We propose a database logic which accounts in a clean declarative fashion for most of the “object-oriented” features such as object identity, complex objects, inheritance, methods, etc. Furthermore, database schema is part of the object language, which allows the user to browse schema and data using the same declarative formalism. The proposed logic has a formal semantics and a sound and complete resolution-based proof procedure, which makes it also computationally attractive.

The paper discusses the issue of views in the Web context. We introduce a set of tools and languages for managing and restructuring data coming from the World Wide Web. We present a specific data model, called the Araneus Data Model, inspired to the structures typically present in Web sites. The model allows us to describe the scheme of a Web hypertext, in the spirit of databases. Based on the

A new definition of complex objects is introduced which provides a denotation for incomplete tuples as well as partially described sets. Set values are "sandwiched" between "complete" and "consistent" descriptions (representing the Smyth and Hoare powerdomains respectively), allowing the maximal values to be arbitrary subsets of maximal elements in the domain of the set. We also examine the use of rules in defining queries over such objects. 1 Introduction A characteristic of "complex-object" [1, 2] databases and "higher-order" relations [3, 4] is that the components of tuples are not restricted to taking only atomic values, but may be other tuples or even sets of tuples. A second property of complex objects and related information structures is that there is a natural ordering on the domain of values with an associated algebra [5, 6, 7]. For example, in Bancilhon and Khoshafian's ordering on tuples [1] [Name) 0 J.Doe 0 ] v [Name) 0 J.Doe 0 ;Age)21] This research was suppor...

Deductive databases result from the integration of relational database and logic programming techniques. However, significant problems remain inherent in this simple synthesis from the language point of view. In this paper, we discuss these problems from four different aspects: complex values, object orientation, higherorderness, and updates. In each case, we examine four typical languages that address the corresponding issues.

Data Types New base types can be added to the EXTRA data model via the EXTRA abstract data type facility. To add a new ADT, the person responsible for adding the type begins by writing (and debugging) the code for the type in the E programming language. E is an extension of C++ [Stro86] that was developed as part of the EXODUS project. E serves as the implementation language for access methods and operators for systems developed using EXODUS. It is also the target language for the query compiler, and (most importantly for our purposes here) the language in which base type extensions will be defined. E extends C++ with a number of features to aid programmers in data- 89 base system programming, including "dbclasses" for persistent storage, class generators for implementing "generic" classes and functions, iterators for use as a control abstraction in writing set operations, and built-in class generators for typed files and variable-length arrays [Rich87]. Suppose that we wanted to add...

Large web sites are becoming repositories of structured information that can benefit from being viewed and queried as relational databases. However, querying these views efficiently requires new techniques. Data usually resides at a remote site and is organized as a set of related HTML documents, with network access being a primary cost factor in query evaluation. This cost can be reduced by exploiting the redundancy often found in site design. We use a simple data model, a subset of the Araneus data model, to describe the structure of a web site. We augment the model with link and inclusion constraints that capture the redundancies in the site. We map relational views of a site to a navigational algebra and show how to use the constraints to rewrite algebraic expressions, reducing the number of network accesses. We show that similar techniques can be used to maintain materialized views over sets of HTML pages.

The purpose of this thesis is to investigate a type system for databases and object-oriented programming and to design a statically typed programming language for these applications. Such a language should ideally have a static type system that supports: • polymorphism and static type inference, • rich data structures and operations to represent various data models for databases including the relational model and more recent complex object models, • central features of object-oriented programming including user definable class hierarchies, multiple inheritance, and data abstraction, • the notion of extents and object-identities for object-oriented databases. Without a proper formalism, it is not obvious that the construction of such a type system is possible. This thesis attempts to construct one such formalism and proposes a programming language that uniformly integrate all of the above features. The specific contributions of this thesis include: • A simple semantics for ML polymorphism and axiomatization of the equational theory of ML. • A uniform generalization of the relational model to arbitrary complex database objects that

We investigate data organization in the World Wide Web. In order to extend traditional database techniques to the Web, we concentrate on stvctved 14eb sevwvs, those servers (now very common) in which data are organized according to precise structures and pages present strong regularities. The paper introduces several tools for the management of structured servers. We present a page ov{ented data model, called the ARANEUS )(t( Jod, inspired to the structures typically present in these servers. The model allows us to describe the scheme of a structured server, in the spirit of databases. Then, we develop a view definition language, called the ARANEUS /{w L(ng(g, based on the notion of v{gat{o in the scheme. It has two features: first, it allows to build relational views of the Web, which can then be queried using any relational query language; second, it allows the definition of derived Web structures from relational views. This can be used to restructure query results and access them as an hypertext or to build derived servers.

Over the last few years several new data models together with their languages have been developed to meet the increasing requirements of engineering or office applications. A major characteristic of these data models is their ability to process and manage complex objects which the relational model does not provide adequate support for. Whereas the problem of query translation for relational languages has provoked broad research activities during the last fifteen years, the analogous problem of translating nonprocedural queries on complex objects into lower level programs for efficient execution has received only little attention. This paper tries to reveal the new aspects of query translation and execution on complex objects as compared to similar activities when processing flat relations. For this purpose, we investigate the essential concepts necessary to perform compilation, optimization, and execution of queries on complex objects.

: Algebraic optimization are both theoretically and practically important for query processing in (nested) relational databases. In this paper, we consider this issue and investigate some algebraic properties concerning to the nested relational operators. We also outline a heuristic optimization algorithm for nested relational expressions by adopting algebraic transformation rules developed in this paper and previous related work. 1 Introduction In the last decade, much research has been carried out on nested relations and complex objects. By relaxing the 1NF assumption, the resulting nested relational model (sometimes called NF 2 ) can support such new applications as office automation, multimedia system, scientific data processing system, engineering design system, and so forth. In order to model these applications we use hierarchical structures rather than flat tables to enable the representation of complex objects. The nested relational model is the basis for bridging the rela...