Timeliness is a fundamental property of Cyber-Physical Systems that has been intensively investigated within the scope of real-time and critical systems. The advent of the Internet of Things, however, brings an intense communication flow between devices and the Internet. In this scenario, modeling time requirements in terms of data, rather than the tasks that manipulate them, may be advantageous as a data-centric design can promptly encompass other first-order requirements, such as geolocation, security, and trustworthiness. In this paper, we propose a strategy to design complex CPSs by modeling their data using the SmartData construct, which, besides encompassing means to handle the aforementioned requirements, also defines the concept of data expiry to guide scheduling decisions. With SmartData, local tasks are scheduled to produce the freshest data and to manipulate them before expiration. Likewise, network packets are scheduled prioritizing data whose expiry is close. We validate the strategy through simulations using Castalia.