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Now showing items 1 - 9 of 9

  • Atomic clustering operations for managing a partitioned cluster online

    A set of six atomic primitives are provided for a database management system that may be used in combination to provide all of the common features and functions of a clustered database, including data failover, auto-healing, and elastic scaling. These six atomic primitives include CREATE, DROP, DETACH, ATTACH, COPY, and PROMOTE. Of particular note, it is shown that by maintaining appropriate metadata, including the status of each instance of each partition in the cluster, the versatility and reliability of this set of primitives is sufficient to implement each of the aforementioned data failover, auto-healing, and elastic scaling functions with high efficiency using a minimal number of these primitives. Each primitive is atomic (such that the cluster clearly in one state or another) and online (a workload of reads and writes is uninterrupted while the primitive runs), and each primitive is scoped to a single partition of data, thereby enabling parallel processing.
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  • Durability implementation plan in an in-memory database system

    A database durability implementation records only committed transactions in a log file. A pair of log files and a pair of snapshot files are maintained. When a snapshot of the database is completed, the ‘current’ log becomes the ‘prior’ log and the other log becomes the ‘current’ log. After the next snapshot is completed, the prior log and prior snapshot may be deleted. Transactions that are not committed are not recorded in the current log, thereby avoiding the need to undo aborted transactions. If a given change is reflected in a completed snapshot, it does not appear in either of the logs; if the change is not yet reflected in a completed snapshot, it is guaranteed to be stored in one of the logs. During recovery, the system assesses both snapshots. The most recent of the completed snapshots is used, and the corresponding log(s) is (are) applied.
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  • Code generation for a family of executable modelling notations

    Adam Prout   Joanne M. Atlee   Nancy A. Day   Pourya Shaker  

    We are investigating semantically configurable model-driven engineering (MDE). The goal of this work is a modelling environment that supports flexible, configurable modelling notations, in which specifiers can configure the semantics of notations to suit their needs and yet still have access to the types of analysis tools and code generators normally associated with MDE. In this paper, we describe semantically configurable code generation for a family of behavioural modelling notations. The family includes variants of statecharts, process algebras, Petri Nets, and SDL88. The semantics of this family is defined using template semantics, which is a parameterized structured operational semantics in which parameters represent semantic variation points. A specific notation is derived by instantiating the family's template semantics with parameter values that specify semantic choices. We have developed a code-generator generator (CGG) that creates a suitable Java code generator for a subset of derivable modelling notations. Our prototype CGG supports 26 semantics parameters, 89 parameter values, and 7 composition operators. As a result, we are able to produce code generators for a sizable family of modelling notations, though at present the performance of our generated code is about an order of magnitude slower than that produced by commercial-grade generators.
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  • Reusing existing query plans in a database system

    A system and method for executing query plans preprocesses a user's queries to identify and extract select parameters of the query, creates a skeletal query with reference to the extracted parameters, creates and compiles an executable version of the skeletal query, then executes the compiled version of the skeletal query using the particular parameters in the current query. The compiled version of the parameterized skeletal query is stored, and when another query is submitted that matches the skeletal query (but with potentially different parameters), the previously compiled skeleton query is executed with the parameters of this latter query.
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  • Deriving document similarity indices

    Methods, systems, and computer program products are provided for deriving and updating document similarity indices for a plurality of documents. The number of maintained similarities can be controlled to conserve CPU and storage resources.
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  • From protyle to proton. William Prout and the nature of matter 1785–1985: By W. H. Brock. Pp. 252. Adam Hilger, Bristol. 1985. £25.00 ($45.00)

    W.A. Smeaton  

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  • W. H. Brock. From Protyle to Proton. William Prout and the Nature of Matter, 1785–1985. Bristol and Boston: Adam Hilger, Ltd., 1985. Pp. xii + 252. ISBN 0-85274-801-9. £25.00, $45.00.

    Nye   Mary Jo  

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  • Semantically Configurable Code Generation

    Adam Prout   Joanne M. Atlee   Nancy A. Day   Pourya Shaker  

    In model-driven engineering (MDE); software development is centred around a formal description (model) of the proposed software system; and other software artifacts are derived directly from the model. We are investigating semantically configurable MDE; in which specifiers are able to configure the semantics of their models. The goal of this work is to provide a modelling environment that offers flexible; configurable modelling notations; so that specifiers are better able to represent their ideas; and yet still provides the types of analysis tools and code generators normally associated with model-driven engineering. In this paper; we present a semantically configurable code-generator generator; which creates a Java-code generator for a modelling notation given the notation’s semantics expressed as a set of parameter values. We are able to simulate multiple different model-based code generators; though at present the performance of our generated code is about an order of magnitude slower than that produced by commercial-grade generators.
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  • Code generation for a family of executable modelling notations

    Adam Prout   Joanne M. Atlee   Nancy A. Day   Pourya Shaker  

    We are investigating semantically configurable model-driven engineering (MDE). The goal of this work is a modelling environment that supports flexible, configurable modelling notations, in which specifiers can configure the semantics of notations to suit their needs and yet still have access to the types of analysis tools and code generators normally associated with MDE. In this paper, we describe semantically configurable code generation for a family of behavioural modelling notations. The family includes variants of statecharts, process algebras, Petri Nets, and SDL88. The semantics of this family is defined using template semantics, which is a parameterized structured operational semantics in which parameters represent semantic variation points. A specific notation is derived by instantiating the family’s template semantics with parameter values that specify semantic choices. We have developed a code-generator generator (CGG) that creates a suitable Java code generator for a subset of derivable modelling notations. Our prototype CGG supports 26 semantics parameters, 89 parameter values, and 7 composition operators. As a result, we are able to produce code generators for a sizable family of modelling notations, though at present the performance of our generated code is about an order of magnitude slower than that produced by commercial-grade generators.
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