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added instructions on semcpl.pl commands print/0 and build/1

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cplint/doc/Makefile
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@ -2,10 +2,10 @@
# to manually edit manual.tex following the instructions at the beginning of
# it
pdf: manual.tex manual.bbl
manual.pdf: manual.tex manual.bbl
pdflatex manual
pdflatex manual
html: manual.tex manual.bbl
manual.html: manual.tex manual.bbl
htlatex manual

133
cplint/doc/manual.html
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@ -7,7 +7,7 @@
<meta name="originator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)">
<!-- html -->
<meta name="src" content="manual.tex">
<meta name="date" content="2007-11-15 13:17:00">
<meta name="date" content="2007-11-16 16:20:00">
<link rel="stylesheet" type="text/css" href="manual.css">
</head><body
>
@ -22,7 +22,7 @@ class="cmr-12">Fabrizio Riguzzi</span>
class="cmr-12">fabrizio.riguzzi@unife.it</span></div>
<br />
<div class="date" ><span
class="cmr-12">November 15, 2007</span></div>
class="cmr-12">November 16, 2007</span></div>
</div>
<h3 class="sectionHead"><span class="titlemark">1 </span> <a
id="x1-10001"></a>Introduction</h3>
@ -90,15 +90,17 @@ class="cmtt-10">semlpadsld.pl</span>, <span
class="cmtt-10">semlpad.pl </span>and <span
class="cmtt-10">semcpl.pl</span>:
<ul class="itemize1">
<li class="itemize">semlpadsld.pl: given an LPAD <span
<li class="itemize"><span
class="cmtt-10">semlpadsld.pl</span>: given an LPAD <span
class="cmmi-10">P</span>, it generates all the instances of <span
class="cmmi-10">P</span>. The
probability of a query <span
class="cmmi-10">Q </span>is computed by identifying all the instances where
<span
class="cmmi-10">P</span>.
The probability of a query <span
class="cmmi-10">Q </span>is computed by identifying all the instances
where <span
class="cmmi-10">Q </span>is derivable by SLDNF resolution.
</li>
<li class="itemize">semlpad.pl: given an LPAD <span
<li class="itemize"><span
class="cmtt-10">semlpad.pl</span>: given an LPAD <span
class="cmmi-10">P</span>, it generates all the instances of <span
class="cmmi-10">P</span>. The
probability of a query <span
@ -106,7 +108,8 @@ class="cmmi-10">Q </span>is computed by identifying all the instances where
<span
class="cmmi-10">Q </span>is derivable by SLG resolution.
</li>
<li class="itemize">semlcpl.pl: given an LPAD <span
<li class="itemize"><span
class="cmtt-10">semlcpl.pl</span>: given an LPAD <span
class="cmmi-10">P</span>, it builds an execution model of <span
class="cmmi-10">P</span>, i.e.,
a probabilistic process that satisfy the principles of universal causation,
@ -355,11 +358,25 @@ ground head&#8221;: in this case, in order to answer the query, all the groundin
culprit clause must be generated, which may be impossible for programs with
function symbols.
<!--l. 168--><p class="indent" > When using <span
class="cmtt-10">cpl.pl</span>, the system can print the above messages plus &#8220;Invalid
program&#8221; in the case in which no execution process exists. The same message can be
returned by <span
class="cmtt-10">semcpl.pl</span>.
<!--l. 170--><p class="indent" > The modules make use of a number of parameters in order to control their
class="cmtt-10">semcpl.pl</span>, you can print the execution process by using the
command <span
class="cmtt-10">print. </span>after <span
class="cmtt-10">p(file). </span>Moreover, you can build an execution
process given a context by issuing the command <span
class="cmtt-10">parse(file)</span>. and then
<span
class="cmtt-10">build(context). </span>where <span
class="cmtt-10">context </span>is a list of atoms that are true in the context.
<span
class="cmtt-10">semcpl.pl </span>can print &#8220;Invalid program&#8221; in the case in which no execution process
exists.
