Contents

• APIs
• Process-Centric APIs
• Task Execution
• Task Coordination

Abstract

Just like every software component has an interface, every open software architecture has an Application programming interface (API) which delimits its boundary, keeping it separate from other systems, while making it possible to connect and interact with them. Process-centric APIs are designed so that processes can flow through them. They are the main entry points for delegating execution, exchanging data, and transferring control back and forth across composable software systems. In this talk we illustrate a small collection of API design patterns derived from assigning the responsibility for determining "who does what when" to different parties, gradually deconstructing what it means to execute a process in a decentralized way.

Conclusions

• Different Process-centric APIs patterns determine where decisions on task execution (who does what when, and why?) and task coordination (what to do next) are taken.
• Classical workflow architectures centralized all these decisions in the engine.
• It does not have to be that way.

Design Patterns for Process-centric APIs

Cesare Pautasso

References

• Tom Lichtenstein, Hassan Atwi, Mathias Weske, and Cesare Pautasso, Loose Collaborations on the Blockchain: Survey and Challenges, Proc. 21st International Conference on Business Process Management - Blockchain Forum, Utrecht, the Netherlands, Springer, pp. 21--35, September, 2023.
• Cesare Pautasso, and Erik Wilde, Push-Enabling RESTful Business Processes, 9th International Conference on Service-Oriented Computing (ICSOC 2011), vol. 7084, Paphos, Cyprus, Springer, pp. 32-46, December, 2011.
• Jesus Bellido, Rosa Alarcón, and Cesare Pautasso, Control-Flow Patterns for Decentralized RESTful Service Composition, ACM Transactions on the Web (TWEB), vol. 8, issue 1, pp. 5:1–5:30, December, 2013.
• Souhaila Serbout, Cesare Pautasso, Uwe Zdun, Olaf Zimmermann, From OpenAPI Fragments to API Pattern Primitives and Smells, Proc. of the European Conference on Pattern Languages of Programs (EuroPLoP 2021), Kloster Irsee, Germany, July 2021
• Cesare Pautasso, Ana Ivanchikj, Silvia Schreier, A Pattern Language for RESTful Conversations, Proc. of the 21st European Conference on Pattern Languages of Programs (EuroPLoP 2016), Kloster Irsee, Germany, July 2016, pp. 4:1-4:22
• Olaf Zimmermann, Mirko Stocker, Daniel Lübke, Uwe Zdun, Cesare Pautasso Patterns for API Design: Simplifying Integration with Loosely Coupled Message Exchanges, Addison-Wesley Signature Series (Vernon): Pearson Education, pp. 544, 2023.
• Cesare Pautasso, Business Process Management: visual lecture notes, Leanpub, 2021