XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (453 page)

For example, the expression:

means the same as:

Similarly, the expression:

means the same as:

It's a matter of personal style which one you choose in these cases. However, if the operator is something more complex than straight equality—for example, if you are comparing the two values using the
compare()
function with a non-default collation—then the only way to achieve the effect within XPath is to use a
some
or
every
expression.

Errors in
some
and
every
Expressions

Dynamic (runtime) errors can occur in
some
and
every
expressions just as in any other kind of XPath expression, and the rules are the same. But for these expressions the rules have some interesting consequences that are worth exploring.

Let's summarize the rules here:

• If a dynamic error occurs when evaluating the
  satisfies
  expression, then the
  some
  or
  every
  expression as a whole fails with an error.
  
• As soon as the system finds an item in the sequence for which the
  satisfies
  expression is true (in the case of
  some
  ) or false (in the case of
  every
  ), it can stop the evaluation. It doesn't need to look any further. This means that it might not notice errors that would be found if it carried on to the bitter end.
  
• The system can process the input sequence in any order that it likes. This means that if there is one item for which evaluating the
  satisfies
  expression returns
  true
  , and another for which it raises an error, then you can't tell whether the
  some
  expression will return
  true
  or raise the error.