Overell Demon Internet Ltd. Please refer to the current edition of the "Internet Official Protocol Standards" STD 1 for the standardization state and status of this protocol.
Distribution of this memo is unlimited. All Rights Reserved. It balances compactness and simplicity, with reasonable representational power. The current document separates out that definition, to permit selective reference. Predictably, it also provides some modifications and enhancements. Appendix A Core supplies rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. It is provided as a convenience and is otherwise separate from the meta language defined in the body of this document, and separate from its formal status.
However, angle brackets may be used around a rule name whenever their presence will facilitate discerning the use of a rule name. This is typically restricted to rule name references in free-form prose, or to distinguish partial rules that combine into a string not separated by white space, such as shown in the discussion about repetition, below. The equal sign separates the name from the definition of the rule. For visual ease, rule definitions are left aligned.
When a rule requires multiple lines, the continuation lines are indented. The left alignment and indentation are relative to the first lines of the ABNF rules and need not match the left margin of the document. Correction to feature set matching reduction rules Security Considerations Author's Address Full Copyright Statement Introduction In RFC , "A Syntax for Describing Media Feature Sets" [ 1 ], an expression format is presented for describing media feature capabilities using simple media feature tags.
This provides a format for message handling agents to describe the media feature content of messages that they can handle. That memo also describes an algorithm for finding the common capabilities expressed by two different feature expressions. This memo contains two corrections to that specification: one fixes an error in the formal syntax specification, and the other fixes an error in the feature set matching algorithm, in the rules for reducing feature comparison predicates.
The first of these corrections affects the normative content of RFC ; the second affects non-normative content. NOTE: Comments like this provide additional nonessential information about the rationale behind this document.
Rule Naming Rule Form Terminal Values External Encodings Concatenation: Rule1 Rule Sequence Group: Rule1 Rule Specific Repetition: nRule Comment: ; Comment Operator Precedence Normative References Informative References Core Rules Common Encoding The current document separates those definitions to permit selective reference. Predictably, it also provides some modifications and enhancements. Appendix B supplies rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications.
Rule Naming The name of a rule is simply the name itself; that is, a sequence of characters, beginning with an alphabetic character, and followed by a combination of alphabetics, digits, and hyphens dashes. However, angle brackets may be used around a rule name whenever their presence facilitates in discerning the use of a rule name.
This is typically restricted to rule name references in free-form prose, or to distinguish partial rules that combine into a string not separated by white space, such as shown in the discussion about repetition, below. The equal sign separates the name from the definition of the rule.
When a rule requires multiple lines, the continuation lines are indented. The left alignment and indentation are relative to the first lines of the ABNF rules and need not match the left margin of the document.
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