diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Indexer/Record/Hydrator/ThesaurusHydrator.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Indexer/Record/Hydrator/ThesaurusHydrator.php
index d115fd37ab..676b8f4bb1 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Indexer/Record/Hydrator/ThesaurusHydrator.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Indexer/Record/Hydrator/ThesaurusHydrator.php
@@ -36,9 +36,9 @@ class ThesaurusHydrator implements HydratorInterface
         // Fields with concept inference enabled
         $structure = $this->helper->getFieldsStructure();
         $fields = array();
-        foreach ($structure as $field => $options) {
+        foreach ($structure as $name => $options) {
             if ($options['thesaurus_concept_inference']) {
-                $fields[$field] = $options['thesaurus_prefix'];
+                $fields[$name] = $options['thesaurus_prefixes'];
             }
         }
         // Hydrate records with concepts
@@ -54,12 +54,13 @@ class ThesaurusHydrator implements HydratorInterface
         }
 
         $terms = array();
-        $fieldMap = array();
-        foreach ($fields as $field => $prefix) {
-            if (isset($record['caption'][$field])) {
-                foreach ($record['caption'][$field] as $value) {
+        $bulkFieldMap = array();
+        foreach ($fields as $name => $prefixes) {
+            if (isset($record['caption'][$name])) {
+                // Loop through all values to prepare bulk query
+                foreach ($record['caption'][$name] as $value) {
                     $terms[] = Term::parse($value);
-                    $fieldMap[] = $field;
+                    $bulkFieldMap[] = $name;
                 }
             }
         }
@@ -70,12 +71,12 @@ class ThesaurusHydrator implements HydratorInterface
 
         foreach ($bulk as $offset => $item_concepts) {
             if ($item_concepts) {
-                $field = $fieldMap[$offset];
+                $name = $bulkFieldMap[$offset];
                 foreach ($item_concepts as $concept) {
-                    $record['concept_path'][$field][] = $concept->getPath();
+                    $record['concept_path'][$name][] = $concept->getPath();
                 }
             } else {
-                $this->candidateTerms->insert($field, $value);
+                $this->candidateTerms->insert($name, $value);
             }
         }
     }
diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/RecordHelper.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/RecordHelper.php
index c6b944c183..18f28ef336 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/RecordHelper.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/RecordHelper.php
@@ -169,13 +169,14 @@ class RecordHelper
                 $field['to_aggregate'] = (bool) $fieldStructure->isAggregable();
 
                 // Thesaurus concept inference
-                // $xpath = "/thesaurus/te[@id='T26'] | /thesaurus/te[@id='T24']";
-                $helper = new ThesaurusHelper();
-
-                // TODO Not the real option yet
-                $field['thesaurus_concept_inference'] = $field['type'] === Mapping::TYPE_STRING;
-                // TODO Find thesaurus path prefixes
-                $field['thesaurus_prefix'] = '/categories';
+                $xpath = $fieldStructure->get_tbranch();
+                if ($field['type'] === Mapping::TYPE_STRING && $xpath ==! '') {
+                    $field['thesaurus_concept_inference'] = true;
+                    $field['thesaurus_prefixes'] = ThesaurusHelper::findPrefixesByXPath($databox, $xpath);
+                } else {
+                    $field['thesaurus_concept_inference'] = false;
+                    $field['thesaurus_prefixes'] = null;
+                }
 
                 //printf("Field \"%s\" <%s> (private: %b)\n", $name, $field['type'], $field['private']);
 
diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Helper.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Helper.php
index 216a9faba7..4ab61cc1a1 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Helper.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Helper.php
@@ -11,27 +11,53 @@
 
 namespace Alchemy\Phrasea\SearchEngine\Elastic\Thesaurus;
 
