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四、字符格式 1、逻辑型标记和物理型标记 在HTML中,有两种类型的标记:逻辑型标记和物理型标记。所谓物理型标记,它明确指定该成分以哪一种样式展示,例如字体标记〈I〉就特指用斜体显示。而逻辑型标记则是按照逻辑上的含义来说明,并不是硬性的规定。如标记〈EM〉表示突出显示,但它并没有指明怎样的突出法,而让浏览器自行处理决定,或许大多数浏览器也会处理成斜体显示。 那么既然物理型标记和逻辑型标记会产生同样的屏幕显示效果,为什么还要区分成这两种标记呢?在纯粹的SGML中,内含和表示是分离的。例如SGML为生成一个一级标题,就把它标记为一个一级标题,而并不指明这个一级标题应当是什么什么样子的,具体的显示样式留待浏览器自己去决定完成。这种逻辑标记方法的好处在于,一旦你想改变一级标题的显示样式时,只要改变浏览器中对于这个
Fourth, the character format 1, the logical type tag and physical tag In HTML, there are two types of tag: logical tag and physical tag. The so-called physical type mark, which explicitly specify the composition in which style, for example, the font mark is specifically indicated in italics. Logical markup is based on the logical meaning, not a hard rule. The tag, for example, is highlighted, but it does not specify what salient method it is, leaving the browser to handle the decision itself, and most browsers may also handle italics. So, since physical and logical tags will produce the same screen display, why distinguish between these two tags? In pure SGML, the inclusion and presentation are separate. For example, SGML generates a first-level title and marks it as a first-level title without indicating what the first-level title should look like. The specific display style is left to the browser to decide on its own. The advantage of this logic tagging method is that once you want to change the display style of a title, just change the browser for this