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If the comet's orbital eccentricity (e) is less than 1, then it is a (long or short) periodic comet. However, the designation "P/" is only applied to comets of period 200 years or less, and of late there's been a trend to only apply "P/" straight away if the comet is of period 30 years or less, with the "P/" only being applied to comets of 30-200 years when it is sighted again at the next return.
The Minor Planet Centre's orbit for PANSTARRS has e=1 because they solve for e=1 at this time until sufficient observations are available (thus far, the observations still only go up to June 11). The JPL orbit is derived from the Minor Planet Centre's database of reported observations but makes different assumptions.
Greg
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