Hi Joseph,
I've added the discussed Xalan Java OpMap component design
information within the page,
https://xalan.apache.org/xalan-j/design/design2_0_0.html (within XPath
Module section).
On Mon, May 18, 2026 at 12:17 AM Joseph Kesselman via dev
<[email protected]> wrote:
>
> Good analysis, Mukul, though perhaps a bit kinder to us than we deserve.
> Probably worth adding to our official documentation.
>
> The xpath and XSLT intermediate representation was originally designed for
> interpretive Xalan. One of the reasons it is so compact is that PCs were much
> smaller and slower at the time so storage and access efficiency was crucial.
> (The same reason DTM its designed essentially at the byte level for
> compactness.) But compactness can also buy performance advantages; it's as
> close to C or ASM data models as Java let us get.
>
> When Sun donated their xslt compiler to Apache, the IBM / Apache team
> adjusted it to share this representation so it could be integrated with
> Xalan. I don't recall how much the Xalan front end had to change to support
> that; not a great deal, I think.
>
> There could certainly be better choices. I've mentioned some of them in past
> discussion of IBM Research's Xylem processor.
--
Regards,
Mukul Gandhi
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