[xsl] XSLT result tree fragment, with XSLT 3.0 and xsl:variable

["Mukul Gandhi mukulg@xxxxxxxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi all,
   While comparing the, data models of XPath 1.0 and 3.1 languages (in the
context of XSLT transformations), I noticed that, XSLT 3.0 doesn't have
(i.e, it doesn't define) a data type named as "result tree fragment"
Whereas, the data type "result tree fragment" is available with XSLT 1.0.

With respect to this topic, I've been comparing the semantics of XSLT
xsl:variable instruction within 1.0 and 3.0 versions of XSLT language.

1) From the XSLT 1.0 spec
A variable is a name that may be bound to a value. The value to which a
variable is bound (the value of the variable) can be an object of any of
the types that can be returned by expressions.
There is a region of the stylesheet tree within which the binding is
visible.

Result Tree Fragments
Variables introduce an additional data-type into the expression language.
This additional data type is called result tree fragment. A variable may be
bound to a result tree fragment instead of one of the four basic XPath
data-types (string, number, boolean, node-set). A result tree fragment
represents a fragment of the result tree.

2) From the XSLT 3.0 spec
The value of the variable is computed using the expression given in the
select attribute or the contained sequence constructor.

I think, from the point of view of XSLT language in general, "result tree
fragment" (from XSLT 1.0) and "sequence constructor" (from XSLT 3.0) both
serialize into the XSLT transformation's output (which typically would be
XML for this discussion). The XSLT 3.0 sequence constructor, shall result
in a value with a XPath 3.1 data type item()+. The XSLT 3.0 language,
defines "sequence constructor" as : A sequence constructor is a sequence of
zero or more sibling nodes in the stylesheet that can be evaluated to
return a sequence of nodes, atomic values, and function items.

It seems to me that, XSLT 1.0's "result tree fragment" (before being
serialized to the output XML) is a well-formed XML fragment. Whereas, XSLT
3.0's sequence constructor is also a well-formed XML fragment, that
evaluates to a sequence of nodes, atomic values, and function items. Other
than, the XPath 3.1 function items (which is not available with XSLT
1.0/XPath 1.0), XSLT 3.0's sequence of nodes and atomic values looks to me,
an intermediate compiler representation that is finally transformed into
the XML document available as a result of XSLT transformation.

Any thoughts about this topic, shall be useful to know.


-- 
Regards,
Mukul Gandhi