An air carrier crew's ICAO formatted DFW NOBLY3 LIT RNAV PDC was different from the old format. The new ICAO format led the crew to believe direct LIT was correct when the new format actually required full route compliance.

Narrative

Departing DFW the PDC reads 'DFW NOBLY3 LIT XXX....' We believed the clearance to be after NOBLY intersection direct LIT. ATC understood after NOBLY fly the LIT transition to LIT. Under the old format prior to Jan 2009; it would show in the release strip as NOBLY3.LIT whereas direct would read NOBLY3..LIT. Now under the ICAO format there are no 'dots' identifying direct or transition. Therefore it appears a direct is indicated after NOBLY. ATC asked what we were doing and indicated many are going direct after NOBLY rather than doing the transition. It appears (as there are no clear examples in our manuals) that if presented as NOBLY3 LIT one must fly the transition whereas after NOBLY if direct it must read NOBLY DCT LIT. However; this is an assumption that I am reasoning based on some examples and comparing flight plan to release. Since the PDC is in the old domestic format and the release is in ICAO format; confusion exists and according to ATC many others are making the same mistake.Callback conversation with reporter revealed the following info: The reporter carried two publications describing PDC formats. The PDC received that day was not covered in the format descriptions available. The closest the crew could come to understanding the clearance; in the moment; was to assume that the NOBLY3 LIT text gave a direct clearance after NOBLY. The 'direct to' clearance on the DFW NOBLY3 LIT is a point of confusion in this case because the crew did not know but assumed afterwards that it was an ICAO format. One station that this pilot's air carrier flies into has added a textual description as the end of the PDC in order to clarify known ambiguities.