Application Coupling Interfaces: A Novel Approach to the Semantic Interoperability Challenge in Integrated Systems Modeling

Many real systems are modeled as networks, where the elements of the system are nodes, and the interactions between the elements are edges. A microservice architecture, in which each microservice is an element of the system, can be utilized to represent these network-based systems models. The challenge is ensuring that the data shared between microservices (i.e., models) accurately represents the interactions between the elements of the modeled system. That is, the interacting microservices must each attribute the same meaning to data being exchanged. This consistency of meaning can be achieved in two ways. Most commonly in systems modeling, there is an a priori fixed global ontology established by the modeling community in which consistency of meaning is maintained by a set of standards/agreements, i.e., data-model based semantic interoperability. While effective, data-model based semantic interoperability requires that new models comprehend and comply with the existing rule sets, limiting the extensibility of the system. Alternately, an ontology-based semantic interoperability approach can be taken. In which case, the needed shared vocabulary and meaning are dynamically derived. This approach overcomes the challenges of a fixed global ontology but poses its own challenges. A number of researchers have proposed that metadata can provide the link needed to derive meaning. However, the implementation of metadata to achieve derived meaning is a complex and multilayered process. In this paper we propose extending the application programming interface (API) paradigm to create application coupling interfaces (ACIs) that support the development of selfidentifying models based on a local ontology rather than global ontology. Within a prescribed environment described in this paper, these ACIs dynamically identify the local ontology and communications protocols and maintain consistency of meaning. This approach is demonstrated on a model of a village energy system representing the interactions between people, energy, and the environment in a west African village.