datatypes on literals?

[Bruce]

Am a little confused:

Is there some way for me to assign a datatype (say xsd:date or
xsd:datetime) to a literal?

Bruce

[Cory Dodt]

I haven't found one, also interested to hear this.  In particular I'd like to assign my own datatypes to literals, e.g. dice expressions:

:monster :hitDice "2d10"^^http://goonmill.org/2007/dice.n3#DiceExpression;

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[Philip Cooper]

You can create a literal with any datatype you wish:

  from rdfalchemy import Literal, Namespace

  OV = Namespace('http://www.example.com/shchema#')

  a = Literal('thing_1',datatype=OV.thing)

a can now be the right hand side of an assignment to a rdfSingle descriptor and all should work fine

Cory: in the case of xsd:date or xsd:datetime, you can already assign a date or datetime instance (from the datetime module) and 

rdfalchemy will place the correct xsd:dateTime or xsd:date datatype on it in the triplestore.

You can look at my page on CustomizingLiterals [1] for a bit more info.  Look at what was done to allow the correct handling of the Decimal class type.

That and the source for Literal [2] should help you to see that a couple of lines will get "automatic" assignment of datatype to work.

Your two other options are to handle it inside a custom descriptor (more code more power less resuability) or just create a Literal by hand (as stated above)

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Phil

[1] http://www.openvest.com/trac/wiki/CustomizingLiterals

[2] http://www.openvest.com/trac/browser/rdfalchemy/trunk/rdfalchemy/Literal.py