3,363 research outputs found
Updating Views Over Recursive XML
We study the problem of updating XML views defined over XML documents. A view update is performed by finding the base updates over the underlying data sources that achieve the desired view update. If such base updates do not exist, the view update is said to be untranslatable and rejected. In SQL, determining whether a view update is translatable is performed using schema level analysis, where the view definition and the base schema are used. XML schemas are more complex than SQL schemas, and can specify recursive types and cardinality constraints. There are two kinds of view updates: single view element update, where the user requires for an update over a particular view element, and a set of view elements update, where the user requires for an update over all view elements that satisfy a given XPath over the view. Accordingly, we propose one solution for each kind of view update problems based on schema level analysis for determining whether an update over XML views is translatable and for finding the translation if one exists, while considering the features of XML schemas
A General Approach for Securely Querying and Updating XML Data
Over the past years several works have proposed access control models for XML
data where only read-access rights over non-recursive DTDs are considered. A
few amount of works have studied the access rights for updates. In this paper,
we present a general model for specifying access control on XML data in the
presence of update operations of W3C XQuery Update Facility. Our approach for
enforcing such updates specifications is based on the notion of query rewriting
where each update operation defined over arbitrary DTD (recursive or not) is
rewritten to a safe one in order to be evaluated only over XML data which can
be updated by the user. We investigate in the second part of this report the
secure of XML updating in the presence of read-access rights specified by a
security views. For an XML document, a security view represents for each class
of users all and only the parts of the document these users are able to see. We
show that an update operation defined over a security view can cause disclosure
of sensitive data hidden by this view if it is not thoroughly rewritten with
respect to both read and update access rights. Finally, we propose a security
view based approach for securely updating XML in order to preserve the
confidentiality and integrity of XML data.Comment: No. RR-7870 (2012
Secure Querying of Recursive XML Views: A Standard XPath-based Technique
Most state-of-the art approaches for securing XML documents allow users to
access data only through authorized views defined by annotating an XML grammar
(e.g. DTD) with a collection of XPath expressions. To prevent improper
disclosure of confidential information, user queries posed on these views need
to be rewritten into equivalent queries on the underlying documents. This
rewriting enables us to avoid the overhead of view materialization and
maintenance. A major concern here is that query rewriting for recursive XML
views is still an open problem. To overcome this problem, some works have been
proposed to translate XPath queries into non-standard ones, called Regular
XPath queries. However, query rewriting under Regular XPath can be of
exponential size as it relies on automaton model. Most importantly, Regular
XPath remains a theoretical achievement. Indeed, it is not commonly used in
practice as translation and evaluation tools are not available. In this paper,
we show that query rewriting is always possible for recursive XML views using
only the expressive power of the standard XPath. We investigate the extension
of the downward class of XPath, composed only by child and descendant axes,
with some axes and operators and we propose a general approach to rewrite
queries under recursive XML views. Unlike Regular XPath-based works, we provide
a rewriting algorithm which processes the query only over the annotated DTD
grammar and which can run in linear time in the size of the query. An
experimental evaluation demonstrates that our algorithm is efficient and scales
well.Comment: (2011
Query-Answer Causality in Databases: Abductive Diagnosis and View-Updates
Causality has been recently introduced in databases, to model, characterize
and possibly compute causes for query results (answers). Connections between
query causality and consistency-based diagnosis and database repairs (wrt.
