public function getDeploymentRevision()
    {
        if ($this->version === false) {

            $version = $this->cache->get('DeploymentRevision');

            if ($version === false) {
                $version = $this->versionDao->getSystemVersion();

                if ($version === false)
                    $version = $this->incrementDeploymentRevision('Initial system version');

                $this->cache->put('DeploymentRevision', $version, 0);
            }

            $this->version = $version;
        }

        return $this->version;
    }