@phdthesis{Nikaj2019,
  author    = {Nikaj, Adriatik},
  title     = {Restful choreographies},
  doi       = {10.25932/publishup-43890},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-438903},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xix, 146},
  year      = {2019},
  abstract  = {Business process management has become a key instrument to organize work as many companies represent their operations in business process models. Recently, business process choreography diagrams have been introduced as part of the Business Process Model and Notation standard to represent interactions between business processes, run by different partners. When it comes to the interactions between services on the Web, Representational State Transfer (REST) is one of the primary architectural styles employed by web services today. Ideally, the RESTful interactions between participants should implement the interactions defined at the business choreography level. The problem, however, is the conceptual gap between the business process choreography diagrams and RESTful interactions. Choreography diagrams, on the one hand, are modeled from business domain experts with the purpose of capturing, communicating and, ideally, driving the business interactions. RESTful interactions, on the other hand, depend on RESTful interfaces that are designed by web engineers with the purpose of facilitating the interaction between participants on the internet. In most cases however, business domain experts are unaware of the technology behind web service interfaces and web engineers tend to overlook the overall business goals of web services. While there is considerable work on using process models during process implementation, there is little work on using choreography models to implement interactions between business processes. This thesis addresses this research gap by raising the following research question: How to close the conceptual gap between business process choreographies and RESTful interactions? This thesis offers several research contributions that jointly answer the research question. The main research contribution is the design of a language that captures RESTful interactions between participants---RESTful choreography modeling language. Formal completeness properties (with respect to REST) are introduced to validate its instances, called RESTful choreographies. A systematic semi-automatic method for deriving RESTful choreographies from business process choreographies is proposed. The method employs natural language processing techniques to translate business interactions into RESTful interactions. The effectiveness of the approach is shown by developing a prototypical tool that evaluates the derivation method over a large number of choreography models. In addition, the thesis proposes solutions towards implementing RESTful choreographies. In particular, two RESTful service specifications are introduced for aiding, respectively, the execution of choreographies' exclusive gateways and the guidance of RESTful interactions.},
  language  = {en}
}
@article{NikajWeskeMendling2019,
  author    = {Nikaj, Adriatik and Weske, Mathias and Mendling, Jan},
  title     = {Semi-automatic derivation of RESTful choreographies from business process choreographies},
  series = {Software and systems modeling},
  volume    = {18},
  journal   = {Software and systems modeling},
  number    = {2},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1619-1366},
  doi       = {10.1007/s10270-017-0653-2},
  pages     = {1195 -- 1208},
  year      = {2019},
  abstract  = {Enterprises reach out for collaborations with other organizations in order to offer complex products and services to the market. Such collaboration and coordination between different organizations, for a good share, is facilitated by information technology. The BPMN process choreography is a modeling language for specifying the exchange of information and services between different organizations at the business level. Recently, there is a surging use of the REST architectural style for the provisioning of services on the web, but few systematic engineering approach to design their collaboration. In this paper, we address this gap in a comprehensive way by defining a semi-automatic method for the derivation of RESTful choreographies from process choreographies. The method is based on natural language analysis techniques to derive interactions from the textual information in process choreographies. The proposed method is evaluated in terms of effectiveness resulting in the intervention of a web engineer in only about 10\% of all generated RESTful interactions.},
  language  = {en}
}
@misc{HaarmannBatoulisNikajetal.2018,
  author    = {Haarmann, Stephan and Batoulis, Kimon and Nikaj, Adriatik and Weske, Mathias},
  title     = {DMN Decision Execution on the Ethereum Blockchain},
  series = {Advanced Information Systems Engineering, CAISE 2018},
  volume    = {10816},
  journal   = {Advanced Information Systems Engineering, CAISE 2018},
  publisher = {Springer},
  address   = {Cham},
  isbn      = {978-3-319-91563-0},
  issn      = {0302-9743},
  doi       = {10.1007/978-3-319-91563-0_20},
  pages     = {327 -- 341},
  year      = {2018},
  abstract  = {Recently blockchain technology has been introduced to execute interacting business processes in a secure and transparent way. While the foundations for process enactment on blockchain have been researched, the execution of decisions on blockchain has not been addressed yet. In this paper we argue that decisions are an essential aspect of interacting business processes, and, therefore, also need to be executed on blockchain. The immutable representation of decision logic can be used by the interacting processes, so that decision taking will be more secure, more transparent, and better auditable. The approach is based on a mapping of the DMN language S-FEEL to Solidity code to be run on the Ethereum blockchain. The work is evaluated by a proof-of-concept prototype and an empirical cost evaluation.},
  language  = {en}
}