Impedance mismatch

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Impedance mismatch

• Impedance mismatch is a problem in electrical
  engineering that occurs when two transmission
  lines or circuits with different impedances are
  connected. This can cause signal reflection
  resulting in noise.
• Impedance is a measure of opposition to a
  sinusoidal electric current.
• In programming terminology, it refers to the
  attempt to connect two systems that have very
  different conceptual bases, most commonly when
  trying to use an SQL database (i.e. relational)
  from an object oriented program. Christopher J.
  Date would argue that a truly relational DBMS
  would pose no such problem, as domains and
  classes are essentially one and the same thing.

http//en.wikipedia.org/wiki/Impedance_mismatch