The rules of writing every paragraph are described together with every cord model definition. The rules are described using two kinds of elements: non-terminal syntactic elements, and terminal syntactic elements.
For example, when we write cell-category we mean that the user should type exactly the characters cell-category, as in the rule. This is a terminal syntactic element.
When we write <number>) we mean that the user will have to type, instead of <number> a number--of his choice--such as 1.3 or 8. This is a non-terminal syntactic element.
In order to distinguish, in the rules below--which are called syntactic rules--the terminal from the non-terminal syntactic elements, the non-terminal ones are written between angle brackets--which are never used in the terminal ones. The non-terminal syntactic elements will be called, for shortness, non-terminals, while the terminal ones will be called teminals.
<letter> ::= A | ... | Z | a | ... | z <digit> ::= 0 | .. | 9 <special-sign> ::= - | _ | & | % | ... <graphic-char> ::= <letter> | <digit> | <special-sign> <integer> ::= <digit>* <number> ::= [-]<digit>*[.<digit>*] <subunit-number> ::= 1[.0] | 0.<digit>* <symbol> ::= <letter><graphic-char>* <string> ::= "<graphic-char>*"