public function validate() {

		$result = parent::validate();

		// Confirm that the current tag has been given a title and doesn't already exist.

		$this->Title = strtolower($this->Title);
		if($result->isValid() && !$this->Title) {
			$result->addError('"Title" required!');
		}
		else if($result->isValid() && MediaTag::get_one(MediaTag::class, array(
			'ID != ?' => $this->ID,
			'Title = ?' => $this->Title
		))) {
			$result->addError('Tag already exists!');
		}

		// Allow extension customisation.

		$this->extend('validateMediaTag', $result);
		return $result;
	}