| slovo | definícia |
abstract syntax
(foldoc) | abstract syntax
A form of representation of data that is
independent of machine-oriented structures and encodings and
also of the physical representation of the data. Abstract
syntax is used to give a high-level description of programs
being compiled or messages passing over a communications link.
A compiler's internal representation of a program will
typically be an abstract syntax tree. The abstract syntax
specifies the tree's structure is specified in terms of
categories such as "statement", "expression" and
"identifier". This is independent of the source syntax
(concrete syntax) of the language being compiled (though it
will often be very similar).
A parse tree is similar to an abstract syntax tree but it
will typically also contain features such as parentheses which
are syntactically significant but which are implicit in the
structure of the abstract syntax tree.
(1998-05-26)
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abstract syntax notation 1
(foldoc) | Abstract Syntax Notation 1
ASN.1
X.208
(ASN.1, X.208, X.680) An
ISO/ITU-T standard for transmitting structured data on
networks, originally defined in 1984 as part of {CCITT
X.409} '84. ASN.1 moved to its own standard, X.208, in 1988
due to wide applicability. The substantially revised 1995
version is covered by the X.680 series.
ASN.1 defines the abstract syntax of information but does
not restrict the way the information is encoded. Various
ASN.1 encoding rules provide the transfer syntax (a
concrete representation) of the data values whose {abstract
syntax} is described in ASN.1. The standard ASN.1 encoding
rules include BER (Basic Encoding Rules - X.209), CER
(Canonical Encoding Rules), DER (Distinguished Encoding
Rules) and PER (Packed Encoding Rules).
ASN.1 together with specific ASN.1 encoding rules facilitates
the exchange of structured data especially between
application programs over networks by describing data
structures in a way that is independent of machine
architecture and implementation language.
OSI Application layer protocols such as X.400 MHS
electronic mail, X.500 directory services and SNMP use
ASN.1 to describe the PDUs they exchange.
Documents describing the ASN.1 notations: ITU-T Rec. X.680,
ISO 8824-1; ITU-T Rec. X.681, ISO 8824-2; ITU-T
Rec. X.682, ISO 8824-3; ITU-T Rec. X.683, ISO 8824-4
Documents describing the ASN.1 encoding rules: ITU-T
Rec. X.690, ISO 8825-1; ITU-T Rec. X.691, ISO 8825-2.
[M. Sample et al, "Implementing Efficient Encoders and
Decoders for Network Data Representations", IEEE Infocom 93
Proc, v.3, pp. 1143-1153, Mar 1993. Available from Logica,
UK].
See also snacc.
(2005-07-03)
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abstract syntax tree
(foldoc) | abstract syntax tree
(AST) A data structure representing something which
has been parsed, often used as a compiler or
interpreter's internal representation of a program while it
is being optimised and from which code generation is
performed. The range of all possible such structures is
described by the abstract syntax.
(1994-11-08)
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