Ontology is an explicit representation of a particular domain of interest.This paper focuses on the inherent problem of intractability (data complexity) due to data capturing for heterogeneous sources. We proposed to follow the tradition of knowledge representation and reasoning processes to develop a smantic web.Building query systems is the ultimate goal for this study.Conjunctive queries were adopted over ontology methods to address the data complexity. The conjunctive queries are the form of queries in first-order logic that deal with conjunction and existential quantification in database atomic formulae.State of the art meteorological and aceanographic domain provides the motivation for this work.We found that thw querying method facilitates the tractability in reasoning and logical systems. Keywords: Ontology, semantic web, conjuntive queries, tractability.