diff --git a/module/VuFindSearch/src/VuFindSearch/Backend/AbstractHandlerMap.php b/module/VuFindSearch/src/VuFindSearch/Backend/AbstractHandlerMap.php
new file mode 100644
index 0000000000000000000000000000000000000000..2e784324e13d20554a29a0533de9b45fc0470251
--- /dev/null
+++ b/module/VuFindSearch/src/VuFindSearch/Backend/AbstractHandlerMap.php
@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * Base class for search backend handler maps.
+ *
+ * PHP version 5
+ *
+ * Copyright (C) Villanova University 2010.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * @category VuFind2
+ * @package Search
+ * @author David Maus <maus@hab.de>
+ * @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link http://vufind.org
+ */
+
+namespace VuFindSearch\Backend;
+
+use VuFindSearch\ParamBag;
+
+/**
+ * Base class for search backend handler maps.
+ *
+ * The handler map maps search functions to parameterizable backend request
+ * handlers. The base class implements the parameter preparation method which
+ * applies query defaults, appends, and invariants to an existing set of
+ * parameters.
+ *
+ * @category VuFind2
+ * @package Search
+ * @author David Maus <maus@hab.de>
+ * @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link http://vufind.org
+ */
+abstract class AbstractHandlerMap
+{
+
+ /**
+ * Prepare final set of parameters for search function.
+ *
+ * Applies the query defaults, appends, and invariants.
+ *
+ * The concept of defaults, appends, and invariants follows SOLR with
+ * regards to the order of the application process: Invariants come last
+ * and overwrite runtime parameters, defaults, and appends.
+ *
+ * @param string $function Name of search function
+ * @param ParamBag $params Parameters
+ *
+ * @return void
+ */
+ final public function prepare($function, ParamBag $params)
+ {
+ $final = $params->getArrayCopy();
+ $defaults = $this->getDefaults($function);
+ $invariants = $this->getInvariants($function);
+ $appends = $this->getAppends($function);
+
+ $final = array_replace($defaults, $final);
+ $final = array_merge_recursive($final, $appends);
+ $final = array_replace($final, $invariants);
+
+ $params->exchangeArray($final);
+ }
+
+ /**
+ * Return query invariants for search function.
+ *
+ * @param string $function Name of search function
+ *
+ * @return array Query invariants
+ */
+ abstract protected function getInvariants($function);
+
+ /**
+ * Return query defaults for search function.
+ *
+ * @param string $function Name of search function
+ *
+ * @return array Query defaults
+ */
+ abstract protected function getDefaults($function);
+
+ /**
+ * Return query appends for search function.
+ *
+ * @param string $function Name of search function
+ *
+ * @return array Query appends
+ */
+ abstract protected function getAppends($function);
+}
\ No newline at end of file
diff --git a/module/VuFindSearch/tests/unit-tests/src/VuFindTest/Backend/AbstractHandlerMapTest.php b/module/VuFindSearch/tests/unit-tests/src/VuFindTest/Backend/AbstractHandlerMapTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..f07cbddb64db1de79191aec98c6255d33e19aaff
--- /dev/null
+++ b/module/VuFindSearch/tests/unit-tests/src/VuFindTest/Backend/AbstractHandlerMapTest.php
@@ -0,0 +1,121 @@
+<?php
+
+/**
+ * Unit tests for handler map base class.
+ *
+ * PHP version 5
+ *
+ * Copyright (C) Villanova University 2010.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * @category VuFind2
+ * @package Search
+ * @author David Maus <maus@hab.de>
+ * @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link http://vufind.org
+ */
+
+namespace VuFindTest\Backend;
+
+use VuFindSearch\Backend\AbstractHandlerMap;
+use VuFindSearch\ParamBag;
+
+use PHPUnit_Framework_TestCase as TestCase;
+
+/**
+ * Unit tests for handler map base class.
+ *
+ * @category VuFind2
+ * @package Search
+ * @author David Maus <maus@hab.de>
+ * @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link http://vufind.org
+ */
+class AbstractHandlerMapTest extends TestCase
+{
+ /**
+ * Test parameter preparation, defaults.
+ *
+ * @return void
+ */
+ public function testPrepareDefaults()
+ {
+ $map = $this->getMockForAbstractClass('VuFindSearch\Backend\AbstractHandlerMap');
+ $map->expects($this->once())
+ ->method('getDefaults')
+ ->will($this->returnValue(array('p1' => array('default'), 'p2' => array('default'))));
+ $map->expects($this->once())
+ ->method('getAppends')
+ ->will($this->returnValue(array()));
+ $map->expects($this->once())
+ ->method('getInvariants')
+ ->will($this->returnValue(array()));
+
+ $params = new ParamBag(array('p2' => array('non-default')));
+ $map->prepare('f', $params);
+ $this->assertTrue($params->contains('p1', 'default'));
+ $this->assertFalse($params->contains('p2', 'default'));
+ $this->assertTrue($params->contains('p2', 'non-default'));
+ }
+
+ /**
+ * Test parameter preparation, appends.
+ *
+ * @return void
+ */
+ public function testPrepareAppends()
+ {
+ $map = $this->getMockForAbstractClass('VuFindSearch\Backend\AbstractHandlerMap');
+ $map->expects($this->once())
+ ->method('getDefaults')
+ ->will($this->returnValue(array()));
+ $map->expects($this->once())
+ ->method('getAppends')
+ ->will($this->returnValue(array('p1' => 'append')));
+ $map->expects($this->once())
+ ->method('getInvariants')
+ ->will($this->returnValue(array()));
+
+ $params = new ParamBag(array('p1' => array('something')));
+ $map->prepare('f', $params);
+ $this->assertTrue($params->contains('p1', 'something'));
+ $this->assertTrue($params->contains('p1', 'append'));
+ }
+
+ /**
+ * Test parameter preparation, invariants.
+ *
+ * @return void
+ */
+ public function testPrepareInvariants()
+ {
+ $map = $this->getMockForAbstractClass('VuFindSearch\Backend\AbstractHandlerMap');
+ $map->expects($this->once())
+ ->method('getDefaults')
+ ->will($this->returnValue(array()));
+ $map->expects($this->once())
+ ->method('getAppends')
+ ->will($this->returnValue(array('p1' => array('append'))));
+ $map->expects($this->once())
+ ->method('getInvariants')
+ ->will($this->returnValue(array('p1' => array('invariant'))));
+
+ $params = new ParamBag(array('p1' => array('something')));
+ $map->prepare('f', $params);
+ $this->assertFalse($params->contains('p1', 'something'));
+ $this->assertFalse($params->contains('p1', 'append'));
+ $this->assertTrue($params->contains('p1', 'invariant'));
+ }
+}
\ No newline at end of file