Online vs Offline Searching

Online/offline searching terminology is derived from online/offline algorithms.

For algorithms, an "online" setting is where input arrives in piece-meal fashion. In other words, the input is a stream of data and is not entirely available prior to starting the algorithm. In an "offline" setting the entire input is available prior to running the algorithm.

Similarly, for searching, an "online" setting is where no information about the system is used a priori to the query being executed, whereas an "offline" setting is where a priori information is available. Vegnos® performs an "online" search whereas most desktop search engines build indices, and when queried, perform "offline" searches on these indices. The benefits of an "offline" query is that searching is faster. However, the side-effects of an "offline" search is that the index requires additional persistant disk space. Furthermore, the index may be inconsistent at the time the query is performed yielding both false-positives (hits when files no longer exist) and false-negatives (no hits when new do files exist).

File name case-sensitivity in NTFS

Generally, file names are case-insensitive in Windows (and NTFS). However, if you use Services for Unix (i.e., POSIX/Interix Layer), you have the option to utilize case-sensitive file names instead.