A Review of integrity constraint maintenance and view updating techniques

Two interrelated problems may arise when updating a database. On one hand, when an update is applied to the database, integrity constraints may become violated. In such case, the integrity constraint maintenance approach tries to obtain additional updates to keep integrity constraints satisfied. On the other hand, when updates of derived or view facts are requested, a view updating mechanism must be applied to translate the update request into correct updates of the underlying base facts. This survey reviews the research performed on integrity constraint maintenance and view updating. It is proposed a general framework to classify and to compare methods that tackle integrity constraint maintenance and/or view updating. Then, we analyze some of these methods in more detail to identify their actual contribution and the main limitations they may present.Postprint (published version

U-Filter: A Lightweight XML View Update Checker

We study in this paper the problem of whether a correct relational update translation can be found for a given update over an XML view. For this, we propose a lightweight update checking framework named U-Filter. It first performs two steps of schemalevel (and thus very inexpensive) checks based on a view definition analysis. Only when necessary, a third checking step, requiring base data access and thus more expensive, is employed. For the latter, we design an internal strategy as well as an external strategy (with respect to the DBMS). This three-step checking process is guaranteed to filter out all XML updates that cannot be translated. Finally, the remaining updates are fed to the update translation engine, which generates the corresponding SQL update statements. Our experiments illustrate the usefulness of U-Filter and the performance impact achievable by the proposed algorithm

Updating XML Views Published over Relational Databases: Towards the Existence of a Correct Update Mapping

XML data management using relational database systems has been intensively studied in the last few years. However, in order for such systems to be viable, they must support not only queries, but also updates over virtual XML views that wrap the relational data. While view updating is a long-standing difficult issue in the relational context, the flexible XML data model and nested XML query language both pose additional challenges for view updating. This paper addresses the question, if for a given update over an XML view, a correct relational update translation exists. First, we propose a clean extended-source theory as criteria for determining whether a given translation mapping is correct. To determine the existence of such a correct mapping, we classify a view update as either un- translatable, conditionally or unconditionally translatable under a given update translation policy. This classification depends on several features of the XML view and the update: (a) granularity of the update at the view side, (b) properties of the view construction, and (c) types of duplication appearing in the view. These features are represented in the Annotated Schema Graph. This is further utilized by our Schema-driven Translatability Reasoning algorithm (STAR) to classify a given update into one of the three above update categories. The correctness of the algorithm is proven using our clean extended-source theory. This technique represents a practical approach that can be applied by any existing view update system in industry and academia for analyzing the translatability of a given update statement before translation of it is attempted. To illustrate the working algorithm, we provide a concrete case study on the translatability of XML view updates

Flexible view update

As uninstantiated windows onto a relational database, views are modified only when the intended update can be realized by updates against the underlying database. Such a conventional restriction can, and must, be relaxed when some relations, as collections of predicates, are composed of both basic and derived facts. Therefore, this paper presents an extended formulation for the problem of view updating based on two notions: the internal state and the perceptible state of a database. Through a clear distinction between these two database states, a mechanism is proposed to facilitate those legitimate view updates that are not necessarily translatable. The proposed mechanism also relies heavily on the normalization theory through functional dependencies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29857/1/0000205.pd

Update-Aware Information Extraction

Information extraction programs (extractors) can be applied to documents to isolate structured versions of some content by creating tabular records corresponding to facts found in the documents. When extracted relations or source documents are updated, we wish to ensure that those changes are propagated correctly. That is, we recommend that extracted relations be treated as materialized views over the document database. Because extraction is expensive, maintaining extracted relations in the presence of frequent document updates comes at a high execution cost. We propose a practical framework to effectively update extracted views to represent the most recent version of documents. Our approach entails conducting static analyses of extraction and update programs within a framework compatible with SystemT, a renowned extraction framework based on regular expressions. We describe a multi-level verification process aimed at efficiently identifying document updates for which we can autonomously compute the updated extracted views. Through comprehensive experimentation, we demonstrate the effectiveness of our approach within real-world extraction scenarios. For the reverse problem, we need to translate updates on extracted views into corresponding document updates. We rely on a translation mechanism that is based on value substitution in the source documents. We classify extractors amenable to value substitution as stable extractors. We again leverage static analyses of extraction programs to study stability for extractors expressed in a significant subset of JAPE, another rule-based extraction language. Using a document spanner representation of the JAPE program, we identify four sufficient properties for being able to translate updates back to the documents and use them to verify whether an input JAPE program is stable

El Mètode dels esdeveniments per a l'Actualització de vistes en bases de dades deductives

En esta tesis se presenta un nuevo método, llamado método de los eventos, para la actualización de vistas en bases de datos deductivas. Este método aumenta la base de datos con un conjunto de reglas, llamadas reglas de transición y de evento, que definen explícitamente las inserciones y las supresiones inducidas por una modificación de la base de datos. Mediante estas reglas, se utiliza la resolución SIDNF para obtener todas las traducciones mínimas que satisfacen una petición de actualización de vista.Una de las contribuciones principales de esta tesis es la demostración del hecho que el método de los eventos es completo en bases de datos estratificados. Es decir, en este tipo de bases de datos dicho método obtiene todas las traducciones validas. Otras ventajas importantes del método son la incorporación de la comprobación de integridad en el proceso de traducción, el tratamiento uniforme de inserciones y supresiones, la posibilidad de prevenir efectos laterales y la traducción de peticiones de modificación de vista.Por todas estas razones, se puede decir que el método de los eventos tiene todo el poder de los métodos propuestos hasta el momento actual para la utilización de vistas en bases de datos deductivas, pero sin presentar algunas de sus limitaciones