Modeling and manipulating the structure of hierarchical schemas for the web

Dalamagas, T; Meliou, A; Sellis, T

dc.contributor.author	Dalamagas, T	en
dc.contributor.author	Meliou, A	en
dc.contributor.author	Sellis, T	en
dc.date.accessioned	2014-03-01T01:28:46Z
dc.date.available	2014-03-01T01:28:46Z
dc.date.issued	2008	en
dc.identifier.issn	0020-0255	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/18967
dc.subject	Hierarchical schemas	en
dc.subject	Schema difference	en
dc.subject	Schema integration	en
dc.subject	Schema intersection	en
dc.subject	Schema union	en
dc.subject	Structural manipulation	en
dc.subject.classification	Computer Science, Information Systems	en
dc.subject.other	Boolean algebra	en
dc.subject.other	Data acquisition	en
dc.subject.other	Hierarchical systems	en
dc.subject.other	Query processing	en
dc.subject.other	Semantic Web	en
dc.subject.other	Set theory	en
dc.subject.other	Trees (mathematics)	en
dc.subject.other	World Wide Web	en
dc.subject.other	Hierarchical schemas	en
dc.subject.other	Schema difference	en
dc.subject.other	Schema integration	en
dc.subject.other	Schema intersection	en
dc.subject.other	Schema union	en
dc.subject.other	Structural manipulation	en
dc.subject.other	Schematic diagrams	en
dc.title	Modeling and manipulating the structure of hierarchical schemas for the web	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.ins.2007.09.022	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.ins.2007.09.022	en
heal.language	English	en
heal.publicationDate	2008	en
heal.abstract	The Semantic Web is the next step of the current Web where information will become more machine-understandable to support effective data discovery and integration. Hierarchical schemas, either in the form of tree-like structures (e.g., DTDs, XML schemas), or in the form of hierarchies on a category/subcategory basis (e.g., thematic hierarchies of portal catalogs), play an important role in this task. They are used to enrich semantically the available information. Up to now, hierarchical schemas have been treated rather as sets of individual elements, acting as semantic guides for browsing or querying data. Under that view, queries like ""find the part of a portal catalog which is not present in another catalog"" can be answered only in a procedural way, specifying which nodes to select and how to get them. For this reason, we argue that hierarchical schemas should be treated as full-fledged objects so as to allow for their manipulation. This work proposes models and operators to manipulate the structural information of hierarchies, considering them as first-class citizens. First, we explore the algebraic properties of trees representing hierarchies, and define a lattice algebraic structure on them. Then, turning this structure into a boolean algebra, we present the operators S-union, S-intersection and S-difference to support structural manipulation of hierarchies. These operators have certain algebraic properties to provide clear semantics and assist the transformation, simplification and optimization of sequences of operations using laws similar to those of set theory. Also, we identify the conditions under which this framework is applicable. Finally, we demonstrate an application of our framework for manipulating hierarchical schemas on tree-like hierarchies encoded as RDF/s files. © 2007 Elsevier Inc. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE INC	en
heal.journalName	Information Sciences	en
dc.identifier.doi	10.1016/j.ins.2007.09.022	en
dc.identifier.isi	ISI:000253184800004	en
dc.identifier.volume	178	en
dc.identifier.issue	4	en
dc.identifier.spage	985	en
dc.identifier.epage	1010	en