com.lexonics.edsel.parser
Class Parser

java.lang.Object
  com.lexonics.edsel.parser.Parser

public final class Parser

extends Object

An Edsel parser.

Edsel, the Easy Data Structure Expression Language, is a notation for representing labeled, attributed directed graphs. This is an application for which XML is commonly used. Edsel, however, is better suited for this purpose than XML, in two ways:

• Edsel is not a markup language. Its syntax is very simple, since it is not encumbered with the somewhat baroque generality that XML inherited from SGML. A complete Edsel parser consists of a 6K-byte Java jar file.
• Unlike XML, Edsel is not strictly hierarchical; it allows the expression of general graph relationships easily and naturally.

An Edsel graph consists of uniquely-labeled attributed nodes connected arbitrarily by labeled directed edges. The notation consists of a sequence of node definitions, each of which gives the node's name and body (its attribute names and value lists, and its outgoing edge names and destination lists). In the following syntax definition, braces denote arbitrary repetition, brackets denote optionality, vertical bars denote alternation, quoted strings denote terminal symbols, uppercase strings denote terminal symbol classes, and the start symbol is graph.

        
                attribute = attribute-name { attribute-value } ';' .
                attribute-name = name .
                attribute-value = STRING .
                graph = { node-definition } .
                name = IDENTIFIER .
                node = node-definition | node-reference .
                node-body = '{' { attribute } [ '|' { outgoing-edge } ] '}' .
                node-definition = node-name node-body .
                node-name = name .
                node-reference = node-name .
                outgoing-edge = outgoing-edge-name { outgoing-edge-destination } ';' .
                outgoing-edge-destination = node .
                outgoing-edge-name = name .
        
        

An IDENTIFIER is a sequence of one or more upper- and lowercase ASCII letters, digits, and hyphens. A STRING is a single-quoted sequence of zero or more Unicode characters; any character may be escaped by a backslash, and single quotes and backslashes must be.

Whitespace may occur freely between tokens and is insignificant. Parenthesized comments may also occur between tokens; comments may be nested.

By convention, the first node may be named -Edsel and have a -version attribute giving the Edsel version (1.0).

Example:

        
        -Edsel { -version '1.0'; }

        (This is a simple example of Edsel.)

        John
        {
                first-name 'John';
                last-name 'Smith';
        |
                wife Mary;
        }

        Mary
        {
                first-name 'Mary';
                last-name 'Smith';
        |
                husband John;
        }
        
        

Nested Class Summary

static class

Parser.ParseException An Edsel parse exception.

Method Summary

static Graph

graph(CharSequence edsel) Parse an Edsel string representation of a graph.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

graph

public static Graph graph(CharSequence edsel)
                   throws Parser.ParseException

Parse an Edsel string representation of a graph.

Parameters:

edsel - The Edsel string representation. Must be non-null.

Returns:

The corresponding Graph.

Throws:

IllegalArgumentException - The Edsel string representation is null

Parser.ParseException - The Edsel string representation is syntactically incorrect.