I find strange problem in Tamino Version 4.4.1.3.

In Tamino schema I have element client with boolean attribute deleted.
I set filter

/client[@deleted='false']

in Tamino X-Plorer and get right results (collection contains such elements).

In X-Query it also works: Here I get count of such elements
X-Query

count(/client[/client[@deleted='false']]) 

works well.

When I call Tamino XQuery Tool from X-Plorer auto generated from filter query is

for $q in input()/client[/client[@deleted='false']]
return $q

XQuery Tool indicates error:
INOXQE6373: Invalid comparison Types: boolean, string; line 2, column 42: =‘false’]] return $q

When I correct this query to

for $q in input()/client[/client[@deleted=false]]
return $q

I get empty result (but in fact collection should contain such elements).

in X-Query, there is not real typing, @boolean=‘false’ is a valid comparion there.
In XQuery, there is strong typing, i.e. you have to use
@boolean=false()
or - better reflecting the boolean datatype
not(@boolean)