Federica Mandreoli

Temporal modelling and management of normative documents in XML format

In this paper, we present the results of a research project concerning the temporal management of normative texts in XML format. In particular, four temporal dimensions (publication, validity, efficacy and transaction times) are used to correctly represent the evolution of norms in time and their resulting versioning. Hence, we introduce a multiversion data model based on XML schema and define basic mechanisms for the maintenance and retrieval of multiversion norm texts. Finally, we describe a prototype management system which has been implemented and evaluated.

A formal model for temporal schema versioning in object-oriented databases

In this paper we present a formal model for the support of temporal schema versions in object-oriented databases. Its definition is partially based on a generic (ODMG compatible) object model and partially introduces new concepts. The proposed model supports all the schema changes which are usually considered in the OODB literature, for which an operational semantics and a formal analysis of their correct behaviour is provided. Semantic issues arising from the introduction of temporal schema versioning in a conventional or temporal database (concerning the interaction between the intensional and extensional levels of versioning and the management of data in the presence of multiple schema versions) are also considered.

Evolution and change in data management — issues and directions

One of the fundamental aspects of information and database systems is that they change. Moreover, in so doing they evolve, although the manner and quality of this evolution is highly dependent on the mechanisms in place to handle it. While changes in data are handled well, changes in other aspects, such as structure, rules, constraints, the model, etc., are handled to varying levels of sophistication and completeness. In order to study this in more detail a workshop on Evolution and Change in Data Management was held in Paris in November 1999. It brought together researchers from a wide range of disciplines with a common interest in handling the fundamental characteristics and the conceptual modelling of change in information and database systems. This short report of the workshop concentrates on some of the general lessons that emerged during the four days.

OLAP query reformulation in peer-to-peer data warehousing

Inter-business collaborative contexts prefigure a distributed scenario where companies organize and coordinate themselves to develop common and shared opportunities, but traditional business intelligence systems do not provide support to this end. To fill this gap, in this paper we envision a peer-to-peer data warehousing architecture based on a network of heterogeneous peers, each exposing query answering functionalities aimed at sharing business information. To enhance the decision making process, an OLAP query expressed on a peer needs to be properly reformulated on the local multidimensional schemata of the other peers. To this end, we present a language for the definition of mappings between the multidimensional schemata of peers and we introduce a query reformulation framework that relies on the translation of mappings, queries, and multidimensional schemata onto the relational level. Then, we formalize a query reformulation algorithm and prove two properties: correctness and closure, that are essential in a peer-to-peer setting. Finally, we discuss the main implementation issues related to the reformulation setting proposed, with specific reference to the case in which the local multidimensional engines hosted by peers use the standard MDX language.

Flexible query answering on graph-modeled data

The largeness and the heterogeneity of most graph-modeled datasets in several database application areas make the query process a real challenge because of the lack of a complete knowledge of the vocabulary used, as well as of the information about the structural relationships between the data. To overcome these problems, flexible query answering capabilities are an essential need. In this paper we present a general model for supporting approximate queries on graph-modeled data. Approximation is both on the vocabularies and the structure. The model is general in that it is not bound to a specific graph data model, rather it gracefully accommodates labeled directed/undirected data graphs with labeled/unlabeled edges. The query answering principles underlying the model are not compelled to a specific data graph, instead they are founded on properties inferable from the data model the data graph conforms to. We complement the work with a ranking model to deal with data approximations and with an efficient top-k retrieval algorithm which smartly accesses ad-hoc data structures and generates the most promising answers in an order correlated with the ranking measures. Experimental results prove the good effectiveness and efficiency of our proposal on different real world datasets.

A temporal data model and management system for normative texts in XML format

In this paper,we present the results of an on-going research activity concerning the temporal management of normative texts in XML format. In particular, four temporal dimensions (publication,validity,efficacy and transaction times) are used to correctly represent the evolution of norms in time and their resulting versioning. Hence, we introduce a multiversion data model based on XML schema and de?ne basic mechanisms for the management of norm texts. Finally, we describe a prototype management system which has been implemented and evaluated.

Approximate Query Answering for a Heterogeneous XML Document Base

In this paper, we deal with the problem of effective search and query answering in heterogeneous web document bases containing documents in XML format of which the schemas are available. We propose a new solution for the structural approximation of the submitted queries which, in a preliminary schema matching process, is able to automatically identify the similarities between the involved schemas and to use them in the query processing phase, when a query written on a source schema is automatically rewritten in order to be compatible with the other useful XML documents. The proposed approach has been implemented in a web service and can deliver middleware rewriting services in any open-architecture XML repository system offering advanced search capabilities.

SRI: exploiting semantic information for effective query routing in a PDMS

The huge amount of data available from Internet information sources has focused much attention on the sharing of distributed information through Peer Data Management Systems (PDMSs). In a PDMS, peers have a schema on their local data, and they are related each other through semantic mappings that can be defined between their own schemas.Querying a PDMS means either flooding the network with messages to all peers or take advantage of a routing mechanism to reformulate a query only on the best peers selected according to some given criteria. As reformulations may lead to semantic approximations, we deem that such approximations can be exploited for locating the semantically best directions to forward a query to.In this paper, we propose a distributed index mechanism where each peer is provided with a Semantic Routing Index (SRI) for routing queries effectively. A fuzzy-oriented model for SRI is presented where operations for creating and maintaining SRIs are well-founded. In addition, we show how SRIs can be employed in the query processing phase with the aim of reducing the space of reformulations. Finally, we conduct a series of meaningful experiments showing the effectiveness of the proposed approach.

Versatile structural disambiguation for semantic-aware applications

In this paper, we propose a versatile disambiguation approach which can be used to make explicit the meaning of structure based information such as XML schemas, XML document structures, web directories, and ontologies. It can be of support to the semantic-awareness of a wide range of applications, from schema matching and query rewriting to peer data management systems, from XML data clustering to ontology-based automatic annotation of web pages and query expansion. The effectiveness of the achieved results has been experimentally proved and is founded both on a flexible exploitation of the structure context, whose extraction can be tailored on the specific application needs, and of the information provided by commonly available thesauri such as WordNet.

A syntactic approach for searching similarities within sentences

Textual data is the main electronic form of knowledge representation. Sentences, meant as logic units of meaningful word sequences, can be considered its backbone. In this paper, we propose a solution based on a purely syntactic approach for searching similarities within sentences, named approximate sub2sequence matching. This process being very time consuming, efficiency in retrieving the most similar parts available in large repositories of textual data is ensured by making use of new filtering techniques. As far as the design of the system is concerned, we chose a solution that allows us to deploy approximate sub2 sequence matching without changing the underlying database.