An EBNF Grammar for Wiki Creole 1.0 [Technical Report]

Comments

1. 

   Shaddy Zeineddine

   2013-02-28

   Another question: What happens with a string of unformatted text which ends with a ~ followed by a newline? Since, “~\n” is a valid escaped sequence and unformatted text can contain escaped sequences. Should the newline be ignored? Should I email you future questions? Also, thank you very much for providing this grammar! It’s really helping me understand how to write my parser. ;D

   Reply
   1. 

      Martin

      2013-02-28

      Hi Shaddy,
      the ~ is part of ANTLR syntax expressing that the following expressions/characters must not occur in the terminal derived from the respective production rule(s).
      In your case, ‘~\n’ includes any character except for a new line assuming that the ~ was not escaped.
      HTH, Martin

      Reply
      1. 

         Shaddy Zeineddine

         2013-02-28

         I’m referring to the ~ as part of a creole escape sequence in a text line:
         text_unformatted
         : ( ~( ITAL …and so on… EOF )
         | forced_linebreak
         | escaped )+
         ;
         escaped
         : ESCAPE STAR STAR
         | ESCAPE .
         ;
         ESCAPE : ‘~’;
         These rules can generate “~\n” is a valid form of text_unformatted. Along with the other rules related to text paragraphs, a text paragraph can look like this:
         // START CREOLE
         this is a valid text_paragraph~
         ~
         ~
         this is part of the same text_line~
         this is still part of the same text_line
         // END CREOLE
         Which means that any ~ at the end of a text line would result in an issue:
         // START CREOLE
         this is a valid text_paragraph ~
         this text_line should belong to a new paragraph, but it doesn’t
         // END CREOLE

         Reply
         1. 

            Martin

            2013-02-28

            What I was trying to say:
            Hi Shaddy, now I got you. Thanks for the examples.
            As you said, ‘~\n’ can be produced. After I had a brief look at the grammar again, we escape the linefeed. If you want to change it, the linefeed can be excluded from the characters/tokens that are allowed after the tilde in the ‘escaped’ rule. When we wrote the paper, (i) we aimed at defining an LR(k) grammar that is not specific to ANTLR but can be deployed to ANTLR for testing and (ii) ANTLR could not handle all the different kinds of ambiguities that the Creole grammar contains quite well. (This was also the reason, why for instance the rules for bold formatting exploded.) With current versions of ANTLR you can easily insert statements to the grammar that make assertions on the Lookahead, e.g. “{ LA(2)!=’\n’ }?”, which allows you to handle the ambiguities.

            Reply
            1. 

               Shaddy Zeineddine

               2013-03-02

               Perfect, thanks!

2. 

   Shaddy Zeineddine

   2013-02-27

   To clarify what I mean. The “**c” part of “ab**c” would not use the text_formattedelement, ital_markup, or text_italcontent symbols, yet, it should be rendered in italics.

   Reply
3. 

   Dirk Riehle

   2013-02-27

   Hi Shaddy,
   how is ab**c invalid?
   Thanks,
   Dirk

   Reply
4. 

   Shaddy Zeineddine

   2013-02-27

   Hey Dirk, I’ve noticed a few rules which look odd to me. Please let me know your thoughts. This is one pair:
   text_line
   :
   text_firstelement ( text_element )* text_lineseparator
   ;
   text_element
   :
   onestar text_unformattedelement
   |
   text_unformattedelement onestar
   |
   text_formattedelement
   ;
   Doesn’t this allow the following invalid text_line?
   ab**c

   Reply
5. Wiki to XML using Ant « PrayogShala

   2009-07-16

   […] of Martin Junghans and Dirk Riehle. They did research on this subject. As a result, they created an EBNF grammar and an XML interchange format (Creole […]

   Reply
6. 

   johannes busse

   2008-01-10

   Thank you and your collaborators for this very useful grammar! It looks complex. But Wiki Text in fact *is* complex to parse. … Johannes

   Reply

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