Giovanna Guerrini

Impact of XML schema evolution on valid documents

In this paper we investigate the problem of XML Schema evolution. We first discuss the different kinds of changes that may be needed on an XML Schema. Then, we investigate how to minimize document revalidation, that is, detecting the document parts potentially invalidated by the schema changes that should be revalidated.

A multigranular spatiotemporal data model

A large percentage of data managed by a variety of different application domains has spatiotemporal characteristics. Unfortunately, traditional geographical information systems do not allow for an easy representation of temporal aspects of spatial data. Moreover, they do not usually support the representation of data at multiple levels of granularity. In this paper we present a multigranular spatiotemporal data model. Our model extends the ODMG model with multiple spatial and temporal granularities. In particular, the model allows for an uniform management of two kinds of spatiotemporal objects: moving entities (e.g. cars, planes, etc.) and temporal maps (i.e., maps representing the change over time of a given geographic area). It also provides a framework for mapping the movement of an entity such as a car onto an underlying geographic area. The model we propose relies on a standard definition of temporal granularity. On the other hand, the representation of spatial entities at multiple granularities is obtained by applying model oriented map generalization principles. In particular, we consider a set of generalization operators that guarantee topological consistency.

Approximate subtree identification in heterogeneous XML documents collections

Due to the heterogeneous nature of XML data for internet applications exact matching of queries is often inadequate. The need arises to quickly identify subtrees of XML documents in a collection that are similar to a given pattern. In this paper we discuss different similarity measures between a pattern and subtrees of documents in the collection. An efficient algorithm for the identification of document subtrees, approximately conforming to the pattern, by indexing structures is then introduced.

Evolving a Set of DTDs According to a Dynamic Set of XML Documents

In this paper we address the problem of evolving a set of DTDs so to obtain a description as precise as possible of the structures of the documents actually stored in a source of XML documents. This problem is highly relevant in such a dynamic and heterogeneous environment as the Web. The approach we propose relies on the use of a classification mechanism based on document structure and on the use of data mining association rules to find out frequent structural patterns in data.

Updating XML schemas and associated documents through exup

Data on the Web mostly are in XML format and the need often arises to update their structure, commonly described by an XML Schema. When a schema is modified the effects of the modification on documents need to be faced. XSUpdate is a language that allows to easily identify parts of an XML Schema, apply a modification primitive on them and finally define an adaptation for associated documents, while Eχup is the corresponding engine for processing schema modification and document adaptation statements. Purpose of this demonstration is to provide an overview of the facilities of the XSUpdate language and of the Eχup system.

X-Evolution: A Comprehensive Approach for XML Schema Evolution

In this paper we present X-Evolution, a Web system developed on top of a commercial DBMS that allows the specification of schema modifications both on a graphical representation of an XML Schema and through a specifically tailored declarative language. X-Evolution supports facilities for performing schema revalidation only when strictly needed and only on the minimal parts of documents affected by the modifications. Moreover, it supports the automatic and query-based adaptation of original schema instances to the evolved schema.

Handling Expiration of Multigranular Temporal Objects

A well-known problem of temporal databases is that the amount of stored data tends to increase very fast. Moreover, detailed data are useful when they are acquired but they often become less relevant after some time. In most cases, after a period of time only summarized data need to be kept, whereas detailed data expire and can be removed from the database. Multigranular temporal databases enhance the expressive power of temporal databases by supporting temporal attributes at different levels of detail. However, in existing approaches the level of detail of an attribute, that is its granularity, depends only on the attribute semantics and does not depend on how recent the attribute values are. This paper proposes an approach supporting the aggregation of different portions of the value of a temporal attribute at different levels of detail, and the deletion or the transfer to tertiary storage of old values at a given level of detail, in order to minimize disk storage occupancy. In the proposed multigranular temporal object-oriented data model, the expiration of attribute values at a given granularity can be specified, together with the action to take when data expire: either aggregation to a coarser granularity, or deletion of values, or both.

Access to Multigranular Temporal Objects

In this paper we discuss access to object attributes in a multigranular temporal object-oriented data model that handles the expiration of dynamic attributes, according to the age of data and their granularity [4]. Different strategies can be applied, with respect to available data and to the preferences specified by the user on either accuracy or efficiency in executing a query. We devise some properties of object access that can be applied to speed up the query process, such as the invariance of the queries results with respect to expiration operations, and the static detection of unsolvability of a query.

A semantic information retrieval advertisement and policy based system for a P2P network

In this paper we propose a semantic based P2P system that incorporates peer sharing policies, which allow a peer to state, for each of the concepts it deals with, the conditions under which it is available to process requests related to that concept. The semantic routing approach, based on advertisements and peer behavior in answering previous requests, takes also into account sharing policies.

REPORT on the EDBT'04 workshop on database technologies for handling XML information on the web

The EDBT04 Workshop on Database <u>T</u>echnologies for H<u>a</u>ndling <u>X</u>ML Information on the Web (DataX04) was held in Heraklion, Crete, on Sunday 14 March, 2004, and attracted approximately 30 participants from different countries.