<!--l. 173--><p class="indent" > When using <span
class="cmtt-10">cpl.pl </span>you can print a partial execution model including all the
clauses involved in the query issued with <span
class="cmtt-10">print. cpl.pl </span>can print the messages
&#8220;Uunsound program&#8221;, &#8220;It requires the choice of a head atom from a non ground
head&#8221; and &#8220;Invalid program&#8221;.
<!--l. 176--><p class="indent" > The modules make use of a number of parameters in order to control their
behavior. They that can be set with the command
<table
@ -368,7 +385,7 @@ class="verbatim"><div class="verbatim">
set(parameter,value).
</div>
</td></tr></table>
<!--l. 173--><p class="nopar" > from the Yap prompt after having loaded the module. The current value can be read
<!--l. 179--><p class="nopar" > from the Yap prompt after having loaded the module. The current value can be read
with
<table
@ -377,7 +394,7 @@ class="verbatim"><div class="verbatim">
setting(parameter,Value).
</div>
</td></tr></table>
<!--l. 178--><p class="nopar" > from the Yap prompt. The available parameters are:
<!--l. 184--><p class="nopar" > from the Yap prompt. The available parameters are:
<ul class="itemize1">
<li class="itemize"><span class="obeylines-h"><span class="verb"><span
class="cmtt-10">epsilon_parsing</span></span></span> (valid for all six modules): if (1 - the sum of the
@ -405,7 +422,7 @@ class="verbatim"><div class="verbatim">
Variables:&#x00A0;[(2,[X=2,X1=1]),(2,[X=1,X1=0]),(1,[])]
</div>
</td></tr></table>
<!--l. 192--><p class="nopar" > where the first element of each couple is the clause number of the input file
<!--l. 198--><p class="nopar" > where the first element of each couple is the clause number of the input file
(starting from 1). In the example above variable <span
class="cmtt-10">X0 </span>corresponds to clause <span
class="cmtt-10">2</span>
@ -428,7 +445,7 @@ class="verbatim"><div class="verbatim">
dotty&#x00A0;cpl.dot&#x00A0;&amp;
</div>
</td></tr></table>
<!--l. 201--><p class="nopar" >
<!--l. 207--><p class="nopar" >
</li>
<li class="itemize"><span class="obeylines-h"><span class="verb"><span
class="cmtt-10">ground_body</span></span></span> (valid for <span
@ -441,15 +458,15 @@ class="cmtt-10">false</span>, ground
constant. In the case where the body contains variables not in the
head, setting it to false means that the body represents an existential
event.</li></ul>
<!--l. 205--><p class="noindent" >
<!--l. 211--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">5 </span> <a
id="x1-50005"></a>Semantic Modules</h3>
<!--l. 206--><p class="noindent" >The three semantic modules need to produce a grounding of the program in order to
<!--l. 212--><p class="noindent" >The three semantic modules need to produce a grounding of the program in order to
compute the semantics. They require an extra file with extension <span
class="cmtt-10">.uni </span>(for universe)
in the same directory where the <span
class="cmtt-10">.cpl </span>file is.
<!--l. 209--><p class="indent" > There are two ways to specify how to ground a program. The first consists in
<!--l. 215--><p class="indent" > There are two ways to specify how to ground a program. The first consists in
providing the list of constants to which each variable can be instantiated. For
example, in our case the current directory will contain a file <span
class="cmtt-10">coin.uni </span>that is a
@ -461,7 +478,7 @@ class="verbatim"><div class="verbatim">
universe(var_list,const_list).
</div>
</td></tr></table>
<!--l. 212--><p class="nopar" > where <span class="obeylines-h"><span class="verb"><span
<!--l. 218--><p class="nopar" > where <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">var_list</span></span></span> is a list of variables names (each must be included in single quotes)
and <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">const_list</span></span></span> is a list of constants. The semantic modules generate the grounding
@ -471,7 +488,7 @@ class="cmtt-10">var_list</span></span></span> with the constants of
class="cmtt-10">const_list</span></span></span>. Note that the variables are identified by name, so a variable with
the same name in two different clauses will be instantiated with the same
constants.
<!--l. 215--><p class="indent" > The other way to specify how to ground a program consists in using mode and
<!--l. 221--><p class="indent" > The other way to specify how to ground a program consists in using mode and
type information. For each predicate, the file <span
class="cmtt-10">.uni </span>must contain a fact of the
form
@ -482,7 +499,7 @@ class="verbatim"><div class="verbatim">
mode(predicate(t1,...,tn)).
