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48
From Structured Documents to Novel Query Facilities
, 1994
"... Structured documents (e.g., SGML) can benefit a lot from database support and more specifically from objectoriented database (OODB) management systems. This paper describes a natural mapping from SGML documents into OODB's and a formal extension of two OODB query languages (one SQLlike and th ..."
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Cited by 233 (34 self)
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Structured documents (e.g., SGML) can benefit a lot from database support and more specifically from objectoriented database (OODB) management systems. This paper describes a natural mapping from SGML documents into OODB's and a formal extension of two OODB query languages (one SQLlike and the other calculus) in order to deal with SGML document retrieval. Although motivated by structured documents, the extensions of query languages that we present are general and useful for a variety of other OODB applications. A key element is the introduction of paths as first class citizens. The new features allow to query data (and to some extent schema) without exact knowledge of the schema in a simple and homogeneous fashion. 1 Introduction Structured documents are central to a wide class of applications such as software engineering, libraries, technical documentation, etc. They are often stored in file systems and document access tools are somewhat limited. We believe that (objectoriented) d...
An Introduction to Spatial Database Systems
 THE VLDB JOURNAL
, 1994
"... We propose a definition of a spatial database system as a database system that offers spatial data types in its data model and query language, and supports ..."
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Cited by 216 (9 self)
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We propose a definition of a spatial database system as a database system that offers spatial data types in its data model and query language, and supports
WebOQL: Restructuring Documents, Databases and Webs
, 1998
"... The widespread use of the Web has originated several new data management problems, such as extracting data from Web pages and making databases accessible from Web browsers, and has renewed the interest in problems that had appeared before in other contexts, such as querying graphs, semistructured da ..."
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Cited by 171 (3 self)
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The widespread use of the Web has originated several new data management problems, such as extracting data from Web pages and making databases accessible from Web browsers, and has renewed the interest in problems that had appeared before in other contexts, such as querying graphs, semistructured data and structured documents. Several systems and languages have been proposed for solving each of these Webdata management problems, but none of these systems addresses all the problems from a unified perspective. Many of these problems essentially amount to data restructuring: we have information represented according to certain structure and we want to construct another representation of (part of) it using a different structure. We present the WebOQL system, which supports a general class of data restructuring operations in the context of the Web. WebOQL synthesizes ideas from query languages for the Web, for semistructured data and for website restructuring. 1 Introduction The widespre...
An algebra for structured text search and a framework for its implementation
 The Computer Journal
, 1995
"... A query algebra is presented that expresses searches on structured text. In addition to traditional fulltext boolean queries that search a predefined collection of documents, the algebra permits queries that harness document structure. The algebra manipulates arbitrary intervals of text, which are ..."
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Cited by 121 (19 self)
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A query algebra is presented that expresses searches on structured text. In addition to traditional fulltext boolean queries that search a predefined collection of documents, the algebra permits queries that harness document structure. The algebra manipulates arbitrary intervals of text, which are recognized in the text from implicit or explicit markup. The algebra has seven operators, which combine intervals to yield new ones: containing, not containing, contained in, not contained in, one of, both of, followed by. The ultimate result of a query is the set of intervals that satisfy it. An implementation framework is given based on four primitive access functions. Each access function finds the solution to a query nearest to a given position in the database. Recursive definitions for the seven operators are given in terms of these access functions. Search time is at worst proportional to the time required to solve the elementary terms in the query. Inverted indices yield search times that compare favourably to those for fulltext boolean searches. Email concerning this paper should be sent to claclark@plg.uwaterloo.ca.
GeoRelational Algebra: A Model and Query Language for Geometric Database Systems
 Int. Conf. on Extending Database Technology
, 1988
"... : The user's conceptual model of a database system for geometric data should be simple and precise: easy to learn and understand, with clearly defined semantics, expressive: allow to express with ease all desired query and data manipulation tasks, efficiently implementable. To achieve these goa ..."
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Cited by 76 (7 self)
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: The user's conceptual model of a database system for geometric data should be simple and precise: easy to learn and understand, with clearly defined semantics, expressive: allow to express with ease all desired query and data manipulation tasks, efficiently implementable. To achieve these goals we propose to extend relational database management systems by integrating geometry at all levels: At the conceptual level, relational algebra is extended to include geometric data types and operators. At the implementation level, the wealth of algorithms and data structures for geometric problems developed in the past decade in the field of Computational Geometry is exploited.  The paper starts from a view of relational algebra as a manysorted algebra which allows to easily embed geometric data types and operators. A concrete algebra for twodimensional applications is developed. It can be used as a highly expressive retrieval and data manipulation language for geometric as well as standard...
Queries and Computation on the Web
, 1997
"... The paper introduces a model of the Web as an infinite, semistructured set of objects. We reconsider the classical notions of genericity and computability of queries in this new context and relate them to styles of computation prevalent on the Web, based on browsing and searching. We revisit severa ..."
