Structure editor - AbsoluteAstronomy.com

A structure editor, also structured editor or projectional editor, is any document editor that is cognizant of the document’s underlying structure

Structure

Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...

. Structure editors can be used to edit hierarchical or marked up

Markup language

A markup language is a modern system for annotating a text in a way that is syntactically distinguishable from that text. The idea and terminology evolved from the "marking up" of manuscripts, i.e. the revision instructions by editors, traditionally written with a blue pencil on authors' manuscripts...

text, computer programs, diagrams, chemical formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

s, and any other type of content with clear and well-defined structure. In contrast, a text editor

Text editor

A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....

is any document editor used for editing plain text files.

Typically, the benefits of text and structure editing are combined in the user interface

User interface

The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...

of a single hybrid tool. For example, Emacs

Emacs

Emacs is a class of text editors, usually characterized by their extensibility. GNU Emacs has over 1,000 commands. It also allows the user to combine these commands into macros to automate work.Development began in the mid-1970s and continues actively...

is fundamentally a text editor, but supports the manipulation of words, sentences, and paragraphs as structures that are inferred from the text. Conversely, Dreamweaver is fundamentally a structure editor for marked up web documents, but supports the display and manipulation of raw HTML

HTML

HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

text as well. Similarly, molecule editor

Molecule editor

A molecule editor is a computer program for creating and modifying representations of chemical structures.Molecule editors can manipulate chemical structure representations in either two- or three-dimensions. Two-Dimensional editors generate output used as illustrations or for querying chemical...

s typically support both graphical and textual input. Structure editing predominates when content is graphical

Graphics

Graphics are visual presentations on some surface, such as a wall, canvas, computer screen, paper, or stone to brand, inform, illustrate, or entertain. Examples are photographs, drawings, Line Art, graphs, diagrams, typography, numbers, symbols, geometric designs, maps, engineering drawings,or...

and textual representations are awkward, e.g., CAD systems and PowerPoint. Text editing predominates when content is largely devoid of structure, e.g., text fields in web forms. WYSIWYG

WYSIWYG

WYSIWYG is an acronym for What You See Is What You Get. The term is used in computing to describe a system in which content displayed onscreen during editing appears in a form closely corresponding to its appearance when printed or displayed as a finished product...

word processing systems such as Word

Microsoft Word

Microsoft Word is a word processor designed by Microsoft. It was first released in 1983 under the name Multi-Tool Word for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS , the Apple Macintosh , the AT&T Unix PC , Atari ST , SCO UNIX,...

, which appear to edit formatted text directly, are essentially structure editors for the underlying marked-up text.

In linguistics

Linguistics

Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

, syntax

Syntax

In linguistics, syntax is the study of the principles and rules for constructing phrases and sentences in natural languages....

is the study of the structure of grammatical utterances, and accordingly syntax-directed editor is a synonym for structure editor. Language-based editor and language-sensitive editor are also synonyms. A language-based editor’s features may be implemented by ad hoc code or by a formal grammar

Formal grammar

A formal grammar is a set of formation rules for strings in a formal language. The rules describe how to form strings from the language's alphabet that are valid according to the language's syntax...

. For example, language sensitivity in Emacs is implemented in the Lisp definition of the edit mode for the given language. In contrast, language sensitivity in an XML editor

XML editor

An XML editor is a markup language editor with added functionality to facilitate the editing of XML. This can be done using a plain text editor, with all the code visible, but XML editors have added facilities like tag completion and menus and buttons for tasks that are common in XML editing, based...

is driven by a formal DTD

Document Type Definition

Document Type Definition is a set of markup declarations that define a document type for SGML-family markup languages...

schema for the given language.

Structure editing has often been employed in source code editor

Source code editor

A source code editor is a text editor program designed specifically for editing source code of computer programs by programmers. It may be a standalone application or it may be built into an integrated development environment ....

s. Each programming language

Programming language

A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....

typically has a well-defined syntax given by a context-free grammar

Context-free grammar

In formal language theory, a context-free grammar is a formal grammar in which every production rule is of the formwhere V is a single nonterminal symbol, and w is a string of terminals and/or nonterminals ....

, and accordingly the meaningful structural elements in source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

written in the language correspond to the grammatical phrases in the text. Early syntax-directed source code editors included Interlisp-D (for Lisp’s limited syntax) and Emily (for PL/I

PL/I

PL/I is a procedural, imperative computer programming language designed for scientific, engineering, business and systems programming applications...

’s rich syntax).

