Smart city residents can save up to 125 hours a year, estimates the market research institute Juniper Research in 2017. Besides New York City, Tokyo and Berlin, 20 additional cities were analyzed for this study. The focus of the investigations was on the extent to which a smart city can have a positive impact on the inhabitants. This includes time savings as well as safe roads, digital administrative services, efficiency or improved health. However, for smart cities to truly add value to every day’s life, it’s not just about innovative ideas. It is of rather great importance that the underlying urban platform can function seamlessly and provide reliable services to relevant stakeholders and citizens. Therefore, an ICT reference architecture should be utilized that lays the foundation for Urban Data Platforms and enables the interoperability of the deployed components.

But what are Smart City solutions? A Smart City is based on the flow of data among various stakeholders and data sources in order to facilitate innovative applications and services. The potential Smart City solutions aim at optimizing the procedures and processes within a city – including those within the city administration itself, in parallel to global urban aspects such as mobility, public transport, energy, citizens participation/engagement, and public safety.

In order to address these domains with the variety of potential use cases, a large number of data sources should be taken into account going beyond the scope of the initial considerations on Open (Governmental) Data pursued in the last decade. In addition to open (governmental) data, dynamic continuous data, such as from sensors or IoT infrastructures, as well as statistical data from public sources should be involved. However, this also adds complexity to the required infrastructure, which includes data centers, communication networks, routers, switches, Wi-Fi access points, cloud services or mobile end-user applications. An environment consisting of such complex data sources should be structured according to standardized rules. Therefore, reference models for information and communication technologies (ICT) are an essential concept and basic requirement within smart cities for various reasons.

For example, there is a need to provide an abstract blueprint and understanding of the ICT developments and strategies within a city. Thereby, ICT reference architectures have the goal to accommodate and characterize existing ICT infrastructures, whilst in parallel enabling the extension and the introduction of new components and solutions. Ideally, a city’s ICT framework is able to leverage Open Source and Open Data-based solutions with data communication through standardized and interoperable interfaces. For this to be possible, abstract interfaces between different conceptual boundaries and associated components must be identified. Moreover, appropriate design principles should be enforced in order to facilitate the creation of integrative solutions compiled form components of different stakeholders (e.g. local SMEs, Open Source initiatives or large industry). This would help cities to avoid vendor-lock-in and to break the continuous dependence from vendors and specific network/service providers. As a result, the entire ICT framework in a city would be even capable of using solutions based on Open Source and Open Data, combined with data communication over standardized and interoperable interfaces.

The DIN SPEC 91357 builds on the European Innovation Partnership (EIP) and its reference architecture that was defined in the scope of a corresponding memorandum of understanding for Smart Cities and Communities (MoU EIP SCC). The aim was to adapt the European reference model (EIP SCC) to the requirements of the German market. The development of the oupPLUS is intended to create a central element for the implementation of standardized smart city concepts in urban areas. This design is based on open interfaces that enable the interoperability between multiple layers with respect to data processing and communication. The layers intrinsically embed aspects of security and privacy in various patterns and guarantee the trustful implementation of multiple use cases.

SAPs describe abstract interfaces that enable the exchange of data / information between components placed in the various artefacts (layers and pillars) of oupPLUS. The main concept that enables Quality Assurance for ICT in Smart Cities is given by the Service Access Points along the layers of the oupPLUS reference architecture.

Thereby, different protocols and data formats of relevance for urban ICT are mapped onto the belonging SAPs and represent a concrete implementation of an SAP. The following standards are being taken into account among others:

• Network Routing and forwarding protocols (e. g. OSPF, RIP, BGP, IPv4/v6, ARP, 6LowPan, ICMP(v6), …)
• Transport Layer Protocols (e. g. TCP, UDP, RTP)
• Tunneling and secure data transmission (z. B. L2PT, IPSec, TLS, …)
• Application / Service Layer Communication Standards (HTTP, CoAP, SOAP, SIP)
• Relevant Formats for Data Representation (XML, JSON, CSV).

Hence, based on such standards mapping to the SAPs, it is possible to realize integrative Smart City ICT solutions. Those are based on the interoperability and exchange of data among the components of different vendors complying to established standards for data communication.

In line with the concepts of oupPLUS, quality assurance is related to assessing the quality of the way a Smart City component implements the protocols, interfaces and data formats assigned to its belonging SAPS. For example, a router would need to be examined with respect to its routing (e.g. OSPF (v3), RIP, BGP) and addressing features (e. g. IPv4/v6, DHCP(v6), ARP, ND). Only then, the router would be accepted as a Smart City component, in example for realizing the routing for an institutional network.

Hence, corresponding test suites are required for evaluating the SAP implementations of a component in line with the overall ICT oupPLUS blueprint. This package of test suites should be based on the belonging standards (e.g. IETF RFCs, ETSI/ISO/DIN/ITU-T standards and specifications). Thereby, the requirements formulated in the standards should be extensively examined within the relevant test cases, e.g. in the form of positive, negative, equivalence and boundary tests.

The procedure is as follows:

1. Mapping of a Smart City component to corresponding layer(s) / pillar(s) of oupPLUS
2. Identification of relevant SAPs based o the oupPLUS layer(s) / pillar(s)
3. Identification of protocols and data formats of relevance according to SAPs
4. Identification of relevant Conformance and Security test suites, which cover the requirements and specification of the relevant protocols and data formats
5. Execution of the relevant Conformance and Security test suites against the SUT (Smart City component)
6. Review of the results and continuous execution until predefined quality criteria achieved

Based on the testing along the Service Access Points, a certification procedure for Smart City ICT components can be setup. This can assure aspects like conformance to standards, robustness and resilience against cyber-attacks as well as interoperability among Smart City components. Beyond this approach, interoperability testing on component level can be exercised between the solutions of different vendors.

Current research considerations of SQC in the urban ICT domain are related to the concepts required for such a certification model and to its feasibility in order to speed up the implementation and deployment of urban ICT spaces and technology (i.e. Smart Cities). This urban ICT spaces should be correspondingly based on highly qualitative components building up integrative solutions in a sustainable and dynamic ICT eco-system, thereby avoiding the dependence on single vendors/operators and enabling scaling up with respect to exchange and access to data/information.