Jacoby, MichaelMichaelJacobyVolz, FriedrichFriedrichVolzWeißenbacher, ChristianChristianWeißenbacherMüller, JensJensMüller2022-11-172022-11-172022https://publica.fraunhofer.de/handle/publica/42881510.1109/etfa52439.2022.9921584As one of the cornerstones of Industry 4.0, the concept of digital twins (DTs) is recently gaining more and more importance. The Asset Administration Shell (AAS) specification by Plattform Industrie 4.0 is a concrete adaption of the DT concept with focus on the domain of industrial production. This paper presents the FA³ST Service, an open source software implementation of the reactive AAS as defined by the specification. FA³ST Service embraces an open architecture making it easy to customize and extend. It also enables synchronization of the DT with the underlying asset or other data sources. Internally, FA³ST Service operates in a protocol-agnostic manner which enables supporting multiple different communication protocols such as HTTP and OPC UA for its AAS-conform API as well as OPC UA and MQTT for connecting assets. By offering a command-line interface, a ready-to-use docker container, and being embeddable into custom applications it supports most application scenarios. FA³ST Service is part of the FA³ST ecosystem which aims to provide tools targeting the whole life cycle of a DT.enAsset Administration ShellAASdigital twinFA³STconference paper