Huiyong Xiao

An ontology-based framework for XML semantic integration

XML is becoming the standard for data interchange on the Web. However, XML and its schema languages do not express semantics but rather structure, such as nesting information. Therefore, semantically equivalent documents often present different document structures. We provide an ontology-based framework that aims to make two XML documents intemperate at the semantic level while retaining their nesting structure. In our global-as-view approach, we generate an RDF ontology for each of the participating XML documents, which preserves the nesting structure of the document. An RDF global ontology is the result of merging the individual ontologies. The global ontology unifies the query access and establishes semantic connections among the underlying individual databases. We consider two types of queries: those that are posed on the global ontology and those that are posed on any of the XML documents, in a P2P fashion. The former type is processed using query translation from an RDF query to an XML query. The latter type entails bidirectional query processing: the translation from an XML query to an RDF query followed by the translation from an RDF query to an XML query. To ensure the correctness of the answer to the query in the latter case, we introduce the concept of reversibility of the query translation.

Peer-to-peer semantic integration of XML and RDF data sources

Peer-to-Peer (P2P) data management systems combine traditional schema-based integration techniques with the P2P infrastructure. In this paper, we propose a P2P data management framework named PEPSINT that semantically integrates heterogeneous XML and RDF data sources, using a hybrid architecture and a global-as-view approach. Our focus is on the query processing techniques over heterogeneous data. Queries in PEPSINT are expressed in XQuery and in RDQL. We consider two types of queries, depending on whether the query is first posed on the super peer or on one of the peers.

Integrating and exchanging XML data using ontologies

While providing a uniform syntax and a semistructured data model, XML does not express semantics but only structure such as nesting information. In this paper, we consider the problem of data integration and interoperation of heterogeneous XML sources and use an ontology-based framework to address this problem at a semantic level. Ontologies are extensively used for domain knowledge representation, by virtue of their conceptualization of the domain, which carries explicit semantics. In our approach, the global ontology is expressed in RDF Schema (RDFS) and constructed using the global-as-view approach by merging individual local ontologies, which represent XML source schemas. We provide a formal model for the mappings between XML schemas and local RDFS ontologies and those between local ontologies and the global RDFS ontology. We consider two cases of query processing, specifically for data integration and for data interoperation. In the first case, the user poses an RDF query on the global ontology, which is answered using all the mapped XML sources. In the second case, a query is posed on a single source and then is mapped to the XML sources that are connected to that source. For each case, we discuss the problem of query containment and present an equivalent query rewriting algorithm for queries expressed in two languages: conjunctive RDQL and conjunctive XQuery.

Ontology Driven Data Integration in Heterogeneous Networks

We propose a layered framework for the integration of syntactically, schematically, and semantically heterogeneous networked data sources. Their hetero- geneity stems from different models (e.g., relational, XML, or RDF), different schemas within the same model, and different terms associated with the same meaning. We use a semantic based approach that uses a global ontology to mediate among the schemas of the data sources. In our framework, a query is expressed in terms of one of the data sources or of the global ontology and is then translated into subqueries on the other data sources using mappings based on a common vocabulary. Metadata represen- tation, global conceptualization, declarative mediation, mapping support, and query processing are addressed in detail in our discussion of a case study.

Using a layered approach for interoperability on the semantic Web

In this paper, we further develop a proposed layered approach for the semantic Web. Our objective is to build a specific solution to the problem of providing data interoperability among different databases, so as to allow for schematic data integration. In particular, we solve the problem of translating queries on a database schema into queries on another database schema, using their relationship with an ontology. We use RDF schema to model the databases and the ontology. A common vocabulary expresses the mappings between each database schema and the ontology.

The problem of ontology alignment on the web: a first report

This paper presents a general architecture and four algorithms that use Natural Language Processing for automatic ontology matching. The proposed approach is purely instance based, i.e., only the instance documents associated with the nodes of ontologies are taken into account. The four algorithms have been evaluated using real world test data, taken from the Google and LookSmart online directories. The results show that NLP techniques applied to instance documents help the system achieve higher performance.

A layered framework supporting personal information integration and application design for the semantic desktop

With the development of inexpensive storage devices, space usage is no longer a bottleneck for computer users. However, the increasingly large amount of personal information poses a critical problem to those users: traditional file organization in hierarchical directories may not be suited to the effective management of personal information because it ignores the semantic associations therein and bears no connection with the applications that users will run. To address such limitations, we present our vision of a semantic desktop, which relies on the use of ontologies to annotate and organize data and on the concept of personal information application (PIA), which is associated with a user’s task. The PIA designer is the tool that is provided for building a variety of PIAs consisting of views (e.g., text, list, table, graph), which are spatially arranged and display interrelated fragments of the overall personal information. The semantic organization of the data follows a layered architecture that models separately the personal information, the domain data, and the application data. The network of concepts that ensues from extensive annotation and explicit associations lends itself well to rich browsing capabilities and to the formulation of expressive database-like queries. These queries are also the basis for the interaction among views of the PIAs in the same desktop or in networked desktops. In the latter case, the concept of desktop service provides for a semantic platform for the integration of information across different desktops and the web. In this paper, we present in detail the semantic organization of the information, the overall system architecture and implementation aspects, queries and their processing, PIAs and the PIA designer, including usability studies on the designer, and the concepts of semantic navigation in a desktop and of interoperation in a network of desktops.