A conceptual modeling approach of MQTT for IoT-based systems

Abstract The Message Queuing Telemetry Transport (MQTT) is one of the most commonly used standard messaging protocols that enable the Internet of Things (IoT). The messaging standard specification document defines the transactions, attributes, conventions, timers, values, types, structures, etc. MQTT encounters wide implementation possibilities: hardware vendors need to implement MQTT drivers for their devices, software vendors need to implement it in their solutions, developers and researchers need an MQTT simulation framework, etc. The IoT technology can enable unlimited number of use cases, and each case has its implementation of the messaging protocol. From the above facts, on the basis that any user needs to have a deep understanding of the specification in order to implement the protocol and also developers need to study it well for improving the protocol, there is a need for a standard conceptual way that conveys the messaging standard specifications, integrates the specifications of the use cases built upon with a more abstracted mental representation, improves the communication between developers, and facilitates the protocols and applications developments. This paper addresses this issue by proposing a graphical conceptual modeling approach for MQTT-based IoT applications called Example-oriented System Conceptual Modeling for MQTT use cases (EoSCM-MQTT). The paper explains the EoSCM-MQTT and gives an example of its use in an MQTT simulation implementation for a specific IoT application: smart parking. EoSCM-MQTT was validated using three methods: comparison, analysis, and implementation. The details and results of the implementation and the conclusions from the comparison and analysis indicated that EoSCM-MQTT has the required characteristics of conceptual models: good syntactic semantic, and pragmatic quality, clarity, coherence, accuracy, flexibility, reliability, and effectiveness.