+use Alchemy\Phrasea\SearchEngine\Elastic\Exception\ThesaurusException;
+use Alchemy\Phrasea\SearchEngine\Elastic\StringUtils;
 use databox;
 use DOMDocument;
 use DOMElement;
 use DOMNode;
+use DOMNodeList;
 use DOMXPath;
-use Elasticsearch\Client;
 
 class Helper
 {
-    public function findNodesByXPath($document, $xpath)
+    const TERM_LANG_ATTR = 'lng';
+    const TERM_VALUE_ATTR = 'v';
+    const PATH_LANG = 'en';
+
+    public static function findPrefixesByXPath(databox $databox, $expression)
     {
-        $tbranch = "/thesaurus/te[@id='T26'] | /thesaurus/te[@id='T24']";
-        $xpath = new \DOMXPath($document);
-        $nodeList = $xpath->query($tbranch);
-        $conceptIds = [];
-        foreach ($nodeList as $node) {
-            if ($node->hasAttribute('id')) {
-                $conceptIds[] = $node->getAttribute('id');
+        $document = self::thesaurusFromDatabox($databox);
+        $xpath = new DOMXPath($document);
+        $nodes = $xpath->query($expression);
+        $prefixes = [];
+        foreach ($nodes as $node) {
+            $path_segments = [];
+            $me_and_parents = [$node];
+            foreach (self::getElementAncestors($node) as $me_and_parents[]);
+            foreach ($me_and_parents as $node) {
+                if (Navigator::isConcept($node)) {
+                    $path_segments[] = self::conceptPathSegment($node);
+                } else {
+                    // Silently skips invalid targeted nodes
+                    break;
+                }
             }
+            $prefixes[] = sprintf('/%s', implode('/', array_reverse($path_segments)));
         }
 
+        return $prefixes;
+    }
+
+    private static function getElementAncestors(DOMElement $element)
+    {
+        $parents = [];
+        while ($element = $element->parentNode) {
+            $parents[] = $element;
+        }
+
+        return $parents;
     }
 
     public static function thesaurusFromDatabox(databox $databox)
@@ -64,4 +90,49 @@ class Helper
 
         return $document;
     }
+
+    public static function conceptPathSegment(DOMElement $element)
+    {
+        // Path segment is named according to the first english term, and
+        // default to the first term.
+        $terms = self::filter($element->childNodes, array(Navigator::class, 'isTerm'));
+        $term = self::find($terms, array('self', 'isPathLang'));
+        if (!$term) {
+            if (isset($terms[0])) {
+                $term = $terms[0];
+            } else {
+                throw new ThesaurusException(sprintf('No term linked to concept at path "%s".', $element->getNodePath()));
+            }
+        }
+
+        return StringUtils::slugify($term->getAttribute(self::TERM_VALUE_ATTR));
+    }
+
+    private static function isPathLang(DOMElement $element)
+    {
+        return $element->getAttribute(self::TERM_LANG_ATTR) === self::PATH_LANG;
+    }
+
+    // DOM Helpers
+
+    private static function filter(DOMNodeList $list, callable $callback)
+    {
+        $filtered = [];
+        foreach ($list as $node) {
+            if (call_user_func($callback, $node)) {
+                $filtered[] = $node;
+            }
+        }
+
+        return $filtered;
+    }
+
+    private static function find(array $list, callable $callback)
+    {
+        foreach ($list as $node) {
+            if (call_user_func($callback, $node)) {
+                return $node;
+            }
+        }
+    }
 }
diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Navigator.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Navigator.php
index c742755305..18b0ccf637 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Navigator.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/Navigator.php
@@ -45,12 +45,12 @@ class Navigator
         }
     }
 
-    private function isConcept(DOMNode $node)
+    public static function isConcept(DOMNode $node)
     {
         return $node instanceof DOMElement && $node->tagName === self::CONCEPT_TAG_NAME;
     }
 
-    private function isTerm(DOMNode $node)
+    public static function isTerm(DOMNode $node)
     {
         return $node instanceof DOMElement && $node->tagName === self::TERM_TAG_NAME;
     }
diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/TermVisitor.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/TermVisitor.php
index 5239cd42c6..9c61133b28 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/TermVisitor.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Thesaurus/TermVisitor.php
@@ -11,24 +11,17 @@
 
 namespace Alchemy\Phrasea\SearchEngine\Elastic\Thesaurus;
 
