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initial comment on RIF Basic Logic Dialect document

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 04 Aug 2008 15:24:13 -0400 (EDT)
Message-Id: <20080804.152413.229489994.pfps@research.bell-labs.com>
To: public-rif-comments@w3.org

Hi:

I'm currently going through
http://www.w3.org/TR/2008/WD-rif-bld-20080730/

I'm having problems with undefined terms, to the extent that I'm worried
about whether I'm understanding the document correctly.  The definition
of a formula says that a formula is a statement of a particular form,
but there is no definition of "statement" in the document at all.
Please let me know what the definition of statement is.

There are other undefined terms used in the definition of language,
e.g., "alphanumeric", "IRI constant", "x:y constant", "positional
symbol", "symbols with named argument".

Many constructs of the language take a sequence of sub-constructs.  In
some places (e.g., for conjunctions) there is the explicit wording that
this sequence can be empty.  In other places (e.g., for universal rules)
there is nothing said about whether the empty sequence is allowed.  I
cannot determine whether an empty sequence is allowed in these cases.
In some places (e.g., positional terms) it seems that an empty sequence
should be allowed; in others (e.g., universal rule) it seems that an
empty sequence should not be allowed.

Several terms and phrases are used before they are defined, including
"predicate symbol" and "subformula".  I suggest that the document be
re-written to not use these terms before they are defined.

There are several odd grammatical constructs that don't seem to make
sense.  For example, the definition of "document" appears to depend on
"the logical content of the document".  I think that this phrase should
be removed from the definition of "document" (perhaps by being put
immediately below the definition).

It seems very strange that the document says in several places that
directives do not affect semantics.  Surely directives affect the
interpretation of the syntax, which has an effect on the semantics.  For
example, xs:foo and xsd:foo have differing status depending on whether
they "expand" to the same IRI.

I don't understand why certain aspects of the grammar are only in the
English text.  For example, why not put the ordering and uniqueness
aspects of the Directives into the grammar?

In places the document alludes to transformations (e.g., eliminating
disjunctions in rule premises) without any wording indicating that these
transformations are benign in a particular context.

I don't understand why the formula in an annotation has to be a frame
formula or the conjunction of frame formulae.  Why are other kinds of
formulae forbidden?

I don't understand the wording concerning conjunctive annotation formula
referring to parts of the annotated term or formula.  

It would be useful to link IRI to the IRI RFC in the definition of the
syntax, not just in the introduction.

The definition of symbol context should be rewritten to something like
"If s occurs as the predicate constant of an atomic subformula", and so
on. 

Why does Example 2 mention CURIES as if the abbreviation mechanism is
outside the language?  Surely the Prefix directive is there explicitly
to allow for such abbreviations?  In any case the Prefix directive and
it use are defined diferently from CURIES.

Why repeat the entire EBNF for the condition language less that two
pages later?

It seems strange to refer to the Prefix and Base directives as macros.
They are only mechanisms to allow the abbreviation of IRIs, and are
certainly not a general-purpose macro facility.

RIF BLD references Section 2 of RIF DTB, which refers back to RIF BLD.
I am unsure whether this introduces a definition loop.


The net outcome of the problems and worries that I have described above
is that I am unsure as to whether the syntax of RIF BLD is well
defined.  I await responses on my above concerns.


Peter F. Patel-Schneider
Bell Labs Research
Received on Monday, 4 August 2008 19:25:43 GMT

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