Page 25 - U4SSC Data and API requirements for centralized smart city platforms

Business microservices: The business microservices consume the data produced either directly
from the sensors or from other business microservices to add value to the SCHub. The key design
principle is that these services must be designed in an API-first way for the consumption, as well
as for the production of their data.

The above system overview leads to the SCHub conceptual architecture, which – like a typical
network hub (ISO, 1994) – consists of layers that enable data flows (Figure 9), which, from bottom to
top, are as follows: the Context layer, the API layer, the Technology layer and the Data Transmission
Function.

Figure 9: SCHub Architecture

The context layer includes the SC standards for transactions and security (Wenge et al., 2014):

1) Basic standards: for data acquisition, transmission, storage, vitalization, and processing.

2) Application standards: for software development, middleware and platforms.

3) Security standards: against threats, information leaking and improper use.

The API layer includes the APIs that enable data transmission and their management functionalities
(design, publish, document, and monitor (Fremantle et al., 2015; Heffner, 2014)). The APIs serve
the receiver and sender roles for data transactions, and their design must ensure openness to
applications and devices, ease of use to developers and citizens (Fremantle et al., 2015), as well
as completeness, consistency, and uniformity (Caelli et al., 1993). Completeness expresses how
efficiently they serve the applications, while consistency and uniformity ensure data transparency.

The APIs are accompanied by documentation, and follow common standards for data formatting,
security and privacy (Gupta et al., 2020), while an access gate is needed for interoperability
(Fremantle et al., 2015; Heffner 2014).

15