Integrating Industrial Middleware in Linked Data Collaboration Networks

Transcription

1 Elektrotechnik & Informationstechnik, Institut für Automatisierungstechnik, Professur Prozessleittechnik Linked Data Adapter for OPC UA Integrating Industrial Middleware in Linked Data Collaboration Networks Markus Graube, Jan Hladik, Leon Urbas ETFA 2016

2 Agenda Motivation Linked Data Transient data in LD Concept Accesing transient data in LD Mapping between OPC UA and Linked Data Implementation Conclusion Linked Data Adapter for OPC UA 2

3 Linked Data as Information Backend Semantic Information model Open-World-Assumption Extensibility References as first class items Light-weight approach Model as you use / Pay as you go Decentral Architecture cross-domain links Linked Data Adapter for OPC UA 3

4 Linked Data Technologies RDF URIs HTTP <Subject> <Predicate> <Object>. unique & dereferencable internet standard for access Ontologies General: RDFS, OWL Domain specific same model as for instances SPARQL graph based query language for RDF Linked Data Adapter for OPC UA 4

5 ComVantage Linked Data Architecture (Ziegler et. al, ETFA 2012) Linked Data Adapter for OPC UA 5

6 Hierarchy Aggregation Variables Functions Classes Methods Inheritance Derefencable References Federated Queries Information models for transient data (Mahnke et. al, 2011, Automation) Already established middlewares OPC UA and Substation Automation (IEC 61850) already provide an established and mature information model LD provides some additional modeling concepts, however focussed on static data IEC X X X - (x) OPC UA X X X X X X X - - Linked Data X X X X X (x) X X X Linked Data Adapter for OPC UA 6

7 Comparison OPC UA and Linked Data OPC UA Origin Automation Industry Characteristics Unique reference via server URL and node ID Advantages Performant dynamic data exchange Realtime capabilities in development Subscriptions Alarms Integration in most automation systems (in the future) Linked Data Origin Semantic Web (IT) Characteristics Unique reference via HTTP URI Advantages Tailored for providing heterogenous decentral information spaces Revisioning mechanisms Large community with big public available data sets Comprehensive tool support Using established internet standards Commonalities Semantic information model Graph based Isomorphic mapping possible Service oriented adapter between both worlds Linked Data Adapter for OPC UA

8 Linked Data OPC UA Adapter Approach OPC UA adapter for accessing transient data in LD Challenges 1. Model transient data in Linked Data 2. Providing a mechanism for accessing this information Linked Data Adapter for OPC UA 8

9 Challenge 1: VOPR vocabulary Resulting process data needs to be modelled by a specific vocabulary Several ontologies are available describing physical quantities and units (e.g. QUDT) describing statistical datasets (RDF data Cube vocabulary) Combination into Vocabulary Of Processvariable Representation (VOPR), which is used to deliver information from the Linked Data adapter and link to the specific REST resources Linked Data Adapter for OPC UA 9

10 Challenge 2: Linked Data Adapter - Access to transient data Cyclic polling and storing in triplestore Simple approach Performance limits Seperation sensors and actuators are semantically described in the LD cloud including information about the access method Direct access to the data via a dedicated Linked Data adapter on demand Linked Data Adapter for OPC UA 10

11 Linked Data Adapter: Live Data Access Application Retrieving of static semantic information from LD cloud hierarchic plant structure Sensor properties Method for accessing sensor data HTTP request LD Adapter Transformation of HTTP requests into middleware calls Read sensors or acuators Write actuators Result Recent value in RDF serialisation (e.g. Turtle) Linked Data Adapter for OPC UA 11

12 Linked Data vs. REST services (Page, De Roure, Martinez, 2011) REST Representational State Transfer Paradigm for web applications Compatible to Linked Data Resources Identification via URIs Preference of HTTP Links Semantic information independant from resource identifier adaptability Linked Data Adapter for OPC UA 12

13 Mapping OPC UA & LD OPC UA NodeId (Namespace + Type + Value) ns=2;i=84 Linked Data HTTP URI Direct Mapping possible Alternative Examples namespace: 2 Identifier: i=84 Namespace: 3 Identifier: s=pumpp Linked Data Adapter for OPC UA 13

14 OPC UA Services as REST requests (1/2) GET request Browse Service?browse ReadAttribte Service?attribute HistoryRead Service?start?end POST request WriteAttribute Service New information in HTTP body CallMethod Service PUT request methodid and parameters in HTTP body addnode Service Information in HTTP body DELETE request deletenode Service Linked Data Adapter for OPC UA 14

15 OPC UA Services as REST requests (2/2) Low Level OPC UA services directly handled by adapter SecureChannel, Session and Discovery Service sets Unsupported OPC UA services MonitoredItem Service Set Subscription Service Set HistoryUpdate BrowseNext RegisterNode/UnregisterNode Linked Data Adapter for OPC UA 15

16 Serialisation (1/2) Browse GET mw:ns/2/i/23 a opcua:node; opcua:browsename Subplant 1 ; opcua:hastypedefinition mw:ns/2/i/61; opcua:organizes mw:ns/2/i/25, mw/ns/2/s/pumpa; mw:ns/2/s/isconnectedto mw:ns/2/i/24. Reading values GET pa?attribute=value [] a vopr:value ; vopr:value 23.0; vopr:attime " T10:50:28Z ; vopr:providedby mw:ns/2/s/pumpa Linked Data Adapter for OPC UA 16

17 Serialisation (2/2) Historical Data GET [] a vopr:historyslice ; vopr:startat " T15:40: ; vopr:endat " T15:44: ; vopr:hashistory[ ]; a rdf:seq ; rdf:_1 [ a vopr:value ; vopr:attime " T15:43: ; vopr:value "67.0"] ; rdf:_2 [ a vopr:value ; vopr:attime " T15:43:49.375"; vopr:value "66.0"]; vopr:providedby mw:ns/2/s/pumpa Linked Data Adapter for OPC UA 17

18 Prototypical Implementation Java Application Prosys OPC UA SDK Jersey Web Service Proof-of-concept Browse, Read, Write, CallMethod Linked Data Adapter for OPC UA 18

19 Conclusion Discussion Integration of OPC UA and LD possible Advantages from both worlds Prototypical implementation shows feasibility Back link from OPC UA to LD necessary Next Steps Reimplementation and performance evaluation Better support of web applications JSON-LD as serialisation Concept for integrating Query Service set into REST service SPARQL-Bridge Linked Data Adapter for OPC UA 19

20 Thank you for your attention! For question, please contact: Prof. Dr. habil. Leon Urbas Technische Universität Dresden Fakultät Elektrotechnik und Informationstechnik Institut für Automatisierungstechnik Tel.: Fax: Besucheradresse: Barkhausen-Bau Georg-Schumann-Str Dresden Postanschrift (Briefe): Technische Universität Dresden Fakultät Elektrotechnik und Informationstechnik Institut für Automatisierungstechnik Dresden