Dynamic SPARQL queries and Datatypes

Wed, 26 Aug 2009 09:24:44 +0000

After some headaches I’ve found how to write dynamic SPARQL queries by passing parameters. For example, to query graph about resources collected last hour this code could be a first approach:

#!/usr/bin/env python
# Dynamic query (example code)

from datetime import datetime
import rdflib
from namespaces import XSD

def last_day():
""" get date """
now = datetime.now()
date = now – timedelta(hours=24)

return date

def get_date_filtered_query():
""" build query """
period = last_day()
mydate = Literal(period, datatype=URIRef(XSD))

query = """
PREFIX rdf:
PREFIX nie:
PREFIX nfo:
PREFIX nao:
PREFIX pimo:
PREFIX xsd:
SELECT ?id
WHERE
{
?id rdf:type ?type .
?id nao:created ?date .
FILTER (?type != pimo:Collection) .
FILTER (xsd:dateTime(?date) >= xsd:dateTime("%s")) .
}
ORDER BY DESC(?date)
""" % mydate

return query

# query graph
query = get_date_filtered_query()
result = graph.query(query)

for id in result.selected:
print id

For more information is worth to take a look W3C XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes. A self explained list of XML datatypes:

xsd:anyURI – URI (Uniform Resource Identifier)
xsd:base64Binary – Binary content coded as “base64″
xsd:boolean – Boolean (true or false)
xsd:byte – Signed value of 8 bits
xsd:date – Gregorian calendar date
xsd:dateTime – Instant of time (Gregorian calendar)
xsd:decimal – Decimal numbers
xsd:double – IEEE 64-bit floating-point
xsd:duration – Time durations
xsd:ENTITIES – Whitespace-separated list of unparsed entity references
xsd:ENTITY – Reference to an unparsed entity
xsd:float – IEEE 32-bit floating-point
xsd:gDay – Recurring period of time: monthly day
xsd:gMonth – Recurring period of time: yearly month
xsd:gMonthDay – Recurring period of time: yearly day
xsd:gYear – Period of one year
xsd:gYearMonth – Period of one month
xsd:hexBinary – Binary contents coded in hexadecimal
xsd:ID – Definition of unique identifiers
xsd:IDREF – Definition of references to unique identifiers
xsd:IDREFS – Definition of lists of references to unique identifiers
xsd:int – 32-bit signed integers
xsd:integer – Signed integers of arbitrary length
xsd:language – RFC 1766 language codes
xsd:long – 64-bit signed integers
xsd:Name – XML 1.O name
xsd:NCName – Unqualified names
xsd:negativeInteger – Strictly negative integers of arbitrary length
xsd:NMTOKEN – XML 1.0 name token (NMTOKEN)
xsd:NMTOKENS – List of XML 1.0 name tokens (NMTOKEN)
xsd:nonNegativeInteger – Integers of arbitrary length positive or equal to zero
xsd:nonPositiveInteger – Integers of arbitrary length negative or equal to zero
xsd:normalizedString – Whitespace-replaced strings
xsd:NOTATION – Emulation of the XML 1.0 feature
xsd:positiveInteger – Strictly positive integers of arbitrary length
xsd:QName – Namespaces in XML-qualified names
xsd:short – 32-bit signed integers
xsd:string – Any string
xsd:time – Point in time recurring each day
xsd:token – Whitespace-replaced and collapsed strings
xsd:unsignedByte – Unsigned value of 8 bits
xsd:unsignedInt – Unsigned integer of 32 bits
xsd:unsignedLong – Unsigned integer of 64 bits
xsd:unsignedShort – Unsigned integer of 16 bits

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Dynamic SPARQL queries and Datatypes