To me I think it's streaming, because it enables transformations on
large data which simply were not possible before.
But it's probably the most complex, too.

On Thu, Oct 3, 2019 at 8:19 PM Graydon graydon@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Oct 03, 2019 at 04:59:28PM -0000, Liam R. E. Quin liam@xxxxxxxxxxxxxxxx scripsit:
> > While i was preparing for a course on XSLT 3 later this month, i
> > wondered whether other people would have favourite features that were
> > introduced in XSLT 3. I know i do.
> >
> > What do you find most useful? Or like the best?
>
> Maps.  I find maps are hands-down the single most useful thing in XSLT 3. (Even
> if that's technically 3.1.)
>
> xsl:mode can clearly do much more than I use it for, but the one-line
> identity template version is a boon to multi-pass processing.
>
> The general... compactness of expression?  I'm not sure what to call it.
>
> <xsl:variable as="xs:integer" name="splitPos" select="min($kids[label = $labelKeys] ! index-of($kids, .))" />
>
> is certainly *possible* in XSLT 1.0, but I'm pretty sure I couldn't
> write it like that.  Possibly better phrased as "it's been awhile since
> I was annoyed by the lack of function".
>
> -- Graydon