Composition of heterogeneous web services: A systematic review.

Initial developments in Service-Oriented Computing (SOC) led to the development of Web Services using the SOAP protocol and an extensive set of tools and methods for composing new services from those existing. Subsequently, other types of services also emerged, such as event-oriented services and RESTful services. Nevertheless, all mentioned service types expose data and functionality, and users can benefit from their composition, regardless of the service type chosen for their implementation. In the Internet of Things, it is relevant to employ event-oriented services for sensing and SOAP, RESTful or lightweight web APIs for control. In the emerging field of microservices, heterogeneity is embraced as a design principle and services that are part of a single system may be implemented using heterogeneous technologies and paradigms. The research question of this review is: How heterogeneous services can be composed? There are several surveys that cover service composition with each of the existing service types, but the composition of heterogeneous services is only marginally addressed. This systematic literature review focuses explicitly on the heterogeneity of the aforementioned service types. A total of 66 documents, published from 2005 to 2018, have been surveyed, targeting all possible combinations of the three service types. In addition to summarizing existing works, the specific methods employed for supporting service type heterogeneity are grouped into archetypes and have their limitations and capabilities analyzed. Despite the large number of documents found, there are several open issues on heterogeneous service composition. The results of this review are confronted with emerging fields in service computing, namely microservices, serverless and IoT, yielding additional research directions.