changed from to Note that many extensions have been withdrawn, as they are superseded by facilities in XPath 2.0 and/or XSLT 2.0.

To allow coexistence, the name of the JAR file for this release has changed to saxon7.jar. The SQL extensions are now in a separate JAR file, saxon7-sql.jar. A transformation can now be executed directly from the JAR file using the command java -jar saxon7.jar in place of java net.sf.saxon.Transform.

Saxon now requires JDK 1.2 or later to run. In consequence, Saxon will no longer work with the Microsoft Java VM, and the Instant Saxon version of the product is therefore no longer available.

Because Saxon no longer runs with the Java VM, it can now be run as an applet within Internet Explorer only if the Sun Java plug-in is installed. You can get this from This may require some configuration changes because of the differences in security policy.

The following sections summarize the main new features. These assume familiarity with the XPath 2.0 and XSLT 2.0 specifications; however, summaries of the new syntax for expressions and XSLT elements are included in this package.

XPath 2.0 Data Model and Language

XSLT 2.0 features

Function Library

I have made the following changes to the function library:

Significant Omissions

In general, features of XSLT 2.0 and XPath 2.0 not listed above have not been implemented. In particular, these include:

Internal changes

As might be expected, the Saxon code has undergone major change internally, which will affect any application making significant use of internal interfaces. Here are some of the highlights:

I have removed documentation of the saxon:trace extension attribute; it seems this hasn't been working for some time.

API changes

SQL extension elements

A new sql:query instruction has been added, to accompany the existing sql:connect, sql:insert, etc.


table The table to be queried (the contents of the FROM clause of the select statement). This is mandatory, the value is an attribute value template.
column The columns to be retrieved (the contents of the SELECT clause of the select statement). May be "*" to retrieve all columns. This is mandatory, the value is an attribute value template.
where The conditions to be applied (the contents of the WHERE clause of the select statement). This is optional, if present the value is an attribute value template.
row-tag The element name to be used to contain each row. Must be a simple name (no colon allowed). Default is "row".
column-tag The element name to be used to contain each column. Must be a simple name (no colon allowed). Default is "col".

The xsl:query instruction writes zero or more row elements to the current result tree, each containing zero or more column elements, which contain the data values.

Thanks to Claudio Thomas [] who supplied the original version of this code.

The SQL extensions are now contained in a separate JAR file, saxon7-sql.jar, which must be on the class path if these extensions are used.

Michael H. Kay
30 April 2002