We propose a novel formalism, called Frame Logic (abbr., F-logic), that accounts in a clean and declarative fashion for most of the structural aspects of object-oriented and frame-based languages. These features include object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. In a sense, F-logic stands in the same relationship to the objectoriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete resolution-based proof theory. A small number of fundamental concepts that come from object-oriented programming have direct representation in F-logic; other, secondary aspects of this paradigm are easily modeled as well. The paper also discusses semantic issues pertaining to programming with a deductive object-oriented language based on a subset of F-logic.

We present a novel language for querying object-oriented databases. The language is built around the idea of extended path expressions that substantially generalize [ZAN83], and on an adaptation of the first-order formalization of object-oriented languages from [KW89, KLW90, KW92]. The language incorporates features not found in earlier proposals; it is easier to use and has greater expressive power. Some of the salient features of our language are: ffl Precise model-theoretic semantics. ffl A very expressive form of path expressions that not only can do joins, selections and unnesting, but can also be used to explore the database schema. ffl Views can be defined and manipulated in a much more uniform way than in other proposals. ffl Database schema can be explored in the very same language that is used to retrieve data. Unlike in relational languages, the user needs not know anything about the system tables that store schema information. ffl The notions of a type and type-correctness have precise meaning. It accommodates a wide variety of queries that might be deemed well- or ill-typed under different circumstances. In particular, we show that there is more than one way of settling the issue of type correctness. For expository purposes and due to space limitation, we chose to make a number of simplifying assumptions and left some features out. A more complete account can be found in [KSK92].

) Mengchi Liu Department of Computer Science University of Regina Regina, Saskatchewan, Canada S4S 0A2 mliu@cs.uregina.ca Abstract This paper presents a novel logic-based language for nested relations. It stands in the same relationship to the nested relation model as Datalog stands to the relational model. The main novelties of the language are the mechanisms for representing both partial and complete information on sets and tuples, and the introduction of a new ordering on interpretations that captures the intended semantics for nested sets, tuples and relations. Under appropriate stratification restrictions, it is shown that the unique minimal and supported model, if it exists, can be computed bottom-up, and therefore used as the intended semantics of the program. 1 Introduction In the past decade, there has been a lot of interest in nested relations, whose tuple components may be sets, tuples or even relations [2, 8, 11, 12, 14, 15]. The extended relational algebra and cal...

Abstract | This paper tells the story of OQL, the standard query language of the Object Database Management Group (ODMG) [30]. The story starts in 1988, at INRIA in the Alta r Group y. The objective of that group was to develop an object-oriented database system [41]. This objective was reached: in September 1991 the O2 database system started its commercial career as the main product of a company called O2Technology [6]. As opposed to its competitors, O2 featured a full- edged query language named O2SQL [22]. The story goes on with the creation of the ODMG in 1991 and the adoption of O2SQL as the standard object query language under its new and nal name: OQL. During the following years, OQL went through some modi cations, the most important ofwhich resulted in OQL 1.2 that o ers some level of compliance with SQL92. On top of providing the expressive power of the SQL92 query language [54], OQL allows objects to be queried. This is a claim also supported by the upcoming SQL3. However, due to its adequacy to the object oriented type system and its functional nature, OQL is much simpler to learn, use and implement. A goal of this paper is to demonstrate this. This paper tells about the mistakes and pertinent choices we made while designing and implementing OQL. I hope it also conveys the great pleasure I had to be part of this adventure. Key words: Object-oriented database, query language 1.

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.

Fox (Finding Objects of eXperiments) is the declarative query language for Moose (Modeling Objects Of Scientific Experiments), an object-oriented data model at the core of a scientific experiment management system (EMS) being developed at Wisconsin. The goal of the EMS is to support scientists in managing their experimental studies and the data that are generated from them. Moose is unique among object-oriented data models in permitting sets to have relationships to classes other than their elements' class, in providing a construct for indexing collections by other collections, such as time series, and in distinguishing structural relationships from non-structural ones. Fox contains several new features necessary to manage experiments, such as support for associative element retrieval from (indexed) sets and highly expressive path expressions. Fox path expressions can traverse any relationship in the schema graph, including inheritance relationships, and in either direction of the rela...

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...

We describe the design and implementation of Relationlog, a persistent deductive database system. Unlike other related systems such as Aditi, CORAL, LDL, LOLA and Nail-Glue, Relationlog supports effective storage, efficient access and inference of large amounts of data with complex structures and provides declarative query language that can define recursive views involving complex data and also a declarative data manipulation language to update databases.

First and foremost, I'd like to thank my family, Chris and Nigel, who were always there for me. Chris resonated with my angst especially well. I'd like to thank my advisor, Don Batory, who alternately provided encouragement and impetus. Finally, I'd like to thank the folks of the Computer Science Department atCalPoly State University in San Luis Obispo, who generously provided computing and lab facilities. The University ofTexas at Austin

We present the hybrid query language HQL/EER for an Extended Entity-Relationship model. As its main characteristic, this language allows a user to use both graphical and textual elements in the formulation of one and the same query. We demonstrate the lookand -feel of this query language by means of examples, and show how syntax and semantics of this language are formally defined using programmed graph rewriting systems. Although we present the language in the context of the EER model, the concept of hybrid languages is applicable in the context of other database models as well. We illustrate this claim by discussing a prototype implementation of a Hybrid Query Tool based on an object-oriented approach, namely the Object Modeling Technique (OMT). 1 Introduction The database research efforts of the past decade have provided us with a wide range of both database models and systems, allowing the user to perform complex manipulations on data structures of high modeling power. Th...