A syntax-directed editor may treat grammar rules as generative

Generative grammar

In theoretical linguistics, generative grammar refers to a particular approach to the study of syntax. A generative grammar of a language attempts to give a set of rules that will correctly predict which combinations of words will form grammatical sentences...

(e.g., offering the user templates

Template (word processing)

The term template, when used in the context of word processing software,refers to a sample "fill-in-the-blank" document that can be completed either by handor through an automated iterative process, such as with a software assistant. Once...

that correspond to one or more steps in a formal derivation of program text) or proscriptive (e.g., preventing a phrase of a given part of speech

Lexical category

In grammar, a part of speech is a linguistic category of words , which is generally defined by the syntactic or morphological behaviour of the lexical item in question. Common linguistic categories include noun and verb, among others...

from being moved to a context where another part of speech is required) or analytic (e.g., parsing textual edits to create a structured representation). Structure editing features in source code editors make it harder to write programs with invalid syntax. Language-sensitive editors may impose syntactic correctness as an absolute requirement (e.g., as did Mentor), or may tolerate syntax error

Syntax error

In computer science, a syntax error refers to an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language....

s after issuing a warning (e.g., as did the Cornell Program Synthesizer). Strict structured editors often make it difficult to perform edits that are easy to perform with plain text editors, which is one of the factors contributing to the lack of adoption of structured editing in some domains, such as source code editing.

Some syntax-directed editors monitor compliance with the context-sensitive

Context-sensitive grammar

A context-sensitive grammar is a formal grammar in which the left-hand sides and right-hand sides of any production rules may be surrounded by a context of terminal and nonterminal symbols...

constraints of a language such as type correctness. Such static-semantic constraints may be specified imperatively

Imperative programming

In computer science, imperative programming is a programming paradigm that describes computation in terms of statements that change a program state...

by actions (e.g., as in Gandalf), or declaratively

Declarative programming

In computer science, declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow. Many languages applying this style attempt to minimize or eliminate side effects by describing what the program should accomplish, rather than...

by an attribute grammar

Attribute grammar

An attribute grammar is a formal way to define attributes for the productions of a formal grammar, associating these attributes to values. The evaluation occurs in the nodes of the abstract syntax tree, when the language is processed by some parser or compiler....

(e.g., as in the Synthesizer Generator) or by unification in a many-sorted algebra (e.g., as in PSG ) or a logic program

Logic programming

Logic programming is, in its broadest sense, the use of mathematical logic for computer programming. In this view of logic programming, which can be traced at least as far back as John McCarthy's [1958] advice-taker proposal, logic is used as a purely declarative representation language, and a...

(e.g., as in Centaur and Pan), with compliance checked by the underlying editing machinery. Structured editors vary in the degree to which they allow its users to perform edits that cause the document to become syntactically or semantically incorrect.

It is common for a language sensitive editor to represent a document as a parse tree

Parse tree

A concrete syntax tree or parse tree or parsing treeis an ordered, rooted tree that represents the syntactic structure of a string according to some formal grammar. In a parse tree, the interior nodes are labeled by non-terminals of the grammar, while the leaf nodes are labeled by terminals of the...

with respect to language’s grammar, or as an abstract syntax tree (AST)

Abstract syntax tree

In computer science, an abstract syntax tree , or just syntax tree, is a tree representation of the abstract syntactic structure of source code written in a programming language. Each node of the tree denotes a construct occurring in the source code. The syntax is 'abstract' in the sense that it...

. For example, a DOM

Document Object Model

The Document Object Model is a cross-platform and language-independent convention for representing and interacting with objects in HTML, XHTML and XML documents. Aspects of the DOM may be addressed and manipulated within the syntax of the programming language in use...

tree is essentially an AST with respect to a given DTD

Document Type Definition

Document Type Definition is a set of markup declarations that define a document type for SGML-family markup languages...

. Frequently, the textual view of that underlying tree is generated by prettyprinting the underlying tree. Editors associated with intentional programming

Intentional Programming

In computer programming, intentional programming is a collection of concepts which enable software source code to reflect the precise information, called intention, which programmers had in mind when conceiving their work...

and language oriented programming for general purpose languages

Programming language

and domain specific languages share many of the features of language-sensitive editors, but aim for greater separation between the underlying representation (the intention

Intention

Intention is an agent's specific purpose in performing an action or series of actions, the end or goal that is aimed at. Outcomes that are unanticipated or unforeseen are known as unintended consequences....

) and the surface representation (text in a programming language).

Although structured editors allow the viewing and manipulation of the underlying document in a structured manner, the file format in which the document is stored on disk may or may not be heavily structured and may or may not be open or standardized (e.g., plain text versus Microsoft Word documents).

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.