eXtensible HyperText Markup Language (XHTML), is a markup language, expression and Hypertext Markup Language (HTML) is similar, but more rigorous syntax. Speaking from the inheritance, HTML is a standards-based Universal Markup Language (SGML) application, is a very flexible markup language, XHTML is based on Extensible Markup Language (XML), XML is an SGML subset. XHTML 1.0 in January 26, 2000 as a W3C Recommendation. XHTML form background XHTML is The Extensible HyperText Markup Language (extensible hypertext markup language) acronym. HTML is a basic WEB page design language, XHTML is an XML-based markup language, it seems some resemblance to HTML, only a few small but important difference, XHTML is playing a role similar to HTML, XML, So, in essence, XHTML is a transitional technology, combined with some of the power of XML and most of the simple nature of HTML. The end of 2000, the International Organization W3C (World Wide Web Consortium) announced the organization released version of XHTML 1.0. XHTML 1.0 HTML 4.0 is a basis in the optimization and improvement of the new language, aimed at XML-based applications. XHTML is an enhancement of the HTML, XHTML is more strict version of HTML is more pure. Its scalability and flexibility to accommodate future network applications will be more demand. Although the ability of powerful XML data conversion, can replace HTML, but the face of thousands of existing HTML-based language designed website, direct use of XML is premature. Thus, in HTML4.0, based on the use of XML to extend its rule, has been XHTML. Therefore, the purpose of establishing XHTML HTML to XML is to achieve the transition. Current international respected in the WEB site design is based on the XHTML standard applications (known as CSS + DIV). Outline XHTML is the successor to the current HTML version. HTML code requirements are relatively loose, so that web authors, the more convenient, but for the machine, the syntax of the language more loosely, to deal with them more difficult for traditional computers, there are still loose the ability compatible syntax, but For many other devices, such as mobile phones, the difficulty is greater. The resulting DTD defined by the rules, syntax requires more stringent XHTML. Most popular browsers can correctly parse XHTML, even if a little old browsers, XHTML as a subset of HTML, and many can be resolved. In other words, almost all Web browsers parse the HTML in the right, while compatible with XHTML. Of course, the complete transfer from HTML to XHTML, but also requires a process. With CSS (Cascading Style Sheets, Cascading Style Sheets) combined, XHTML can play a real power; This allows to achieve the separation of style with the same content, but also an organic combination of web page code, in another separate file, you can also mixed variety of XML applications, such as MathML, SVG. The transition from HTML to XHTML relatively small changes, mainly to meet the XML. The biggest change is that the document must be well-formed, all tags must be closed, that is the start tag must have a corresponding closing tag. In addition, XHTML, all tags must be lowercase. HTML 2.0 has been in accordance with tradition, many people are the label capitalized, this significant difference between the two. In XHTML, all the parameters, including numbers, must be enclosed in double quotes (in SGML and HTML, the quotes are not necessary, when the content is only numbers, letters and other special characters allowed, you can without the quotes). All elements, including empty elements, such as img, br, etc., must also be closed to achieve the way in the start tag by adding a slash at the end, such as <code> <nowiki> <img… /> </ nowiki> </ code> , <code> <nowiki> </ nowiki> </ code>. Omitted parameters, such as <code> <nowiki> <option selected> </ nowiki> </ code>, does not allow, must <code> <nowiki> <option selected="selected"/> </ nowiki> </ code>. Detailed differences between the two, by [http://www.w3.org/TR/xhtml1/ # diffs W3C XHTML instructions] to get access.
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