Design of a Linked Data-enabled Microservice Platform for the Industrial Internet of Things Bachelor Thesis by Ferdinand Mutsch¨ Chair of Pervasive Computing Systems/TECO Institute of Telematics Department of Informatics First Reviewer: Prof. Dr. Michael Beigl Second Reviewer: Prof. Dr. Hannes Hartenstein Advisor: Andrei Miclaus 01/05/2016 { 31/10/2016 Ich versichere wahrheitsgem¨aß, die Arbeit selbstst¨andig angefertigt, alle benutzten Hilfsmittel vollst¨andig und genau angegeben und alles kenntlich gemacht zu haben, was aus Arbeiten anderer unver¨andert oder mit Ab¨anderungen entnommen wurde. Karlsruhe, den 31. Oktober 2016 iv v Zusammenfassung W¨ahrend der aktuelle Trend in Richtung hochgradig digitalisierter Smart Facto- ries fur¨ die Fertigungsindustrie betr¨achtliches Potential zur Steigerung von Leis- tungsf¨ahigkeit, Flexibilit¨at und Produktivit¨at birgt, tun sich Unternehmen im All- gemeinen noch immer schwer, entsprechende Technologie einzufuhren.¨ Ein Kern- problem ist der Mangel an einheitlichen, standardisierten L¨osungen, die auf dem Hallenboden ohne spezifisches Expertenwissen und einen hohen Zeit- und Koste- naufwand integriert werden k¨onnen. Im Hinblick darauf pr¨asentiert diese Arbeit sowohl Architektur, als auch konkrete Implementierung einer Internet of Things Softwareplattform mit Fokus auf technolo- gische Einheitlichkeit und unkomplizierte Integration und Benutzung. Als Richtlinie hierfur¨ wird in Kooperation mit Industriepartnern ein praxisnaher Anwendungsfall erarbeitet. Des Weiteren wird pr¨asentiert, wie universelle Webtechnologie gewinnbrin- gend mit neusten Software-Design Trends, m¨achtigen Techniken der Maschine-zu- Maschine Interaktion und allgemein verst¨andlichen Konzepten im Bereich User Ex- perience kombiniert werden kann. Dabei wird ausfuhrlich¨ auf Struktur der Soft- ware, M¨oglichkeiten zur Echtzeitkommunikation und Machine-zu-Maschine Inter- aktion, sowie auf einheitliche Datenintegration und Benutzerfreundlichkeit einge- gangen. Am Ende des Prozesses steht eine fertige Softwarel¨osung als Proof-of- Concept, sowie eine Sammlung von Vorschl¨agen und Best Practices zur Integration von smarter Technologie auf dem Hallenboden. In einer abschließenden Evaluierung wird die Leistungsf¨ahigkeit und Tauglichkeit der Softwareplattform fur¨ bestimmte praktische Anwendungsf¨alle untersucht. Zudem werden abschließend noch offene Fragen und weiterhin ben¨otigte Entwicklungsschritte bis hin zu einem fertigen Pro- dukt aufgezeigt. vi vii Abstract While recent trends towards highly digitized, smart factories entail substantial chances for manufacturing companies to boost their performance, flexibility and productivity, the industry commonly struggles to adopt suitable technology. One major problem is a lack of uniform, standardized solutions, which could be integrated to the shop floor without the necessity of highly specialized technical expert knowledge and a large amount of planning and restructuring. Addressing that problem, this work proposes an architecture design as well as a concrete implementation of a Internet Of Things software platform, which mainly focuses on technological uniformity and ease of adoption and usage. As a guideline, a real-world use case elaborated in cooperation with industry partners is presented. Further on, it is shown, how general purpose web technology can be combined ad- vantageously with recent architectural-, operational- and cultural trends in software design, powerful machine-to-machine interaction techniques and common user expe- rience concepts. In-depth thoughts on software structure, just-in-time communica- tion, machine-to-machine interaction, uniform data integration and user experience are conducted to finally obtain a working proof-of-concept software alongside recom- mendations and best practices for adopting smart technology on the shop floor. An eventual evaluation investigates the designed platform regarding both performance and suitability for particular real-world scenarios and recommends further endeavor to be conducted towards achieving an actual product. viii Contents 1 Introduction1 1.1 Motivation.................................1 1.2 Structure.................................1 2 Background3 2.1 Industry 4.0 and the Digital Transformation..............3 2.1.1 Overview and Terminology....................3 2.1.2 Characteristics..........................3 2.1.3 Components............................4 2.1.4 Design Principles.........................4 2.2 Semantic Web and Linked Data.....................5 2.2.1 Ontologies.............................6 2.2.2 RDF................................6 2.2.3 JSON-LD.............................6 2.2.4 SPARQL..............................7 2.2.5 Linked Data Principles......................7 2.3 Design Patterns for Distributed Architectures.............7 2.3.1 Microservices...........................8 2.3.2 Microservices vs. SOA......................9 2.3.3 Serverless............................. 