Package org.tweetyproject.arg.delp.parser

Class DelpParser

java.lang.Object

org.tweetyproject.commons.Parser<DefeasibleLogicProgram,Formula>

org.tweetyproject.arg.delp.parser.DelpParser

All Implemented Interfaces:

DelpParserConstants

public class DelpParser
extends Parser<DefeasibleLogicProgram,Formula>
implements DelpParserConstants

This class implements a parser for defeasible logic programs. The BNF for defeasible logic program files is given by (start symbol is THEORY)

 THEORY                 ::== (EXPRESSION)+
 EXPRESSION             ::== FACT | STRICTRULE | DEFEASIBLERULE
 FACT                   ::== LITERAL + "."
 STRICTRULE             ::== LITERAL + "<-" + RULEBODY + "."
 DEFEASIBLERULE         ::== LITERAL + "-<" + RULEBODY + "."
 RULEBODY               ::== LITERAL | LITERAL + "," + RULEBODY
 LITERAL                ::== "~" + ATOM | ATOM
 ATOM                   ::== PREDICATE | PREDICATE + "(" + TERMLIST + ")"
 TERMLIST               ::== TERM | TERM + "," + TERMLIST
 TERM                   ::== VARIABLE | CONSTANT | QUOTED_STRING

 PREDICATE is a sequence of symbols from {a,...,z,A,...,Z,0,...,9,_,-} with a letter at the beginning.
 VARIABLE is a sequence of symbols from {a,...,z,A,...,Z,0,...,9,_,-} with an uppercase letter at the beginning.
 CONSTANT is  a sequence of symbols from {a,...,z,A,...,Z,0,...,9,_,-} with an lowercase letter at the beginning.
 QUOTED_STRING is all characters between double quotes.
 

Field Summary

Fields

Modifier and Type	Field	Description
Token	jj_nt	Next token.
Token	token	Current token.
DelpParserTokenManager	token_source	Generated Token Manager.

Fields inherited from interface org.tweetyproject.arg.delp.parser.DelpParserConstants

DEFAULT, EOF, NAME, QUOTED, tokenImage

Constructor Summary

Constructors

Constructor	Description
DelpParser()	Constructs a new `DelpParser` instance with an empty input reader.
DelpParser(InputStream stream)	Creates a new parser instance with the specified input stream.
DelpParser(InputStream stream, String encoding)	Creates a new parser instance with the specified input stream and character encoding.
DelpParser(Reader stream)	Creates a new parser instance with the specified reader.
DelpParser(DelpParserTokenManager tm)	Creates a new parser instance with the specified token manager.

Method Summary

Modifier and Type	Method	Description
final FolAtom	Atom(DefeasibleLogicProgram delp, FolSignature signature)	Parses an atom (predicate with optional terms) from the input.
final void	disable_tracing()	Disable tracing.
final void	enable_tracing()	Enable tracing.
final void	Expression(DefeasibleLogicProgram delp, FolSignature signature)	Parses an expression in the defeasible logic program.
final FolFormula	Formula(FolSignature signature)	Parses a formula from the given signature.
ParseException	generateParseException()	Generate ParseException.
final Token	getNextToken()	Retrieves the next token in the input stream.
FolSignature	getSignature()	Return the signature
final Token	getToken(int index)	Retrieves a specific token from the input stream by its index.
final FolFormula	Literal(DefeasibleLogicProgram delp, FolSignature signature)	Parses a literal, which could be an atom or its negation.
DefeasibleLogicProgram	parseBeliefBase(Reader reader)	Parses a defeasible logic program from the given reader.
Formula	parseFormula(Reader reader)	A formula here is a Literal, that is an Atom or a negated Atom.
void	ReInit(InputStream stream)	Reinitializes the parser with a new input stream.
void	ReInit(InputStream stream, String encoding)	Reinitializes the parser with a new input stream and character encoding.
void	ReInit(Reader stream)	Reinitializes the parser with a new reader.
void	ReInit(DelpParserTokenManager tm)	Reinitializes the parser with a new token manager.
final Term	Term(DefeasibleLogicProgram delp, FolSignature signature)	Parses a term (either a variable or a constant) from the input.
final DefeasibleLogicProgram	Theory(FolSignature signature)	Parses a defeasible logic program from a given signature.

Methods inherited from class org.tweetyproject.commons.Parser

isNumeric, parseBeliefBase, parseBeliefBaseFromFile, parseFormula, parseFormulaFromFile, parseListOfBeliefBases, parseListOfBeliefBases, parseListOfBeliefBasesFromFile, parseListOfBeliefBasesFromFile

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

token_source

public DelpParserTokenManager token_source

Generated Token Manager.

token

public Token token

Current token.

jj_nt

public Token jj_nt

Next token.

Constructor Details

DelpParser

public DelpParser()

Constructs a new `DelpParser` instance with an empty input reader.

DelpParser

public DelpParser(InputStream stream)

Creates a new parser instance with the specified input stream.

Parameters:

stream - The input stream to be used by the parser.

DelpParser

public DelpParser(InputStream stream,
 String encoding)

Creates a new parser instance with the specified input stream and character encoding.

Parameters:

stream - The input stream to be used by the parser.

encoding - The character encoding of the input stream. If null, the default encoding is used.

DelpParser

public DelpParser(Reader stream)

Creates a new parser instance with the specified reader.

Parameters:

stream - The reader to be used by the parser.

DelpParser

public DelpParser(DelpParserTokenManager tm)

Creates a new parser instance with the specified token manager.

Parameters:

tm - The token manager to be used by the parser.

