XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (765 page)

FORX0003

Regular expression matches zero-length string

The functions
replace()
and
tokenize()
disallow use of a regular expression that would match a zero-length string. This rule exists because there is no obviously correct interpretation of what such a regular expression should mean.

FORX0004

Invalid replacement string

Indicates an error in the string supplied as the third argument of the
replace()
function. If the string contains a
\
character, this must be followed by either
\
or
$
, and if the string contains a
$
that is not preceded by a
$
, then it must be followed by a digit.

FOTY0012

Argument node does not have a typed value

Raised when the
data()
function is called supplying an element which according to the schema has element-only content. Such an element has no typed value. The call on
data()
might be implicit in some other operation that atomizes its operands.

XPDY0002

Evaluation of an expression relies on some part of the dynamic context that has not been assigned a value

For example, within a stylesheet function there is no context item, so a reference to
.
or
position()
will cause this error.

XPDY0050

The dynamic type of the operand of a treat expression does not match the type specified by the treat expression

The
treat as
expression is an assertion: when you say
$x treat as xs:integer
, you are asserting that at runtime, the variable
$x
will contain an
xs:integer
. If you get it wrong, and the variable contains some other value, this is the error that will be reported.