在分布式数据库的垂直分片中,为保证全局数据的可重构和最小冗余,分片满足的必要条件是(53)。
Networks can be interconnected by different devices. In the physical layer, networks can be connected by(66)or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept(67), examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have(68)network layer, the router may be able to translate between the packet formats. In the transport layer we fmd transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message(69). As an example, gateways between Internet e-mail and X.400 e-mail must(70)the e-mail message and change various header fields.
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容量为64块的Cache采用组相联方式映像,字块大小为128个字,每4块为一组。若主存容量为4096块,且以字编址,那么主存地址应为(7)位,主存区号应为(8)位。
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关于事务的故障与恢复,下列描述正确的是(54)。
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The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable(71 )of the technical requirements for the software product.During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the sofrware must perform. and each(72)that it must meet. The starting point is usually a set of high-level requirements from the(73)that describe the project or problem.In either case, the requirements definition team formulates an overall concept for the system and then defines(74)showing how the system will be operated, publishes the system and operations concept document, and conducts a system concept review(SCR).Following the SCR, the team derives(75)requirements for the system from the high level requirements and the system and operations concept. Using structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirement.
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不能激活触发器执行的操作是(55)。
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某一非确定性有限自动机(NFA)的状态转换图如下图所示,与该NFA等价的正规式是(28),与该NFA等价的DFA是(29)。
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关于分布式数据库,下列说法错误的是______。
A)在分布式数据库系统中,分片透明性主要是指数据分片的分配位置对用户是透明的,用户无须关注每个分片被分配的场地
B)对于用户而言,一个分布式数据库系统从逻辑上看如同一个集中式数据库,用户可在任何一个场地执行全局应用和局部应用
C)分布式数据库的查询处理代价既包括CPU和I/O代价,也需要考虑场地间传输数据所需的通信代价
D)在分布式数据库查询中,导致场地间数据传输量大的主要原因是数据问的连接操作和并操作
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以下不属于防火墙的优点的是()。
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软件测试文档包括______。
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关于自动化测试,下面说法正确的是______。
A) 通常自动化测试会比手工测试发现更多的缺陷
B) 手工测试时,测试者可以运用其想象力和创造力对测试进行改进,但自动化测试工具不具备想象力,只能按原计划的测试方法指令进行
C) 运行相同的测试.自动化测试一定会比手工测试更加有效
D) 在自动化测试中,测试的艰巨任务是验证期望输出的正确性