Author: andy
Date: Thu May 30 17:37:31 2019
New Revision: 1860412
URL: http://svn.apache.org/viewvc?rev=1860412&view=rev
Log:
GeoSPARQl documentartion
Added:
jena/site/trunk/content/documentation/geosparql/
jena/site/trunk/content/documentation/geosparql/geosparql-fuseki.md
jena/site/trunk/content/documentation/geosparql/index.md
Added: jena/site/trunk/content/documentation/geosparql/geosparql-fuseki.md
URL:
http://svn.apache.org/viewvc/jena/site/trunk/content/documentation/geosparql/geosparql-fuseki.md?rev=1860412&view=auto
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30 17:37:31 2019
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+Title: GeoSPARQL Fuseki
+
+This application provides a HTTP server compliant with the GeoSPARQL standard.
+It uses the embedded server Fuseki from Apache Jena and provides additional
parameters for dataset loading.
+
+The project uses the GeoSPARQL implementation from the [GeoSPARQL Jena
project](index).
+Currently, there is no GUI interface as provided in the Fuseki distribution.
+
+A subset of the EPSG spatial/coordinate reference systems are included by
default from the Apache SIS project (http://sis.apache.org).
+The full EPSG dataset is not distributed due to the the EPSG terms of use
being incompatible with the Apache Licence.
+Several options are available to include the EPSG dataset by setting the
`SIS_DATA` environment variable (http://sis.apache.org/epsg.html).
+
+It is expected that at least one Geometry Literal or Geo Predicate is present
in a dataset.
+A spatial index is created and new data cannot be added to the index once
built.
+The spatial index can optionally be stored for future usage and needs to
removed from a TDB folder if the index is to rebuilt.
+
+## Getting Started
+GeoSPARQL Fuskei can be accessed as an embedded server using Maven etc. from
Maven Central or run from the command line.
+SPARQL queries directly on Jena Datasets and Models can be done using
+the [GeoSPARQL Jena project](index).
+
+```
+<dependency>
+ <groupId>org.apache.jena</groupId>
+ <artifactId>fuseki-geosparql</artifactId>
+ <version>...</version>
+</dependency>
+```
+
+### Command Line
+Run from the command line (see `releases` tab) and send queries over HTTP.
+
+Get Started Example:
+`.\geosparql-fuseki.bat -rf "geosparql_test.rdf>xml" -i`
+
+The example file `geosparql_test.rdf` in the GitHub repository contains
several geometries in geodectic WGS84 (EPSG:4326).
+The example file `geosparql_test_27700.rdf` is identical but in the projected
OSGB36 (EPSG:27770) used in the United Kingdom.
+Both will return the same results as GeoSPARQL treats all SRS as being
projected.
+RDFS inferencing is applied using the GeoSPARQL schema to infer additional
relationships (which aren't asserted in the example files) that are used in the
spatial operations and data retrieval.
+
+Examples:
+
+* Load RDF file (XML format) into memory and run server:
`.\geosparql-fuseki.bat -rf "test.rdf>xml"`
+
+* Load RDF file (TTL format: default) into memory, apply GeoSPARQL schema with
RDFS inferencing and run server: `.\geosparql-fuseki.bat -rf "test.rdf" -i`
+
+* Load RDF file into memory, write spatial index to file and run server:
`.\geosparql-fuseki.bat -rf "test.rdf" -si "spatial.index"`
+
+* Load RDF file into persistent TDB and run server: `.\geosparql-fuseki.bat
-rf "test.rdf>xml" -t ".\TestTDB"`
+
+* Load from persistent TDB and run server: `.\geosparql-fuseki.bat -t
".\TestTDB"`
+
+* Load from persistent TDB, change port and run server:
`.\geosparql-fuseki.bat -t ".\TestTDB" -p 3030`
+
+ See [rdf-tables](https://github.com/galbiston/rdf-tables) in _Output
Formats/Serialisations_ for supported RDF format keywords.
+
+__N.B.__ Windows Powershell will strip quotation pairs from arguments and so
triple quotation pairs may be required, e.g. """test.rdf>xml""". Otherwise,
logging output will be sent to a file called "xml". Also, "The input line is
too long" error can mean the path to the .bat exceeds the character limit and
needs shortening.
+
+### Embedded Server
+Run within a Java application to provide GeoSPARQL support over HTTP to other
applications:
+
+`GeosparqlServer server = new GeosparqlServer(portNumber, datasetName,
isLoopbackOnly, dataset, isUpdate);`
+
+## SPARQL Query Example
+Once the default server is running it can be queried using Apache Jena as
follows:
+
+```
+String service = "http://localhost:3030/ds";;
+String query = ....;
+try (QueryExecution qe = QueryExecutionFactory.sparqlService(service, query)) {
+ ResultSet rs = qe.execSelect();
+ ResultSetFormatter.outputAsTSV(rs);
+}
+```
+
+The server will respond to any valid SPARQL HTTP so an alternative SPARQL
framework can be used.
+More information on SPARQL querying using Apache Jena can be found on their
website (https://jena.apache.org/tutorials/sparql.html).
+
+## SIS_DATA Environment Variable
+The Apache SIS library is used to support the recognition and transformation
of Coordinate/Spatial Reference Systems.
+These Reference Systems are published as the EPSG dataset.
+The full EPSG dataset is not distributed due to the EPSG terms of use being
incompatible with the Apache Licence.
+A subset of the EPSG spatial/coordinate reference systems are included by
default but the wider dataset may be required.
+Several options are available to include the EPSG dataset by setting the
`SIS_DATA` environment variable (http://sis.apache.org/epsg.html).
+
+An embedded EPSG dataset can be included in an application by adding the
following dependency:
+
+* Gradle dependency in `build.gradle`
+```
+ext.sisVersion = "0.8"
+implementation "org.apache.sis.non-free:sis-embedded-data:$sisVersion"
+```
+
+* Maven dependency in `pom.xml`
+```
+<dependency>
+ <groupId>org.apache.sis.non-free</groupId>
+ <artifactId>sis-embedded-data</artifactId>
+ <version>0.8</version>
+</dependency>
+```
+
+## Command Line Arguments
+
+Boolean options that have false defaults only require "--option" to make true
in release v1.0.7 or later.
