Breadcrumb predicates.

includes/breadcrumb.inc

@@ -54,6 +54,8 @@ function islandora_get_breadcrumbs($object) {
  *   An array of links representing the breadcrumb trail, "root" first.
  */
 function islandora_get_breadcrumbs_recursive($pid, FedoraRepository $repository, array &$context = NULL) {
+  module_load_include('inc', 'islandora', 'includes/utilities');
+
   // Before executing the query, we have a base case of accessing the top-level
   // collection.
   if ($context === NULL) {
@@ -102,9 +104,13 @@ EOQ;
     $filter_map = function ($filter) {
       return "FILTER($filter)";
     };
-    $collection_predicate_filters = "sameTerm(?collection_predicate, <fedora-rels-ext:isPartOf>)";
-    $collection_predicate_filters .= " || sameTerm(?collection_predicate, <fedora-rels-ext:isMemberOfCollection>) || sameTerm(?collection_predicate, <fedora-rels-ext:isMemberOf>)";
-    $query_filters[] = $collection_predicate_filters;
+    $object = islandora_object_load($pid);
+    $breadcrumb_predicates = islandora_invoke_hook_list(ISLANDORA_BREADCRUMB_FILTER_PREDICATE_HOOK, $object->models, array($object));
+    $same_term_map = function ($predicate) {
+      return "sameTerm(?collection_predicate, <$predicate>)";
+    };
+    $collection_predicate_filters = array_map($same_term_map, $breadcrumb_predicates);
+    $query_filters[] = implode(' || ', $collection_predicate_filters);
     $query_order = "ORDER BY DESC(?label)";
     $query = format_string($query, array(
       '!optionals' => !empty($query_optionals) ? ('OPTIONAL {{' . implode('} UNION {', $query_optionals) . '}}') : '',
@@ -114,7 +120,6 @@ EOQ;
     $query = format_string($query, array(
       '!pid' => $pid,
     ));
-
     $results = $repository->ri->sparqlQuery($query, 'unlimited');
 
     if (count($results) > 0 && $context['level'] > 0) {

islandora.api.php

@@ -794,3 +794,17 @@ function hook_islandora_metadata_display_info() {
     ),
   );
 }
+
+/**
+ * Defines predicates to be searched for when constructing breadcrumbs.
+ *
+ * @return array
+ *   An array containing strings of predicates to be ORed together to be
+ *   matched on in SPARQL.
+ */
+function hook_islandora_get_breadcrumb_query_predicates() {
+  return array(
+    'somepredicate',
+    'someotherpredicate,'
+  );
+}

islandora.module

@@ -49,6 +49,7 @@ define('ISLANDORA_POST_INGEST_HOOK', 'islandora_ingest_post_ingest');
 define('ISLANDORA_PRE_PURGE_OBJECT_HOOK', 'islandora_pre_purge_object');
 define('ISLANDORA_POST_PURGE_OBJECT_HOOK', 'islandora_post_purge_object');
 define('ISLANDORA_UPDATE_RELATED_OBJECTS_PROPERTIES_HOOK', 'islandora_update_related_objects_properties');
+define('ISLANDORA_BREADCRUMB_FILTER_PREDICATE_HOOK', 'islandora_get_breadcrumb_query_predicates');
 
 // @todo Add Documentation.
 define('ISLANDORA_OBJECT_INGESTED_HOOK', 'islandora_object_ingested');
@@ -2186,3 +2187,14 @@ function islandora_schedule_cache_clear_for_batch() {
   // iterations/operations of a single batch.
   $batch['islandora_cache_clear_scheduled'] = TRUE;
 }
+
+/**
+ * Implements hook_islandora_get_breadcrumb_query_predicates().
+ */
+function islandora_islandora_get_breadcrumb_query_predicates(AbstractObject $object) {
+  return array(
+    'fedora-rels-ext:isPartOf',
+    'fedora-rels-ext:isMemberOfCollection',
+    'fedora-rels-ext:isMemberOf',
+  );
+}