# IoT-Enabled Smart Cities: Evolution and Outlook
## 3 Key Technologies Developed
### IoT Platforms
oneM2M is agnostic to the IoT information model used, i.e., it can store and handle any type of IoT information. * **OMA Lightweight M2M (LwM2M)** is a protocol for IoT device management and service enablement. It is standardized by the Open Mobile Alliance (OMA) [72]. LwM2M defines and application layer communication protocol between a LwM2M server and a LwM2M client located on each device. The device management functionalities are connectivity management, provisioning of security credentials, firmware updates and remote device diagnostics. The service enablement functionalities are sensor and meter readings, actuation and configuration of devices. * **NGSI-LD** provides a Context Information Management API and an underlying linked data-based information model resulting in a knowledge graph. NGSI-LD is specified by the Industry Specification Group on cross-cutting Context Information Management of the European Telecommunications Standards Institute (ETSI ISG CIM) [73]. It represents the evolution of the NGSI context interfaces originally standardized in OMA and later evolved in the FIWARE open-source ecosystem. Applications can manage, retrieve and discover the information they need, using filters and geographic scopes to limit the results to what is relevant. Using NGSI-LD, applications get information on a suitable abstraction level and independent of device technology specific data models. To help cities in building future-proof and interoperable smart city infrastructures, there are city networks like Open & Agile Smart Cities (OASC) [74] and Eurocieties [75]. They give cities a voice and help in developing solutions that can be replicated across cities. Especially, OASC has defined a set of Minimum Interoperability Mechanisms (MIMs) [76]. MIMs define a common basis to ensure interoperability of solutions:  
* MIM 1 is called _OASC Context Information Management_ and relates to the API that allows accessing to real-time context information. The recommended standard for this is NGSI-LD. * MIM 2 is called _OASC Data Models_ and refers to guidelines and a catalogue of common data models that enable interoperability for applications and systems among cities. There are several data models already proposed (e.g., SAREF [77] supported by ETSI, OneDM [78] supported by the Zigbee Alliance) but OASC seems to focus on the models by Smart Data Models initiative [79], which it recently joined. * MIM3 is called _OASC Ecosystem Transactions Management_ and refers to the Marketplace API that exposes functionality like catalogue, ordering and revenue management. Here, the TM Forum Open APIs [80] are proposed for building interoperable solutions. Further MIMs like Personal Data Management and Fair Artificial Intelligence and Algorithms are currently under development. An important role in this respect is played by open-source frameworks, which often provide reference implementations for standards. An example of such a framework is FIWARE [81] that is used by Santander introduced in Section 2.2. FIWARE is an open-source ecosystem managed by the FIWARE Foundation. It offers a set of open-source components that provide the functionality to assemble a smart city platform. Often the components implement standards like NGSI-LD or oneM2M. On this basis a smart city platform can be built and complemented with commercial components and applications where needed. Due to the general availability of the open-source components and by building on standards, it is nevertheless much easier to change providers or integrate existing deployments, avoiding vendor lock-in. Last but not least, as pointed out in the context of OASC MIM 2, data models are critical for creating a global digital single market of interoperable and replicable (portable) smart solutions in multiple domains. Such models provide an essential element in the common technical ground needed for standards-based open innovation and procurement. One set of common data models is being developed by the Smart Data Models initiative6.