</div>
</td></tr></table>
<!--l. 218--><p class="nopar" > that specifies the number and types of each argument of the predicate. Then, the list
<!--l. 224--><p class="nopar" > that specifies the number and types of each argument of the predicate. Then, the list
of constants that are in the domain of each type <span
class="cmtt-10">ti </span>must be specified with a fact of
the form
@ -493,7 +510,7 @@ class="verbatim"><div class="verbatim">
type(ti,list_of_constants).
</div>
</td></tr></table>
<!--l. 223--><p class="nopar" > The file <span
<!--l. 229--><p class="nopar" > The file <span
class="cmtt-10">.uni </span>can contain both universe and mode declaration, the ones to be used
depend on the value of the parameter <span
class="cmtt-10">grounding</span>: with value <span
@ -501,15 +518,15 @@ class="cmtt-10">variables</span>, the
universe declarations are used, with value <span
class="cmtt-10">modes </span>the mode declarations are
used.
<!--l. 226--><p class="indent" > With <span
<!--l. 232--><p class="indent" > With <span
class="cmtt-10">semcpl.pl </span>only mode declarations can be used.
<!--l. 230--><p class="noindent" >
<!--l. 236--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">6 </span> <a
id="x1-60006"></a>Extensions</h3>
<!--l. 231--><p class="noindent" >In this section we will present the extensions to the syntax of LPADs and CP-logic
<!--l. 237--><p class="noindent" >In this section we will present the extensions to the syntax of LPADs and CP-logic
programs that <span
class="cmtt-10">cplint </span>can handle.
<!--l. 233--><p class="indent" > The first is the use of some standard Prolog predicates. The bodies can contain
<!--l. 239--><p class="indent" > The first is the use of some standard Prolog predicates. The bodies can contain
the built-in predicates:
<table
@ -531,7 +548,7 @@ is/2
&#x00A0;<br />length/2
</div>
</td></tr></table>
<!--l. 250--><p class="nopar" > The bodies can also contain the following library predicates:
<!--l. 256--><p class="nopar" > The bodies can also contain the following library predicates:
<table
class="verbatim"><tr class="verbatim"><td
@ -543,7 +560,7 @@ member/2
&#x00A0;<br />nth/3
</div>
</td></tr></table>
<!--l. 259--><p class="nopar" > plus the predicate
<!--l. 265--><p class="nopar" > plus the predicate
<table
class="verbatim"><tr class="verbatim"><td
@ -551,8 +568,8 @@ class="verbatim"><div class="verbatim">
average/2
</div>
</td></tr></table>
<!--l. 263--><p class="nopar" > that, given a list of numbers, computes its arithmetic mean.
<!--l. 266--><p class="indent" > When using <span
<!--l. 269--><p class="nopar" > that, given a list of numbers, computes its arithmetic mean.
<!--l. 272--><p class="indent" > When using <span
class="cmtt-10">lpadsld.pl</span>, the bodies can contain the predicates <span
class="cmtt-10">setof/3 </span>and
<span
@ -565,13 +582,13 @@ class="verbatim"><div class="verbatim">
setof(Z,&#x00A0;(term(X,Y))^foo(X,Y,Z),&#x00A0;L).
</div>
</td></tr></table>
<!--l. 269--><p class="nopar" > returns all the instantiations of <span
<!--l. 275--><p class="nopar" > returns all the instantiations of <span
class="cmtt-10">Z </span>such that there exists an instantiation of <span
class="cmtt-10">X </span>and <span
class="cmtt-10">Y</span>
for which <span
class="cmtt-10">foo(X,Y,Z) </span>is true.
<!--l. 272--><p class="indent" > An example of the use of <span
<!--l. 278--><p class="indent" > An example of the use of <span
class="cmtt-10">setof </span>and <span
class="cmtt-10">bagof </span>is in the file <span
class="cmtt-10">female.cpl</span>:
@ -600,18 +617,18 @@ male(C):M/P&#x00A0;;&#x00A0;female(C):F/P:-
&#x00A0;<br />known_male(e).
