1. The process of aligning attributes, their values, or both across schemas.
2. A mapping from one attribute or attribute value pair to another attribute or attribute value pair.
3. The aggregate of all mappings between attributes or attribute value pairs across schemas.
For example, an attribute <Power Requirements>, which captures both voltage and frequency requirements for safely operating an electronic device, may be mapped to two separate attributes, <Operating Voltage> and <Operating Frequency> to preserve one concept per attribute. Another example would be an attribute that captures values as a range, e.g. “3 in – 5 in,” being mapped to two separate attributes that capture minimum and maximum values, respectively.