Web API/service technology has been attracting considerable attention and the REST (REpresentational State Transfer) architecture is now widely accepted as mainstream technology. Nonetheless, developing the means by which to discover RESTful Web APIs/services is crucial to the further development of this technology. Unfortunately, existing search engines for RESTful Web APIs/services provide only keyword-based or tag-based search functions. A failure to take into account the semantics and/or characteristics (e.g., their interface compatibility) greatly hampers the ability to find suitable APIs/services. In this study, we propose a novel approach to the discovery of RESTful Web API/services, referred to as Test-Oriented API Search with Semantic Interface Compatibility (TASSIC). This scheme involves expanding the terms of Web API/service documents based on DBpedia and WordNet. Unsuitable APIs/services are then filtered out using a systematic process, as follows: 1) calculation of semantic similarity between a set of candidate APIs/services and a user query, 2) analysis of interface compatibility between candidate APIs/services using the Hungarian Algorithm, 3) invocation of candidate APIs/services to verify functionality and availability, and 4) analysis of similarity between the actual response of the candidate services and the expected response specified in the user query. The proposed TASSIC increases the likelihood of matching APIs/services that are semantically equivalent or similar to user queries. Unit test and acceptance test are used to verify that a set of candidate APIs/services are actually available and that they actually meets user requirements. Experiment results demonstrate the efficacy of TASSIC, the accuracy of which is superior to that of existing methods.

Existing Web API search engines allow only category-based browsing and keyword- or tag-based searches for RESTful services. In other words, they do not enable the discovery or composition of real-world RESTful services by application developers. This paper outlines a novel scheme, called Transformation–Annotation–Discovery (TAD), which transforms OpenAPI (Swagger) documents related to RESTful services into a graph structure and then automatically annotates the semantic concepts on graph nodes using Latent Dirichlet Allocation (LDA) and WordNet. TAD can then be used for service composition based on the user requirements specified in two modules: a service discovery chain and logical-operation-based composition. The service discovery chain uses the Hungarian algorithm to assess service interface compatibility in order to facilitate the retrieval of services capable of bridging the gap between specified user requirements and the discovered services. The logical-operation-based composition module identifies services that semantically fit the user requirements, based on the structure of the service flow. Those candidate services are then sent to service discovery chains to enable the simultaneous search for potential composition solutions. System prototype and experiment results demonstrate the feasibility and efficacy of the proposed scheme.