SDF2 o 2

A summary of changes from SDf.2.1 to SDF.2.2 :

• The syntax of ATerms will be used for SDF attributes for example: A -> B {left} B -> C {aap(noot,mies)}

• SDF layout is defined in a separate module and imported at the top. This allows other modules to be reused without inheriting the SDF layout and comment conventions.

• ATerm and SDF unquoted literals are distinguished using the sort UQSdfLiteral^?.

• The "definition" keyword is removed. An SDF definition is just a sequence of SDF modules: Module* -> Definition

• The following file extensions will be used for SDF modules and definitions:
  • .sdf for SDF modules
  • .def for SDF definitions

• The SDF grammar will contain constructor annotations which define the abstract syntax of SDF

• Three new constructors are introduced in AsFix^?:
  • qlit to represent quoted literals
  • uqlit to represent unquoted literals
  • flatlex to represent flattened lexicals

• The production sorts Symbols -> Grammar has been replaced bu sorts Sorts -> Grammar

Unresolved Issues

• Do we need directly visible kernel syntax?

• Are there convincing examples of kernel syntax?
• Why can these not be handled by lexical syntax?

• How do the sorts in kernel syntax and other sections relate?

• Do we need aliases?

• Why Symbols in parameter list following module name?

• Keyword "Set" should be "set"

• Do we need the "(" Symbol "=>" Symbol ")" syntax?

• Why are the lookaheads "" {Lookahead ","}* "^?" visible? Should belong to kernel syntax.

• How to add GrammarAnnotations^??