| 摘要 |
Digital data storage conventionally requires an election to be made between retaining data on-line, which consumes expensive media, or moving it to a far cheaper archive medium, which is relatively inacessible. This specification discloses a hybrid arrangement in which all material is retained on-line, but is progressively degraded as it becomes less useful, with off-line storage of the source material. On-line browsing of an entire library remains possible, but without incurring the expense of maintaining the entire library at source quality on-line.
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