JADE Language Syntax

The syntax definition for JADE methods and schema files uses the Extended Backus Naur Formalism (EBNF). An EBNF specification is a sequence of syntax rules.

EBNF symbols are used to precisely and concisely specify the syntax. The symbols used in EBNF are:

• Parentheses (that is, the ( and ) symbols) group alternative terms

• The vertical bar (|) separates alternative terms

• Brackets ([]) identify optional expressions

• Braces ({ }) identify expressions that can occur zero or more times

• Character sequences enclosed in double quotes ("") identify terminal symbols, or keywords, of the JADE language

• An identifier is a sequence of letters and digits, beginning with a letter

The following example shows meals that are defined with a sequence of EBNF symbols.

appetizer = "artichoke" | "oysters"
dessert = "ice cream" | "fruit"
fruit = "apple" | "orange" | "pear"
meat = "beef" | "lamb" | "fish"
vegetable = "broccoli" | "carrots" | "peas"
meal = [appetiser] meat ("potatoes" | "rice") {vegetable} [dessert]

Examples of meals defined by these rules are:

beef potatoes
artichoke fish rice peas broccoli ice cream
lamb rice carrots carrots carrots peas broccoli pear
oysters beef rice orange

A JADE method has the following syntax.

method-name ([parameters]) [: return-type] [method-options];
[constants
    constant-declarations]
[vars
    variable-declarations]
begin
    JADE-instructions
[epilog
    epilog-instructions]
end;