+Release v1.0.6 and earlier use the form "--option true".
+
+### 1) Port
+```
+--port, -p
+```
+
+The port number of the server. Default: 3030
+
+### 2) Dataset name
+```
+--dataset, -d
+```
+
+The name of the dataset used in the URL. Default: ds
+
+### 3) Loopback only
+```
+--loopback, -l
+```
+
+The server only accepts local host loopback requests. Default: true
+
+### 4) SPARQL update allowed
+```
+--update, -u
+```
+
+The server accepts updates to modify the dataset. Default: false
+
+### 5) TDB folder
+```
+--tdb, -t
+```
+
+An existing or new TDB folder used for the dataset. Default set to memory
dataset.
+If accessing a dataset for the first time with GeoSPARQL then consider the
`--inference`, `--default_geometry` and `--validate` options. These operations
may add additional statements to the dataset.
+
+### 6) Load RDF file into dataset
+```
+--rdf_file, -rf
+```
+
+Comma separated list of [RDF file path#graph name&RDF format] to load into
dataset. Graph name is optional and will use default graph. RDF format is
optional (default: ttl) or select from one of the following: json-ld, json-rdf,
nt, nq, thrift, trig, trix, ttl, ttl-pretty, xml, xml-plain, xml-pretty.
+e.g. `test.rdf#test&xml,test2.rdf` will load _test.rdf_ file into _test_ graph
as _RDF/XML_ and _test2.rdf_ into _default_ graph as _TTL_.
+
+Consider the `--inference`, `--default_geometry` and `--validate` options.
These operations may add additional statements to the dataset.
+
+### 7) Load Tabular file into dataset
+```
+--tabular_file, -tf
+```
+
+Comma separated list of [Tabular file path#graph name|delimiter] to load into
dataset. See RDF Tables for table formatting. Graph name is optional and will
use default graph. Column delimiter is optional and will default to COMMA. Any
character except ':', '^' and '|'. Keywords TAB, SPACE and COMMA are also
supported.
+e.g. `test.rdf#test|TAB,test2.rdf` will load _test.rdf_ file into _test_ graph
as _TAB_ delimited and _test2.rdf_ into _default_ graph as _COMMA_ delimited.
+
+See RDF Tables project (https://github.com/galbiston/rdf-tables) for more
details on tabular format.
+
+Consider the `--inference`, `--default_geometry` and `--validate` options.
These operations may add additional statements to the dataset.
+
+### 8) GeoSPARQL RDFS inference
+```
+--inference, -i
+```
+
+Enable GeoSPARQL RDFS schema and inferencing (class and property hierarchy).
Inferences will be applied to the dataset. Updates to dataset may require
server restart. Default: false
+
+### 9) Apply hasDefaultGeometry
+```
+--default_geometry, -dg
+```
+
+Apply hasDefaultGeometry to single Feature hasGeometry Geometry statements.
Additional properties will be added to the dataset. Default: false
+
+### 10) Validate Geometry Literals
+```
+--validate, -v
+```
+
+Validate that the Geometry Literals in the dataset are valid. Default: false
+
+### 11) Convert Geo predicates
+```
+--convert_geo, -c
+```
+
+Convert Geo predicates in the data to Geometry with WKT WGS84 Point
GeometryLiteral. Default: false
+
+### 12) Remove Geo predicates
+```
+--remove_geo, -rg
+```
+
+Remove Geo predicates in the data after combining to Geometry.
+
+### 13) Query Rewrite enabled
+```
+--rewrite, -r
+```
+
+Enable query rewrite extension of GeoSPARQL standard to simplify queries,
which relies upon the 'hasDefaultGeometry' property. The 'default_geometry' may
be useful for adding the 'hasDefaultGeometry' to a dataset. Default: true
+
+### 14) Indexing enabled
+```
+--index, -x
+```
+
+Enable caching of re-usable data to improve query performance. Default: true
+See [GeoSPARQL Jena project](index) for more details.
+
+### 15) Index sizes
+```
+--index_sizes, -xs
+```
+
+List of Index item sizes: [Geometry Literal, Geometry Transform, Query
Rewrite]. Unlimited: -1, Off: 0 Unlimited: -1, Off: 0, Default: -1,-1,-1
+
+### 16) Index expiries
+```
+--index_expiry, -xe
+```
+
+List of Index item expiry in milliseconds: [Geometry Literal, Geometry
Transform, Query Rewrite]. Off: 0, Minimum: 1001, Default: 5000,5000,5000
+
+### 17) Spatial Index file
+```
+--spatial_index, -si
+```
+
+File to load or store the spatial index. Default to "spatial.index" in TDB
folder if using TDB and not set. Otherwise spatial index is not stored.
+
+### 18) Properties File
+Supply the above parameters as a file:
+```console
+$ java Main @/tmp/parameters
+```
+
+## Future Work
+* GUI to assist users when querying a dataset.
+
+
Added: jena/site/trunk/content/documentation/geosparql/index.md
URL:
http://svn.apache.org/viewvc/jena/site/trunk/content/documentation/geosparql/index.md?rev=1860412&view=auto
==============================================================================
--- jena/site/trunk/content/documentation/geosparql/index.md (added)
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+Title: Apache Jena GeoSPARQL
+
+An implementation of GeoSPARQL 1.0 standard for SPARQL query or API.
+
+## Features
+This implementation follows the 11-052r4 OGC GeoSPARQL standard
(http://www.opengeospatial.org/standards/geosparql).
+The implementation is pure Java and does not require any set-up or
configuration of any third party relational databases and geospatial extensions.
