[BioC] Illumine bead array PROBE_TYPE values

[heyi xiao]

Hello list,
I am working on illumine bead array expression data. The data was output from GenomeStudio with probe annotation. There is a column called PROBE_TYPE, with three values: A, I and S. What do these values mean, antisense, intron and sense? Antisense and sense are string relative to the target gene, not to the reference genome, right? Why intron and antisense probes are needed? I couldn’t find the description info on Internet. Thanks a lot!
Heyi