This July 2015 update attempts to incorporate in subsequent Federal Circuit rulings after the Alice decision from June of last year. However, recent jurisprudence have not offered much additional insight as to what exactly defines an "abstract idea". As various district judges have noted, an abstract idea pursuant to Alice is one that is roughly determined by a "I know it when I see it" review. See Eclipse IP v. McKinley Equipment (C.D. Cal. 2014).
In view of this critical gap, the US PTO has instructed its examiners to abide strictly to court decisions finding for patent ineligibility under 35 USC 101, and to only find an abstract idea in patent prosecution, when the concept of the invention parallels one that has been found to be abstract in a court decision.
A list of court decisions, as well as the latest eligibility guidance, is maintained by the US PTO at http://www.uspto.gov/patent/laws-and-regulations/examination-policy/2014-interim-guidance-subject-matter-eligibility-0.