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Cited by 63 (3 self)
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The paper introduces a model of the Web as an infinite, semistructured set of objects. We reconsider the classical notions of genericity and computability of queries in this new context and relate them to styles of computation prevalent on the Web, based on browsing and searching. We revisit several wellknown declarative query languages (firstorder logic, Datalog, and Datalog with negation) and consider their computational characteristics in terms the notions introduced in this paper. In particular, we are interested in languages or fragments thereof which can be implemented by browsing, or by browsing and searching combined. Surprisingly, stratified and wellfounded semantics for negation turn out to have basic shortcomings in this context, while inflationary semantics emerges as an appealing alternative.
GraphDB: Modeling and Querying Graphs in Databases
 Proc. of the 20th VLDB Conference
, 1994
"... We propose a data model and query language that integrates an explicit modeling and querying of graphs smoothly into a standard database environment. For standard applications, some key features of objectoriented modeling are offered such as object classes organized into a hierarchy, object identit ..."
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Cited by 59 (4 self)
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We propose a data model and query language that integrates an explicit modeling and querying of graphs smoothly into a standard database environment. For standard applications, some key features of objectoriented modeling are offered such as object classes organized into a hierarchy, object identity, and attributes referencing objects. Querying can be done in a familiar style with a derive statement that can be used like a select... from... where. On the other hand, the model allows for an explicit representation of graphs by partitioning object classes into simple classes, link classes, and path classes whose objects can be viewed as nodes, edges, and explicitly stored paths of a graph (which is the whole database instance). For querying graphs, the derive statement has an extended meaning in that it allows one to refer to subgraphs of the database graph. A powerful rewrite operation is offered for the manipulation of heterogeneous sequences of objects which often occur as a result of accessing the database graph. Additionally there are special graph operations like determining a shortest path or a subgraph and the model is extensible by such operations. Besides being attractive for standard applications, the model permits a natural representation and sophisticated querying of networks, in particular of spatially embedded networks like highways, public transport, etc.
Gral: An Extensible Relational Database System for Geometric Applications
 PROC. OF THE 15TH INTL. CONF. ON VERY LARGE DATA BASES
, 1989
"... We describe the architecture of a relational database system that is extensible by userdefined data types and operations, including relation operations. The central concept is to use languages based on manysorted algebra to represent queries as well as query execution plans. This leads to a simple ..."
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Cited by 50 (13 self)
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We describe the architecture of a relational database system that is extensible by userdefined data types and operations, including relation operations. The central concept is to use languages based on manysorted algebra to represent queries as well as query execution plans. This leads to a simple and clean extensible system architecture, eases the task of an application developer by providing a uniform framework, and also simplifies rulebased optimization. As a case study the extensions needed for a geometric database system are considered.
SecondOrder Signature: A Tool for Specifying Data Models
 Query Processing, and Optimization. Proc. ACM SIGMOD Conf
, 1993
"... We propose a framework for the specification of extensible database systems. A particular goal is to implement a software component for parsing and rulebased optimization that can be used with widely varying data models and query languages as well as representation and query processing systems. T ..."
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Cited by 38 (27 self)
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We propose a framework for the specification of extensible database systems. A particular goal is to implement a software component for parsing and rulebased optimization that can be used with widely varying data models and query languages as well as representation and query processing systems. The key idea is to use secondorder signature (and algebra), a system of two coupled manysorted signatures, where the toplevel signature offers kinds and type constructors and the bottomlevel signature provides polymorphic operations over the types defined as terms of the top level. Hence the top level can be used to define a data or representation model and the bottom level to describe a query algebra or a query processing algebra. We show the applicability of this framework by examples drawn from relational modeling and query processing.
Explicit Graphs in a Functional Model for Spatial Databases
 IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING
, 1994
"... Observing that networks are ubiquitous in applications for spatial databases, we define a new data model and query language that especially supports graph structures. This model integrates concepts of functional data modeling with ordersorted algebra. Besides object and data type hierarchies grap ..."
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Cited by 28 (8 self)
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Observing that networks are ubiquitous in applications for spatial databases, we define a new data model and query language that especially supports graph structures. This model integrates concepts of functional data modeling with ordersorted algebra. Besides object and data type hierarchies graphs are available as an explicit modeling tool, and graph operations are part of the query language. Graphs have three classes of components, namely nodes, edges, and explicit paths. These are at the same time object types within the object type hierarchy and can be used like any other type. Explicit paths are useful because “real world ” objects often correspond to paths in a network. Furthermore, a dynamic generalization concept is introduced to handle heterogeneous collections of objects in a query. In connection with spatial data types this leads to powerful modeling and querying capabilities for spatial databases, in particular for spatially embedded networks such as highways, rivers, public transport, and so forth. We use multilevel ordersorted algebra as a formal framework for the specification of our model. Roughly spoken, the first level algebra defines types and operations of the query language whereas the second level algebra defines kinds (collections of types) and type constructors as functions between kinds and so provides the types that can be used at the first level.