Data Types

Type Hierarchy

The system of types used in the Semantic Aspect Meta Model (and subsequently in the models conforming to the Semantic Aspect Meta Model) is largely based on a subset of the XML Schema Definition 1.1 (XSD, [xmlschema11-2]), including the types such as data ranges. In addition to types from XSD, the type langString is included as described in the RDF [rdf11] specification; it is used to represent strings with an explicit language tag. Using these types allows for example the distinction between a plain string and a dateTime string, unlike in JSON. The JSON data of a Property with a certain type uses the most convenient corresponding JSON type, i.e. booleans for XSD boolean, number for all numeric types, JSON object for Entities and string for everying else.

The following figure shows the type hierarchy, in which arrows are interpreted as "is a subtype of and can therefore be cast to". The types anyType and anySimpleType are "special" types of the XSD type hierarchy and should not be directly used.

All data types inheriting from anySimpleType are called scalar, i.e. every allowed data type except samm:Entity is scalar.

The Entity type corresponds to the Entity Meta Model element as described in section Meta Model Elements.

The following table lists the types allowed in the Aspect Models, with references to their definition in the respective standards and an informative description of their value space.

Table 1. Data Types
	Data Type	Value Range	Sample Values
Core Types	`xsd:string`	Character strings	'Hello world', 'Καλημέρα κόσμε', 'コンニチハ'
	`xsd:boolean`	true, false	true, false
	`xsd:decimal`	Arbitrary-precision decimal numbers	-1.23, 126789672374892739424.543233, +100000.00, 210
	`xsd:integer`	Arbitrary-size integer numbers	-1, 0, 126789675432332938792837429837429837429, +100000
IEEE-floating-point numbers	`xsd:double`	64-bit floating point numbers incl. ±Inf, ±0, NaN	-1.0, +0.0, -0.0, 234.567e8, -INF, NaN
IEEE-floating-point numbers	`xsd:float`	32-bit floating point numbers incl. ±Inf, ±0, NaN	-1.0, +0.0, -0.0, 234.567e8, -INF, NaN
Time and date	`xsd:date`	Dates (yyyy-mm-dd) with or without timezone	'2000-01-01', '2000-01-01Z', '2000-01-01+12:05'
	`xsd:time`	Times (hh:mm:ss.sss…) with or without timezone	'14:23:00', '14:23:00.527634Z', '14:23:00+03:00'
	`xsd:dateTime`	Date and time with or without timezone	'2000-01-01T14:23:00', '2000-01-01T14:23:00.66372+14:00'
	`xsd:dateTimeStamp`	Date and time with required timezone	'2000-01-01T14:23:00.66372+14:00'
Recurring and partial dates	`xsd:gYear`	Gregorian calendar year	'2000', '2000+03:00'
	`xsd:gMonth`	Gregorian calendar month	'--04', '--04+03:00'
	`xsd:gDay`	Gregorian calendar day of the month	'---04', '---04+03:00'
	`xsd:gYearMonth`	Gregorian calendar year and month	'2000-01', '2000-01+03:00'
	`xsd:gMonthDay`	Gregorian calendar month and day	'--01-01', '--01-01+03:00'
	`xsd:duration`	Duration of time	'P30D', '-P1Y2M3DT1H', 'PT1H5M0S'
	`xsd:yearMonthDuration`	Duration of time (months and years only)	'P10M', 'P5Y2M'
	`xsd:dayTimeDuration`	Duration of time (days, hours, minutes, seconds only)	'P30D', 'P1DT5H', 'PT1H5M0S'
Limited-range integer numbers	`xsd:byte`	-128…+127 (8 bit)	-1, 0, 127
	`xsd:short`	-32768…+32767 (16 bit)	-1, 0, 32767
	`xsd:int`	2147483648…+2147483647 (32 bit)	-1, 0, 2147483647
	`xsd:long`	-9223372036854775808…+9223372036854775807 (64 bit)	-1, 0, 9223372036854775807
	`xsd:unsignedByte`	0…255 (8 bit)	0, 1, 255
	`xsd:unsignedShort`	0…65535 (16 bit)	0, 1, 65535
	`xsd:unsignedInt`	0…4294967295 (32 bit)	0, 1, 4294967295
	`xsd:unsignedLong`	0…18446744073709551615 (64 bit)	0, 1, 18446744073709551615
	`xsd:positiveInteger`	Integer numbers >0	1, 7345683746578364857368475638745
	`xsd:nonNegativeInteger`	Integer numbers ≥0	0, 1, 7345683746578364857368475638745
	`xsd:negativeInteger`	Integer numbers <0	-1, -23487263847628376482736487263847
	`xsd:nonPositiveInteger`	Integer numbers ≤0	-1, 0, -93845837498573987498798987394
Encoded binary data	`xsd:hexBinary`	Hex-encoded binary data	'6b756d6f77617368657265'
Encoded binary data	`xsd:base64Binary`	Base64-encoded binary data	'a3Vtb3dhc2hlcmU='
Miscellaneous types	`xsd:anyURI`	Absolute or relative URIs and IRIs	'http://example.org/', 'urn:samm:com.mycompany.myapplication:1.0.0#errorState'
	`samm:curie`	Compact URI/IRI (well-known prefix + element name)	'xsd:string', 'unit:hectopascal'
	`rdf:langString`	Strings with language tags	"Hello"@en, "Hallo"@de. Note that this is written in RDF/Turtle syntax, and that only "Hello" and "Hallo" are the actual values.

The following types defined by the XSD and RDF specifications, respectively, are considered unsuitable in Aspect models and should not be used:

xsd:language, xsd:normalizedString, xsd:token, xsd:NMTOKEN, xsd:Name, xsd:NCName, xsd:QName, xsd:ENTITY, xsd:ID, xsd:IDREF, xsd:NOTATION, xsd:IDREFS, xsd:ENTITIES, xsd:NMTOKENS, rdf:HTML and rdf:XMLLiteral.

Implicit Conversions

The following implicit data type conversions are allowed, i.e. when a type A can be cast to type B according to the following table, A is allowed where B is required. Implicit conversion is transitive, i.e. when A can be cast to B and B can be cast to C then A can also be cast to C.

Table 2. Allowed implicit conversions
Type		Type
`xsd:byte`	can be cast to	`xsd:short`
`xsd:short`	can be cast to	`xsd:int`
`xsd:int`	can be cast to	`xsd:long`
`xsd:long`	can be cast to	`xsd:integer`
`xsd:integer`	can be cast to	`xsd:decimal`
`xsd:unsignedByte`	can be cast to	`xsd:unsignedShort`
`xsd:unsignedShort`	can be cast to	`xsd:unsignedInt`
`xsd:unsignedInt`	can be cast to	`xsd:unsignedLong`
`xsd:unsignedLong`	can be cast to	`xsd:nonNegativeInteger`
`xsd:positiveInteger`	can be cast to	`xsd:nonNegativeInteger`
`xsd:nonNegativeInteger`	can be cast to	`xsd:integer`
`xsd:negativeInteger`	can be cast to	`xsd:nonPositiveInteger`
`xsd:nonPositiveInteger`	can be cast to	`xsd:integer`
`xsd:dateTimeStamp`	can be cast to	`xsd:dateTime`
`xsd:yearMonthDuration`	can be cast to	`xsd:duration`
`xsd:dayTimeDuration`	can be cast to	`xsd:duration`

Currently, implicit type conversions are allowed for the description of example values of Properties.