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12
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 47 (2 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.
RealmBased Spatial Data Types: The ROSE Algebra
 VLDB JOURNAL
, 1995
"... Spatial data types or algebras for database systems should (1) be fully general, that is, closed under set operations, (2) have formally defined semantics, (3) be defined in terms of finite representations available in computers, (4) offer facilities to enforce geometric consistency of related spat ..."
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Cited by 42 (3 self)
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Spatial data types or algebras for database systems should (1) be fully general, that is, closed under set operations, (2) have formally defined semantics, (3) be defined in terms of finite representations available in computers, (4) offer facilities to enforce geometric consistency of related spatial objects, and (5) be independent of a particular DBMS data model, but cooperate with any. We present an algebra that uses realms as geometric domains underlying spatial data types. A realm, as a general database concept, is a finite, dynamic, userdefined structure underlying one or more system data types. Problems of numerical robustness and topological correctness are solved within and below the realm layer so that spatial algebras defined above a realm have very nice algebraic properties. Realms also interact with a DMBS to enforce geometric consistency on object creation or update. The ROSE algebra is defined on top of realms and offers general types to represent point, line, and region features, together with a comprehensive set of operations. It is described within a polymorphic type system and interacts with a DMBS data model and query language through an abstract object model interface. An example integration of ROSE into the objectoriented data model 02 and its query language is presented.
Plug and Play with Query Algebras: SECONDO  A Generic DBMS Development Environment
, 2000
"... We present SECONDO, a new generic environment supporting the implementation of database systems for a wide range of data models and query languages. On the one hand, this framework is more flexible than common extensible and objectrelational systems, offering the full extensibility of secondorder ..."
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Cited by 29 (13 self)
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We present SECONDO, a new generic environment supporting the implementation of database systems for a wide range of data models and query languages. On the one hand, this framework is more flexible than common extensible and objectrelational systems, offering the full extensibility of secondorder signature, the formal basis for data and query language definitions in SECONDO. On the other hand, it is much more complete and structured than database system toolkits. Extensibility is provided by the concept of algebra modules defining and implementing new types (type constructors, in fact) and operators. Support functions are used to register them with the system frame. After a review of secondorder signature essentials, this paper presents the system functionality, given by a uniform set of user commands valid for all data models, and the extensible system architecture. All common DBMS features are implemented in the system frame; only purely data model dependent functionality is coded in algebra modules, supported by a variety of tools. Furthermore, we describe the key strategies for extensible query processing in the SECONDO environment and explain the structure of algebra modules.
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 29 (19 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.
Realms: A Foundation for Spatial Data Types in Database Systems
 3RD INT. SYMP. ON ADVANCES IN SPATIAL DATABASES, LNCS 692
, 1993
"... Spatial data types or algebras for database systems should (i) be fully general (which means, closed under set operations, hence e.g. a region value can be a set of polygons with holes), (ii) have formally defined semantics, (iii) be defined in terms of finite representations available in computers, ..."
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Cited by 26 (10 self)
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Spatial data types or algebras for database systems should (i) be fully general (which means, closed under set operations, hence e.g. a region value can be a set of polygons with holes), (ii) have formally defined semantics, (iii) be defined in terms of finite representations available in computers, (iv) offer facilities to enforce geometric consistency of related spatial objects, and (v) be independent of a particular DBMS data model, but cooperate with any. We offer such a definition in two papers. The central idea, introduced in this (first) paper, is to use realms as geometric domains underlying spatial data types. A realm as a general database concept is a finite, dynamic, userdefined structure underlying one or more system data types. A geometric realm defined here is a planar graph over a finite resolution grid. Problems of numerical robustness and topological correctness are solved below and within the realm layer so that spatial algebras defined above a realm enjoy very nice algebraic properties. Realms also interact with a DBMS to enforce geometric consistency on object creation or update.
Modeling Spatial Objects with Undetermined Boundaries Using the Realm/ROSE Approach
 IN BURROUGH AND FRANK [2
, 1996
"... The purposes of this paper are twofold, namely first to present general criteria for the design of spatial data types that are necessary and valid for the modeling of spatial objects regardless whether we consider objects with sharp or undetermined boundaries, and second to show how the concepts of ..."
