public function allow($identities)
	{
		// Implicit deny by default.
		$result = null;

		// Check that the inputs are valid.
		if (!empty($identities))
		{
			if (!is_array($identities))
			{
				$identities = array($identities);
			}

			foreach ($identities as $identity)
			{
				// Technically the identity just needs to be unique.
				$identity = (int) $identity;

				// Check if the identity is known.
				if (isset($this->data[$identity]))
				{
					$result = (boolean) $this->data[$identity];

					// An explicit deny wins.
					if ($result === false)
					{
						break;
					}
				}

			}
		}

		return $result;
	}