XML is similar to SGML, that can also use the DTD mechanism to specify the supported elements and their permitted combinations as document structure. XML was developed as a simpler alternative. The HTML document fragment: Para 1 Para 2 Para 3can thus be inferred to be equivalent to: Para 1 Para 2 Para 3(If one paragraph element cannot contain another, any currently open paragraph must be closed before starting another.)Because of this implied behavior, based on the combination of the DTD and the individual document, it is not possible to infer elements from the document tags alone, but only by also using an SGML or HTML aware parser, with knowledge of the DTD. Also the DTD states that paragraph elements cannot be nested. As a simple example, the start tag indicating the start of a paragraph element should be closed by a end tag, indicating the end of the element. It is part of general SGML behavior that where only one valid structure is possible (per the DTD), it is not generally a requirement that the document explicitly states that structure. As is generally understood, the position of an element is indicated as spanning from a start tag, possibly including some child content, and is terminated by an end tag. The elements are only generated after the parsing step, from these tags. HTML documents contain tags, but do not contain the elements. Only in the rarest cases would the parser abandon parsing altogether. A valid model was produced, no matter how bad the. The resultant model was often not correct (i. The parsing process was also required to. For example, the title node represents the title of the document.Ĭoncepts. Many HTML nodes represent semantics, or meaning. Nodes can also have content, including other nodes and text. Each node can have HTML attributes specified. HTML is composed of a tree of HTML nodes, such as text nodes. An HTML element is an individual component of an HTML document or web page, once this has been parsed into the Document Object Model.
0 kommentar(er)
