The text in section 18.2.5 is:

"If a dynamic error occurs when evaluating the initial-value expression of xsl:accumulator, or the select expression of xsl:accumulator-rule, then..."

However, an accumulator rule can also have a sequence constructor, instead of a select expression.

I think this is implied (I mean, it doesn't make sense if we meant an error in the sequence constructor should be raised in an unpredictable way), but I suggest we make it explicit.

I propose something along those lines:

"If a dynamic error occurs when evaluating the initial-value expression of xsl:accumulator, or the select expression or sequence constructor of xsl:accumulator-rule, then..."