</div>
</td></tr></table>
<!--l. 293--><p class="nopar" > The disjunctive rule expresses the probability of a person of unknown sex of being
<!--l. 299--><p class="nopar" > The disjunctive rule expresses the probability of a person of unknown sex of being
male or female depending on the number of males and females that are known. This
is an example of the use of expressions in the probabilities in the head that depend
on variables in the body. The probabilities are well defined because they always sum
to 1 (unless <span
class="cmtt-10">P </span>is 0).
<!--l. 297--><p class="indent" > Another use of <span
<!--l. 303--><p class="indent" > Another use of <span
class="cmtt-10">setof </span>and <span
class="cmtt-10">bagof </span>is to have an attribute depend on an
aggregate function of another attribute, similarly to what is done in PRM and
CLP(BN).
<!--l. 299--><p class="indent" > So, in the classical school example (available in <span
<!--l. 305--><p class="indent" > So, in the classical school example (available in <span
class="cmtt-10">student.cpl</span>) you can find the
following clauses:
@ -627,7 +644,7 @@ student_rank(S,h):0.6&#x00A0;;&#x00A0;student_rank(S,l):0.4:-
&#x00A0;<br />&#x00A0;&#x00A0;&#x00A0;&#x00A0;average(L,Av),Av&#x00A0;=&#x003C;&#x00A0;1.5.
</div>
</td></tr></table>
<!--l. 309--><p class="nopar" > where <span class="obeylines-h"><span class="verb"><span
<!--l. 315--><p class="nopar" > where <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">registr_stu(R,S)</span></span></span> expresses that registration <span
class="cmtt-10">R </span>refers to student <span
class="cmtt-10">S </span>and
@ -637,7 +654,7 @@ class="cmtt-10">R </span>reports grade <span
class="cmtt-10">G </span>which is a natural
number. The two clauses express a dependency of the rank of the student from the
average of her grades.
<!--l. 312--><p class="indent" > Another extension can be used with <span
<!--l. 318--><p class="indent" > Another extension can be used with <span
class="cmtt-10">lpadsld.pl </span>in order to be able to represent
reference uncertainty of PRMs. Reference uncertainty means that the link structure
of a relational model is not fixed but is uncertain: this is represented by having the
@ -659,13 +676,13 @@ uniform(cites_cited(C,P),P,L):-
&#x00A0;<br />&#x00A0;&#x00A0;&#x00A0;&#x00A0;bagof(Pap,paper_topic(Pap,ai),L).
</div>
</td></tr></table>
<!--l. 319--><p class="nopar" > The first clauses states that the paper <span
<!--l. 325--><p class="nopar" > The first clauses states that the paper <span
class="cmtt-10">P </span>cited in a citation <span
class="cmtt-10">C </span>is selected
uniformly from the set of all papers with topic theory. The second clauses
expresses that the citing paper is selected uniformly from the papers with topic
ai.
<!--l. 324--><p class="indent" > These clauses make use of the predicate
<!--l. 330--><p class="indent" > These clauses make use of the predicate
<table
class="verbatim"><tr class="verbatim"><td
@ -673,7 +690,7 @@ class="verbatim"><div class="verbatim">
uniform(Atom,Variable,List)
</div>
</td></tr></table>
<!--l. 327--><p class="nopar" > in the head, where <span
<!--l. 333--><p class="nopar" > in the head, where <span
class="cmtt-10">Atom </span>must contain <span
class="cmtt-10">Variable</span>. The meaning is the following:
the set of all the atoms obtained by instantiating <span
@ -686,7 +703,7 @@ class="cmmi-10">&#x2215;N </span>where <span
class="cmmi-10">N </span>is the length of
<span
class="cmtt-10">List</span>.
<!--l. 331--><p class="indent" > A more elaborate example is present in file <span class="obeylines-h"><span class="verb"><span
<!--l. 337--><p class="indent" > A more elaborate example is present in file <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">paper_ref.cpl</span></span></span>:
<table
@ -705,13 +722,13 @@ uniform(cites_citing(C,P),P,L):-
&#x00A0;<br />&#x00A0;&#x00A0;&#x00A0;&#x00A0;cites_cited_group(C,T),bagof(Pap,paper_topic(Pap,T),L).
