The Java compiler itself is highly skilled in guessing the various meanings of the period character as separator between packages, subpackages, classes, inner classes, and methods and variables.
Here is what the thing that they're talking about in the excerpt looks like:
package com.horstmann.corejava // an example of a Java package
Employee.getSalary() // an example of a method call in Java
I asked my American friend why there was no article in front of separator and his answer was, first of all, that the sentence sounded completely fine to him and that you could put a definite article there, but you don't need to. As to why that was the case, no explanation followed.
Later on, he added that this is more like saying what the role is, not what the thing itself is. Alright, that makes total sense, but is there some sort of rule of thumb that can help you determine whether to use an article or leave it out altogether (whether we're talking about a role or not a role)? Obviously, the author could have gone with the "article" possibility (I don't see anything wrong with that), but he evidently didn't choose to go that way. There must have been something that prompted him to forgo sticking in an article. So, I'm really curious as to what was going on in his head at that moment and what exactly prompted him to make the decision that he made.
If you have anything to say about this grammar problem, please feel free to share your thoughts and ideas.