+
+It implements the six Conformance Classes described in the GeoSPARQL document:
+
+* Core
+* Topology Vocabulary
+* Geometry Extension
+* Geometry Topology
+* RDFS Entailment Extension
+* Query Rewrite Extension
+
+The WKT (as described in 11-052r4) and GML 2.0 Simple Features Profile
(10-100r3) serialisations are supported.
+Additional serialisations can be implemented by extending the
+`org.apache.jena.geosparql.implementation.datatype.GeometryDatatype`
+and registering with Apache Jena's `org.apache.jena.datatypes.TypeMapper`.
+
+All three spatial relation families are supported: _Simple Feature_,
_Egenhofer_ and _RCC8_.
+
+Indexing and caching of spatial objects and relations is performed _on-demand_
during query execution.
+Therefore, set-up delays should be minimal.
+
+Benchmarking of the implementation against Strabon and Parliament has found it
to be comparable or quicker.
+The benchmarking used was the Geographica query and dataset
(http://geographica.di.uoa.gr/).
+Publication of the benchmarking results are forthcoming.
+
+## Additional Features
+The following additional features are also provided:
+
+* Geometry properties are automatically calculated and do not need to be
asserted in the dataset.
+* Conversion between EPSG spatial/coordinate reference systems is applied
automatically. Therefore, mixed datasets or querying can be applied. This is
reliance upon local installation of Apache SIS EPSG dataset, see __Key
Dependencies__.
+* Units of measure are automatically converted to the appropriate units for
the coordinate reference system.
+* Geometry, transformation and spatial relation results are stored in
persistent and configurable time-limited caches to improve response times and
reduce recalculations.
+* Dataset conversion between serialisations and spatial/coordinate reference
systems. Tabular data can also be loaded, see RDF Tables project
(https://github.com/galbiston/rdf-tables).
+* Functions to test Geometry properties directly on Geometry Literals have
been included for convenience.
+
+## Getting Started
+GeoSPARQL Jena can be accessed as a library using Maven etc. from Maven
Central.
+
+```
+<dependency>
+ <groupId>org.apache.jena</groupId>
+ <artifactId>jena-geosparql</artifactId>
+ <version>...</version>
+</dependency>
+```
+
+A HTTP server (SPARQL endpoint) using is available - for details, see the
[Geosparql Fuseki documentation](geosparql-fuseki).
+
+### SPARQL Query Configuration
+Using the library for SPARQL querying requires one line of code.
+All indexing and caching is performed during query execution and so there
should be minimal delay during initialisation.
+This will register the Property Functions with ARQ query engine and configures
the _indexes_ used for time-limited caching.
+
+There are three _indexes_ which can be configured independently or switched
off.
+These _indexes_ retain data that may be required again when a query is being
executed but may not be required between different queries.
+Therefore, the memory usage will grow during query execution and then recede
as data is not re-used.
+All the _indexes_ support concurrency and can be set to a maximum size or
allowed to increase capacity as required.
+
+* _Geometry Literal_: Geometry objects following de-serialisation from
`Geometry Literal`.
+* _Geometry Transform_: Geometry objects resulting from coordinate
transformations between spatial reference systems.
+* _Query Rewrite_: results of spatial relations between `Feature` and
`Geometry` spatial objects.
+
+Testing has found up to 20% improvement in query completion durations using
the indexes.
+The _indexes_ can be configured by size, retention duration and frequency of
clean up.
+
+* Basic setup with default values: `GeoSPARQLConfig.setupMemoryIndex()`
+
+* Indexes set to maximum sizes: `GeoSPARQLConfig.setupMemoryIndexSize(50000,
50000, 50000)`
+
+* Indexes set to remove objects not used after 5 seconds:
`GeoSPARQLConfig.setupMemoryIndexExpiry(5000, 5000, 5000)`
+
+* No indexes setup (Query rewrite still performed but results not stored) :
`GeoSPARQLConfig.setupNoIndex()`
+
+* No indexes and no query rewriting: `GeoSPARQLConfig.setupNoIndex(false)`
+
+* Reset indexes and other stored data: `GeoSPARQLConfig.reset()`
+
+A variety of configuration methods are provided in
+`org.apache.jena.geosparql.configuration.GeoSPARQLConfig`.
+Caching of frequently used but small quantity data is also applied in several
_registries_, e.g. coordinate reference systems and mathematical
transformations.
+
+Example GeoSPARQL query:
+
+```
+PREFIX geo: <http://www.opengis.net/ont/geosparql#>
+
+SELECT ?obj
+WHERE{
+ ?subj geo:sfContains ?obj
+}ORDER by ?obj
+```
+
+### Querying Datasets & Models with SPARQL
+
+The setup of GeoSPARQL Jena only needs to be performed once in an application.
+After it is setup querying is performed using Apache Jena's standard query
methods.
+
+To query a Model with GeoSPARQL or standard SPARQL:
+
+```
+GeoSPARQLConfig.setupMemoryIndex();
+Model model = .....;
+String query = ....;
+
+try (QueryExecution qe = QueryExecutionFactory.create(query, model)) {
+ ResultSet rs = qe.execSelect();
+ ResultSetFormatter.outputAsTSV(rs);
+}
+```
+
+More information on SPARQL querying using Apache Jena can be found on their
website (https://jena.apache.org/tutorials/sparql.html).
+If your dataset needs to be separate from your application and accessed over
HTTP then you probably need
+the [GeoSPARQL Fuseki project](geosparql-fuseki).
+The GeoSPARQL functionality needs to be setup in the application or Fuseki
server where the dataset is located.
+
+It is **recommended** that `hasDefaultGeometry` properties are included in the
dataset to access all functionality.
+It is **necessary** that `SpatialObject` classes are asserted or inferred
(i.e. a reasoner with the GeoSPARQL schema is applied) in the dataset.
+Methods to prepare a dataset can be found in
`org.apache.jena.geosparql.configuration.GeoSPARQLOperations`.
+
+### API
+The library can be used as an API in Java.