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Cited by 19 (12 self)
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The purposes of this paper are twofold, namely first to present general criteria for the design of spatial data types that are necessary and valid for the modeling of spatial objects regardless whether we consider objects with sharp or undetermined boundaries, and second to show how the concepts of a type system for spatial objects with sharp boundaries can be suitably transferred and extended to the modeling of spatial objects with undetermined boundaries. The most relevant design criteria of such a type system comprise generality, closure properties, rigorous definition, finite resolution, numerical robustness, topological correctness, geometric consistency, extensibility and data model independence of spatial data types. The Realm/ROSE approach allows for these design criteria and offers an appropriate definition of a type system for spatial objects with sharp boundaries. An extension of the Realm/ROSE model is proposed that shows how general region objects with undetermined bound...
Progress in Computational Methods for Representing Geographic Concepts
 INTERNATIONAL JOURNAL OF GEOGRAPHICAL INFORMATION SCIENCE
, 1999
"... Over the last ten years, a subfield of GIScience has been recognized that addresses the linkage between human thought regarding geographic space and the mechanisms of implementing these in computational models. This research area has developed an identity through a series of successful international ..."
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Cited by 14 (1 self)
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Over the last ten years, a subfield of GIScience has been recognized that addresses the linkage between human thought regarding geographic space and the mechanisms of implementing these in computational models. This research area has developed an identity through a series of successful international conferences and the establishment of a journal. It has also been complemented through community activities such as international standardization efforts and GIS interoperability. Historically, much of the advancement in computational methods has occurred ator close tothe implementation level, as exemplified by the attention on the development of spatial access methods. Significant progress has been made at the levels of spatial data models and spatial query languages, although we note the lack of a comprehensive theoretical framework comparable to the relational data model in databases management systems. The difficult problems that need future research efforts are at the highly abstract level of capturing semantics of geographic information. A cognitive motivation is most promising as it shapes the focus on the users' needs and points of view, rather than on efficiency as in the case of a bottomup system design. We also identify the need for new research in fields, models of qualitative spatial information, temporal aspects, knowledge discovery, and the integration of GIS with database management systems.
GraphDB: A Data Model and Query Language for Graphs in Databases
 Proc. 20th Int. Conf. on Very Large Data Bases
, 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 identi ..."
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Cited by 10 (0 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 hetereogeneous 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. It is possible to compute additions to the database graph as well as restrictions in a query. 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. The GraphDB model is meant to be implemented; system architecture and a representation and query processing strategy are outlined in the paper.
Building a ConstraintBased Spatial Database System: Model, Languages, and Implementation
 Information Systems
, 2003
"... This paper presents DEDALE, a spatial database system which provides an abstract and nonspecialized data model and query language for representating and manipulating geometric data in arbitrary dimension. ..."
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Cited by 7 (1 self)
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This paper presents DEDALE, a spatial database system which provides an abstract and nonspecialized data model and query language for representating and manipulating geometric data in arbitrary dimension.
Secondo/QP: Implementation of a Generic Query Processor
, 1997
"... : In an extensible database system, evaluation of a query plan is done in cooperation between a collection of operator implementation functions and a component of the DBMS that we call the query processor. Basically, the query processor constructs an operator tree for the query plan and then calls a ..."
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Cited by 4 (3 self)
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: In an extensible database system, evaluation of a query plan is done in cooperation between a collection of operator implementation functions and a component of the DBMS that we call the query processor. Basically, the query processor constructs an operator tree for the query plan and then calls an evaluator function which traverses the tree, calling the operator functions in each node. This seemingly simple strategy is complicated by the fact that operator functions must be able to call for the evaluation of parameter expressions (e.g. predicates), and must be able to process streams of objects in a pipelined manner. Although query processing along these lines is implemented in most database systems, and certainly in all extensible database systems, the details of programming the parameter passing, organizing the interaction between stream operators, etc. are tricky, and seem to be buried in the code of the respective systems. We are not aware of any simple, crisp, clear published ...