@conference {2021:europlop:api-fragments,
	title = {From OpenAPI Fragments to API Pattern Primitives and Design Smells},
	booktitle = {European Conference on Pattern Languages of Programs (EuroPLoP{\textquoteright}21)},
	year = {2021},
	month = {July},
	publisher = {ACM},
	organization = {ACM},
	address = {Virtual Kloster Irsee, Germany},
	abstract = {In the past few years, the OpenAPI Specification (OAS) has emerged as a standard description language for accurately modeling Web APIs.
Today, thousands of OpenAPI descriptions can be found by mining open source repositories. In this paper, we attempt to exploit these artifacts to extract commonly occurring building blocks used in Web API structures, in order to assist Web API designers in their modelling task. Our work is based on a fragmentation mechanism, that starts from  OpenAPI descriptions of Web APIs to extract their structures, then fragment these structures into smaller blocks. This approach enabled us to extract a large dataset of reoccurring fragments from a collection of 6619 API specifications.  
Such fragments have been found multiple times in the same or across different APIs. We have classified the most reoccurring fragments into four pattern primitives used to expose in the API access to collections of items.  We distinguish for each primitive variants from design smells. This classification is based on the specific combinations of operations associated with the collection items and on an in-depth analysis of their natural language labels and descriptions. The resulting pattern primitives are intended to support designers who would like to introduce one or more collections for a specific class of items in their HTTP-based API.},
	keywords = {API, API fragments, design smells, OpenAPI, patterns},
	doi = {10.1145/3489449.3489998},
	url = {https://zenodo.org/record/5727094$\#$.YZ97mFMo-0o},
	author = {Souhaila Serbout and Cesare Pautasso and Uwe Zdun and Olaf Zimmermann}
}
@conference {2021:plop,
	title = {Patterns on Designing API Endpoint Operations},
	booktitle = {28th Conference on Pattern Languages of Programs (PLoP{\textquoteright}21)},
	year = {2021},
	month = {October},
	publisher = {ACM},
	organization = {ACM},
	address = {Virtual},
	abstract = {Domain-driven design (DDD) is often applied when implementing microservices or communicating through APIs in distributed
systems. APIs expose a published language that provides a view on entire domain models or subsets of such models. Hence,
tactical DDD patterns such as Aggregate, Service, and Entity may not only structure API implementations, but also guide API
specification work. In our previous work, we described endpoint-level patterns for this context. In this paper, we present three
complementary patterns, namely Aggregated Domain Operation on API Endpoint, Event-Based API Endpoint Operation, and
CRUD-Based API Operation. These patterns aim to derive API operations from the operations of Domain Services and Entities
as well as Domain Events. We also discuss variants of these patterns, such as their combination with the patterns Command
Query Responsibility Segregation (CQRS) and Publish/Subscribe. Our pattern mining work is based on a data set from an
empirical study of 32 grey literature sources investigating practitioner views on deriving API designs from DDD models.},
	keywords = {API, Domain-Driven Design},
	author = {Apitchaka Singjai and Uwe Zdun and Olaf Zimmermann and Mirko Stocker and Cesare Pautasso}
}
@conference {2019:map:europlop,
	title = {Interface Evolution Patterns {\textemdash} Balancing Compatibility and Flexibility across Microservices Lifecycles},
	booktitle = {24th European Conference on Pattern Languages of Programs (EuroPLoP 2019)},
	year = {2019},
	month = {July},
	publisher = {ACM},
	organization = {ACM},
	address = {Irsee, Germany},
	abstract = {Remote Application Programming Interfaces (APIs) are technology enablers for distributed system trends such as cloud-native application development. API providers find it hard to design their remote APIs so that they can be evolved easily; refactoring and extending an API while preserving backward compatibility is particularly challenging. If APIs are evolved poorly, clients are critically impacted; high costs to adapt and compensate for downtimes may result. For instance, if an API provider publishes a new incompatible API version, existing clients might break and not function properly until they are upgraded to support the new version. Hence, applying adequate strategies for evolving service APIs is one of the core problems in API governance, which in turn is a prerequisite for successfully integrating service providers with their clients in the long run. Although many patterns and pattern languages are concerned with API and service design and related integration technologies,patterns guiding the evolution of APIs are missing to date. Extending our pattern language on Microservice API Patterns (MAP), we introduce a set of patterns focusing on API evolution strategies in this paper: API Description, Version Identifier, Semantic Versioning, Eternal Lifetime Guarantee, Limited Lifetime Guarantee, Two in Production, Aggressive Obsolescence, and Experimental Preview.The patterns have been mined from public Web APIs and industry projects the authors have been involved in.},
	keywords = {API, API Evolution, Microservices, patterns},
	doi = {10.1145/3361149.3361164},
	url = {https://dl.acm.org/citation.cfm?id=3361164},
	author = {Daniel L{\"u}bke and Olaf Zimmermann and Cesare Pautasso and Uwe Zdun}
}
@conference {2018:map:icsoc,
	title = {Guiding Architectural Decision Making on Quality Aspects of Microservice APIs},
	booktitle = {16th International Conference on Service-Oriented Computing (ICSOC 2018)},
	volume = {11236},
	year = {2018},
	month = {November},
	pages = {73-89},
	publisher = {Springer},
	organization = {Springer},
	address = {Hangzhou, Zhejiang, China},
	abstract = {Microservice APIs represent the client perspective on microservice-based software architecture design and related practices. Major issues in API design concern the quality aspects of the API. However, it is not well understood today what the established practices related to those quality aspects are, how these practices are related, and what the major decision drivers are. This leads to great uncertainty in the design process. In this paper, we report on a qualitative, in-depth study of 31 widely used APIs plus 24 API specifications, standards, and technologies. In our study we identified six recurring architectural design decisions in two API design contexts with a total of 40 decision options and a total of 47 decision drivers. We modelled our findings in a formal, reusable architectural decision model. We measured the uncertainty in the resulting design space with and without use of our model, and found that a substantial uncertainty reduction can be potentially achieved by applying our model.
},
	keywords = {API, Microservices, quality},
	doi = {10.1007/978-3-030-03596-9_5},
	author = {Uwe Zdun and Mirko Stocker and Olaf Zimmermann and Cesare Pautasso and Daniel L{\"u}bke}
}