+The main class to handle geometries and their spatial relations is the
`GeometryWrapper`.
+This can be obtained by parsing the string representation of a geometry using
the appropriate datatype (e.g. WKT or GML).
+Alternatively, a Literal can be extracted automatically using the
`GeometryWrapper.extract()` method and registered datatypes.
+The `GeometryWrapperFactory` can be used to directly construct a
`GeometryWrapper`.
+There is overlap between spatial relation families so repeated methods are not
specified.
+
+* Parse a `Geometry Literal`: `GeometryWrapper geometryWrapper =
WKTDatatype.INSTANCE.parse("POINT(1 1)");`
+
+* Extract from a Jena Literal: `GeometryWrapper geometryWrapper =
GeometryWrapper.extract(geometryLiteral);`
+
+* Create from a JTS Geometry: `GeometryWrapper geometryWrapper =
GeometryWrapperFactory.createGeometry(geometry, srsURI, geometryDatatypeURI);`
+
+* Create from a JTS Point Geometry: `GeometryWrapper geometryWrapper =
GeometryWrapperFactory.createPoint(coordinate, srsURI, geometryDatatypeURI);`
+
+* Convert CRS/SRS: `GeometryWrapper otherGeometryWrapper =
geometryWrapper.convertCRS("http://www.opengis.net/def/crs/EPSG/0/27700";)`
+
+* Spatial Relation: `boolean isCrossing =
geometryWrapper.crosses(otherGeometryWrapper);`
+
+* DE-9IM Intersection Pattern: `boolean isRelated =
geometryWrapper.relate(otherGeometryWrapper, "TFFFTFFFT");`
+
+* Geometry Property: `boolean isEmpty = geometryWrapper.isEmpty();`
+
+The GeoSPARQL standard specifies that WKT Geometry Literals without an SRS URI
are defaulted to CRS84 `http://www.opengis.net/def/crs/OGC/1.3/CRS84`.
+
+## Key Dependencies
+
+### GeoSPARQL
+The OGC GeoSPARQL standard supports representing and querying geospatial data
on the Semantic Web.
+GeoSPARQL defines a vocabulary for representing geospatial data in RDF, and it
defines an extension to the SPARQL query language for processing geospatial
data.
+In addition, GeoSPARQL is designed to accommodate systems based on qualitative
spatial reasoning and systems based on quantitative spatial computations.
+
+The GeoSPARQL standard is based upon the OGC Simple Features standard
(http://www.opengeospatial.org/standards/sfa) used in relational databases.
+Modifications and enhancements have been made for usage with RDF and SPARQL.
+The Simple Features standard, and by extension GeoSPARQL, simplify
calculations to Euclidean planer geometry.
+Therefore, datasets using a geographic spatial/coordinate reference system,
which are based on latitude and longitude on an ellipsoid, e.g. WGS84, will
have minor error introduced.
+This error has been deemed acceptable due to the simplification in calculation
it offers.
+
+### Apache Jena
+A Java framework for building Semantic Web and Linked Data applications.
+The framework provides standard compliance for RDF and SPARQL and include
extensions for persistent storage (TDB) and HTTP server (Fuseki).
+
+### Apache SIS/SIS_DATA Environment Variable
+Apache Spatial Information System (SIS) is a free software, Java language
library for developing geospatial applications.
+SIS provides data structures for geographic features and associated meta-data
along with methods to manipulate those data structures.
+The library is an implementation of GeoAPI 3.0 interfaces and can be used for
desktop or server applications.
+
+A subset of the EPSG spatial/coordinate reference systems are included by
default.
+The full EPSG dataset is not distributed due to the EPSG terms of use being
incompatible with the Apache Licence.
+Several options are available to include the EPSG dataset by setting the
`SIS_DATA` environment variable (http://sis.apache.org/epsg.html).
+
+An embedded EPSG dataset can be included in a Gradle application by adding the
following dependency to `build.gradle`:
+```
+ext.sisVersion = "0.8"
+implementation "org.apache.sis.non-free:sis-embedded-data:$sisVersion"
+```
+
+### Java Topology Suite
+The JTS Topology Suite is a Java library for creating and manipulating vector
geometry.
+
+## Note
+The following are implementation points that may be useful during usage.
+
+### GeoSPARQL Schema
+An RDF/XML schema has been published for the GeoSPARQL v1.0 standard (v1.0.1 -
http://schemas.opengis.net/geosparql/1.0/geosparql_vocab_all.rdf).
+This can be applied to Jena Models
(https://jena.apache.org/documentation/inference/) to provide RDFS and OWL
inferencing on a GeoSPARQL conforming dataset.
+However, the published schema does not conform with the standard.
+
+The property `hasDefaultGeometry` is missing from the schema and instead the
`defaultGeometry` property is stated.
+
+This prevents RDFS inferencing being performed correctly and has been reported
to the OGC Standards Tracker.
+A corrected version of the schema is available in the `Resources` folder.
+
+### Spatial Relations
+The GeoSPARQL and Simple Features standard both define the DE-9IM intersection
patterns for the three spatial relation families.
+However, these patterns are not always consistent with the patterns stated by
the JTS library for certain relations.
+
+For example, GeoSPARQL/Simple Features use `TFFFTFFFT` _equals_ relations in
_Simple Feature_, _Egenhofer_ and _RCC8_.
+However, this does not yield the usually expected result when comparing a pair
of point geometries.
+The Simple Features standard states that the boundary of a point is empty.
+Therefore, the boundary intersection of two points would also be empty so give
a negative comparison result.
+
+JTS, and other libraries, use the alternative intersection pattern of
`T*F**FFF*`.
+This is a combination of the _within_ and _contains_ relations and yields the
expected results for all geometry types.
+
+The spatial relations utilised by JTS have been implemented as the extension
`spatial:equals` filter and property functions.
+A user can also supply their own DE-9IM intersection patterns by using the
`geof:relate` filter function.
