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Testbed-12 Semantic Portrayal, Testbed-12 Semantic Portrayal, Registry and Mediation Registry and Mediation

Engineering Report (OGC 16-059)Engineering Report (OGC 16-059)101st OGC Technical Committee

Taichung, TaiwanStephane Fellah

06 December 2016

Copyright © 2016 Open Geospatial ConsortiumCopyright © 2016 Open Geospatial Consortium

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AgendaAgenda

Copyright © 2016 Open Geospatial Consortium

• Scope• Document Outline• Semantic Registry Information Model• Semantic Registry Service• SRIM Schema Application Profile• Semantic Mediation Service• Semantic Portrayal Ontologies• Semantic Portrayal Service• Future Works

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Scope

• Semantic Registry Service• Investigate the usage of DCAT to integrate multi-catalogs (CSW 2.0, CSW 3.0, CSW ebRIM)• Design a REST API to access DCAT-related information• Use Registry to register, search and discover Dataset and Services• Use Registry to register, search and discover Schema and Schema Mapping discovery• Use Registry to register, search and discover Semantic Portrayal Information

• Semantic Mediation Service• Define CSW ebRIM profile for Schema and Schema Mapping• Integrate CSW ebRIM with Semantic Registry• Define a Semantic Application profile for describing Schema and Schema Mapping• Focus on XML Schemas and XSLT Transformations for this testbed• Define REST API for Semantic Mediation Service to search and discover Schema and Schema

Mappings, perform transformation and validation.

• Semantic Portrayal Service• Support of text, point, line and area-based map symbologies• Enhance Testbed 11 Portrayal Ontologies by defining Symbolizers and Graphics Microtheories• Investigate use of Semantic Registry as Semantic Portrayal Catalog.• Define REST API for Semantic Portrayal Service


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Document Outline

• Overview• Status Quo & New Requirements Statement • Targeted Solutions and Recommendations• Semantic Registry Service• Semantic Mediation Service• Semantic Portrayal Service• Appendix A:Semantic Registry Information Model• Appendix B: SRIM Schema Application Profile• Appendix C: Semantic Portrayal Ontologies• Appendix D: Semantic Registry REST API• Appendix E: Semantic Mediation REST API• Appendix F: Semantic Portrayal Service REST API

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Semantic Registry Information Model(SRIM)


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Analysis

• Standards reviewed: • DCAT, DCAT-AP, ADMS, GeoDCAT-AP, Project Open Data (POD), CSW ebRIM,

ISO 19115-3, ISO 19139

• Report of issues found (20+) with mapping of ISO 19139 to DCAT (section 8.4.2)

• Major issue with identification of resources• Inability to refer to SKOS controlled vocabularies• Poor service metadata. Lack of standard classification of service types and

description of other REST APIs specification (Swagger, RAML,..) …

• DCAT is mostly focused on describing Datasets. GeoDCAT-AP provides a good foundation for geospatial data

• DCAT is not sufficient to describe services, schema, schema mappings, portrayal information => Needs a generalization of DCAT

• No well-established REST API for accessing DCAT• GeoSPARQL and Linked Data formats based on RDF/XML and Turtle too

complex for web clients. Needs of JSON and Resource oriented REST API


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Semantic Registry Information Model

• Core Ontology for Semantic Registry• Superset of DCAT• Introduce concepts of Register and Item (superclass of dcat:Dataset), ItemClass• All DCAT terms are preserved (a lot used in srim:Item).• Defined set of core reusable classes and properties• Extensible to define Application Profiles• Application Profiles developed during Testbed 12

– Service and Dataset– Schema Application Profile (Schema, Schema Mapping)– Portrayal Information

• SRIM introduces the notion of Release (3-layer approach) • Version tracking is using PAV ontology.• Service is a first class object (extension of Distribution)• Introduction of Standard URIs and APIDocument class to describe service APIs (simplified

description of APIs, instead of complex description of ISO 19119).• Appendix A: SRIM Core Ontology.

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Three-Layer Approach

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Semantic Registry Service

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REST API

Use for Level 3 Hypermedia REST API Schema Agnostic (JSON payload) Definition of Link Relation Types for each Service Decoupling Service API with Client Ecosystem Self-describing API and extensibility Explorable API (HAL Browser demonstrated)

All three Services implement:Level 2 supports JSON-LDURL Patterns of REST API are Non NormativeLevel 3 HAL+JSON(-LD)Linked Data (RDF/XML, Turtle, N-Triples)JSON can be converted to RDF form using JSON-LD Context.

Hypermedia Application Language (HAL)

Richardson Maturity Model

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Semantic Registry Clients

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Semantic Registry Client

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Resources for Semantic Registry Service

• Registers CRUD + Faceted search• Capabilities• JSON-LD Context • Items CRUD + Faceted Search • Item Class • GeoSPARQL• Harvester Sources• Harvester Types• Harvest operation• Harvester Objects (incomplete)• Harvester Results (incomplete)•

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Semantic Mediation Service

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Semantic Mediation Service Requirements

• SRIM Profile for schema and schema mapping• Semantic Registry as a service shall interface with the Schema

Registry which enables the discovery of XML Schemas, transformation logic, and ontologies.

• Support of XML Schema and XSL Transformation• Harvesting of Schema and Schema mapping from CSW ebRIM• Representation of schema and schema mapping using Linked

Data representation• Definition of REST API• Validation of Document against Schema• Transformation from document from Schema A to Schema B.• Transformation chaining

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Three-Layer Approach

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SRIM Schema Application Profile

• Schema and Schema Mapping

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• Implemented as a client of the Semantic Registry which stores schema information

• Definition of ebRIM Profile for Schema and Schema Mapping• Use of SRIM Schema Application Profile• Schema and Schema Mapping Harvester from ebRIM CSW• Level 2 and 3 REST API (JSON-LD, HAL+JSON, Linked Data Representation)• Provide convenience APIs to access following resources:

– Capabilities– JSON-LD Context– Schemas– Schema Mappings– Validator– Transform– SPARQL Endpoint


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Semantic Portrayal Service

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Semantic Portrayal Ontologies

• Testbed 11 Portrayal Ontologies limited to point-based Symbols – Focus on Emergency Management Symbologies

• What’s new in Testbed 12 ?– Refinement and correction to Style Ontology– Focus on FeatureTypeStyle– Text, Point, Line and Area Symbols– Graphics Ontology– Symbolizer Ontology– Better Alignment with SLD and SE (moved away from ISO 19117)– Use of OpenStreet Data and Style as testcase (see OGC 16-059)

• Out of scope for this testbed– Raster Symbolizer– Composite Symbols

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Portrayal Ontologies

Style

Symbolizer Graphics

Symbol

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Semantic Portrayal Ontologies

Style Ontology Symbol Ontology

Symbolizer OntologyGraphic Ontology

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Semantic Portrayal Service

• Implemented as a client of the Semantic Registry which stores portrayal information

• Level 2 and 3 REST API (JSON-LD, HAL+JSON, Linked Data Representation)

• Provide convenience APIs to access following resources:– Capabilities– JSON-LD Context– SymbolSets– Symbols– Styles– Symbol Renderer– Feature Data Renderer– SPARQL Endpoint

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Semantic Portrayal Registry

Portrayal Application Profile in Semantic Registry

Semantic Registry REST API SPARQL Endpoint

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Future Works

• Best practices for SRIM and ISO 19115 change modification

• SRIM Layer and Map Profile• Pubsub and federation of Registry• Web of Vocabulary Ontology and Service• Application of Shape Constraint Language (SHACL) for

Linked Data• Composite Symbology and alternates renderers for

Semantic Portrayal Service.

testbed-12 semantic portrayal, registry and mediation engineering report presentation

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