- From: Andy Seaborne <andy.seaborne@epimorphics.com>
- Date: Tue, 26 Jul 2011 15:57:51 +0100
- To: public-rdf-dawg-comments@w3.org
On 18/07/11 11:06, Kathrin Dentler wrote: > Dear SPARQL WG, > > For medical applications such as guideline-based decision support, > clinical trial recruitment or the calculation of clinical quality > indicators, it is often necessary to select patients with a certain age > at a certain moment; e.g. "select all patients older than 18". To > retrieve those patients, the current (or some other) date needs to be > subtracted from the patient's date of birth. This is currently not > possible in SPARQL. > > Some XPath Arithmetic operators for numeric types are already included > in the SPARQL Working Draft. To enable full usage of the type > xsd:dateTime, could you also include the operators on durations, dates > and times from the XQuery 1.0 and XPath 2.0 Functions and Operators > Recommendation? > > The most important one for the use-case above would be: > op:subtract-dateTimes($arg1 as xs:dateTime, $arg2 as xs:dateTime) as > xs:dayTimeDuration. > > Best regards, > Kathrin Dentler Kathrin, Thank you for your comment about SPARQL's requirement from XQuery/XPath Functions and Operators. SPARQL requires any implementation to provide a core set of datatypes and a core set of operations on those datatypes. It also provide an extensibility mechanism [1] whereby an implementation can, within the spec, include additional operators and additional coverage by existing operators beyond the core set. An implementation can add op:subtract-dateTimes($arg1 as xs:dateTime, $arg2 as xs:dateTime) as xs:dayTimeDuration so while it is not a requirement of a minimally compliant SPARQL processor, implementations are free to add such operation. There is a balance in the set of datatypes and operators, and the costs of implementations in supporting that set. The working group has chosen to define a subset of the full XQuery/XPath Functions and Operators as being required; many implementations already go beyond this core set. The required set of datatypes and operators in SPARQL 1.1 for xsd:dateTime is the same as that in SPARQL 1.0. The working group feels this is the right balance and hope implementations will provide the additional specific operators that certain domains require. Any additional functions can provided by an implementation and called directly by their URI: op:subtract-dateTimes(?date1, ?date2) We would be grateful if you would acknowledge that your comment has been answered by sending a reply to this mailing list. Andy, on behalf of the SPARQL-WG [1] http://www.w3.org/TR/sparql11-query/#operatorExtensibility
Received on Tuesday, 26 July 2011 14:58:34 UTC