GenI- A natural language generator (specifically, an FB-LTAG surface realiser)

Safe HaskellSafe-Infered




This module performs the core of lexical selection and anchoring.


Lexical selection algorithms

type LexicalSelector = Macros -> Lexicon -> Sem -> IO LexicalSelectionSource

See Configuration if you want to use GenI with a custom lexical selection function.

data LexicalSelection Source

The result of the lexical selection process




lsAnchored :: [TagElem]

the main result: a set of elementary trees (ie. anchored trees)

lsLexEntries :: [LexEntry]

if available, lexical entries that were used to produce anchored trees (useful for identifying anchoring failure)

lsWarnings :: GeniWarnings

HINT: use mempty to initialise to empty

defaultLexicalSelector :: Macros -> Lexicon -> Sem -> IO LexicalSelectionSource

Performs standard GenI lexical selection as described in

This is just defaultLexicalSelection lifted into IO

defaultLexicalSelection :: Macros -> Lexicon -> Sem -> LexicalSelectionSource

Helper for defaultLexicalSelector (Standard GenI lexical selection is actually pure)

This is just defaultLexicalChoice and defaultAnchoring

missingLexEntries :: [TagElem] -> [LexEntry] -> [LexEntry]Source

missingLexEntries ts lexs returns any of the lexical candidates lexs that were apparently not anchored succesfully.

TODO: it does this by (wrongly) checking for each lexical item to see if any of the anchored trees in ts have identical semantics to that lexical item. The better way to do this would be to throw a subsumption check on top of items reported missing, because it's possible for the trees to add semantics through unification.

Selecting candidate lemmas

defaultLexicalChoice :: Lexicon -> Sem -> [LexEntry]Source

Select and returns the set of entries from the lexicon whose semantics subsumes the input semantics.

chooseCandI :: Sem -> [LexEntry] -> [LexEntry]Source

chooseCandI sem l attempts to unify the semantics of l with sem If this succeeds, we use return the result(s); if it fails, we reject l as a lexical selection candidate.

mergeSynonyms :: [LexEntry] -> [LexEntry]Source

mergeSynonyms is a factorisation technique that uses atomic disjunction to merge all synonyms into a single lexical entry. Two lexical entries are considered synonyms if their semantics match and they point to the same tree families.

FIXME: 2006-10-11 - note that this is no longer being used, because it breaks the case where two lexical entries differ only by their use of path equations. Perhaps it's worthwhile just to add a check that the path equations match exactly.


type LexCombine a = MaybeT (Writer [LexCombineError]) aSource

The LexCombine monad supports warnings during lexical selection and also failure via Maybe

lexTell :: LexCombineError -> LexCombine ()Source

Note an anchoring error

defaultAnchoring :: Macros -> [LexEntry] -> Sem -> LexicalSelectionSource

defaultAnchoring schemata lex sem implements the later half of lexical selection (tree anchoring and enrichement). It assumes that lex consists just of the lexical items that have been selected, and tries to combine them with the tree schemata.

This function may be useful if you are implementing your own lexical selection functions, and you want GenI to take over after you've given it a [LexEntry]




:: Sem 
-> Macros 
-> LexEntry 
-> ([LexCombineError], [TagElem])

any warnings, plus the results

Given a lexical item, looks up the tree families for that item, and anchor the item to the trees.

combineOne :: Sem -> LexEntry -> SchemaTree -> LexCombine [TagElem]Source

Combine a single tree with its lexical item to form a bonafide TagElem. This process can fail, however, because of filtering or enrichement


enrich helpers

enrichBy :: SchemaTree -> PathEqPair -> LexCombine SchemaTreeSource

Helper for enrich (enrich by single path equation)

enrichFeat :: AvPair GeniVal -> Flist [GeniVal] -> Maybe (Flist [GeniVal], Subst)Source

enrichFeat av fs attempts to unify av with fs

Note here that fs is an Flist [GeniVal] rather than the usual Flist GeniVal you may expect. This is because it comes from SchemaTree which allows non-atomic disjunctions of GeniVal which have to be flatten down to at most atomic disjunctions once lexical selection is complete.

missingCoanchors :: LexEntry -> SchemaTree -> [Text]Source

missingCoanchors l t returns the list of coanchor node names from l that were not found in t

lexEquations :: LexEntry -> Writer [LexCombineError] ([AvPair GeniVal], [PathEqPair])Source

Split a lex entry's path equations into interface enrichement equations or (co-)anchor modifiers

seekCoanchor :: NodePathEqLhs -> SchemaTree -> Maybe SchemaNodeSource

seekCoanchor lhs t returns Just node if t contains exactly one node that can be identified by lhs, Nothing if it contains none.

It crashes if there is more than one such node, because this should have been caught earlier by GenI.

matchNodeName :: NodePathEqLhs -> SchemaNode -> BoolSource

matchNodeName lhs n is True if the lhs refers to the node n

matchNodeNameHelper :: Text -> SchemaNode -> BoolSource

matchNodeNameHelper recognises “anchor“ by convention; otherwise, it does a name match

Lemanchor mechanism

_lemanchor :: TextSource

The name of the lemanchor attribute (by convention; see source)

setOrigin :: Text -> Tree (GNode v) -> Tree (GNode v)Source

setOrigin n t marks the nodes in t as having come from a tree named n