> What is wrong with my syntax that uses params? Are params allowed in
> Xpath expression?

yes but as in most languages, variables hold values not fragments of
language syntax. In C (or java or ...) you can't put part of an
expression like " + 1" into a string variable x and then just use
1 x
to have it evaluate to 2.

/tr_string[@str=$str]/$toLang

is legal syntax but as the expression  $toLang doesn't depend on teh
context node it just produces a sequence of multiple copies of $toLang
as many  as there are nodes in document('')/*/trans:tr/tr_string[@str=$str]


David

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