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What is the purpose of an ending tag?
The end tag functions exactly like a right parenthesis or a closing quotation mark or a right curly brace. It contains no data of its own; it simply ends the most recent (innermost) tag with the same name. XML requires a matching end tag for each start tag.
What is SGML tag?
The Standard Generalized Markup Language (SGML, defined in [ISO8879]), is a language for defining markup languages. The SGML declaration specifies which characters and delimiters may appear in the application. The document type definition (DTD). The DTD defines the syntax of markup constructs.
What are the differences between HTML and SGML?
HTML restricts SGML by defining a list of tags that are allowed to be used. XML restricts SGML by not allowing unclosed or empty start and end tags, and forces attributes to be explicit. XML also has a large number of additional restrictions that are not found in SGML.
What’s the difference between XML and HTML tags?
While very similar in many respects, it has a few key differences. First, XML always needs close tags, and has a special syntax for tags that don’t need a close tag. In HTML, some tags, such as img are always assumed to be empty and close themselves. Others, like p may close implicitly based on other content.
When to use an empty tag in XML?
See the W3C specs for XML and XHTML: An element with no content is said to be empty. The representation of an empty element is either a start-tag immediately followed by an end-tag, or an empty-element tag. Empty-element tags may be used for any element which has no content, whether or not it is declared using the keyword EMPTY.
Why is SGML used as a document markup language?
The syntax of SGML is closer to the COCOA format. As a document markup language, SGML was originally designed to enable the sharing of machine-readable large-project documents in government, law, and industry. Many such documents must remain readable for several decades—a long time in the information technology field.