ABSTRACT With the advent of handheld computers and embedded computing devices, a unique opportuni... more ABSTRACT With the advent of handheld computers and embedded computing devices, a unique opportunity is emerging that will allow people to easily access and modify digital information in relation to a physical object at hand. In particular, the combination,of a handheld device and a sensor ,is beginning ,to demonstrate ,its usefulness as a ,mobile information appliance through which users can
Redundant data for fast retrieval increase costs of updates in distributed multidatabase systems.... more Redundant data for fast retrieval increase costs of updates in distributed multidatabase systems. In this paper, costs of updates are reduced by introducing further redundancies. Duplicate values-redundant data that are obtained from relationships of original values-must be updated to preserve their currency when original values are updated. To update duplicate values, relationships of original data are retrieved in order to determine which duplicate values must be updated. If a file with duplicate values satisfies the super-key condition introduced in this paper, one can perform the retrieval required for updates faster. Redundant data is added to a database site to satisfy the condition
Distributed multiuser hypermedia environments provide not only information sharing mechanisms but... more Distributed multiuser hypermedia environments provide not only information sharing mechanisms but also user col- laboration/ communication facilities. The provision of in - tegrated views of heterogeneous information resources is necessary to create common understanding among the users who are possibly distributed in terms of geography and time. However, requirements of customization must also be con- sidered since such diverse users
We describe data structures that allow efficient updates of materialized classes derived from rel... more We describe data structures that allow efficient updates of materialized classes derived from relationship of classes in object bases. Materialization of derived classes reduces costs of retrievals and increases costs of updates. Costs of updates increase remarkably when several paths of objects derive the same object. If object bases satisfy the superkey condition proposed in this paper, consistencies of object bases are maintained by local navigations and the remarkable increase of the costs is avoided. Any object base can be transformed to satisfy the superkey condition by adding extra classes and their objects. In this manner, increasing redundancies allows efficient updates.
The paper describes a concept and facilities of the VIEW Classroom, a distance education system s... more The paper describes a concept and facilities of the VIEW Classroom, a distance education system supporting interactions between a teacher and students. In a classroom a basic interaction between them is performed by questions and answers. In distributed education systems such an one-to-many interaction frequently implies difficulties in selecting by a teacher essential questions, and causes overload of a teacher and delays in the answering. The VIEW Classroom System provides a facility for the teacher to specify key phrases associated with locations of the teaching material. These phrases can be referred by students in their questions. A teacher can select essential students1 problems from a list of questions ordered either by the predefined priority or by the frequency of questions. To avoid delays in answering questions the system provides a question support facility which makes possible to answer some questions automatically, by reusing previous answers to similar questions. The VIEW Classroom System provides a question accumulation mechanism and a graphical user interface.
Materialized views are important in databases, particularly in data warehouses, where they are us... more Materialized views are important in databases, particularly in data warehouses, where they are used to speed up query processing on large amounts of data. These views need to be maintained incrementally in response to database updates. In this paper we investigate the problem of incremental maintenance of a materialized view in response to changes to the base data. We show that a materialized view can be maintained without accessing the view itself by materializing additional relations. We firstly give an algorithm for determining what additional relations need to be materialize in order to maintain a view incrementally. We then propose an algorithm for updating the materialized view (and the additional relations) based on the optimized operator tree used for evaluating the view as a query. A materialized view is updated by propagating updates to the nodes of its operator tree in a bottom-up fashion, where each node contains a relational algebraic operator and computes an intermediate expression. Our algorithm derives the exact update at every intermediate node in the tree, including the materialized view. Finally, we compare our incremental algorithm with the naive algorithm that recomputes the view from scratch.
ABSTRACT With the advent of handheld computers and embedded computing devices, a unique opportuni... more ABSTRACT With the advent of handheld computers and embedded computing devices, a unique opportunity is emerging that will allow people to easily access and modify digital information in relation to a physical object at hand. In particular, the combination,of a handheld device and a sensor ,is beginning ,to demonstrate ,its usefulness as a ,mobile information appliance through which users can
Redundant data for fast retrieval increase costs of updates in distributed multidatabase systems.... more Redundant data for fast retrieval increase costs of updates in distributed multidatabase systems. In this paper, costs of updates are reduced by introducing further redundancies. Duplicate values-redundant data that are obtained from relationships of original values-must be updated to preserve their currency when original values are updated. To update duplicate values, relationships of original data are retrieved in order to determine which duplicate values must be updated. If a file with duplicate values satisfies the super-key condition introduced in this paper, one can perform the retrieval required for updates faster. Redundant data is added to a database site to satisfy the condition
Distributed multiuser hypermedia environments provide not only information sharing mechanisms but... more Distributed multiuser hypermedia environments provide not only information sharing mechanisms but also user col- laboration/ communication facilities. The provision of in - tegrated views of heterogeneous information resources is necessary to create common understanding among the users who are possibly distributed in terms of geography and time. However, requirements of customization must also be con- sidered since such diverse users
We describe data structures that allow efficient updates of materialized classes derived from rel... more We describe data structures that allow efficient updates of materialized classes derived from relationship of classes in object bases. Materialization of derived classes reduces costs of retrievals and increases costs of updates. Costs of updates increase remarkably when several paths of objects derive the same object. If object bases satisfy the superkey condition proposed in this paper, consistencies of object bases are maintained by local navigations and the remarkable increase of the costs is avoided. Any object base can be transformed to satisfy the superkey condition by adding extra classes and their objects. In this manner, increasing redundancies allows efficient updates.
The paper describes a concept and facilities of the VIEW Classroom, a distance education system s... more The paper describes a concept and facilities of the VIEW Classroom, a distance education system supporting interactions between a teacher and students. In a classroom a basic interaction between them is performed by questions and answers. In distributed education systems such an one-to-many interaction frequently implies difficulties in selecting by a teacher essential questions, and causes overload of a teacher and delays in the answering. The VIEW Classroom System provides a facility for the teacher to specify key phrases associated with locations of the teaching material. These phrases can be referred by students in their questions. A teacher can select essential students1 problems from a list of questions ordered either by the predefined priority or by the frequency of questions. To avoid delays in answering questions the system provides a question support facility which makes possible to answer some questions automatically, by reusing previous answers to similar questions. The VIEW Classroom System provides a question accumulation mechanism and a graphical user interface.
Materialized views are important in databases, particularly in data warehouses, where they are us... more Materialized views are important in databases, particularly in data warehouses, where they are used to speed up query processing on large amounts of data. These views need to be maintained incrementally in response to database updates. In this paper we investigate the problem of incremental maintenance of a materialized view in response to changes to the base data. We show that a materialized view can be maintained without accessing the view itself by materializing additional relations. We firstly give an algorithm for determining what additional relations need to be materialize in order to maintain a view incrementally. We then propose an algorithm for updating the materialized view (and the additional relations) based on the optimized operator tree used for evaluating the view as a query. A materialized view is updated by propagating updates to the nodes of its operator tree in a bottom-up fashion, where each node contains a relational algebraic operator and computes an intermediate expression. Our algorithm derives the exact update at every intermediate node in the tree, including the materialized view. Finally, we compare our incremental algorithm with the naive algorithm that recomputes the view from scratch.
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Papers by Shin'ichi Konomi