Dyadic TGDs - A new paradigm for ontological query answering
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Marte, Cinzia
Greco, Gianluigi
Manna, Marco
Guerriero, Francesca
Leone, Nicola
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Dottorato di Ricerca in Matematica e Informatica . Ciclo XXXIII; Ontology-BasedQueryAnswering(OBQA)consistsinqueryingdata–
bases bytakingontologicalknowledgeintoaccount.Wefocusona
logical frameworkbasedonexistentialrulesor tuple generatingdepen-
dencies (TGDs), alsoknownasDatalog±, whichcollectsthebasicde-
cidable classesofTGDs,andgeneralizesseveralontologyspecification
languages.
While thereexistlotsofdifferentclassesintheliterature,inmost
cases eachofthemrequiresthedevelopmentofaspecificsolverand,
only rarely,thedefinitionofanewclassallowstheuseofexisting
systems. Thisgapbetweenthenumberofexistentparadigmsandthe
numberofdevelopedtools,promptedustodefineacombinationof
Shy and Ward (twowell-knownclassesthatenjoygoodcomputational
properties)withtheaimofexploitingthetooldevelopedfor Shy.
Nevertheless,studyinghowtomergethesetwoclasses,wehavereal-
ized thatitwouldbepossibletodefine,inamoregeneralway,the
combinationofexistingclasses,inordertomakethemostofexisting
systems.
Hence, inthiswork,startingfromtheanalysisofthetwoaforemen-
tioned existingclasses,wedefineamoregeneralclass,named Dyadic
TGDs, thatallowstoextendinauniformandelegantwayallthede-
cidable classes,whileusingtheexistentrelatedsystems.Atthesame
time, wedefinealsoacombinationof Shy and Ward, named Ward+,
and weshowthatitcanbeseenasaDyadicsetofTGDs.
Finally,tosupportthetheoreticalpartofthethesis,weimplementa
BCQ evaluationalgorithmfortheclass Ward+, thattakesadvantage
of anexistingsolverdevelopedfor Shy.Soggetto
Ontological Query Answering; Database query languages; Datalog; Tuple Generating Dependencies; Complexity
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