In an ideal world a system incorporating both redundancy and diverse design would provide good protection against both random component failure and some forms of design faults. It would not, however, provide protection against mistakes within the specification, as even diverse systems will generally be attempts to implement the same specification.

Research had shown that getting different teams to design a module does not remove the likelihood of similar faults in the implementations. The results showed that although the programs were each extremely reliable, they showed many common faults. Despite this finding, it is generally accepted that diverse design had great value in reducing common-mode failures, although it cannot guarantee freedom from such problems. Diverse design has also been shown to be of benefit in locating ambiguities within the specification, as different teams usually adopt diverse interpretations.

6.2 Types of faults

Nature

random faults:

The primary cause of random faults is hardware component failure. Statistical analysis may make it possible to estimate the likelihood of it failing within a given period of time.

systematic faults (design faults):

mistakes in the specification of the system; mistakes in the software; and mistakes in the  hardware design

   Duration

   permanent faults:

       This kind of faults remain in existence indefinitely, or untill some corrective action is taken, are termed permanent faults. Design faults, including software faults, are always permanent, as are many hardware components.

   transient faults

   This kind of faults can appear and then disappear after a short time.

   intermittent faults

   These faults, appear, disappear and then reappear at some later time.

Extent

   localized fault

      It may affect only a single hardware or software module

   global fault

       It has effects which permeate throughout the system

The Model-View-Controller (MVC) pattern separates the modeling of the domain, the presentation, and the actions based on user input into three separate classes [Burbeck92]:

Figure 1: MVC class structure 

Figure 2: Behavior of the passive model

Figure 3: Using Observer to decouple the model from the view in the active model

Figure 4: Behavior of the active model

新增環境變數:

variable name:  CATALINA_HOME

variable value: C:\apache-tomcat-6.0.18

命令提示字元視窗

(1) Start Up Tomcat

 C:\Documents and Settings\user>
 C:\Documents and Settings\user> C:\apache-tomcat-6.0.18\bin\startup.bat

(2) After startup, the default web applications included with Tomcat will be
    available by visiting:

       http://localhost:8080/

(3) Shut Down Tomcat
 C:\Documents and Settings\user>
 C:\Documents and Settings\user> C:\apache-tomcat-6.0.18\bin\shutdown.bat

詳細文件請看:C:\apache-tomcat-6.0.18\RUNNING.txt

My computer右鍵->Properties->Advanced->Environment Variables

JRE 是 JDK 的子集

皆為Java開發工作環境tool kits

once in a while = sometimes
Most teachers expect to correct their students’ spelling mistakes once in a while.

criminology = 刑事學
Buckinghamshire = 白金漢郡(英格蘭南部)
perpetrator = 犯罪者,加害者,行兇者
better off = 景況教佳
do away with = 廢掉,去掉
The senior lecturer in criminology at Bucks New University in Buckinghamshire, England, sees so many misspellings in papers submitted by first-year students that he says we’d be better off letting the perpetrators off the hook and doing away with certain spelling rules altogether.

zero in on = 向…集中注意力,對準
cull = 選拔,揀出
Smith zeroes in on 10 candidates for variant spellings, culled from his students’ most commonly misspelled (or mispelled, as Smith suggests) words.

nerd = 討厭的人
stake = 棍子
proposal = 提案
Word nerds aren’t the only ones with a stake in the proposal.

advocate = 提倡
An international organization that has advocated simplified spellings since 1908.

illustrious = 有名的
malcontent = 不滿現狀的人,反抗者
Smith and Bovill are part of a long and illustrious line of spelling malcontents.

lexicography = 辭典編撰
lobby for = 從事幕後活動
traumatic = 外傷的
traumatic childhood spelling experiences
小時後拼字拼不對被挨打的經驗
Benjamin Franklin, Andrew Carnegie, Teddy Roosevelt and even Noah Webster, father of American lexicography, all lobbied for spelling reform, their reasons ranging from traumatic childhood spelling experiences to the hope that easier communication would promote peace.

institute = 制定
These countries have all instituted such reforms.

amend = 修定
Portugal in May amended its spelling to follow the simpler Brazilian rules.

aptly = 適切地,巧妙地
Since 1755, when the English language was standardized in Samuel Johnson’s aptly named Dictionary of the English Language, many variant spellings have become widely accepted on both sides of the pond.

purist = 純粹主義者
language purists

on the table = 公開的,擺在桌面上的
crowd = 一幫,一伙
Joe Pickett, executive editor of the American Heritage Dictionary, says that changes to dictionary entries are always on the table, but he and his seven fellow editors are a tough crowd.

rigorous = 嚴厲的
scrutiny = 細查
panel = (有代表性的)一組調查對象
orthographic = 拼字正確的
whizz (whiz) = 專家,絕頂聰明的人
Any word that seems to be a good candidate for an update undergoes rigorous scrutiny as the editors seek input from a panel of some 200 orthographic and lexicographic whizzes.

rote = 機械性的背誦,反覆
“In the 21st century, why learn by heart rote spelling when you can just type it into a computer and spell-check?” he asks.

• An array initializer can appear only in an array declaration.

        CORRECT!!

          int[ ] vec = {0,2,4,6}

        WRONG!!

          int[ ] vec;

          vec = {0,2,4,6};

• An array initializer can be an element of an array initializer. For example, the following:

          int[ ][ ] matrix = { {0 , 0 , 0 , 0} , {1 , 2 , 3} } ;

matrix = new int [3][4];

String s1 = new String(“abc”);

String s2 = new String(“abc”);

s1==s2 returns false, while s1.equals(s2) returns true.

The variables s1 and s2 contain different reference values, denoting different objects. But as String, these objects are considered equal.