protected function loadFilterDependencies($activateDependencies = true)
    {
        if (! $this->filterOptions) {
            $maxLength = $this->get('gaf_calc_name', 'maxlength');

            $this->filterOptions = array();
            foreach ($this->filterDependencies as $dependencyClass) {
                $dependency = $this->agenda->newFilterObject($dependencyClass);
                if ($dependency instanceof FilterModelDependencyAbstract) {

                    $this->filterOptions[$dependency->getFilterClass()] = $dependency->getFilterName();

                    if ($activateDependencies) {
                        $dependency->setMaximumCalcLength($maxLength);
                        $this->addDependency($dependency);
                    }
                }
            }
            asort($this->filterOptions);
        }

        return $this->filterOptions;
    }