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I rather like the phrase "impedance mismatch". I understand it was derived from the realm of electronics, and it's now also commonly applied to problems with object-relational database mapping.

I've heard it used to describe more general misunderstandings between people, and I think it's a very neat phrase. For example, person A wants to communicate some information to person B. The message from A to B inherently includes some assumptions about what person A believes that person B believes about the world. If these assumptions are incorrect, person B's interpretation of the message may differ from the interpretation person A expected. There is an impedance mismatch between their understandings, and so the message fails to communicate all of the intended information.

Surprisingly, Google doesn't seem to return any results for the phrase "impedance mismatch" that don't relate to electronics, sound or ORDBMS. Is this use of the phrase really that uncommon? Am I perhaps using it incorrectly?

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  • I can find Impedance Matching and I know it is a hot thing in the HIFI world, but I have never heard it in a database or object-model context... – oerkelens Jul 30 '14 at 14:10
  • That's because very few people use accurate electronic metaphors. Impedance is a term like resistance that measures difficulty of some form of electron transfer in a given medium or object. Both are formed from Latin verbs that have been borrowed into English: impede and resist, which are pretty close to synonymous in English. So resistance gets used metaphorically, and impedance doesn't. As to mismatch, that only works if you know that several impedances are involved and they must match properly; this isn't necessarily true of resistance. – John Lawler Jul 30 '14 at 14:17
  • Probably the technical term you are looking for is Presupposition, which refers to things that must be taken for granted that can't be denied if a sentence is to be interpreted -- one type of what's loosely called "connotation", usually associated with particular predicates. – John Lawler Jul 30 '14 at 14:20
  • Also if there is an impedance mismatch in a circuit, some of the signal is reflected. – geometrikal Jul 30 '14 at 14:23
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    Bottom line: Go ahead and use it with your geeky electrical engineering friends (or DBMS CS friends), but be ready for an impedance mismatch if your try to use it with the world at large. – Jim Jul 30 '14 at 14:30
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In my experience, I have heard impedance mismatch used informally to indicate any kind of mismatch. (I don't claim anything beyond this personal experience.)

I think I have heard it used more in connection with matching that might be complex and involve a process that is being abstracted from (or even is unknown by the reporter).

IOW, instead of referring to what kind of mismatch is involved or how matching fails, impedance mismatch is used in these cases to gloss over the particulars and just indicate that the things do not match or fit together.

I think the term is used sometimes somewhat ironically: something that is originally quite technical and precise is used to gloss over any details or explanation of what the mismatch really amounts to. Using impedance mismatch this way is a bit like saying that the two things do not match in some way not to be revealed - perhaps some mysterious, unobvious, or unfathomable way.

(It's like the cartoon showing an ostensibly clear-cut technical proof that has a step miracle happens (or magic happens).

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  • Yeah, I like the suggestion of abstract or ironic usage. In this case I'm trying to be somewhat technically correct; I came across the question because I'm researching integration of simulation models, and when the output from one is compatible with the input of another then the integration is compatible, but if the models make different assumptions about that same value then the results may be misleading. I just wanted to check if I could call that an impedance mismatch without sounding ignorant. I guess I'm still not entirely sure. – Pie21 Jul 31 '14 at 7:22
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    I'd suggest that if the context is technical then if you use the term informally you will also want to explain what you mean by it in technical terms, IOW, specify its meaning rigorously, if you expect it to convey a technical meaning in addition to the general, informal one. – Drew Jul 31 '14 at 14:21
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Purely for what it's worth as a survey result,

*) I've never ever heard it used in the natty social way you describe. So yeah it must be pretty rare or new.

I think it's clever - good one. It sounds like something, oh, Ben Aaranovitch would write. Did you hear it in a film or something?

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  • It was mainly one of my computer science friends at uni, but I feel like I've heard it from multiple sources. I think it's maybe just one of those times where you catch yourself fabricating memories. – Pie21 Jul 31 '14 at 7:13

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