Re: current draft of SWSL Rules design doc

From: Sandro Hawke (
Date: 07/27/04

  • Next message: Benjamin Grosof: "overview slides on SWSL Rules"
    >    a. Constants
    >        A constant is either a literal or a URI.
    >        URI:
    >          - a complete URI (protocol://location...)
    > 	   - a Qname (prefix:...)
    > 	 Both must conform to the W3 specs.
    The "//" is only present in some situations, so you cannot rely on it
    to syntactically distinguish between URIs and QNames.  (For example,
    "" is a URI.)  Technically, QNames conform to
    the URI syntax; they are not disjoint.  In practice, almost every URI
    in use violates the QName syntaxs (eg with the "@" in mailto), so you
    could carve out the QName part of the URI syntax, but that's still
    kind of risky.
    I don't have a great alternative.   N3 uses angle-brackets around URIs
    and nothing around QNames.   SWI Prolog has URIs be atoms (surrounded
    by single-quotes, in normal prolog syntax) and QNames be terms with a
    ":" infix operator (which are usually rewritten at parse-time).
          -- sandro

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