+
+### Spatial Relations and Geometry Shapes/Types
+The spatial relations for the three spatial families do not apply to all
combinations of the geometry shapes (`Point`, `LineString`, `Polygon`) and
their collections (`MultiPoint`, `MultiLineString`, `MultiPolygon`).
+Therefore, some queries may not produce all the results that may initially be
expected.
+
+Some examples are:
+* In some relations there may only be results when a collection of shapes is
being used, e.g. two multi-points can overlap but two points cannot.
+* A relation may only apply for one combination but not its reciprocal, e.g. a
line may cross a polygon but a polygon may not cross a line.
+* The _RCC8_ family only applies to `Polygon` and `MultiPolygon` types.
+
+Refer to pages 8-10 of 11-052r4 GeoSPARQL standard for more details.
+
+### Equals Relations
+The three equals relations (_sfEquals_, _ehEquals_ and _rccEquals_) use
spatial equality and not lexical equality.
+Therefore, some comparisons using these relations may not be as expected.
+
+The JTS description of _sfEquals_ is:
+* True if two geometries have at least one point in common and no point of
either geometry lies in the exterior of the other geometry.
+
+Therefore, two empty geometries will return false as they are not spatially
equal.
+Shapes which differ in the number of points but have the same geometry are
equal and will return true.
+
+e.g. `LINESTRING (0 0, 0 10)` and `LINESTRING (0 0, 0 5, 0 10)` are spatially
equal.
+
+### Query Rewrite Extension
+The Query Rewrite Extension provides for simpler querying syntax.
+`Feature` and `Geometry` can be used in spatial relations without needing the
relations to be asserted in the dataset.
+This also means the `Geometry Literal` does not need to be specified in the
query.
+In the case of `Features` this requires the `hasDefaultGeometry` property to
be used in the dataset.
+
+This means the query:
+
+```
+ ?subj geo:hasDefaultGeometry ?subjGeom .
+ ?subjGeom geo:hasSerialization ?subjLit .
+
+ ?obj geo:hasDefaultGeometry ?objGeom .
+ ?objGeom geo:hasSerialization ?objLit .
+
+ FILTER(geof:sfContains(?subjLit, ?objLit))
+```
+
+becomes:
+
+```
+ ?subj geo:sfContains ?obj .
+```
+
+Methods are available to apply the `hasDefaultGeometry` property to every
`Geometry` with a single `hasGeometry`
+property, see `org.apache.jena.geosparql.configuration.GeoSPARQLOperations`.
+
+Depending upon the spatial relation, queries may include the specified
`Feature` and `Geometry` in the results.
+e.g. FeatureA is bound in a query on a dataset only containing FeatureA and
GeometryA. The results FeatureA and GeometryA are returned rather than no
results.
+Therefore, filtering using `FILTER(!sameTerm(?subj, ?obj))` etc. may be needed
in some cases.
+The query rewrite functionality can be switched off in the library
configuration, see `org.apache.jena.geosparql.configuration.GeoSPARQLConfig`.
+
+Each dataset is assigned a Query Rewrite Index to store the results of
previous tests.
+There is the potential that relations are tested multiple times in a query
(i.e. *Feature-Feature*, *Feature-Geometry*, *Geometry-Geometry*,
*Geometry-Feature*).
+Therefore, it is useful to retain the results for at least a short period of
time.
+
+Iterating through all combinations of spatial relations for a dataset
containing _n_ Geometry Literals will produce 27*n*^2 true/false results
(asserting the true result statements in a dataset would be a subset).
+Control is given on a dataset basis to allow choice in when and how storage of
rewrite results is applied, e.g. store all found results on a small dataset but
on demand for a large dataset.
+
+This index can be configured on a global and individual dataset basis for the
maximum size and duration until unused items are removed.
+Query rewriting can be switched on independently of the indexes, i.e. query
rewriting can be performed but an index is configured to not store the result.
+
+### Dataset Conversion
+Methods to convert datasets between serialisations and spatial/coordinate
reference systems are available in:
+`org.apache.jena.geosparql..configuration.GeoSPARQLOperations`
+
+The following list shows some of the operations that can be performed.
+Once these operations have been performed they can be serialised to file or
stored in a Jena TDB to remove the need to reprocess.
+
+* Load a Jena Model from file: `Model dataModel =
RDFDataMgr.loadModel("data.ttl");`
+
+* Convert `Feature-GeometryLiteral` to the GeoSPARQL
`Feature-Geometry-GeometryLiteral` structure: `Model geosparqlModel =
GeoSPARQLOperations.convertGeometryStructure(dataModel);`
+
+* Convert `Feature-Lat, Feature-Lon` Geo predicates to the GeoSPARQL
`Feature-Geometry-GeometryLiteral` structure, with option to remove Geo
predicates: `Model geosparqlModel =
GeoSPARQLOperations.convertGeoPredicates(dataModel, true);`
+
+* Assert additional `hasDefaultGeometry` statements for single `hasGeometry`
triples, used in Query Rewriting:
`GeoSPARQLOperations.applyDefaultGeometry(geosparqlModel);`
+
+* Convert Geometry Literals to the WGS84 spatial reference system and WKT
datatype: `Model model = GeoSPARQLOperations.convert(geosparqlModel,
"http://www.opengis.net/def/crs/EPSG/0/4326";,
"http://www.opengis.net/ont/geosparql#wktLiteral";);`
+
+* Apply GeoSPARQL schema with RDFS inferencing and assert additional
statements in the Model: `GeoSPARQLOperations.applyInferencing(model);`
+
+* Apply commonly used GeoSPARQL prefixes for URIs to the model:
`GeoSPARQLOperations.applyPrefixes(model);`
+
+* Create Spatial Index for a Model within a Dataset for spatial querying:
`Dataset dataset = SpatialIndex.wrapModel(model);`
+
+Other operations are available and can be applied to a Dataset containing
multiple Models and in some cases files and folders.
+These operations do __not__ configure and setup the GeoSPARQL functions or
indexes that are required for querying.
