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triple.c

/**
 * Copyright 2008 Digital Bazaar, Inc.
 *
 * This file is part of librdfa.
 * 
 * librdfa is Free Software, and can be licensed under any of the
 * following three licenses:
 * 
 *   1. GNU Lesser General Public License (LGPL) V2.1 or any 
 *      newer version
 *   2. GNU General Public License (GPL) V2 or any newer version
 *   3. Apache License, V2.0 or any newer version
 * 
 * You may not use this file except in compliance with at least one of
 * the above three licenses.
 * 
 * See LICENSE-* at the top of this software distribution for more
 * information regarding the details of each license.
 *
 * Handles all triple functionality including all incomplete triple
 * functionality.
 *
 * @author Manu Sporny
 */
#include "stdlib.h"
#include "string.h"
#include "stdio.h"
#include "rdfa_utils.h"
#include "rdfa.h"

rdftriple* rdfa_create_triple(const char* subject, const char* predicate,
   const char* object, rdfresource_t object_type, const char* datatype,
   const char* language)
{
   rdftriple* rval = (rdftriple*)malloc(sizeof(rdftriple));

   // clear the memory
   rval->subject = NULL;
   rval->predicate = NULL;
   rval->object = NULL;
   rval->object_type = object_type;
   rval->datatype = NULL;
   rval->language = NULL;

   //printf("SUBJECT  : %s\n", subject);
   //printf("PREDICATE: %s\n", predicate);
   //printf("OBJECT   : %s\n", object);
   //printf("DATATYPE : %s\n", datatype);
   //printf("LANG     : %s\n", language);
   
   // a triple needs a subject, predicate and object at minimum to be
   // considered a triple.
   if((subject != NULL) && (predicate != NULL) && (object != NULL))
   {
      rval->subject = rdfa_replace_string(rval->subject, subject);
      rval->predicate = rdfa_replace_string(rval->predicate, predicate);
      rval->object = rdfa_replace_string(rval->object, object);

      // if the datatype is present, set it
      if(datatype != NULL)
      {
         rval->datatype = rdfa_replace_string(rval->datatype, datatype);
      }

      // if the language was specified, set it
      if(language != NULL)
      {
         rval->language = rdfa_replace_string(rval->language, language);
      }
   }

   return rval;
}

void rdfa_print_triple(rdftriple* triple)
{
   if(triple->object_type == RDF_TYPE_NAMESPACE_PREFIX)
   {
      printf("%s %s: <%s> .\n",
         triple->subject, triple->predicate, triple->object);
   }
   else
   {
      if(triple->subject != NULL)
      {
         if((triple->subject[0] == '_') && (triple->subject[1] == ':'))
         {
            printf("%s\n", triple->subject);
         }
         else
         {
            printf("<%s>\n", triple->subject);
         }
      }
      else
      {
         printf("INCOMPLETE\n");
      }

      if(triple->predicate != NULL)
      {
         printf("   <%s>\n", triple->predicate);
      }
      else
      {
         printf("   INCOMPLETE\n");
      }
   
      if(triple->object != NULL)
      {
         if(triple->object_type == RDF_TYPE_IRI)
         {
            if((triple->object[0] == '_') && (triple->object[1] == ':'))
            {
               printf("      %s", triple->object);
            }
            else
            {
               printf("      <%s>", triple->object);
            }
         }
         else if(triple->object_type == RDF_TYPE_PLAIN_LITERAL)
         {
            printf("      \"%s\"", triple->object);
            if(triple->language != NULL)
            {
               printf("@%s", triple->language);
            }
         }
         else if(triple->object_type == RDF_TYPE_XML_LITERAL)
         {
            printf("      \"%s\"^^rdf:XMLLiteral", triple->object);
         }
         else if(triple->object_type == RDF_TYPE_TYPED_LITERAL)
         {
            if((triple->datatype != NULL) && (triple->language != NULL))
            {
               printf("      \"%s\"@%s^^%s",
                  triple->object, triple->language, triple->datatype);
            }
            else if(triple->datatype != NULL)
            {
               printf("      \"%s\"^^%s", triple->object, triple->datatype);
            }
         }
         else
         {
            printf("      <%s> <---- UNKNOWN OBJECT TYPE", triple->object);
         }

         printf(" .\n");
      }
      else
      {
         printf("      INCOMPLETE .");
      }
   }
}

void rdfa_free_triple(rdftriple* triple)
{
   free(triple->subject);
   free(triple->predicate);
   free(triple->object);
   free(triple->datatype);
   free(triple->language);
   free(triple);
}

