Page 47 - Redefining smart city platforms: Setting the stage for Minimal Interoperability Mechanisms - A U4SSC deliverable on city platforms

6 Interoperability that is minimal yet sufficient

Having a well-designed architecture based on platforms is not enough. Cities and communities
traditionally collect data in silos, and different city departments are likely to use different data
models and processes. Consequently, within the city it is vital to address the need of interoperability.
Just as importantly, for a city to benefit from tried and tested, and cost-effective, smart city products
and services, it needs to ensure that it follows widespread city practice and standards.

However, given the range of requirements, as covered in the previous section, it is important to
identify approaches and mechanisms that will enable minimal but sufficient interoperability to allow
a good foundation to be laid for the smart city platform.

6.1 Interoperability points

A fundamental principle when designing system architectures is to establish which parts are tightly
coupled and which ones are more loosely coupled. If everything is tightly coupled, data sharing is
easier and more predictable, but it also makes the entire system more vulnerable to failures and
more difficult to change. One way to balance the needs for easy data interoperability between
smart city platforms and the integrity of the same is to identify common interoperability points (also
known as Pivotal Points of Interoperability) and then to use Minimal Interoperability Mechanisms
(MIMs) to enable effective, robust and future-proof integration of the platforms.

Interoperability points represent the main technical interfaces between smart city platforms and
external systems. Interoperability points are also a way to access basic smart city IoT functionalities
(sensor networks and actuators such as intelligent traffic management systems, building information
management, utility infrastructure related to water and waste flows) and in particular to consume
and provide data between and around those systems. Such points and mechanisms assure not only
the replicability of solutions (i.e., services, applications) on different smart cities and communities
that are compliant with them, but also the interchangeability of components and providers.
They are partially or completely decoupled from the specific technological implementation and
deployment of the architectural components. Interoperability points are the logical and conceptual
representation of a set of open APIs that can be instantiated concretely to provide a technologically
specific implementation.

In general, there are two interoperability points in a generic smart city platform:
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– Southbound interfaces: Represent the main way for interacting with IoT devices/middleware
and managing relevant IoT data. They include a set of interfaces used to connect a smart
city platform to heterogeneous IoT devices and middleware. The southbound interfaces are
intended to be exchanging IoT data with a smart city platform, hiding the complexity of the IoT
protocols and communication issues, which are not covered by this Recommendation.

– Northbound interfaces: Include a set of interfaces that provide IoT data and its elaboration
to the external system and application interacting with the smart city platform. Not all the

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