+
+### Spatial Index
+A Spatial Index can be created to improve searching of a dataset.
+The Spatial Index is expected to be unique to the dataset and should not be
shared between datasets.
+Once built the Spatial Index cannot have additional items added to it.
+
+A Spatial Index is required for the `jena-spatial` property functions and is
optional for the GeoSPARQL spatial relations.
+Only a single SRS can be used for a Spatial Index and it is recommended that
datasets are converted to a single SRS, see `GeoSPARQLOperations`.
+
+Setting up a Spatial Index can be done through
`org.apache.jena.geosparql.configuration.GeoSPARQLConfig`.
+Additional methods for building, loading and saving Spatial Indexes are
provided in `org.apache.jena.geosparql.spatial.SpatialIndex`.
+
+### Units URI
+Spatial/coordinate reference systems use a variety of measuring systems for
defining distances.
+These can be specified using a URI identifier, as either URL or URN, with
conversion undertaken automatically as required.
+It should be noted that there is error inherent in spatial reference systems
and some variation in values may occur between different systems.
+
+The following table gives some examples of units that are supported (additonal
units can be added to the `UnitsRegistry` using the `javax.measure.Unit` API.
+These URI are all in the namespace `http://www.opengis.net/def/uom/OGC/1.0/`
and here use the prefix `units`.
+
+URI | Description
+---- | ----
+units:kilometre or units:kilometer | Kilometres
+units:metre or units:meter | Metres
+units:mile or units:statuteMile | Miles
+units:degree | Degrees
+units:radian | Radians
+
+Full listing of default Units can be found in
`org.apache.jena.geosparql.implementation.vocabulary.Unit_URI`.
+
+## Geography Markup Language Support (GML)
+The supported GML profile is GML 2.0 Simple Features Profile (10-100r3), which
is a profile of GML 3.2.1 (07-036r1).
+The profile restricts the geometry shapes permitted in GML 3.2.1 to a subset,
see 10-100r3 page 22.
+The profile supports Points, LineString and Polygon shapes used in WKT. There
are also additional shape serialisations available in the profile that do not
exist in WKT or JTS to provide simplified representations which would otherwise
use LineStrings or Polygons.
+Curves can be described by LineStringSegment, Arc, Circle and
CircleByCenterPoint. Surfaces can be formed similarly to Polygons or using
Curves.
+These additional shapes can be read as part of a dataset or query but will not
be produced if the SRS of the shape is transformed, instead a LineString or
Polygon representation will be produced.
+
+Details of the GML structure for these shapes can be found in the
[geometryPrimitives.xsd](http://www.datypic.com/sc/niem21/s-geometryPrimitives.xsd.html),
[geometryBasic0d1d.xsd](http://www.datypic.com/sc/niem21/s-geometryBasic0d1d.xsd.html),
[geometryBasic2d.xsd](http://www.datypic.com/sc/niem21/s-geometryBasic2d.xsd.html)
and
[geometryAggregates.xsd](http://www.datypic.com/sc/niem21/s-geometryAggregates.xsd.html)
schemas.
+
+The labelling of collections is as follows:
+
+Collection | Geometry
+------------- | -------------
+MultiPoint | Point
+MultiCurve | LineString, Curve
+MultiSurface | Polygon, Surface
+MultiGeometry | Point, LineString, Curve, Polygon, Surface
+
+## Apache Jena Spatial Functions/WGS84 Geo Predicates
+The `jena-spatial` module contains several SPARQL functions for querying
datasets using the WGS84 Geo predicates for latitude
(`http://www.w3.org/2003/01/geo/wgs84_pos#lat`) and longitude
(`http://www.w3.org/2003/01/geo/wgs84_pos#long`).
+These `jena-spatial` functions are supported for both Geo predicates and
Geometry Literals, i.e. a GeoSPARQL dataset.
+Additional SPARQL filter functions have been provided to convert Geo predicate
properties into WKT strings and calculate Great Circle and Euclidean distances.
+
+### Supported Features
+The Geo predicate form of spatial representation is restricted to only 'Point'
shapes in the WGS84 spatial/coordinate reference system.
+The Geo predicates are properties of the `Feature` and do not use the
properties and structure of the GeoSPARQL standard, including Geometry Literals.
+Methods are available to convert datasets from Geo predicates to GeoSPARQL
structure, see: `org.apache.jena.geosparql.configuration.GeoSPARQLOperations`
+
+The spatial relations and query re-writing of GeoSPARQL outlined previously
has been implemented for Geo predicates.
+However, only certain spatial relations are valid for `Point` to `Point`
relationships.
+Refer to pages 8-10 of 11-052r4 GeoSPARQL standard for more details.
+
+Geo predicates can be converted to Geometry Literals in query and then used
with the GeoSPARQL filter functions.
+
+```
+ ?subj wgs:lat ?lat .
+ ?subj wgs:long ?lon .
+ BIND(spatialF:convertLatLon(?lat, ?lon) as ?point) .
+ BIND("POLYGON((...))"^^<http://www.opengis.net/ont/geosparql#wktLiteral>
AS ?box) . #Coordinate order is Lon/Lat without stated SRS URI.
+ FILTER(geof:sfContains(?box, ?point))
+```
+
+Alternatively, utilising more shapes, relations and spatial reference systems
can be achieved by converting the dataset to the GeoSPARQL structure.
+
+```
+ ?subj geo:hasGeometry ?geom .
+ ?geom geo:hasSerialization ?geomLit .
+ BIND("POLYGON((...))"^^<http://www.opengis.net/ont/geosparql#wktLiteral>
AS ?box) . #Coordinate order is Lon/Lat without stated SRS URI.
+ FILTER(geof:sfContains(?box, ?geomLit))
+```
+
+Datasets can contain both Geo predicates and Geometry Literals without
interference.
+However, a dataset containing both types will only examine those `Features`
which have Geometry Literals for spatial relations, i.e. the check for Geo
predicates is a fallback when Geometry Literals aren't found.