#ifndef LIBRDFA_IN_RAPTOR
/**
 * Generates a namespace prefix triple for any application that is
 * interested in processing namespace changes.
 *
 * @param context the RDFa context.
 * @param prefix the name of the prefix
 * @param IRI the fully qualified IRI that the prefix maps to.
 */
void rdfa_generate_namespace_triple(
   rdfacontext* context, const char* prefix, const char* iri)
{
   rdftriple* triple =
      rdfa_create_triple(
         "@prefix", prefix, iri, RDF_TYPE_NAMESPACE_PREFIX, NULL, NULL);
   if(context->processor_graph_triple_callback)
     context->processor_graph_triple_callback(triple, context->callback_data);
}
#endif

/**
 * Completes all incomplete triples that are part of the current
 * context by matching the new_subject with the list of incomplete
 * triple predicates.
 *
 * @param context the RDFa context.
 */
void rdfa_complete_incomplete_triples(rdfacontext* context)
{
   // 10. If the [ skip element ] flag is 'false', and [ new subject ]
   //     was set to a non-null value, then any [ incomplete triple ]s
   //     within the current context should be completed:
   //
   // The [ list of incomplete triples ] from the current [ evaluation
   // context ] ( not the [ local list of incomplete triples ]) will
   // contain zero or more predicate URIs. This list is iterated, and
   // each of the predicates is used with [ parent subject ] and
   // [ new subject ] to generate a triple. Note that at each level
   // there are two , lists of [ incomplete triple ]s; one for the
   // current processing level (which is passed to each child element
   // in the previous step), and one that was received as part of the
   // [ evaluation context ]. It is the latter that is used in
   // processing during this step.
   unsigned int i;
   for(i = 0; i < context->incomplete_triples->num_items; i++)
   {
      rdfalist* incomplete_triples = context->incomplete_triples;
      rdfalistitem* incomplete_triple = incomplete_triples->items[i];
      
      if(incomplete_triple->flags & RDFALIST_FLAG_FORWARD)
      {
         // If [direction] is 'forward' then the following triple is generated:
         //
         // subject
         //    [parent subject]
         // predicate
         //    the predicate from the iterated incomplete triple
         // object
         //    [new subject]
         rdftriple* triple =
            rdfa_create_triple(context->parent_subject,
               (const char*)incomplete_triple->data, context->new_subject, 
               RDF_TYPE_IRI, NULL, NULL);
         context->default_graph_triple_callback(triple, context->callback_data);
      }
      else
      {
         // If [direction] is not 'forward' then this is the triple generated:
         //
         // subject
         //    [new subject]
         // predicate
         //    the predicate from the iterated incomplete triple
         // object
         //    [parent subject]
         rdftriple* triple =
            rdfa_create_triple(context->new_subject,
               (const char*)incomplete_triple->data, context->parent_subject, 
               RDF_TYPE_IRI, NULL, NULL);
         context->default_graph_triple_callback(triple, context->callback_data);
      }
      free(incomplete_triple);
   }
   context->incomplete_triples->num_items = 0;
}

void rdfa_complete_type_triples(
   rdfacontext* context, const rdfalist* type_of)
{
   // 6.1 One or more 'types' for the [new subject] can be set by
   // using @type_of. If present, the attribute must contain one or
   // more URIs, obtained according to the section on URI and CURIE
   // Processing, each of which is used to generate a triple as follows:
   //
   // subject
   //    [new subject]
   // predicate
   //    http://www.w3.org/1999/02/22-rdf-syntax-ns#type
   // object
   //    full URI of 'type'
   unsigned int i;

   rdfalistitem** iptr = type_of->items;
   for(i = 0; i < type_of->num_items; i++)
   {
      rdfalistitem* curie = *iptr;
      
      rdftriple* triple = rdfa_create_triple(context->new_subject,
         "http://www.w3.org/1999/02/22-rdf-syntax-ns#type",
         (const char*)curie->data, RDF_TYPE_IRI, NULL, NULL);
      
      context->default_graph_triple_callback(triple, context->callback_data);
      iptr++;
   }
}

void rdfa_complete_relrev_triples(
   rdfacontext* context, const rdfalist* rel, const rdfalist* rev)
{
   // 7. If in any of the previous steps a [current object  resource]
   // was set to a non-null value, it is now used to generate triples
   unsigned int i;

   // Predicates for the [current object resource] can be set by using
   // one or both of the @rel and @rev attributes.

