Re: Beginner - Help Needed!

On Jul 1, 2008, at 2:00 AM, Rangarajan Krishnamoorthy wrote:

> Russ,
> Thanks a lot for the quick reply. I noticed Chapter 6 lists the PLI.  
> Did you mean Chapter 6 or 7 in your reply (1)?

Well, I just checked and it seems that the numbering of the on-line  
HTML manual and the PDF manual are different.  So, in the PDF manual  
the Chapter is number 6.  It is number 7 in the on-line manual.  This  
will be fixed when we next generate the documentation.

> Consider the following scenario. I have loaded PowerLoom into my  
> Lisp. Instead of saying (in-package "STELLA"), I do the following:

OK, that works.

> CL-USER 1 > (STELLA::defconcept person)
> |c|PERSON

> CL-USER 2 > (STELLA::assert (person john))
> |P|(PERSON JOHN)

> CL-USER 3 > (STELLA::ask (person john))
> TRUE

> CL-USER 4 > (STELLA::ask (person peter))
> UNKNOWN
>
> CL-USER 5 > (STELLA::retrieve all (person ?x))
> There is 1 solution:
>
> #1: ?X=JOHN
>
> CL-USER 6 > (setf matches (STELLA::retrieve all (person ?x)))
> There is 1 solution:
>  #1: ?X=JOHN
>
> CL-USER 7 > matches
> There is 1 solution:
>  #1: ?X=JOHN
>
> Notice that when I retrieve the matches (as in CL-USER 6 prompt), I  
> expect to get a "Lisp" form. That would allow me to use the matches  
> in my Lisp code. But that is not what I get (see CL-USER 7).

Well, you actually do get a Lisp object back.  It is just that it has  
a custom print function that formats it to look pretty to an  
interactive user.  The actual object type is a QUERY-ITERATOR, and you  
can access the elements using the Stella iterator interface.

But it would, at this point, be more convenient to use the PLI  
(PowerLoom interface) functions that are defined in the PLI package  
instead.  They are designed to be called from code.

> So, to restate my original question, how do I programmatically  
> interact with PowerLoom so that I get the results of queries/ 
> computations into my Lisp environment? I will most probably define  
> the domain knowledge (concepts, relations, functions, rules, etc.)  
> in a Powerloom file, load it into my Lisp environment (using the "in- 
> package" format you indicated), but issue queries from Lisp code.  
> Hope I have conveyed my usage scenario.

Yes, defining the domain content in a PowerLoom file is the best way  
to do it.  You would then do things like the following with the PLI  
functions.  A lot of the interaction functions come in an object  
version and a string version. In Lisp, the string version names start  
with "s-".  These are the functions described in Chapter 6(or 7).  The  
string version allows you to use string inputs rather than having to  
construct Stella or PowerLoom objects to pass to the other functions.

I'll illustrate this using the business.plm file that has the  
annotated example knowledge base in it.

(pli:load "kbs/business.plm" stella::null)

(setq matches
      (pli:s-retrieve "all (company ?c)" "BUSINESS" stella::null))
   ;; This returns an object of type PLI-ITERATOR.
   ;; There are accessor functions for getting the elements out of the  
iteration.
   ;;    pli:next? will advance the iterator to the next element and  
return
   ;;              stella::TRUE if there is such an element.
   ;;              PowerLoom's stella::FALSE in conveniently cl:nill  
in Common Lisp
   ;;    Then there are a large number of pli:get-nth-... accessors  
that can be used
   ;;         to get elements of the tuple.  Note that the elements  
will be some
   ;;         type of Stella object, including wrapped literals like  
numbers or strings.

(loop with module = (pli:get-module "BUSINESS" stella::null)
       while (stella::next? matches)
       do (print (pli:get-nth-value matches 0 module stella::null)))

   ;; Since this particular retrieval returns a simple list of elements,
   ;; each tuple of the answer has only one item in it, so the index is
   ;; always 0.  What follows is an example that shows a more  
complicated
   ;; query.

(setq matches2
      (pli:s-retrieve "all (and (company ?c) (company-name ?c ?name))"  
"BUSINESS" stella::null))

(loop with module = (pli:get-module "BUSINESS" stella::null)
       while (stella::next? matches2)
       do (format t "~A is called ~A~%"
                  (pli:get-nth-value matches2 0 module stella::null)
                  (pli:get-nth-string matches2 1 module stella::null)))
    ;; In this case, each value of the PL-Iterator is a tuple with 2  
elements, and
    ;;   the second one is a string type.  We get them using 0-based  
indexing into
    ;;   the tuple values.

