public static function register_taxonomies() {

		// Register the topic-tag taxonomy.
		register_taxonomy(
			bbp_get_topic_tag_tax_id(),
			bbp_get_topic_post_type(),
			apply_filters( 'bbp_register_topic_taxonomy', array(
				'labels'                => bbp_get_topic_tag_tax_labels(),
				'rewrite'               => bbp_get_topic_tag_tax_rewrite(),
				'capabilities'          => bbp_get_topic_tag_caps(),
				'update_count_callback' => 'bbp_update_topic_tag_count',
				'query_var'             => true,
				'show_tagcloud'         => true,
				'hierarchical'          => false,
				'show_in_nav_menus'     => false,
				'public'                => true,
				'show_ui'               => bbp_allow_topic_tags() && current_user_can( 'bbp_topic_tags_admin' ),
				'source'                => 'bbpress'
			)
		) );
	}