I'm doing some research in NLP, and thought you guys would be the best to ask this.
When looking at an English sentence, it is sometimes hard for a computer to distinguish between proper nouns, such as Bill, and common (non-proper) nouns, such as bill as in He gave me a bill.
At first I thought, 'Oh, I'll just see if it's capitalized.' I'm wary to do this though, since I'm not sure if that pattern will hold as a rule.
Then, I noticed that every time a common noun begins a sentence (and almost always when it is used in a sentence), it is preceded by one of the articles a, an, or the. Is this a rule I can count on? Can anyone think of counterexamples?