+Therefore, it is **not** recommended to insert new Geo predicate properties
after a dataset has been converted to GeoSPARQL structure (unless corresponding
Geometry and Geometry Literals are included).
+
+### Filter Functions
+These filter functions are available in the
`http://jena.apache.org/function/spatial#` namespace and here use the prefix
`spatialF`.
+
+Function Name | Description
+------------- | -------------
+*?wktString* **spatialF:convertLatLon**(*?lat*, *?lon*) | Converts Lat and Lon
double values into WKT string of a Point with WGS84 SRS.
+*?wktString* **spatialF:convertLatLonBox**(*?latMin*, *?lonMin*, *?latMax*,
*?lonMax*) | Converts Lat and Lon double values into WKT string of a Polygon
forming a box with WGS84 SRS.
+*?boolean* **spatialF:equals**(*?geomLit1*, *?geomLit2*) | True, if *geomLit1*
is spatially equal to *geomLit2*.
+*?boolean* **spatialF:nearby**(*?geomLit1*, *?geomLit2*, *?distance*,
*?unitsURI*) | True, if *geomLit1* is within *distance* of *geomLit2* using the
distance *units*.
+*?boolean* **spatialF:withinCircle**(*?geomLit1*, *?geomLit2*, *?distance*,
*?unitsURI*) | True, if *geomLit1* is within *distance* of *geomLit2* using the
distance *units*.
+*?radians* **spatialF:angle**(*?x1*, *?y1*, *?x2*, *?y2*) | Angle clockwise
from y-axis from Point(x1,y1) to Point (x2,y2) in 0 to 2Ï radians.
+*?degrees* **spatialF:angleDeg**(*?x*, *?y1*, *?x2*, *?y2*) | Angle clockwise
from y-axis from Point(x1,y1) to Point (x2,y2) in 0 to 360 degrees.
+*?distance* **spatialF:distance**(*?geomLit1*, *?geomLit2*, *?unitsURI*) |
Distance between two Geometry Literals in distance *units*. Chooses distance
measure based on SRS type. Great Circle distance for Geographic SRS and
Euclidean otherwise.
+*?radians* **spatialF:azimuth**(*?lat1*, *?lon1*, *?lat2*, *?lon2*) | Forward
azimuth clockwise from North between two Lat/Lon Points in 0 to 2Ï radians.
+*?degrees* **spatialF:azimuthDeg**(*?lat1*, *?lon1*, *?lat2*, *?lon2*) |
Forward azimuth clockwise from North between two Lat/Lon Points in 0 to 360
degrees.
+*?distance* **spatialF:greatCircle**(*?lat1*, *?lon1*, *?lat2*, *?lon2*,
*?unitsURI*) | Great Circle distance (Vincenty formula) between two Lat/Lon
Points in distance *units*.
+*?distance* **spatialF:greatCircleGeom**(*?geomLit1*, *?geomLit2*,
*?unitsURI*) | Great Circle distance (Vincenty formula) between two Geometry
Literals in distance *units*. Use
`http://www.opengis.net/def/function/geosparql/distance` from GeoSPARQL
standard for Euclidean distance.
+*?geomLit2* **spatialF:transform**(*?geomLit1*, *?datatypeURI*, *?srsURI*) |
Transform Geometry Literal by Datatype and SRS.
+*?geomLit2* **spatialF:transformDatatype**(*?geomLit1*, *?datatypeURI*) |
Transform Geometry Literal by Datatype.
+*?geomLit2* **spatialF:transformSRS**(*?geomLit1*, *?srsURI*) | Transform
Geometry Literal by SRS.
+
+### Property Functions
+These property functions are available in the
`http://jena.apache.org/spatial#` namespace and here use the prefix `spatial`.
+This is the same namespace as the `jena-spatial` functions utilise and these
form direct replacements.
+The subject `Feature` may be bound, to test the pattern is true, or unbound,
to find all cases the pattern is true.
+These property functions require a `Spatial Index` to be setup for the dataset.
+
+The optional *?limit* parameter restricts the number of results returned. The
default value is -1 which returns all results. No guarantee is given for
ordering of results.
+The optional *?unitsURI* parameter specifies the units of a distance. The
default value is kilometres through the string or resource
`http://www.opengis.net/def/uom/OGC/1.0/kilometre`.
+
+The `spatial:equals` property function behaves the same way as the main
GeoSPARQL property functions. Either, both or neither of the subject and object
can be bound. A `Spatial Index` is **not** required for the dataset with the
`spatial:equals` property function.
+
+Function Name | Description
+------------- | -------------
+*?spatialObject1* **spatial:equals** *?spatialObject2* | Find *spatialObjects*
(i.e. *features* or *geometries*) that are spatially equal.
+*?feature* **spatial:intersectBox**(*?latMin* *?lonMin* *?latMax* *?lonMax* [
*?limit*]) | Find *features* that intersect the provided box, up to the *limit*.
+*?feature* **spatial:intersectBoxGeom**(*?geomLit1* *?geomLit2* [ *?limit*]) |
Find *features* that intersect the provided box, up to the *limit*.
+*?feature* **spatial:withinBox**(*?latMin* *?lonMin* *?latMax* *?lonMax* [
*?limit*]) | Find *features* that intersect the provided box, up to the *limit*.
+*?feature* **spatial:withinBoxGeom**(*?geomLit1* *?geomLit2* [ *?limit*]) |
Find *features* that are within the provided box, up to the *limit*.
+*?feature* **spatial:nearby**(*?lat* *?lon* *?radius* [ *?unitsURI* [
*?limit*]]) | Find *features* that are within *radius* of the *distance* units,
up to the *limit*.
+*?feature* **spatial:nearbyGeom**(*?geomLit* *?radius* [ *?unitsURI* [
*?limit*]]) | Find *features* that are within *radius* of the *distance* units,
up to the *limit*.
