Daniel@0: # module uripattern
Daniel@0: 
Daniel@0: by Samer Abdallah, UCL, 2014
Daniel@0: 
Daniel@0: 
Daniel@0: This directory contains several alternative implementations of a small URI grammar
Daniel@0: which supports both generation and parsing (pattern-matching) of URIs.
Daniel@0: 
Daniel@0: There are two variants of the language. The earlier design is quite flexible but
Daniel@0: leads to heavily non-deterministic parsing, which is perhaps not what one wants
Daniel@0: for URI computations which might potentially be called very frequently. The later
Daniel@0: design reduces or eliminates this non-determinism, depending on the implementatation.
Daniel@0: 
Daniel@0: ### Grammar
Daniel@0: 
Daniel@0: We describe the pattern grammar in terms of an algebraic datatype for the pattern language.
Daniel@0: 
Daniel@0: 
Daniel@0: 	uri_pattern ---> prefix:uri_part
Daniel@0: 	               ; uri_part.
Daniel@0: 
Daniel@0: 	P :: prefix :- rdf_current_prefix(P). % any registered prefix atom
Daniel@0: 	M :: macro_invocation :- uripattern:def(M,_).
Daniel@0: 
Daniel@0: 	uri_part ---> \macro_invocation
Daniel@0: 	            ; uri_part/uri_part   % slash separated concatenation
Daniel@0: 					; uri_part+uri_part   % direct concatenation
Daniel@0: 				   ; num(number)         % decimal repn of number
Daniel@0: 					; enc(atomic)         % HTML form-encoded atom
Daniel@0: 					; atm(atomic)         % any atomic value
Daniel@0: 					; <any ground atom>
Daniel@0: 					.
Daniel@0: 
Daniel@0: The more deterministic grammar removes direct concatenation and arbitrary atom parsing
Daniel@0: but adds a tail/1 functor to capture all the remaining characters in the URI:
Daniel@0: 
Daniel@0: 	uri_part ---> \macro_invocation
Daniel@0: 	            ; uri_part/uri_part   % slash separated concatenation
Daniel@0: 				   ; num(number)         % decimal repn of number
Daniel@0: 					; enc(atomic)         % HTML form-encoded atom
Daniel@0: 					; tail(atomic)        % matches rest of URI
Daniel@0: 					; <any ground atom>
Daniel@0: 					.
Daniel@0: 
Daniel@0: This grammar as written is not quite strict enough to enforce the rule that any tail/1
Daniel@0: term must be the last thing in the pattern. The implementations are slightly less strict
Daniel@0: than this this specification.
Daniel@0: 
Daniel@0: 
Daniel@0: ### Example
Daniel@0: 
Daniel@0: Given the following declarations:
Daniel@0: 	
Daniel@0: 	:- rdf_register_prefix(eg,'http://wwww.example.org/').
Daniel@0: 	uripattern:def(matrix(X,Y),num(X)/num(Y)).
Daniel@0: 
Daniel@0: Then URIs can be generated as follows:
Daniel@0: 
Daniel@0: 	pattern_uri(eg:home,A).
Daniel@0: 			~> A='http://www.example.org/home'
Daniel@0: 	pattern_uri(eg:files/tail('home/chomsky/.profile'),A).
Daniel@0: 			~> A='http://www.example.org/files/home/chomsky/.profile'
Daniel@0: 	pattern_uri(eg:people/enc('Chomsky, N')/pets,A).   
Daniel@0: 			~> A='http://www.example.org/people/Chomsky%2c%20N/pets'
Daniel@0: 	pattern_uri(eg:chessboard/matrix(3,6),A).
Daniel@0: 			~> A='http://www.example.org/chessboard/3/6'
Daniel@0: 
Daniel@0: URIs can also be parsed, eg as follows
Daniel@0: 
Daniel@0: 	pattern_uri(eg:files/tail(Path),       'http://www.example.org/files/home/chomsky/.profile').
Daniel@0: 			~> Path=
Daniel@0: 	pattern_uri(eg:people/enc(Name)/pets,  'http://www.example.org/people/Chomsky%2c%20N/pets').
Daniel@0: 			~> Name='Chomsky, N'
Daniel@0: 	pattern_uri(eg:chessboard/matrix(X,Y), 'http://www.example.org/chessboard/3/6').
Daniel@0: 			~> X=3, Y=6
Daniel@0: 
Daniel@0: 
Daniel@0: ### Implementations
Daniel@0: 
Daniel@0: There are several implementations:
Daniel@0: 
Daniel@0: uripattern\_constraint : Works by splicing atoms and uses delayed goals to handle arbitrary modes.
Daniel@0: 
Daniel@0: uripattern\_string : Works by splicing strings.
Daniel@0: 
Daniel@0: uripattern\_atom : Works by splicing atoms.
Daniel@0: 
Daniel@0: uripattern\_dcg :	Converts URI to and from a list of codes and uses a DCG.
Daniel@0: 
Daniel@0: uripattern\_detdcg : A more deterministic DCG
Daniel@0: 
Daniel@0: uripattern\_detstring : A more deterministic version of string splicing.
Daniel@0: 
Daniel@0: