ELFIE Relations

Draft set of relations to be provided in responses. This is a common set that can be applied to all features (classes). It assumes that we are dealing with instances of either gsp:Feature or time:TemporalEntity (with skos:Concepts being a useful proxy for either).

The set has been created to support the fundamental goal of ELFIE: linking data objects describing environmental features using a formalized/well-known set of relations as captured in published 'normative' JSON-LD contexts. It also considers these recommendations from the Spatial Data on the Web WG (SDW) Best Practices:

1. Best Practice 2: Make your spatial data indexable by search engines
2. Best Practice 3: Link resources together to create the Web of data

Criteria for selection:

• Follow recommended in best practices, specifically the use of schema.org for indexing (from JSON-LD and SDW).
• Close to a first order/core ontology (for example RDFS, OWL)
• Defined by the OGC and/or the W3C (GSP, TIME, SOSA)
• Are widely used (SKOS, DC, FOAF)
• Have a rdfs:domain that is, or is nearly, a top-level class (rdfs:Class, owl:Thing, skos:Concept, gsp:Feature, time:TemporalEntity)

VIEW	RELATION	COMMENT
elf-basic	rdfs:type	The type, or types if multiple representations are available, of the resource.
elf-basic	schema:name	A useful summary label. May concatenate a set of labels from multiple instances. Multilingual. (Was rdfs:label.)
elf-index		Includes elf-basic
elf-index	schema:description	A useful summary description. (JY: or dcterms:description?) (Was rdfs:comment.)
elf-index	schema:sameAs	Other instances of the same non-information resource - therefore properties can be merged. Is the sameAs owl:sameAs. (If not ... skos:exactMatch?)
elf-index	schema:image	A typical or thumbnail image of the feature. ABHR: change from foaf:img as that implies the resource is a foaf:Person. Domain of foaf:depiction is owl:Thing. 2017-08-02: latest change from foaf to schema.org ... inline with JSON-LD best practice. Debatable decision.
elf-index	schema:geo	A representative geometry useful for thumbnails or location maps. Not for measurement or analysis.
elf-net		Includes elf-net-basic, elf-net-spatial and elf-net-topology. (For the feature's mother - who wants to know about all the relationships.)
elf-net-basic	skos:related	A summary set of related features. ABHR: Needed? -> S.Grellet : yes we have to keep it as not all network links will be of type spatial (ex : linking piezometer to aquifer or aquifer to river when the interaction zone is not clear or aquifer/river to management area/zone). -> ABHR: OK. This would work well for the summary (not necessarily complete) of relations - as with other summaries (e.g. gsp:hasGeometry) the specifics are handled by the domain representations. (Some of your examples might be handled with topological statements.)
elf-net-spatial	gsp:sfIntersects	See OGC 11-052r4, Table 1.
elf-net-spatial	gsp:sfTouches	See OGC 11-052r4, Table 1.
elf-net-spatial	gsp:sfWithin	See OGC 11-052r4, Table 1.
elf-net-spatial	gsp:Interacts	Shorthand for ~gsp:sfDisjoint or everything but disjoint
elf-net-temporal	time:after	See OGC 16-071r2, Section 4.2.
elf-net-temporal	time:before	See OGC 16-071r2, Section 4.2.
elf-net-temporal	time:intervalAfter	See OGC 16-071r2, Section 4.2.
elf-net-temporal	time:intervalBefore	See OGC 16-071r2, Section 4.2.
elf-net-temporal	time:intervalDuring	See OGC 16-071r2, Section 4.2.

Notes:

• elf-basic can be used for multiple resources (i.e. when multiple representations are available)
• elf-basic allows an agent to test that a resource is worth getting (ABHR: perhaps no longer necessary if we construct links as an id, type and name 'stub' object)
• elf-basic allows an browser to construct a labelled hyper-link
• elf-index supports ... well ... indexing. (Was previously elf-preview.)
• elf-index can only meaningfully be used for single representations
• elf-index allows a browser to construct a summary view of the resource (similar to a Google Knowledge Panel)
• elf-net-spatial chose the Simple Features topology relations over Egenhofer and RCC8 from GeoSPARQL, well ... just because.

Change Notes:

Initial versions of the relation list attempted to address matters of provenance and access (see the notes and table below). As these were only partial implementation of a large range of available relations they cause much confusion for very little gain so they have been moved for the preview relation set and been replaced with relations that support the indexing requirements. In some cases relations have been kept, but replaced with their schema.org equivalents.

• elf-preview is now elf-index.
• elf-preview allows an agent to establish equivalence and provenance of a resource (they may be different representations but from the same creator)
• elf-preview allows an agent to discover basic access constraints (right now licensing)

Deprecated relations

VIEW	RELATION	COMMENT
elf-preview	owl:versionInfo	Version number.
elf-preview	dcterms:creator	The creator/owner of the resource.
elf-preview	gsp:hasGeometry	A representative geometry useful for thumbnails or location maps. Not for measurement or analysis. Replaced with schema.org geometries because it was ambigious (ontologies like SOSA use it for precise locations) and not expected by we crawlers.
elf-preview	dcterms:license	License constraints