BNF Tools Version 2.0: Migration Notes

Discovered features in version 1.0 and their migration status, as well as further migration notes are summarised below.

Core Features:

1. BNF front-end - lexer, parser, linker, etc.
2. Model serialisation - translates a textual representation to and from an Ecore model
3. IDE - provides editors and other IDE features, e.g. outline, auto-completion, syntax highlighting, quick-fixing, etc.

Validation Rules:

These rules will give warnings in the editor if they find inconsistencies and constraint violations in the code.

1. checkUpdateGrammarConsistency: checks if the grammar is an updated grammar, for consistency validation between the original grammar and the new grammar
   • status: not migrated
2. checkReferencedOnlyOnce: checks if there are rules that are only referenced only once, this is an inlining hint
   • status: migrated
3. checkPassthroughRule: checks if a rule gets just passed through, e.g. a ::= b, b ::= "literal" <=> a ::= "literal", which is better for EBNF
   • status: migrated
4. checkEqualAlternative: checks if a rule has equal alternatives, e.g.: a::= d | d
   • status: migrated
5. checkDuplicateRules: checks if there is another rule that has the same right hand side, e.g.: a ::= "literal" | b, c ::= "literal" | b
   • status: migrated
6. checkSubruleDuplicates: checks if there are identical parts of right hand sides, this is an extract subrule hint e.g. a::= b c d and f::= e c d <=> a::= b g and f::= e g with g::= c d
   • status: not migrated
7. checkUnusedRule: checks if a rule never used (except for the first rule)
   • status: migrated
8. checkNameIsUnique: checks if the name of a rule is already in use e.g. a ::= "end", a ::= "fin"
   • status: migrated

Generation:

Generating an intermediate xsl-fo representation for all BNF grammars, which can then be rendered to PDF or RTF using apache-fop

• status: partially migrated, merge or delta grammars not supported (were they in the original implementation?)

Formatting:

Automated formatting support

• legacy: had some formatting support, but it was commented out in the main project
• migrated: line-break after every rule, white-spaces after all literals, possible update to line-break and double tab after all >|< bars

Refactoring and Quick-fixing:

Automated restructuring and quick fixing support.

1. auto numbering of rules
   • status: not migrated
2. remove unused rules
   • status: migrated
3. replacement of pass-through rules
   • status: not migrated
4. uppercase token rules
   • status: not migrated
5. find references
   • status: provided by xtext2
6. renaming
   • status: provided by xtext2
7. inline rules referenced only once
   • status: not migrated

Grammar Composition:

Three grammar types:

• grammar: normal grammar
• delta grammar: different notation for an extension grammar,
  • adds new rules to a grammar (regular rules) and adds changes to rules of the extended grammar (extension rules) (can be automatically created)
• merge grammar: for merging extensions

The legacy version had an automatic composition process for merge grammars with a small pop-up-menu.

• status: at the moment no support for grammar composition in the migrated version