Method Details

parseBeliefBase

public DefeasibleLogicProgram parseBeliefBase(Reader reader)
                                       throws ParserException

Parses a defeasible logic program from the given reader.

This method initializes the parser with the provided reader and parses the input to construct a DefeasibleLogicProgram. It uses the current logical signature to guide the parsing process.

Specified by:

parseBeliefBase in class Parser<DefeasibleLogicProgram,Formula>

Parameters:

reader - The reader from which the defeasible logic program is read.

Returns:

A DefeasibleLogicProgram constructed from the input.

Throws:

ParserException - If an error occurs during parsing.

parseFormula

public Formula parseFormula(Reader reader)
                     throws ParserException

A formula here is a Literal, that is an Atom or a negated Atom. The class DelpQuery encapsulates the following. The Atom is either a DeLP predicate (a predicate with arity > 0) or a DeLP constant or variable (a predicate with arity == 0). In the case of a real predicate, test all arguments whether they are DeLP variables (= begin with upper case letter) or DeLP constants. All predicates and constants need to be present in the current signature to parse.

Specified by:

parseFormula in class Parser<DefeasibleLogicProgram,Formula>

Parameters:

reader - the reader to parse from

Returns:

a Formula, which is always a DelpQuery in this implementation, that has been successfully parsed with the current signature in mind

Throws:

ParserException - if the reader cannot be successfully parsed into a formula

getSignature

public FolSignature getSignature()

Return the signature

Returns:

the signature

Theory

public final DefeasibleLogicProgram Theory(FolSignature signature)
                                    throws ParseException

Parses a defeasible logic program from a given signature.

Parameters:

signature - The signature that defines the vocabulary of the logic program.

Returns:

A DefeasibleLogicProgram instance representing the parsed program.

Throws:

ParseException - If an error occurs during parsing.

Expression

public final void Expression(DefeasibleLogicProgram delp,
 FolSignature signature)
                      throws ParseException

Parses an expression in the defeasible logic program.

Parameters:

delp - The defeasible logic program to which parsed components are added.

signature - The signature that defines the vocabulary of the logic program.

Throws:

ParseException - If an error occurs during parsing.

Formula

public final FolFormula Formula(FolSignature signature)
                         throws ParseException

Parses a formula from the given signature.

Parameters:

signature - The signature that defines the vocabulary of the logic program.

Returns:

A FolFormula representing the parsed formula.

Throws:

ParseException - If an error occurs during parsing.

Literal

public final FolFormula Literal(DefeasibleLogicProgram delp,
 FolSignature signature)
                         throws ParseException

Parses a literal, which could be an atom or its negation.

Parameters:

delp - The defeasible logic program to which the literal might be added.

signature - The signature that defines the vocabulary of the logic program.

Returns:

A FolFormula representing the parsed literal.

Throws:

ParseException - If an error occurs during parsing.

Atom

public final FolAtom Atom(DefeasibleLogicProgram delp,
 FolSignature signature)
                   throws ParseException

Parses an atom (predicate with optional terms) from the input.

This method constructs a FolAtom by parsing a predicate name followed by a sequence of terms, if present. The predicate is added to the signature if it is not already present, and its arity is checked for correctness. If the arity is incorrect, a ParseException is thrown.

Parameters:

delp - The defeasible logic program to which the predicate might be added.

signature - The logical signature to which the predicate might be added.

Returns:

A FolAtom constructed from the parsed predicate and terms.

Throws:

ParseException - If an error occurs during parsing, such as an incorrect predicate arity.

Term

public final Term Term(DefeasibleLogicProgram delp,
 FolSignature signature)
                throws ParseException

Parses a term (either a variable or a constant) from the input.

This method constructs a Term based on the input token. It handles variables (identified by uppercase names) and constants (both plain and quoted). If a quoted term is encountered, the quotes are removed before creating the constant.

Parameters:

delp - The defeasible logic program used for creating constants (if needed).

signature - The logical signature used for creating constants (if needed).

Returns:

A Term constructed from the parsed token.

Throws:

ParseException - If an error occurs during parsing.

ReInit

public void ReInit(InputStream stream)

Reinitializes the parser with a new input stream.

Parameters:

stream - The new input stream to be used by the parser.

ReInit

public void ReInit(InputStream stream,
 String encoding)

Reinitializes the parser with a new input stream and character encoding.

Parameters:

stream - The new input stream to be used by the parser.

encoding - The character encoding of the new input stream. If null, the default encoding is used.

ReInit

public void ReInit(Reader stream)

Reinitializes the parser with a new reader.

Parameters:

stream - The new reader to be used by the parser.

ReInit

public void ReInit(DelpParserTokenManager tm)

Reinitializes the parser with a new token manager.

Parameters:

tm - The new token manager to be used by the parser.

getNextToken

public final Token getNextToken()

Retrieves the next token in the input stream.

This method advances to the next token by either using the previously cached next token or fetching a new token from the token source if there is no cached next token. The token stream is updated and the token index and generation are incremented accordingly.

Returns:

The next Token in the input stream.

getToken

public final Token getToken(int index)

Retrieves a specific token from the input stream by its index.

This method traverses the token stream to reach the token at the specified index. If the token at the given index is not already available, it fetches the necessary tokens from the token source until the desired token is reached.

Parameters:

index - The zero-based index of the token to retrieve.

Returns:

The Token at the specified index in the input stream.

generateParseException

public ParseException generateParseException()

Generate ParseException.

Returns:

the ParseException

enable_tracing

public final void enable_tracing()

Enable tracing.

disable_tracing

public final void disable_tracing()

Disable tracing.