There has been considerable internal reorganization to support the introduction of XSLT
packages. In the expression tree, compile-time methods no longer have access to the
Executable, which represents the stylesheet as a whole, but rather get the same
information from the StylesheetPackage which represents a package (or unit of compilation).
The mechanisms for registering collations have been greatly simplified. All collations are
now known globally at the level of a Configuration. The
Configuration maintains a table of collations, where
collations can be registered by URI, and also a CollationURIResolver, where collation
URIs can be handled programmatically. The ability to define collations locally for a
particular query or stylesheet is discontinued; in general, the methods that permitted this
have been deprecated, and if they are used, they cause the collation to be registered at the
Configuration level. The default collation URI can however still be defined on
a per-query or per-stylesheet level (indeed, in XSLT it can be defined for any element within
a stylesheet, and for XQuery it can be defined for each module making up a query).
The implementation of regular expressions has changed, to reduce the incidence of stack overflows caused by backtracking. Saxon is now better at detecting expressions where backtracking cannot arise (which eliminates the need to keep data for the purpose of backtracking), and where if does arise, the depth of recursion now depends only on the complexity of the regular expression, and not on the length of the input string.
The implementation of maps has changed. It is now based on a hash trie data structure, specifically a cut-down version of the open source Java hash trie implementation by Michael Froh. The new implementation gives comparable timings for initial building of a map and for map retrieval, and substantially better times for workloads where additions to the map and retrievals are intermixed; the performance of map:remove() is vastly improved.
The SequenceIterator interface has
changed so that it no longer supports the methods
position(). This means that during normal expression processing, there is no
longer a need for every iterator to keep track of the context item and context position. These
values are now maintained only when the iterator is used as the current focus, that is, when
it is stored in the XPathContext object,
and this is achieved by wrapping the
SequenceIterator in a FocusTrackingIterator that maintains
In Saxon 9.5, some interfaces such as SequenceIterator were defined as parameterized (generic) types, on the same model as
collections and iterators in the standard Java class library. In 9.6, an attempt was made to
complete this process, and to apply it also to Sequence and its subclasses. This attempt was eventually abandoned because it led to
excessive complexity and excessive numbers of compilation warnings, and was proving to give
very little benefit, largely because most uses of these interfaces are in fact generic: they
apply to all sequences of items, not to sequences of specific kinds of item. So SequenceIterator has reverted to being a
non-parameterized class. Generics are used, however, in the interface for reflexive calling of
Java extension functions, where types such as
now be used to indicate the expected type precisely, giving much better type checking.