could you please explain me the difference between rdfs:domain and rdfs:range with an example? and when should i use domain and when range? i have read h w3c rdf primer but i did not understand the difference
From a simplistic point of view, the domain and range properties are there to give you insight into the way that the property links a subject to an object.
In the case of the domain property, when you link a subject to an object using a property with this associated attribute, then the subject qualifies as a type of thing specified in the domain. For example, we look at a vocabulary and we see that the domain of our property is a Project. So, simply put, as long as the subject being described using the “name” attribute is a type of project (or could be a type of project), then you should have no problem going ahead using that term to describe that thing, because most other people will interpret that if something is described using this term, then it is a project. You'll find it is not only humans but also machines (or reasoners in this case) that make the same inferences.
The range works exactly like the domain, but with this one, it applies to the object of the statement and not the subject. A word of caution; you might at times come across instances where the domain or range applies to more than one thing. In this case, it means that the subject or object (domain or range) is all of the types specified (the intersection not the union).