   // If present, @rel will contain one or more URIs, obtained
   // according to the section on CURIE and URI Processing each of
   // which is used to generate a triple as follows:
   //
   // subject
   //    [new subject]
   // predicate
   //    full URI
   // object
   //    [current object resource]   
   if(rel != NULL)
   {
      rdfalistitem** relptr = rel->items;
      for(i = 0; i < rel->num_items; i++)
      {
         rdfalistitem* curie = *relptr;
      
         rdftriple* triple = rdfa_create_triple(context->new_subject,
            (const char*)curie->data, context->current_object_resource, 
            RDF_TYPE_IRI, NULL, NULL);
      
         context->default_graph_triple_callback(triple, context->callback_data);
         relptr++;
      }
   }

   // If present, @rev will contain one or more URIs, obtained
   // according to the section on CURIE and URI Processing each of which
   // is used to generate a triple as follows:
   //
   // subject
   //    [current object resource]
   // predicate
   //    full URI
   // object
   //    [new subject] 
   if(rev != NULL)
   {
      rdfalistitem** revptr = rev->items;
      for(i = 0; i < rev->num_items; i++)
      {
         rdfalistitem* curie = *revptr;
      
         rdftriple* triple = rdfa_create_triple(
            context->current_object_resource, (const char*)curie->data,
            context->new_subject, RDF_TYPE_IRI, NULL, NULL);
      
         context->default_graph_triple_callback(triple, context->callback_data);
         revptr++;
      }
   }
}

void rdfa_save_incomplete_triples(
   rdfacontext* context, const rdfalist* rel, const rdfalist* rev)
{
   unsigned int i;
   // 8. If however [current object resource] was set to null, but
   // there are predicates present, then they must be stored as
   // [incomplete triple]s, pending the discovery of a subject that
   // can be used as the object. Also, [current object resource]
   // should be set to a newly created [bnode]
   context->current_object_resource = rdfa_create_bnode(context);

   // If present, @rel must contain one or more URIs, obtained
   // according to the section on CURIE and URI Processing each of
   // which is added to the [local local list of incomplete triples]
   // as follows:
   //
   // predicate
   //    full URI
   // direction
   //    forward
   if(rel != NULL)
   {
      rdfalistitem** relptr = rel->items;
      for(i = 0; i < rel->num_items; i++)
      {
         rdfalistitem* curie = *relptr;

         rdfa_add_item(
            context->local_incomplete_triples, curie->data,
               (liflag_t)(RDFALIST_FLAG_FORWARD | RDFALIST_FLAG_TEXT));
         
         relptr++;
      }
   }
   
   // If present, @rev must contain one or more URIs, obtained
   // according to the section on CURIE and URI Processing, each of
   // which is added to the [local list of incomplete triples] as follows:
   //
   // predicate
   //    full URI
   // direction
   //    reverse
   if(rev != NULL)
   {
      rdfalistitem** revptr = rev->items;
      for(i = 0; i < rev->num_items; i++)
      {
         rdfalistitem* curie = *revptr;

         rdfa_add_item(
            context->local_incomplete_triples, curie->data,
               (liflag_t)(RDFALIST_FLAG_REVERSE | RDFALIST_FLAG_TEXT));

         revptr++;
      }
   }   
}

void rdfa_complete_object_literal_triples(rdfacontext* context)
{
   // 9. The next step of the iteration is to establish any
   // [current object literal];
   //
   // Predicates for the [current object literal] can be set by using
   // @property. If present, a URI is obtained according to the
   // section on CURIE and URI Processing, and then the actual literal
   // value is obtained as follows:
   char* current_object_literal = NULL;
   rdfresource_t type = RDF_TYPE_UNKNOWN;   

   unsigned int i;
   rdfalistitem** pptr;
   