-use Alchemy\Phrasea\SearchEngine\Elastic\StringUtils;
-use Alchemy\Phrasea\SearchEngine\Elastic\Exception\ThesaurusException;
+use Alchemy\Phrasea\SearchEngine\Elastic\Thesaurus\Helper;
 use Closure;
 use Elasticsearch\Client;
-use DOMDocument;
-use DOMNodeList;
 use DOMElement;
-use DOMNode;
 
 class TermVisitor implements VisitorInterface
 {
-    const TERM_TAG_NAME = 'sy';
     const TERM_ID_ATTR = 'id';
     const TERM_LANG_ATTR = 'lng';
     const TERM_VALUE_ATTR = 'v';
 
-    const PATH_LANG = 'en';
-
     private $path = [];
     private $termCallback;
 
@@ -39,20 +32,20 @@ class TermVisitor implements VisitorInterface
 
     public function visitConcept(DOMElement $element)
     {
-        array_push($this->path, $this->getConceptPathSegment($element));
+        array_push($this->path, Helper::conceptPathSegment($element));
     }
 
     public function visitTerm(DOMElement $element)
     {
-        $raw_value = $this->getTermValue($element);
+        $raw_value = $element->getAttribute(self::TERM_VALUE_ATTR);
         $object = Term::parse($raw_value);
         $term = [
             'raw_value' => $raw_value,
             'value'     => $object->getValue(),
             'context'   => $object->getContext(),
             'path'      => $this->getCurrentPathAsString(),
-            'lang'      => $this->getTermAttribute($element, self::TERM_LANG_ATTR),
-            'id'        => $this->getTermAttribute($element, self::TERM_ID_ATTR)
+            'lang'      => $element->getAttribute(self::TERM_LANG_ATTR),
+            'id'        => $element->getAttribute(self::TERM_ID_ATTR)
         ];
 
         call_user_func($this->termCallback, $term);
@@ -67,66 +60,4 @@ class TermVisitor implements VisitorInterface
     {
         return sprintf('/%s', implode('/', $this->path));
     }
-
-    private function getConceptPathSegment(DOMElement $element)
-    {
-        // Path segment is named according to the first english term, and
-        // default to the first term.
-        $terms = $this->filter($element->childNodes, array($this, 'isTerm'));
-        $term = $this->find($terms, array($this, 'isPathLang'));
-        if (!$term) {
-            if (isset($terms[0])) {
-                $term = $terms[0];
-            } else {
-                throw new ThesaurusException(sprintf('No term linked to concept at path "%s".', $element->getNodePath()));
-            }
-        }
-
-        return StringUtils::slugify($this->getTermValue($term));
-    }
-
-    private function isTerm(DOMNode $node)
-    {
-        return $node instanceof DOMElement && $node->tagName === self::TERM_TAG_NAME;
-    }
-
-    private function isPathLang(DOMElement $element)
-    {
-        return $element->getAttribute(self::TERM_LANG_ATTR) === self::PATH_LANG;
-    }
-
-    private function getTermValue(DOMElement $term)
-    {
-        return $this->getTermAttribute($term, self::TERM_VALUE_ATTR);
-    }
-
-    private function getTermAttribute(DOMElement $term, $attribute)
-    {
-        if ($term->hasAttribute($attribute)) {
-            return $term->getAttribute($attribute);
-        }
-    }
-
-    // DOM Helpers
-
-    private function filter(DOMNodeList $list, Callable $callback)
-    {
-        $filtered = [];
-        foreach ($list as $node) {
-            if (call_user_func($callback, $node)) {
-                $filtered[] = $node;
-            }
-        }
-
-        return $filtered;
-    }
-
-    private function find(array $list, Callable $callback)
-    {
-        foreach ($list as $node) {
-            if (call_user_func($callback, $node)) {
-                return $node;
-            }
-        }
-    }
 }