Lets say I have three models/tables: operating_systems, words, and programming_languages:

# operating_systems
name:string created_by:string family:string
Windows     Microsoft         MS-DOS
Mac OS X    Apple             UNIX
Linux       Linus Torvalds    UNIX
UNIX        AT&T              UNIX

# words
word:string defenitions:string
window      (serialized hash of defenitions)
hello       (serialized hash of defenitions)
UNIX        (serialized hash of defenitions)

# programming_languages
name:string created_by:string example_code:text
C++         Bjarne Stroustrup #include <iostream> etc...
HelloWorld  Jeff Skeet        h
AnotherOne  Jon Atwood        imports 'SORULEZ.cs' etc...

When a user searches hello, the system shows the defenitions of 'hello'. This is relatively easy to implement. However, when a user searches UNIX, the engine must choose: word or operating_system. Also, when a user searches windows (small letter 'w'), the engine chooses word, but should also show Assuming 'windows' is a word. Use as an <a href="etc..">operating system</a> instead.

Can anyone point me in the right direction with parsing and choosing the topic of the search query? Thanks.

Note: it doesn't need to be able to perform calculations as WA can do.