## 6 Semantic Event Description  
As our system consists of many components dealing with events, communication between these components needs to be considered. We created a common message format to describe events that could be used for bidirectional exchange of information between event detectors and dashboards, containing the details needed for event visualization and feedback capturing. This way, components only need to understand a single message format, instead of one per communication path. Since our system contains both semantic and non-semantic components, we opted for a semantic format. Semantic descriptions use the Resource Description Framework (RDF) [22], a standard data exchange format representing data as a set of facts (also called triples), expressed as subject-predicate-object relationships such as \"Event 1 was detected by detector X\". The resources used as subject, predicate or object are represented by an IRI (Internationalized Resource Identifier), facilitating the uniqueness and unambiguity of identifiers. Most often, IRIs are constructed using URLs (Uniform Resource Locators), i.e., addresses of resources on the Internet. In addition to resources, triple objects may be literals, i.e., data-typed values such as a date or a number. A set of triples is called a (knowledge) graph. Reuse of resources from other graphs is highly encouraged. Vocabularies or ontologies are graphs that bundle reusable resources and relationships and additional information such as restrictions and logic rules. Because of these mechanisms, using the RDF standard as a common event message format allows detectors and dashboards to unambiguously refer to specific events, detectors, sensors, sensor observations, etc. Moreover, the addition of identified resource relations, restrictions and logic rules enable machine-understandable semantics: consumers of event information messages can interpret the meaning of the described resources. This enables semantic reasoning about the event information, which is the basis of the knowledge-driven event detectors and automated event dashboarding presented in this paper. An example event description can be found in Listing 1. Please note that we use the Notation3 (N3) [23] to serialize the RDF. N3 is one of the standard serialization formats of RDF and provides good human-readability and low verbosity. ```
``` opprefix xzd: <[[http://www.w3.org/2001/XMLSchemsD](http://www.w3.org/2001/XMLSchemsD)]([http://www.w3.org/2001/XMLSchemsD](http://www.w3.org/2001/XMLSchemsD))>. @prefix sosa: <[[http://www.w3.org/ms/sosa/](http://www.w3.org/ms/sosa/)]([http://www.w3.org/ms/sosa/](http://www.w3.org/ms/sosa/))>. @prefix folio: <[[http://HSCENervices.github.io/Folio-Qntology/Folio.owl](http://HSCENervices.github.io/Folio-Qntology/Folio.owl)]([http://HSCENervices.github.io/Folio-Qntology/Folio.owl](http://HSCENervices.github.io/Folio-Qntology/Folio.owl))>. @prefix sns: <[[http://www.org/ms/](http://www.org/ms/)]([http://www.org/ms/](http://www.org/ms/))>. @prefix sns: <[[https://idlab-id.tenteng.io/api/vl/vocabary/](https://idlab-id.tenteng.io/api/vl/vocabary/)]([https://idlab-id.tenteng.io/api/vl/vocabary/](https://idlab-id.tenteng.io/api/vl/vocabary/))>. @prefix ns5: <[[https://idlab-id.tenteng.io/api/vl/boolecians/](https://idlab-id.tenteng.io/api/vl/boolecians/)]([https://idlab-id.tenteng.io/api/vl/boolecians/](https://idlab-id.tenteng.io/api/vl/boolecians/))>. @prefix dcterms: <[[http://purl.org/dcterms/](http://purl.org/dcterms/)]([http://purl.org/dcterms/](http://purl.org/dcterms/))>. @prefix proc: <[[http://www.w3.org/ms/provprov](http://www.w3.org/ms/provprov)]([http://www.w3.org/ms/provprov](http://www.w3.org/ms/provprov))>. @prefix rdfs: <[[http://www.w3.org/2000/01/rdf-schemaD](http://www.w3.org/2000/01/rdf-schemaD)]([http://www.w3.org/2000/01/rdf-schemaD](http://www.w3.org/2000/01/rdf-schemaD))>.