Tova Milo

Dynamic XML documents with distribution and replication

The advent of XML as a universal exchange format, and of Web services as a basis for distributed computing, has fostered the apparition of a new class of documents: dynamic XML documents. These are XML documents where some data is given explicitly while other parts are given only intensionally by means of embedded calls to web services that can be called to generate the required information. By the sole presence of Web services, dynamic documents already include inherently some form of distributed computation. A higher level of distribution that also allows (fragments of) dynamic documents to be distributed and/or replicated over several sites is highly desirable in todays Web architecture, and in fact is also relevant for regular (non dynamic) documents.The goal of this paper is to study new issues raised by the distribution and replication of dynamic XML data. Our study has originated in the context of the Active XML system [1, 3, 22] but the results are applicable to many other systems supporting dynamic XML data. Starting from a data model and a query language, we describe a complete framework for distributed and replicated dynamic XML documents. We provide a comprehensive cost model for query evaluation and show how it applies to user queries and service calls. Finally, we describe an algorithm that, for a given peer, chooses data and services that the peer should replicate to improve the efficiency of maintaining and querying its dynamic data.

Similarity-based queries

We develop a domain-independent framework for defining qneries in terms of similarity of objects. Our framework has three components: a pattern language, a transformation rule language, and a query language. The pattern language specifies classes of objects, the transformation rule language defines similarity by specifying the similarity-preserving transformations, and the whole package is wrapped in a general query language. The framework can be “tuned” to the needs of a specific application domain, such as time sequences, molecules, text strings or images, by the choice of these languages. We demonstrate the framework by presenting a specific instance on a specific domain – the domain of sequences. We start with sequences over a finite alphabet, and then consider sequences over infinite ordered domains. The basic pattern language weuseis regular expressions, and the query language is calculus-based. We show that even when the pattern/query languages chosen are not too powerful, the approximation framework obtained is very strong. We study the properties of the framework, and in particular present expressive power and complexity results.

Correspondence and translation for heterogeneous data

Data integration often requires a clean abstraction of the different formats in which data are stored, and means for specifying the correspondences/relationships between data in different worlds and for translating data from one world to another. For that, we introduce in this paper a middleware data model that serves as a basis for the integration task, and a declarative rules language for specifying the integration. We show that using the language, correspondences between data elements can be computed in polynomial time in many cases, and may require exponential time only when insensitivity to order or duplicates are considered. Furthermore, we show that in most practical cases the correspondence rules can be automatically turned into translation rules to map data from one representation to another. Thus, a complete integration task (derivation of correspondences, transformation of data from one world to the other, incremental integration of a new bulk of data, etc.) can be specified using a single set of declarative rules.

The Active XML project: an overview

This paper provides an overview of the Active XML project developed at INRIA over the past five years. Active XML (AXML, for short), is a declarative framework that harnesses Web services for distributed data management, and is put to work in a peer-to-peer architecture. The model is based on AXML documents, which are XML documents that may contain embedded calls to Web services, and on AXML services, which are Web services capable of exchanging AXML documents. An AXML peer is a repository of AXML documents that acts both as a client by invoking the embedded service calls, and as a server by providing AXML services, which are generally defined as queries or updates over the persistent AXML documents. The approach gracefully combines stored information with data defined in an intensional manner as well as dynamic information. This simple, rather classical idea leads to a number of technically challenging problems, both theoretical and practical. In this paper, we describe and motivate the AXML model and language, overview the research results obtained in the course of the project, and show how all the pieces come together in our implementation.

Compact Labeling Scheme for Ancestor Queries

We consider the following problem. Given a rooted tree

Active XML: peer-to-peer data and web services integration

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Database and XML Technologies

, label the nodes of

Typechecking for XML transformers

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Views in a Large Scale XML Repository

in the most compact way such that, given the labels of two nodes

XML with data values: typechecking revisited

u