The first article also refers to 'film' work. The second is more about the 'net' excerpt:
The problem of ``fixation'` as it relates to photo's on the Net will usually arise in the context of whether or not a photograph was ``copied'` by an infringer. Certain ephemeral artworks like the type produced by Christo, have been the subject of controversy in terms of the fixation requirement for copyright protection.
In the context of copyright protection for computer programs the Ninth Circuit held in MAI Systems Corp. v. Peak Computer Inc., that ``copying for purposes of copyright law occurs when a computer program is transferred from a permanent storage device to a computer's RAM [random access memory].'` The court described fixation as ``sufficiently permanent or stable to permit [them] to be perceived, reproduced, or otherwise communicated for a period of more than transitory duration.'` This decision as it relates to photos on the net may be a practical problem of proof. Net photos, like Christo's sculptures, may be here today, gone tomorrow. Consequently the problem will be a whether a ``copyright claimant will be able to provide a court documentary evidence of the copyrightable subject matter.'`