</div>
</td></tr></table>
<!--l. 344--><p class="nopar" > where the cited paper depends on the topic of the citing paper. In particular, if the
<!--l. 350--><p class="nopar" > where the cited paper depends on the topic of the citing paper. In particular, if the
topic is theory, the cited paper is selected uniformly from the papers about theory
with probability 0.9 and from the papers about ai with probability 0.1. if
the topic is ai, the cited paper is selected uniformly from the papers about
theory with probability 0.01 and from the papers about ai with probability
0.99.
<!--l. 347--><p class="indent" > PRMs take into account as well existence uncertainty, where the existence of
<!--l. 353--><p class="indent" > PRMs take into account as well existence uncertainty, where the existence of
instances is also probabilistic. For example, in the paper domain, the total number of
citations may be unknown and a citation between any two paper may have a
probability of existing. For example, a citation between two paper may be more
@ -733,7 +750,7 @@ cites(X,Y):0.005&#x00A0;:-
&#x00A0;<br />&#x00A0;&#x00A0;&#x00A0;&#x00A0;paper_topic(X,ai),paper_topic(Y,ai).
</div>
</td></tr></table>
<!--l. 360--><p class="nopar" > This is an example where the probabilities in the head do not sum up to one so the
<!--l. 366--><p class="nopar" > This is an example where the probabilities in the head do not sum up to one so the
null event is automatically added to the head. The first clause states that, if the topic
of a paper <span
class="cmtt-10">X </span>is theory and of paper <span
@ -742,10 +759,10 @@ there is a citation from <span
class="cmtt-10">X </span>to <span
class="cmtt-10">Y</span>. The other clauses consider the remaining cases for the
topics.
<!--l. 365--><p class="noindent" >
<!--l. 371--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">7 </span> <a
id="x1-70007"></a>Additional Files</h3>
<!--l. 366--><p class="noindent" >In the directory where Yap keeps the library files (usually <span
<!--l. 372--><p class="noindent" >In the directory where Yap keeps the library files (usually <span
class="cmtt-10">/usr/local/share/ Yap</span>)
you can find the directory <span
class="cmtt-10">cplint </span>that contains the files:
@ -846,7 +863,7 @@ class="cmtt-10">invalid.cpl</span>: programs taken from <span class="cite">[<a
href="#XCP-logic-unp">13</a>]</span>. <span
class="cmtt-10">invalid.cpl </span>is an example
of a program that is invalid but sound.</li></ul>
<!--l. 390--><p class="noindent" >The files <span
<!--l. 396--><p class="noindent" >The files <span
class="cmtt-10">*.uni </span>that are present for some of the examples are used by the
semantical modules. Some of the example files contain in an initial comment
some queries together with their result.
@ -854,18 +871,18 @@ class="cmtt-10">*.uni </span>that are present for some of the examples are used
<li class="itemize">Subdirectory <span
class="cmtt-10">doc</span>: contains this manual in latex, html and pdf.</li></ul>
<!--l. 393--><p class="noindent" >
<!--l. 399--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">8 </span> <a
id="x1-80008"></a>License</h3>
<!--l. 398--><p class="noindent" ><span
<!--l. 404--><p class="noindent" ><span
class="cmtt-10">cplint</span>, as Yap, follows the Artistic License 2.0 that you can find in Yap CVS root
dir. The copyright is by Fabrizio Riguzzi.
<!--l. 403--><p class="indent" > The program uses the library <a
<!--l. 409--><p class="indent" > The program uses the library <a
href="http://vlsi.colorado.edu/\protect \unhbox \voidb@x \penalty \@M \relax \unhbox \voidb@x \special {t4ht@+&{35}x00A0{59}}x{}fabio/" > CUDD </a> for manipulating BDDs that is included in
glu. For the use of CUDD, the following license must be accepted:
<!--l. 408--><p class="indent" > Copyright (c) 1995-2004, Regents of the University of Colorado
<!--l. 410--><p class="indent" > All rights reserved.
