The invention provides an optical disk recording and reproduction method which suppresses a drop of the throughput of an optical disk apparatus by retrying caused by a read error. A similarity calculating unit calculates similarities between key contents designated by the retrieval keys and a plurality of retrievable contents, based on feature quantities of contents that are supplied from a feature quantity extraction unit and a feature quantity database. In one set of embodiments, these techniques include determining one or more browser dependencies that require the thin client to operate within a web browser. At least two of the address banks in certain embodiments also share physical memory locations for at least one redundant interior bit. The initiator systems can be thermal initiator systems, photoinitiator systems, or combinations thereof. Other embodiments may be described and claimed.