Many years ago I did temp work at a company called RightSoft, which made a grammar checking program (back when such utilities, along with spell checkers, were standalone) called RightWriter. It was unique among grammar checkers in that it wasn't dictionary-based, but used a syntactical analysis algorithm combined with a simple expert system to make its recommendations. It also looked at your complete file and generated markup, like an editor might, rather than going through in an interactive mode. You could read the marked-up file for its notations and make corrections that you wanted or ignore ones that you didn't think made sense. (Unlike other programs which confidently told you stupid things, RightWriter phrased everything as a question--"is this correct?"--which seemed to encourage you to think, "Yes, it is, thanks.") Then another run back through the program removed the markup.
In short, RightWriter was a grammar checking program that didn't suck. Naturally, it didn't survive.
Anyway, I'm reminded of it after seeing an LJ widget that analyzes your journal's "reading level"; this is something that RightWriter did by default to text that was run through it. (I'm reformatting the HTML, which is kind of borked.)
Grade Level: 10
|Average words per sentence:||21.19|
|Average syllables per word:||1.44|
|Total words in sample:||4959|