integrity constrain violations) have been established in the literature. In
this work we establish connections between query causality and abductive
diagnosis and the view-update problem. The unveiled relationships allow us to
obtain new complexity results for query causality -the main focus of our work-
and also for the two other areas.Comment: To appear in Proc. UAI Causal Inference Workshop, 2015. One example
was fixe
Type-Based Detection of XML Query-Update Independence
This paper presents a novel static analysis technique to detect XML
query-update independence, in the presence of a schema. Rather than types, our
system infers chains of types. Each chain represents a path that can be
traversed on a valid document during query/update evaluation. The resulting
independence analysis is precise, although it raises a challenging issue:
recursive schemas may lead to infer infinitely many chains. A sound and
complete approximation technique ensuring a finite analysis in any case is
presented, together with an efficient implementation performing the chain-based
analysis in polynomial space and time.Comment: VLDB201
Report on the XBase Project
This project addressed the conceptual fundamentals of data storage,
investigating techniques for provision of highly generic storage facilities
that can be tailored to produce various individually customised storage
infrastructures, compliant to the needs of particular applications. This
requires the separation of mechanism and policy wherever possible. Aspirations
include: actors, whether users or individual processes, should be able to bind
to, update and manipulate data and programs transparently with respect to their
respective locations; programs should be expressed independently of the storage
and network technology involved in their execution; storage facilities should
be structure-neutral so that actors can impose multiple interpretations over
information, simultaneously and safely; information should not be discarded so
that arbitrary historical views are supported; raw stored information should be
open to all; where security restrictions on its use are required this should be
achieved using cryptographic techniques. The key advances of the research were:
1) the identification of a candidate set of minimal storage system building
blocks, which are sufficiently simple to avoid encapsulating policy where it
cannot be customised by applications, and composable to build highly flexible
storage architectures 2) insight into the nature of append-only storage
components, and the issues arising from their application to common storage
use-cases
Incremental View Maintenance For Collection Programming
In the context of incremental view maintenance (IVM), delta query derivation
is an essential technique for speeding up the processing of large, dynamic
datasets. The goal is to generate delta queries that, given a small change in
the input, can update the materialized view more efficiently than via
recomputation. In this work we propose the first solution for the efficient
incrementalization of positive nested relational calculus (NRC+) on bags (with
integer multiplicities). More precisely, we model the cost of NRC+ operators
and classify queries as efficiently incrementalizable if their delta has a
strictly lower cost than full re-evaluation. Then, we identify IncNRC+; a large
fragment of NRC+ that is efficiently incrementalizable and we provide a
semantics-preserving translation that takes any NRC+ query to a collection of
IncNRC+ queries. Furthermore, we prove that incremental maintenance for NRC+ is
within the complexity class NC0 and we showcase how recursive IVM, a technique
that has provided significant speedups over traditional IVM in the case of flat
queries [25], can also be applied to IncNRC+.Comment: 24 pages (12 pages plus appendix
Using Links to prototype a Database Wiki
Both relational databases and wikis have strengths that make them attractive for use in collaborative applications. In the last decade, database-backed Web applications have been used extensively to develop valuable shared biological references called curated databases. Databases offer many advantages such as scalability, query optimization and concurrency control, but are not easy to use and lack other features needed for collaboration. Wikis have become very popular for early-stage biocuration projects because they are easy to use, encourage sharing and collaboration, and provide built-in support for archiving, history-tracking and annotation. However, curation projects often outgrow the limited capabilities of wikis for structuring and efficiently querying data at scale, necessitating a painful phase transition to a database-backed Web application. We perceive a need for a new class of general-purpose system, which we call a Database Wiki, that combines flexible wiki-like support for collaboration with robust database-like capabilities for structuring and querying data. This paper presents DBWiki, a design prototype for such a system written in the Web programming language Links. We present the architecture, typical use, and wiki markup language design for DBWiki and discuss features of Links that provided unique advantages for rapid Web/database application prototyping
Twelve Theses on Reactive Rules for the Web
Reactivity, the ability to detect and react to events, is an
essential functionality in many information systems. In particular, Web
systems such as online marketplaces, adaptive (e.g., recommender) systems,
and Web services, react to events such as Web page updates or
data posted to a server.
This article investigates issues of relevance in designing high-level programming
languages dedicated to reactivity on the Web. It presents
twelve theses on features desirable for a language of reactive rules tuned
to programming Web and Semantic Web applications
XML for Domain Viewpoints
Within research institutions like CERN (European Organization for Nuclear
Research) there are often disparate databases (different in format, type and
structure) that users need to access in a domain-specific manner. Users may
want to access a simple unit of information without having to understand detail
of the underlying schema or they may want to access the same information from
several different sources. It is neither desirable nor feasible to require
users to have knowledge of these schemas. Instead it would be advantageous if a
user could query these sources using his or her own domain models and
abstractions of the data. This paper describes the basis of an XML (eXtended
Markup Language) framework that provides this functionality and is currently
being developed at CERN. The goal of the first prototype was to explore the
possibilities of XML for data integration and model management. It shows how
XML can be used to integrate data sources. The framework is not only applicable
to CERN data sources but other environments too.Comment: 9 pages, 6 figures, conference report from SCI'2001 Multiconference
on Systemics & Informatics, Florid
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