Agile 2015 a-geo-label-for-the-sensor-web
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Agile 2015 a-geo-label-for-the-sensor-web
- 1. A GEO label for the Sensor Web Daniel Nüst, 52°North Initiative for Geospatial Open Source GmbH, d.nuest@52north.org Victoria Lush, Aston University, lushv@aston.ac.uk AGILE 2015, Lisbon
- 2. Motivation & Approach Improve sensor data discovery for increasing amount of data in the sensor web smart cities big data metadata is not sexy, but necessary, and an image says more then a thousand words… Adapt GEO label to sensor web 1. Support sensor web datasources for labels 2. Integrating the label with sensor web metadata
- 3. GEO LABEL What is the GeoViQua …
- 4. Motivation GEOSS has millions of datasets GEO Science and Technology Committee proposed to establish a GEO label – a label “related to the scientific relevance, quality, acceptance and societal needs for activities in support of GEOSS” https://www.earthobservations.org/documents/geo_xi/ 5_3_GEOSS_Highlights_Massacand_Desconnets.pdf
- 5. What is the GEO label? http://geolabel.info and http://geolabel.net
- 6. GEO label facets producer profile producer comments lineage information standards compliance quality information user feedback expert review citations information
- 7. GEO label API Web service interface for label generation (SOA) XML API svg (and png) Portals Data services POST or ref Transformation Transformation Transformation
- 9. Sensor data discovery • Dynamic • Duality of instances and services • Interoperability standards rather complex > Profiles SensorML Profile for Discovery (Jirka et al.) identification, classification, temporal validity, capabilities, contact, location, interfaces, inputs and outputs of a stationary sensor and its components
- 10. A GEO LABEL FOR THE SENSOR WEB The Sensor Web Label – „SWL“
- 11. Requirements / Use case Scenario: stationary in-situ sensors • OGC Sensor Web Enablement Standards – SensorML – Sensor Observation Service – XML • Dynamic integration on client-side • Dynamic integration on the server side • Static integration in sensor and service metadata
- 12. Mappings
- 13. Mappings
- 14. Mappings
- 15. Labels within metadata documents • adding sensor labels in-line so that the whole label information is available in a form of SVG encoded as XML • as a reference to an online resource, such as a call to the GEO label API Schematron rules for defining valid integrations Challenge: denoting link/SVG as label
- 20. Prototype Integrated in open source project GEO-label-java https://github.com/52North/GEO-label-java/
- 21. Summary • Information for labels is available in SWE standards,but not all dynamic aspects of SWE are in the label • Going beyond GEO label: Integration • Requirements fulfilled completely for second generation standards (inline vs. ref) • Inline integration pros/cons: size, SOA, string matching (non- semantic) • Need pratical experience and users for consensus of suggested markups • Transformation file concept works! • Usefulness depends on portals > labels will increase portals‘ usability
- 22. Future Work Extending the SWL • New facets because discovery profile could not be mapped: standards compliance wrt APIs, license, valid time Extending data sources for SWL • SSN ontology and semantic web technology • IoT standards • SensorML 2.0 (typeOf), document hierarchies
- 24. THANK YOU! Questions? Comments? Feel free to get in touch @nordholmen or d.nuest@52north.org
Editor's Notes
- a visual metadata summary which can be integrated in discovery websites or catalogues to help users quickly grasp the availability of information and determine fitness-for-use
- The standards supported by the GEO label, namely ISO, FGDC, and the GeoViQua Quality Model, are XML-based. The specific XML fields to derive the availability and the contents of the label’s facets are defined using the XPath [4] expressions. XPath is a query language for XML documents and it is used to select and evaluate suitable elements to build the label’s facets. The expressions for one standard are grouped in the form of transformations which are stored as JSON files and contain fields to (i) check information availability, (ii) build a hover-over text based on a string template and XPaths to fill the placeholders, and (iii) add a drilldown URL hyperlink to the facet. The original mappings are available online and Figure 2 shows an excerpt of a transformer file. Multiple transformations can be applied to the same metadata document. http://geoviqua.github.io/geolabel/
- dynamic structure of sensor networks, user context and domain, and the duality of sensors instances and sensor services. Interoperability is crucial for the discovery mechanisms to work, since no singular platform can be assumed [11]. Because the existing standards are complex to accommodate requirements of different domains, profiles are defined to simplify uptake and increase interoperability. The SensorML Profile for Discovery [9] is a profile for SensorML 1.0.1. It specifies a subset of the standard, effectively taking away options and judgements calls from the implementers. It covers the identification, classification, temporal validity, capabilities, contact, location, interfaces, inputs and outputs of a stationary sensor and its components.
- There are three ways to integrate the SWL in a distributed sensor web architecture, and all of these should be supported by an SWL framework: (i) dynamic integration on the client-side, e.g., a desktop GIS generates a label for a dataset based on embedded metadata or a reference to a metadata document; (ii) dynamic integration on the server side, e.g., a broker or portal generates a label on the fly and extends the metadata in its response with an inline or referenced label; and (iii) static integration into the sensor and service metadata, e.g., as a reference to an online or offline resource for the label or inline within a metadata document.
- A screenshot of a Schematron document with rules to report both referenced and inline SWL in SensorML 2.0 documents.
- SUBTYPE
- The more recent standard provides extension points which can hold any kind of XML content. This makes the inline integration of an SVG-based inline SWL possible. Figure 6 shows a Schematron document for reporting embedded labels using a specific element <geolabel /> either in an extension or within SVG metadata; Figure 7 is the corresponding example document.
- A screenshot of an SOS 2.0 capabilities document excerpt displayed with Firefox browser. Within a swe:extension Element an intermediate <geolabel> element holds a reference to an SWL.
- Inline: sizes larger, not really SOA, require string matching
- New facets > survey Hierarchies: need also mechanisms to retrieve this