+*?feature* **spatial:withinCircle**(*?lat* *?lon* *?radius* [ *?unitsURI* [
*?limit*]]) | Find *features* that are within *radius* of the *distance* units,
up to the *limit*.
+*?feature* **spatial:withinCircleGeom**(*?geomLit* *?radius* [ *?unitsURI* [
*?limit*]]) | Find *features* that are within *radius* of the *distance* units,
up to the *limit*.
+
+The Cardinal Functions find all `Features` that are present in the specified
direction.
+In Geographic spatial reference systems (SRS), e.g. WGS84 and CRS84, the
East/West directions wrap around.
+Therefore, a search is made from the shape's edge for up to half the range of
the SRS (i.e. 180 degrees in WGS84) and will continue across the East/West
boundary if necessary.
+In other SRS, e.g. Projected onto a flat plane, the East/West check is made
from the shape's edge to the farthest limit of the SRS range, i.e. there is no
wrap around.
+
+Cardinal Function Name | Description
+------------- | -------------
+*?feature* **spatial:north**(*?lat* *?lon* [ *?limit*]) | Find *features* that
are North of the Lat/Lon point (point to +90 degrees), up to the *limit*.
+*?feature* **spatial:northGeom**(*?geomLit* [ *?limit*]) | Find *features*
that are North of the Geometry Literal, up to the *limit*.
+*?feature* **spatial:south**(*?lat* *?lon* [ *?limit*]) | Find *features* that
are South of the Lat/Lon point (point to -90 degrees), up to the *limit*.
+*?feature* **spatial:southGeom**(*?geomLit* [ *?limit*]) | Find *features*
that are South of the Geometry Literal, up to the *limit*.
+*?feature* **spatial:east**(*?lat* *?lon* [ *?limit*]) | Find *features* that
are East of the Lat/Lon point (point plus 180 degrees longitude, wrapping
round), up to the *limit*.
+*?feature* **spatial:eastGeom**(*?geomLit* [ *?limit*]) | Find *features* that
are East of the Geometry Literal, up to the *limit*.
+*?feature* **spatial:west**(*?lat* *?lon* [ *?limit*]) | Find *features* that
are West of the Lat/Lon point (point minus 180 degrees longitude, wrapping
round), up to the *limit*.
+*?feature* **spatial:westGeom**(*?geomLit* [ *?limit*]) | Find *features* that
are West of the Geometry Literal, up to the *limit*.
+
+## Geometry Property Filter Functions
+The GeoSPARQL standard provides a set of properties related to geometries, see
Section 8.4.
+These are applied on the Geometry resource and are automatically determined if
not asserted in the data.
+However, it may be necessary to retrieve the properties of a Geometry Literal
directly without an associated Geometry resource.
+Filter functions to do this have been included as part of the
`http://www.opengis.net/def/function/geosparql/` namespace as a minor variation
to the GeoSPARQL standard.
+The relevant functions using the `geof` prefix are:
+
+Geometry Property Filter Function Name | Description
+------------- | -------------
+*?integer* **geof:dimension**(*?geometryLiteral*) | Topological dimension,
e.g. 0 for Point, 1 for LineString and 2 for Polygon.
+*?integer* **geof:coordinateDimension**(*?geometryLiteral*) | Coordinate
dimension, e.g. 2 for XY coordinates and 4 for XYZM coordinates.
+*?integer* **geof:spatialDimension**(*?geometryLiteral*) | Spatial dimension,
e.g. 2 for XY coordinates and 3 for XYZM coordinates.
+*?boolean* **geof:isEmpty**(*?geometryLiteral*) | True, if geometry is empty.
+*?boolean* **geof:isSimple**(*?geometryLiteral*) | True, if geometry is simple.
+*?boolean* **geof:isValid**(*?geometryLiteral*) | True, if geometry is
topologically valid.
+
+A dataset that follows the GeoSPARQL Feature-Geometry-GeometryLiteral can have
simpler SPARQL queries without needing to use these functions by taking
advantage of the Query Rewriting functionality.
+The `geof:isValid` filter function and `geo:isValid` property for a Geometry
resource are not part of the GeoSPARQL standard but have been included as a
minor variation.
+
+## Future Work
+
+* Implementing GeoJSON as a `GeometryLiteral` serialisation
(https://tools.ietf.org/html/rfc7946).
+
+## Contributors
+The following individuals have made contributions to this project:
+
+* Greg Albiston
+* Haozhe Chen
+* Taha Osman
+
+## Why Use This Implementation?
+There are several implementations of the GeoSPARQL standard.
+The conformance and completeness of these implementations is difficult to
ascertain and varies between features.
+
+However, the following may be of interest when considering whether to use this
implementation based on reviewing several alternatives.
+
+This Implementation|Other Implementations
+---------- | ----------
+Implements all six components of the GeoSPARQL standard.|Generally partially
implement the Geometry Topology and Geometry Extensions. Do not implement the
Query Rewrite Extension.
+Pure Java and does not require a supporting relational database. Configuration
requires a single line of code (although Apache SIS may need some setting up,
see above).|Require setting up a database, configuring a geospatial extension
and setting environment variables.
+Uses Apache Jena, which conforms to the W3C standards for RDF and SPARQL. New
versions of the standards will quickly feed through.|Not fully RDF and SPARQL
compliant, e.g. RDFS/OWL inferencing or SPARQL syntax. Adding your own schema
may not produce inferences.
+Automatically determines geometry properties and handles mixed cases of units
or coordinate reference systems. The GeoSPARQL standard suggests this approach
but does not require it.|Tend to produce errors or no results in these
situations.
+Performs indexing and caching on-demand which reduces set-up time and only
performs calculations that are required.|Perform indexing in the data loading
phase and initialisation phase, which can lead to lengthy delays (even on
relatively small datasets).
+Uses JTS which does not truncate coordinate precision and applies spatial
equality.|May truncate coordinate precision and apply lexical equality, which
is quicker but does not comply with the GeoSPARQL standard.
