Data Types

Knowledge statements contain scalar objects -- literals. Literals are either language-tagged string rdf:langString or type-safe values containing a reference to data-type (e.g. xsd:string). This section defines rules how semantic data types are serialized to Erlang native formats.

Primitive Data Types

Knowledge statements contain scalar objects -- literals. Literals are either language-tagged string rdf:langString or type-safe values containing a reference to data-type (e.g. xsd:string). This section defines data-types supported by the library, its mapping to Erlang native types and relation to existed schema(s) and ontologies.

URI / IRI

The data type represents a Uniform Resource Identifier / Internationalized Resource Identifier. Used to uniquely identify concept, objects, etc.

Lang	Data type
Erlang	`-type {iri, uri()}
Semantic	?XSD_ANYURI
Text	<uri>
	prefix:suffix
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#string"

binary

The binary data-type represents character strings in knowledge statements. The language strings are annotated with corresponding language tag.

Lang	Data type
Erlang	-type binary().
Semantic	?XSD_STRING
Text	"string"
	"string"^^xsd:string
	"string"@en
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#string"

integer

The library derives an arbitrary-precision Integers from Erlang (only limited by available memory on the machine).

Lang	Data type
Erlang	-type integer().
Semantic	?XSD_INTEGER
	?XSD_LONG
	?XSD_INT
	?XSD_SHORT
	?XSD_BYTE
Text	10
	"10"^^xsd:integer
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#integer"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#long"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#int"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#short"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#byte"

float

The value is the IEEE 754 double-precision 64-bit floating point type.

Lang	Data type
Erlang	-type float().
Semantic	?XSD_DECIMAL
	?XSD_FLOAT
	?XSD_DOUBLE
Text	10.1
	"10.1"^^xsd:decimal
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#decimal"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#float"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#double"

boolean

The value is either true or false, representing a logic values

Lang	Data type
Erlang	-type true | false.
Semantic	?XSD_BOOLEAN
Text	`true
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#boolean"

datetime

The date-time value is closely related to calendar dates and times described by ISO 8601, covering AD and BC eras. Erlang native date format is triple of integers giving micro-seconds precision. The external representation is ISO 8601.

Lang	Data type
Erlang	-type {integer(), integer(), integer()}.
Semantic	?XSD_DATETIME
Text	ISO8601
	2007-04-05T14:30:00Z
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#dateTime"

recursive date/times

XSD defines set of recursive data-types. These types are also translated to native datetime format.

Lang	Data type
Erlang	-type {{integer(), integer(), integer()}, {integer(), integer(), integer()}}.
Semantic	?XSD_DATE
	?XSD_TIME
	?XSD_YEARMONTH
	?XSD_YEAR
	?XSD_MONTHDAY
	?XSD_MONTH
	?XSD_DAY
Text	ISO8601
	2007-04-05
	14:30:00Z
	2007-04
	--04-05
	2007
	04
	05
RDF	xmlns:xsd="http://www.w3.org/2001/XMLSchema#date"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#time"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#gYearMonth"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#gYear"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#gMonthDay"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#gMonth"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema#gDay"

Geo Point

The geographical coordinates are encoded using either GeoHash or latitude/longitude pair. GeoHash is encoded using georss:hash that ensures precision about 3.7cm x 1.8cm. The latitude/longitude pair is encoded georss:point as tuple of floats.

Lang	Data type
Erlang	`-type binary()
Semantic	?GEORSS_HASH
	?GEORSS_POINT
Text	"ueh6xc"^^georss:hash
	25.7,62.1
RDF	xmlns:georss="http://www.georss.org/georss/point"
	xmlns:georss="http://www.georss.org/georss/hash"

GeoJson

The data type facilitates operations with geospatial data as defined by https://tools.ietf.org/html/rfc7946

Lang	Data type
Erlang	-type #{<<"type">> => _, <<"coordinates">> => _}.
Semantic	?GEORSS_JSON
Text	(type: ..., coordinates: ...)
RDF	xmlns:georss="http://www.georss.org/georss/json"

not supported

• xmlns:xsd="http://www.w3.org/2001/XMLSchema#duration"
• xmlns:xsd="http://www.w3.org/2001/XMLSchema#hexBinary"
• xmlns:xsd="http://www.w3.org/2001/XMLSchema#base64Binary"

Reference

1. http://www.w3.org/TR/xmlschema-2/
2. https://en.wikipedia.org/wiki/Geohash