From: Sandro Hawke (sandro@w3.org)
Date: 05/28/03
> As promised, please find, attached, the list of built-ins. This is a
> draft, a new version will be available next week with much more details.
Understood; feel free to answer my questions in that new version
instead of e-mail, if that works better.
General question: how do you propose to organize built-ins in terms of
input vs. output vs. bi-directional parameters? EG addition and
subtraction can be the same predicate:
sum(3,4,7) true if 3+4=7
sum(3,4,?x) binds ?x to 7 if unbound
sum(3,?y,7) binds ?y to 4 if unbound
This is a little odd for addition, but I guess it's common in Prolog
for list-append.
> 3. More Built-ins:
> ----------------
> 3.1 Assign =
What does this mean in a KR language, where it doesn't make sense to
talk about changing the value of something?
> 3.2 Increment ++
> 3.3 Decrement --
Ditto, unless you just mean +1 and -1.
> 3.4 Power **
> 3.5 Abs (absolute value)
> 3.6 Min
> 3.7 Max
>
> 4. Data Types
> --------------
> Our approach is to integrate XML Part 2, Data Types:
> http://www.w3.org/TR/xmlschema-2/
What kind of built-ins does that give you? For example, the datatype
"duration" [1] represents a length of time via a 6-tuple of <year,
month, day, hour, minute, second>. It has an ordering, and the
following "constraining facets":
* pattern
* enumeration
* whiteSpace
* maxInclusive
* maxExclusive
* minInclusive
* minExclusive
So what built-ins does that suggest we should have associated with the
xsd:duration type?
> 5. String built-ins:
> -----------------
> 5.1 str-length returns the length of a given string in charact
> ers
> 5.2 str-cat string concatenation
> 5.3 str-compare compares 2 strings
> 5.4 str-index returns the position of the first argum
> ent within the =
> second argument
> 5.5 is-String returns TRUE if the argument is a strin
> g, FALSE =
> otherwise
> 5.6 sub-string returns a substring from a string argument give
> n two =
> 1-based indices
> 5.7 str-upcase returns the given string argument in Uppercase
> 5.8 str-lowcase retrns the given string argument in lowercase
Do you really want hyphens in names? stringLength is probably more in
keeping with current naming wisdom. Is isString different from
checking to see if it's in the String class?
What are strings, btw? Are they XSD strings, RDF plain literals (are
those xsd strings?), or something else.
> 6. I/O Streams built-ins:
> -----------------------
> 6.1 open Open a file or a stream
> 6.2 read Read from stream or file
> 6.3 write Write to a stream or file
> 6.4 close close file or stream
I'd suggest that file handling and URI handling be unified. Opening
and reading a file is pretty much the same as GET of an HTTP URI. If
the default basename is file: with the current directory, the
difference is only noticable on filenames starting with something that
looks like a URI scheme name.
"write" is of course not a side-effect-free (sensing) operation.
> 6.5 printout sends unformatted output to a given str
> eam/router
... this is an enormous can of worms.... What kind of formatting are
you suggesting "write" has?
> 7. Control and debugging built-ins:
> ---------------------------------
> 7.1 run invoke an inference cycle
> 7.2 query run a query
> 7.3 halt halts an inference/query cycle
> 7.4 reset reset the fact base
> 7.5 show-facts returns the list of asserted facts
> 7.5 show-rules returns the list of rules
> 7.8 debug runs in a debug mode: traces all rule firings
> 7.9 assert assert new facts
> 7.10 retract retract facts
> 7.11 load-facts asserts facts loaded from a file
> 7.12 load-rules loads rules from a file
> 7.13 evaluate evaluates a string input as command lin
> e input and =
> returns the result
> 7.14 clear clear engine from all its contents: rules, fact
> s, etc.
Most of these are not sensing operations either. I don't know how you
expect to fit them into a KR language. Any ideas?
-- sandro
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