10 3 Manufacturing Shop Floor Scenario 11 4 Design 15 4.1 Overall Requirements........................... 15 4.2 Architecture................................ 17 4.2.1 Web Technology......................... 17 4.2.2 Distributed Architectures with Microservices.......... 18 4.2.2.1 Advantages....................... 19 4.2.2.2 Drawbacks....................... 20 4.2.2.3 Culture and Prerequisites............... 22 4.2.2.4 The Serverless Paradigm................ 23 4.2.2.5 Conclusion....................... 23 4.3 Communication.............................. 24 4.3.1 Event Collaboration....................... 24 4.3.2 Passive Communication..................... 24 4.3.3 Active Communication...................... 25 4.4 Data Integration............................. 26 4.5 Dynamic Service Composition...................... 26 x Contents 4.5.1 The Findability Problem..................... 26 4.5.2 Hypermedia-controlled Web APIs................ 27 4.5.3 Semantic Web APIs....................... 27 4.5.4 Hypermedia Formats....................... 28 4.5.5 Discovery............................. 32 4.5.5.1 Self-registration..................... 32 4.5.5.2 Client-side discovery.................. 33 4.5.5.3 Discovery by traversal................. 33 4.5.5.4 Conclusion....................... 33 4.5.6 Summary............................. 34 4.6 Apps as Building Blocks......................... 34 4.6.1 Compliance Requirements.................... 35 4.6.1.1 Compliance Level 0................... 35 4.6.1.2 Compliance Level 1................... 36 4.6.1.3 Compliance Level 2................... 36 4.6.2 App Store............................. 36 4.7 Conclusion................................. 37 5 Implementation 39 5.1 Demonstrative Scenario.......................... 39 5.2 Technology Stack............................. 41 5.3 Pub/Sub Technologies.......................... 41 5.3.1 Discussion............................. 41 5.3.2 Conclusion............................. 43 5.4 App Interface Design........................... 43 5.4.1 Active and Passive Communication............... 44 5.4.2 Self-describing Hypermedia APIs................ 45 5.5 Containerized Deployment........................ 48 5.5.1 Advantages............................ 48 5.5.2 Disadvantages........................... 49 5.5.3 Deployment Strategy....................... 50 5.5.3.1 "Where" to deploy................... 50 5.5.3.2 "How" to deploy.................... 51 5.5.4 Summary............................. 51 5.6 App Store................................. 52 5.6.1 Frontend.............................. 53 5.6.2 Backend.............................. 53 5.7 Conclusion................................. 55 5.7.1 App Requirements........................ 55 5.7.1.1 Compliance Level 0................... 55 5.7.1.2 Compliance Level 1................... 56 5.7.1.3 Compliance Level 2................... 57 5.7.2 Overall Requirements....................... 57 5.7.3 Architecture Stack........................ 58 6 Related Work 59 6.1 Web Things................................ 59 6.2 S-ToPSS.................................. 59 6.3 SemIoT.................................. 60 Contents i 6.4 Sense2Web................................. 60 6.5 Semantic Sensor Web........................... 60 6.6 Fraunhofer Industrial Data Space.................... 60 7 Evaluation 63 7.1 Summative Assessment.......................... 63 7.1.1 Workshop Demonstration Scenario............... 63 7.1.2 Feedback.............................. 64 7.1.3 Discussion............................. 65 7.2 Performance Evaluation......................... 65 7.2.1 Methodology and Setup..................... 65 7.2.2 Measuring Just-in-Time Capability............... 68 7.2.2.1 Results......................... 68 7.2.2.2 Discussion........................ 68 7.2.3 Comparison of Publish / Subscribe Technologies........ 70 7.2.3.1 Results......................... 71 7.2.3.2 Discussion........................ 71 7.2.3.3 Future Work...................... 75 7.2.4 Comparison between HTTP/1.1 and HTTP/2.0........ 75 7.2.4.1 Results......................... 76 7.2.4.2 Discussion........................ 77 8 Conclusion & Future Work 79 8.1 Summary................................. 79 8.2 Conclusion and Relevance........................ 80 8.3 Future Work................................ 80 Bibliography 81 ii Contents 1. Introduction 1.1 Motivation According to recent studies, companies are given a chance to increase their perfor- mance, flexibility and productivity by around 40 % when properly applying digiti- zation [1]. As a result, the topic of