The general super-type of all returned items is STELLA::OBJECT, and  
those things which are not wrapped literals are subclasses of  
STELLA::LOGIC-OBJECT.

The mismatch in package names is a bit unfortunate.  I plan to remedy  
that shortly.  It will be in the next incremental release.

Also note that stella::NULL and stella::NULL-STRING are different  
objects, as are stella::NULL-INTEGER and stella::NULL-FLOAT.  This is  
necessary because of type restrictions, particular with Common Lisp  
implementations like CMUCL and SBCL that are very strict about  
datatypes.

>
>
> Regards,
> Rangarajan
>
> ----- Original Message ----- From: "Thomas Russ" <[email protected]>
> To: "Rangarajan Krishnamoorthy" <[email protected]>
> Cc: <[email protected]>
> Sent: Tuesday, July 01, 2008 9:46 AM
> Subject: Re: [PowerLoom Forum] Beginner - Help Needed!
>
>
>
> On Jun 30, 2008, at 7:42 PM, Rangarajan Krishnamoorthy wrote:
>
>> Hi,
>> I have just downloaded PowerLoom on Windows. I am using LispWorks  
>> 5.1. Although the documentation of PowerLoom talks about the  
>> language and API, I do not find examples of how to call the API  
>> from Lisp. I could not even get started with simple examples using  
>> the API from Lisp.
>
> First off, I apologize because we have not yet had the opportunity to
> finish the lisp-specific section of the manual.
>
> Fortunately, the Lisp interface is straight-forward, since the
> documentation of the functions are all in the Lisp syntax.  The key
> items that are missing from the documentation are:
>
> 1.  The PowerLoom Interface functions from section 7 are all in the  
> PLI
> package.  Those API functions are exported and are intended for use
> from your own Lisp program.
>
> 2.  All other PowerLoom functions are in the STELLA package, but are
> not exported.  This includes all of the normal PowerLoom functions.   
> So
> it is often convenient to just operate in the STELLA package.  This
> works well for interactive development using the Lisp environment.
>
> So, to use PowerLoom in Lisp one would need to do the following:
>
> (load "load-powerloom.lisp")
> (in-package "STELLA")
> ;; At this point you can just type PowerLoom commands,
> ;; or you could go through the annotated example in the manual.
>
> (defconcept Person)
> (deffunction age ((?p person) (?age integer)))
> (defrelation friend ((?p1 person) (?p2 person)))
>
> (assert (person fred))
> (assert (person rajiv))
> (assert (and (age fred 20) (age rajiv 19) (friend fred rajiv)))
>
> (ask (age fred 20))
> (ask (age fred 30))
> (retrieve all (friend ?x rajiv))
>
> (defconcept teenager ((?p person))
>   :<=> (and (person ?p)
>             (< (age ?p) 20)
>             (> (age ?p) 12)))
>
> (retrieve all (teenager ?p))
> (retrieve all (and (teenager ?p) (age ?p ?age)))
>
>
>
>
>>
>> There is some mention of "translation" to C++, etc. Does it mean  
>> that PowerLoom code can be translated to Lisp (or C++) and then  
>> used in that mode? How do I invoke the translator?
>
> PowerLoom itself has already been translated to Lisp, Java and C++.
> This is done by using our underlying Stella language, which has such a
> translator.  More information and an incomplete manual can be found at
> http://www.isi.edu/isd/LOOM/Stella/index.html
>
> When using Stella to write programs, one would normally build a
> "system" which has a description of the files and Stella modules
> (namespaces) involved.  Then the translator is invoked with
>
>  (make-system "system-name" :target-language)
>
> where the :target-language is one of :common-lisp :java or :cpp
> and "system-name" is the name of your system.
>
>>
>> Thanks for your help.
>
> I hope this helps to get you started.  If this isn't quite enough,
> please ask further questions and we'll help you get started.
>
>
>
>>
>> Regards,
>> Rangarajan_______________________________________________
>> powerloom-forum mailing list
>> [email protected]
>> http://mailman.isi.edu/mailman/listinfo/powerloom-forum
>