in visual prolog there is "domains" section in a prolog program in which you can define types. Is there any similar thing in swi-prolog?
In visual prolog a type is defined like:
domains
NewType = thing1; thing2
No. But there is mode declaration in Mercury. Mercury is more than Prolog; it is a functional-logic language. Mercury still has a lot of Prolog syntax.
SWI-Prolog is a standard Prolog. It only uses mode declarations in documentation1 as information for the users. Such declarations can be placed in comments of modules for documentation-parsing programs to compile.
In standard Prologs, outside of comments, such declarations are only allowed (and reqired) in very special situations. The block predicate of Sicstus Prolog for instance requires them.
Block/1 is used for co-routing(lazy evaluation, delay etc.). I've only seen block used in one program in my life, PAKCS2, an interpreter for another functional-logic language. When the interpreter was ported to SWI, block/1 was not used.
1 Type and mode declarations in SWI Source Documentation
2 PAKCS, a program using the block/1 predicate (PAKCS is an implementation of the curry language.)