CS 6795 Semantic Web Techniques

Assignment 1


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1) Using the space below, recursively define a unary predicate (relation) evenlength in Prolog, which tests -- without using any (numeric) built-ins -- whether its list input argument Lst has an even length (so that a length predicate applied to input argument Lst would bind its output argument to 0 or 2 or 4 or ...). For readability, use anonymous variables where possible. Hint: First consider the base case(s) of the recursion. Test your predicate definition with at least the predicate calls evenlength([]), evenlength([a]), evenlength([a,b]), evenlength([a,b,c]), and evenlength([a,b,c,d]). In one sentence, below your definition, explain what it does for non-ground calls like evenlength([r,X,b,X]).

 

 

 

 

 

2) Consider the following oversimplified proposal of a node-labeled ordered tree for flights starting from a fixed airport, instantiated with leaves for a particular flight:

                          flight
                       /        |            \
 
                      /         |              \
             pilots   attendants    dynamic-information
             /     \                        /         |                          \
            /       \                    /            |                            \
  name     name         date        destination                 fare
    |  \            |  \              |              /          \                         \
    |    \          |   \             |             /            \                          \
  first last   first last   8/15    code           airport              730
    |       |       |       |                   /                     |         \
  A.  Rist   B.  Meyrs           /                       |             \
                                           /                                         \
                                       YFC                   city        province
                                                                      |                      |
                                                             Fredericton          NB


a)
Do the missing leaf data for attendants cause any (XML-level) issue?

b) Give a well-formed XML element for the tree using a pretty-print layout.

c) Give a b)-equivalent Prolog term.

d) Write a DTD that defines flights according to the original a)-tree or b)-element without structural generalization (e.g. there are exactly two pilots).

e) Extend the DTD such that one or more subelements for attendants must appear, each specifying a name in a form exactly as for the pilots.
 

For a) through e), use the space below and attach more sheets of paper as necessary (write on both sides of sheets).

 


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