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81.
本文以某校校园网Web日志挖掘为例,首先阐述如何进行Web挖掘,其次运用该理论分析该校Web日志得到用户上网行为习惯,并给出合理化建议,最后引出进一步探索的方向,为以后工作奠定基础。本文采用的挖掘方法具有通用性和实用性,对于类似时序序列趋势分析都可参考本文。 相似文献
82.
83.
数据库推理问题是数据库安全研究的重要组成部分,主要研究推理通道的检测方法和控制策略。该文提出一种动态控制推理通道的方法。该方法为每个推理通道建立一个标识集合,利用集合中元素和推理通道中对象的关联来控制查询的处理,使用户能灵活地访问数据但又得不到足够的信息来推理。与以前提出的方案不同,该方案保证了数据的最大可用性,同时有效地阻止推理并保持了快速的查询处理能力。 相似文献
84.
为智能仪表提供一种“十进制浮点数”,其特点是值域宽、值准确,它能代替整、长整型、三字节浮点数、四字节浮点数、BCD码数。用它通信可简化和统一仪表的通信协议,为制定仪表通用通信协议标准创造条件。 相似文献
85.
主要介绍了光三角式距离传感器测距系统的结构组成和原理 ,分析了参数之间的转换关系 ,论述了以单片机为核心构成检测电路的原理和性能 ,以及单片机的软件功能。最后给出检测系统的主要技术指标。 相似文献
86.
The MultiDimER model is a conceptual model used for representing a multidimensional view of data for Data Warehouse (DW) and
On-Line Analytical Processing (OLAP) applications. This model includes a spatial extension allowing spatiality in levels,
hierarchies, fact relationships, and measures. In this way decision-making users can represent in an abstract manner their
analysis needs without considering complex implementation issues and spatial OLAP tools developers can have a common vision
for representing spatial data in a multidimensional model. In this paper we propose the transformation of a conceptual schema
based on the MultiDimER constructs to an object-relational schema. We based our mapping on the SQL:2003 and SQL/MM standards
giving examples of commercial implementation using Oracle 10g with its spatial extension. Further we use spatial integrity
constraints to ensure the semantic equivalence of the conceptual and logical schemas. We also show some examples of Oracle
spatial functions, including aggregation functions required for the manipulation of spatial data. The described mappings to
the object-relational model along with the examples using a commercial system show the feasibility of implementing spatial
DWs in current commercial DBMSs. Further, using integrated architectures, where spatial and thematic data is defined within
the same DBMS, facilitates the system management simplifying data definition and manipulation.
相似文献
Esteban ZimányiEmail: |
87.
{In a seminal paper of 1989, Fredman and Saks proved lower bounds for some important data-structure problems in the cell
probe model. In particular, lower bounds were established on worst-case and amortized operation cost for the union-find problem and the prefix sum problem. The goal of this paper is to turn their proof technique into a general tool that can be applied to different problems
and computational models. To this end we define two quantities: Output Variability depends only on the model of computation. It indicates how much variation can be found in the results of a program with
certain resource bounds. This measures in some sense the power of a model. Problem Variability characterizes in a similar sense the difficulty of the problem.
}
Our Main Theorem shows that by comparing a model's output variability to a problem's problem variability, lower bounds on
the complexity of solving the problem on the given model may be inferred. The theorem thus shows how to separate the analysis
of the model of computation from that of the problem when proving lower bounds.
We show how the results of Fredman and Saks fit our framework by computing the output variability of the cell probe model
and the problem variability for problems considered in their paper. This allows us to reprove their lower bound results, and
slightly extend them. The main purpose of this paper though is to present the generalized technique.
Received January 25, 1999; revised July 30, 1999. 相似文献
88.
本文从互连网发展的趋势入手,对路径模式发掘进行了研究。先简要介绍数据库发掘的概况及网上数据发掘的特点,后结合关联法和组合概率法,并以算法和实例详细对之进行分析。 相似文献
89.
James W. Hooper 《International journal of parallel programming》1985,14(2):83-105
Rapid prototyping of software and hardware is recognized as a very important step in timely, cost-effective system development. The complexity inherent in designing distributed computing systems and distributed problem solutions emphasizes the need for effective rapid prototyping tools. ADL/ADS is a testbed user interface tool for experimentation with critical research and design issues pertaining to distributed data processing (DDP). The experimenter expresses a candidate distributed system in terms of experiment objects, along with attributes and relationships. The experiment objects represent hardware, software, and behavior. This paper provides a brief overview of ADL/ADS, and gives especial emphasis to the Behavior Prototyping Language (BPL) within ADL/ADS. BPL is designed for expressing Behavior Modules (B_MODULEs)—the most versatile of the behavior objects. BPL incorporates set-theoretical approaches, and provides syntax designed for effectively describing manipulations of experiment objects, and their attributes and relationships. 相似文献
90.