I'm just a Prolog beginner, but this:

#+begin_src prolog
edge(a,b).
edge(a,e).
edge(b,d).
edge(b,c).
edge(c,a).
edge(e,b).
tedge(Node1,Node2) :-
        edge(Node1,SomeNode),
        edge(SomeNode,Node2).
#+end_src

keeps giving me this:

executing Prolog code block...
executing Prolog source code block
org-babel-execute:prolog: Wrong type argument: char-or-string-p, ni

BTW, should it be

(eval-after-load 'org
  '(require 'ob-prolog))

or 

(eval-after-load "org"
  '(require 'ob-prolog))

. . . org in quotes?

On Thu, May 14, 2015 at 5:03 PM, Bjarte Johansen <bjarte.johansen@infomedia.uib.no> wrote:

> On 14 May 2015, at 20:22, Puneeth Chaganti <punchagan@gmail.com> wrote:
>
> On Thu, May 14, 2015 at 11:41 PM, Lawrence Bottorff <borgauf@gmail.com> wrote:
>>
>> Confused by the requirement:
>>
>> ;; To activate ob-prolog add the following to your init.el file:
>> ;;
>> ;;  (eval-after-load 'org
>> ;;    '(require 'org-prolog))
>
>
> I'm guessing its a typo and should be ob-prolog. The file provides ob-prolog.

Yes, I typed it wrong. Thank you for bringing it to my attention. I also discovered that it is better to use `org-babel-do-load-languages’ instead as well. I will change the recommendation tomorrow.

Regards,
Bjarte