<!--l. 412--><p class="indent" > Redistribution and use in source and binary forms, with or without modification,
<!--l. 414--><p class="indent" > Copyright (c) 1995-2004, Regents of the University of Colorado
<!--l. 416--><p class="indent" > All rights reserved.
<!--l. 418--><p class="indent" > Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
<ul class="itemize1">
<li class="itemize">Redistributions of source code must retain the above copyright notice, this
@ -878,7 +895,7 @@ are permitted provided that the following conditions are met:
<li class="itemize">Neither the name of the University of Colorado nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.</li></ul>
<!--l. 429--><p class="noindent" >THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS
<!--l. 435--><p class="noindent" >THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS
<br class="newline" />AND CONTRIBUTORS &#8221;AS IS&#8221; AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
@ -892,7 +909,7 @@ INTERRUPTION) HOWEVER CAU-SED
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
<!--l. 443--><p class="indent" > <span
<!--l. 449--><p class="indent" > <span
class="cmtt-10">lpad.pl</span>, <span
class="cmtt-10">semlpad.pl </span>and <span
class="cmtt-10">cpl.pl </span>are based on the SLG system by <a

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@ -1,15 +1,15 @@
%% uncomment the following for htlatex compilation
\documentclass{article}
\usepackage{graphicx}
\DeclareGraphicsExtensions{.png, .gif, .jpg}
\newcommand{\href}[2]{\Link[#1]{}{} #2 \EndLink}
\newcommand{\hypertarget}[2]{\Link[]{}{#1} #2 \EndLink}
\newcommand{\hyperlink}[2]{\Link[]{#1}{} #2 \EndLink}
%\documentclass{article}
%\usepackage{graphicx}
%\DeclareGraphicsExtensions{.png, .gif, .jpg}
%\newcommand{\href}[2]{\Link[#1]{}{} #2 \EndLink}
%\newcommand{\hypertarget}[2]{\Link[]{}{#1} #2 \EndLink}
%\newcommand{\hyperlink}[2]{\Link[]{#1}{} #2 \EndLink}
%% uncomment the following for pdflatex compilation
%\documentclass[a4paper,12pt]{article}
%\usepackage[pdftex]{graphicx}
%\DeclareGraphicsExtensions{.pdf,.png,.jpg}
%\RequirePackage[hyperindex]{hyperref}
\documentclass[a4paper,12pt]{article}
\usepackage[pdftex]{graphicx}
\DeclareGraphicsExtensions{.pdf,.png,.jpg}
\RequirePackage[hyperindex]{hyperref}
@ -165,7 +165,13 @@ After having parsed a program, in order to read in a new program you must restar
When using \texttt{lpad.pl}, the system can print the message ``Uunsound program'' in the case in which an instance with a three valued well founded model is found. Moreover, it can print the message ``It requires the choice of a head atom from a non ground head'': in this case, in order to answer the query, all the groundings of the culprit clause must be generated, which may be impossible for programs with function symbols.
When using \texttt{cpl.pl}, the system can print the above messages plus ``Invalid program'' in the case in which no execution process exists. The same message can be returned by \texttt{semcpl.pl}.
When using \texttt{semcpl.pl}, you can print the execution process by using the command \texttt{print.}
after \texttt{p(file).} Moreover, you can build an execution process given a context by issuing the command \texttt{parse(file)}. and then
\texttt{build(context).} where \texttt{context} is a list of atoms that are true in the context.
\texttt{semcpl.pl} can print ``Invalid program'' in the case in which no execution process exists.
When using \texttt{cpl.pl} you can print a partial execution model including all the clauses involved in the query issued with \texttt{print.} \texttt{cpl.pl} can print the messages ``Uunsound program'', ``It requires the choice of a head atom from a non ground head'' and ``Invalid program''.
The modules make use of a number of parameters in order to control their behavior. They that can be set with the command
\begin{verbatim}
@ -461,4 +467,4 @@ Copyright (C) 1993 Southern Methodist University, 1993 SUNY at Stony Brook, see
%\usepackage[pdftex]{graphicx}
%\DeclareGraphicsExtensions{.pdf,.png,.jpg}
%\RequirePackage[hyperindex]{hyperref}
%\fi
%\fi