Draft to include styles for features

spec/document.adoc

@@ -88,6 +88,8 @@ include::sections/11-geometry_extension.adoc[]
 
 include::sections/12-geometry_topology_extension.adoc[]
 
+include::sections/12a-style_extension.adoc[]
+
 include::sections/13-rdfs_entailment_extension.adoc[]
 
 include::sections/14-query_rewrite_extension.adoc[]

spec/sections/12a-style_extension.adoc

@@ -0,0 +1,165 @@
+[#geometry_style_extension]
+== Geometry Style Extension
+
+This section establishes the introduction of geometry styles into the GeoSPARQL standard.
+
+Geometries are visualized differently under different circumstances and in different map visualization contexts, as defined by legal or preferential, e.g. community-driven efforts.
+
+A geometry style is hereby defined as a set of instructions representing the geometry in a given context.
+
+This extension contains and represents the essential elements of the OGC Styled layer and OGC Symbology Encoding standar description standard without implementing the rules for their application.
+The latter might be implemented as SHACL or reasoning rules and, for now, fall out of the scope of GeoSPARQL.
+
+==== Class: geo:Style
+
+The class http://www.opengis.net/ont/geosparql#Style[`geo:Style`] depicts the abstract representation of the style of a geospatial feature and is defined by the following:
+
+```turtle
+geo:Style
+    a rdfs:Class, owl:Class ;
+    rdfs:isDefinedBy geo: ;
+    skos:prefLabel "Style"@en ;
+    skos:definition "A representation of a way to style a geospatial feature on e.g. a map representation."@en ;
+    skos:note "A Feature Style expresses one or many style representations which can be used to display a spatial object in a suitable rendering."@en ;
+.
+```
+
+[#req_geostyle_style-class]
+|===
+| *Req {counter:req}* Implementations shall allow the RDFS class <<Class: geo:Style, `geo:Style`>> to be used in SPARQL graph patterns.
+|http://www.opengis.net/spec/geosparql/1.0/req/core/style-class[`http://www.opengis.net/spec/geosparql/1.0/req/core/style-class`]
+|===
+
+==== Class: geo:StyleIcon
+
+The class http://www.opengis.net/ont/geosparql#StyleIcon[`geo:StyleIcon`] depicts the abstract representation of the image used by a style of a geospatial feature and is defined by the following:
+
+```turtle
+geo:StyleIcon
+    a rdfs:Class, owl:Class ;
+    rdfs:isDefinedBy geo: ;
+    skos:prefLabel "StyleIcon"@en ;
+    skos:definition "A representation of an image which is used in representations of a geo:Style ."@en ;
+.
+```
+
+[#req_geostyle_styleicon-class]
+|===
+| *Req {counter:req}* Implementations shall allow the RDFS class <<Class: geo:StyleIcon, `geo:StyleIcon`>> to be used in SPARQL graph patterns.
+|http://www.opengis.net/spec/geosparql/1.0/req/core/styleicon-class[`http://www.opengis.net/spec/geosparql/1.0/req/core/styleicon-class`]
+|===
+
+==== Property: geo:hasStyle
+
+The property http://www.opengis.net/ont/geosparql#hasStyle[`geo:hasStyle`] links a <<Class: geo:SpatialObject, `geo:SpatialObject`>> to a <<Class: geo:Style, `geo:Style`>> representation.
+
+```turtle
+ex:mystyle rdf:type geo:Style .
+ex:myfeature rdf:type geo:Feature .
+ex:myfeature_geom rdf:type sf:Point .
+ex:myfeature geo:hasGeometry ex:myfeature_geom .
+ex:myfeature geo:hasStyle geo:mystyle .
+.
+```
+
+[#req_geostyle_hasstyle-property]
+|===
+| *Req {counter:req}* Implementations shall allow the property <<Property: geo:hasStyle, `geo:hasStyle`>> to be used in SPARQL graph patterns.
+|http://www.opengis.net/spec/geosparql/1.0/req/geostyle/hastyle-property[`http://www.opengis.net/spec/geosparql/1.0/req/geostyle/hasstyle-property`]
+|===
+
+==== Property: geo:hasIcon
+
+The property http://www.opengis.net/ont/geosparql#hasIcon[`geo:hasIcon`] links a <<Class: geo:Style, `geo:Style`>> to a <<Class: geo:StyleIcon, `geo:StyleIcon`>> representation.
+
+```turtle
+ex:mystyle rdf:type geo:Style.
+ex:myfeature rdf:type geo:Feature .
+ex:myfeature_geom rdf:type sf:Point .
+ex:myfeature geo:hasGeometry ex:myfeature_geom .
+ex:myfeature geo:hasStyle geo:mystyle .
+geo:mystyle geo:hasIcon geo:mystyle_icon .
