[DTB] missing string predicates?

to compare if number N1 is less than N2

pred:numeric-less-than(N1 N2)

to compare if string S1 is less than S2

pred:numeric-less-than(func:compare(S1 S2) 0)

I would prefer

pred:string-less-than(S1 S2)

I propose we add

pred:string-equal
pred:string-not-equal
pred:string-greater-than
pred:string-less-than
pred:string-greater-than-or-equal
pred:string-less-than-or-equal

I also propose we either
a. remove func:compare

or

b. rename to func:string-compare, and add
func:numeric-compare
func:date-time-compare
... and so on for all builtin types that are comparable