   // * as a [plain literal] if:
   //   o @content is present;
   //   o or all children of the [current element] are text nodes;
   //   o or there are no child nodes; TODO: Is this needed?
   //   o or the body of the [current element] does have non-text
   //     child nodes but @datatype is present, with an empty value.
   //
   // Additionally, if there is a value for [current language] then
   // the value of the [plain literal] should include this language
   // information, as described in [RDF-CONCEPTS]. The actual literal
   // is either the value of @content (if present) or a string created
   // by concatenating the text content of each of the descendant
   // elements of the [current element] in document order.
   if((context->content != NULL))
   {
      current_object_literal = context->content;
      type = RDF_TYPE_PLAIN_LITERAL;
   }
   else if(strchr(context->xml_literal, '<') == NULL)
   {      
      current_object_literal = context->plain_literal;
      type = RDF_TYPE_PLAIN_LITERAL;
   }
   else if(strlen(context->plain_literal) == 0)
   {
      current_object_literal = (char*)"";
      type = RDF_TYPE_PLAIN_LITERAL;
   }
   else if((context->xml_literal != NULL) &&
           (context->datatype != NULL) &&
           (strlen(context->xml_literal) > 0) &&
           (strcmp(context->datatype, "") == 0))
   {
      current_object_literal = context->plain_literal;
      type = RDF_TYPE_PLAIN_LITERAL;
   }

   
   // * as an [XML literal] if:
   //    o the [current element] has any child nodes that are not
   //      simply text nodes, and @datatype is not present, or is
   //      present, but is set to rdf:XMLLiteral.
   //
   // The value of the [XML literal] is a string created by
   // serializing to text, all nodes that are descendants of the
   // [current element], i.e., not including the element itself, and
   // giving it a datatype of rdf:XMLLiteral.
   if((current_object_literal == NULL) &&
      (strchr(context->xml_literal, '<') != NULL) &&
      ((context->datatype == NULL) ||
       (strcmp(context->datatype,
               "http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral") == 0)))
   {
      current_object_literal = context->xml_literal;
      type = RDF_TYPE_XML_LITERAL;
   }
   
   // * as a [typed literal] if:
   //    o @datatype is present, and does not have an empty
   //      value.
   //
   // The actual literal is either the value of @content (if present)
   // or a string created by concatenating the value of all descendant
   // text nodes, of the [current element] in turn. The final string
   // includes the datatype URI, as described in [RDF-CONCEPTS], which
   // will have been obtained according to the section on CURIE and
   // URI Processing.
   if((context->datatype != NULL) && (strlen(context->datatype) > 0))
   {
      if(context->content != NULL)
      {
         current_object_literal = context->content;
         type = RDF_TYPE_TYPED_LITERAL;
      }
      else if(strcmp(context->datatype,
               "http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral") != 0)
      {
         current_object_literal = context->plain_literal;
         type = RDF_TYPE_TYPED_LITERAL;
      }
   }

   // TODO: Setting the current object literal to the plain literal in
   //       the case of xsd:string isn't mentioned in the syntax
   //       processing document.
   if((current_object_literal == NULL) && (context->datatype != NULL) &&
      (strcmp(
         context->datatype, "http://www.w3.org/2001/XMLSchema#string") == 0))
   {
      current_object_literal = context->plain_literal;
      type = RDF_TYPE_TYPED_LITERAL;
   }
   
   // The [current object literal] is then used with each predicate to
   // generate a triple as follows:
   //
   // subject
   //    [new subject]
   // predicate
   //    full URI
   // object
   //    [current object literal]
   pptr = context->property->items;
   for(i = 0; i < context->property->num_items; i++)
   {
      
      rdfalistitem* curie = *pptr;
      rdftriple* triple = NULL;
      
      triple = rdfa_create_triple(context->new_subject,
         (const char*)curie->data, current_object_literal, type, 
         context->datatype, context->language);
      
      context->default_graph_triple_callback(triple, context->callback_data);
      pptr++;
   }

   // TODO: Implement recurse flag being set to false
   //
   // Once the triple has been created, if the [datatype] of the
   // [current object literal] is rdf:XMLLiteral, then the [recurse]
   // flag is set to false
   context->recurse = 0;
}

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