+geo:mystyle_icon geo:markerIcon "<svg>....</svg>"^^geo:svgLiteral .
+```
+
+[#req_geostyle_hasstyle-property]
+|===
+| *Req {counter:req}* Implementations shall allow the property <<Property: geo:hasIcon, `geo:hasIcon`>> to be used in SPARQL graph patterns.
+|http://www.opengis.net/spec/geosparql/1.0/req/geostyle/hastyle-property[`http://www.opengis.net/spec/geosparql/1.0/req/geostyle/hasstyle-property`]
+|===
+
+==== Property: geo:markerIcon
+
+The property http://www.opengis.net/ont/geosparql#markerIcon[`geo:markerIcon`] links a <<Class: geo:Style, `geo:Style`>> to a representation of an icon which can be used on map representation as a marker or along or within a geometry. The value of this property may either be an SVG representation in a geo:svgLiteral or a link to an image representation, represented as an xsd:anyURI.
+
+```turtle
+ex:mystyle rdf:type geo:Style .
+ex:mystyle geo:hasIcon ex:mystyle_icon .
+ex:mystyle_icon geo:markerIcon "<svg>...</svg>"^^geo:svgLiteral .
+ex:mystyle_icon geo:markerIcon "http://......jpg"^^xsd:anyURI .
+```
+
+==== Property: geo:rotation
+
+The property http://www.opengis.net/ont/geosparql#rotation[`geo:rotation`] defines the rotation of a StyleIcon instance in degrees, as an xsd:double literal.
+
+```turtle
+ex:mystyle rdf:type geo:Style .
+ex:mystyle geo:hasIcon ex:mystyle_icon .
+ex:mystyle_icon geo:rotation "170.0"^^xsd:double .
+```
+
+==== Property: geo:asGeoCSS
+
+The property http://www.opengis.net/ont/geosparql#asGeoCSS[`geo:asGeoCSS`] links a <<Class: geo:Style, `geo:Style`>> to a serialization of the style in CSS rendered in a geo:geocssLiteral.
+
+```turtle
+ex:mystyle rdf:type geo:Style .
+ex:mystyle geo:asGeoCSS "stroke:black,fill:red,stroke-width:3,fill-opacity:0.6"^^geo:geocssLiteral
+.
+```
+
+[#req_geostyle_iconcss-property]
+|===
+| *Req {counter:req}* Implementations shall allow the properties <<Property: geo:markerIcon, `geo:markerIcon`>> and <<Property: geo:asGeoCSS, `geo:asGeoCSS`>> to be used in SPARQL graph patterns.
+|http://www.opengis.net/spec/geosparql/1.0/req/geostyle/iconcss-property[`http://www.opengis.net/spec/geosparql/1.0/req/geostyle/iconcss-property`]
+|===
+
+==== Datatype: geo:geocssLiteral
+
+The literal http://www.opengis.net/ont/geosparql#geocssLiteral[`geo:geocssLiteral`] encodes a subset of CSS statements that apply to geometry representations.
+The subset of CSS expressions limited to the statements which apply to SVG representations.
+In particular, these are the following attributes and the special marker attribute which indicates a marker shape as Well-Known Name (see Symbology Encoding standard)
+
+```css
+fill: color
+stroke: color
+stroke-width: number
+fill-opacity: number
+opacity: number 
+dashArray: array of numbers
+markertype: square | circle | triangle | star | cross | x
+```
+This allows for the modification of all visible parts of a geometry on a map, as defined in the OGC Styled layer descriptor standard.
+
+[#req_geostyle_geocss-literal]
+|===
+| *Req {counter:req}* All RDFS Literals of type <<RDFSDatatype: geo:geocssLiteral, `geo:geocssLiteral`>> shall consist of a set of definitions of cascading stylesheets which are meant to modify the given geometry while displayed in a viewer application.
+|http://www.opengis.net/spec/geosparql/1.0/req/geostyle/geocss-literal[`http://www.opengis.net/spec/geosparql/1.0/req/geostyle/geocss-literals`]
+|===
+
+==== Datatype: geo:svgLiteral
+
+The literal http://www.opengis.net/ont/geosparql#svgLiteral[`geo:svgLiteral`] encodes an SVG representation in plain text.
+
+```svg
+ex:mystyle geo:markerIcon "<svg viewBox=\"0 0 100 100\" xmlns=\"http://www.w3.org/2000/svg\"><circle cx=\"50\" cy=\"50\" r=\"50\"/></svg>"^^geo:svgLiteral .
+```
+[#req_geostyle_svg-literal]
+|===
+| *Req {counter:req}* All RDFS Literals of type <<RDFSDatatype: geo:svgLiteral, `geo:svgLiteral`>> shall consist of a Scalable Vector Graphics expression (SVG), which may be used to visualize geometries on a given map representation.
+|http://www.opengis.net/spec/geosparql/1.0/req/geostyle/svg-literal[`http://www.opengis.net/spec/geosparql/1.0/req/geostyle/svg-literals`]
+|===
+
+
+