I might receive more and more properties I haven't planned into my schema/bitmap/bitvector layout.

Use a two-step schema.

  1. Each attribute/value pair gets added to a single table with an auto-incrementing primary key when it is first seen.

    Using your example above, 'color:grey', 'material:wood', & 'surface:rough' are your attribute/value pairs (A/V pairs).

    The auto-incremented 'id' value becomes that A/V pair's bit position in the data records.

  2. The data records are variable length strings of bits.

    As the number of A/V pairs increase, so do the length of (new) records, but the bit positions of existing A/V pairs retain their original meanings, so the schema does not need to change.

To select records, you build up a bit mask with bits set for the sought A/V pairs, and then AND it with each record. For similarity, count the resultant bits.

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In reply to Re^3: What is the best way to store and look-up a "similarity vector"? by BrowserUk
in thread What is the best way to store and look-up a "similarity vector" (correlating, similar, high-dimensional vectors)? by isync

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