sorry to be jumping in here but I was just wondering if you have a precise
definition of "business logic", mainly cause you seem like the kind of guy
who might actually have a meaningful definition, it being a phrase I hear
too often with nothing but a vague "feeling" of what it means in the
context.

OT, but what the heck.
Nobody has a precise but universal definition of the term
"business logic". One man's busines is someone else's
presentation.
Anyway, an attempt: there is business logic, presentation, and
a grey area.
Business logic is transactions, dealing with database access,
doing complicated calculations, drawing charts, perform spell
checking.
Presentation is placing stuff on a screen or paper, defining
fonts, colors, border line width and that stuff.
Grey area is doing totals per page in long paged forms, looking
up internationalized text for code values, calculating weekdays
from UNIX time stamps, localized formatting of numbers and so on.

Well, get it back on topic:
If it's easy to do in XSLT, it is often presentation.
If it seems to be hard or impossible in XSLT, in particular if
you feel the need to store calculated trees in variables and
run templates on them again, or if you have lots of xsl:if
and xsl:choose, or lots of recursive templates, it is probably
business logic.

Does this help?
J.Pietschmann