Caching is orthogonal to recursion... Explain ?

Question

Although it's true that some recursive-nameserver configurations are (sloppily) referred to as "caching", e.g., by RHEL/Fedora/CentOS, that's a really bad name for that function -- because caching is orthogonal to recursion.

Theoretically, you could write a nameserver that does recursive service but doesn't cache its results. (That would be a bit perverse, and I don't know of any.) Conversely, nameserver packages that cache but know nothing about how to recurse and instead do less-helpful alternative iterative service are common: dnsmasq, pdnsd, etc. ... ...

Above text source: http://linuxgazette.net/170/lan.html

Please explain what does the author means by "caching is orthogonal to recursion" ?

Answer 1

caching is orthogonal to recursion?

Caching doesn't require/imply recursion.

The term "orthogonal" is meant to be interpreted from a mathematical sense loosely has "the things have nothing in common i.e. separate concepts".

Answer 2

From Wikipedia's definition of orthogonal:

For example, a car has orthogonal components and controls (e.g. accelerating the vehicle does not influence anything else but the components involved exclusively with the acceleration function).

The author is saying that whether a nameserver caches is nothing to do with whether it can recurse.

Answer 3

It mean it is one feature is independent with the other one. Or have bothe feature have no influence with the other one. So they can be implemented independantly

in a programming point of view, two orthogonal features

do_work(bool feature1, bool feature2)
{
  // do common work

  if(feature1)
  { //... do this }

   // do common work

  if(feature2)
  { // do work }

  // do common work
}

or: if they are not orthogonal:

you need to do this: ( and it may have case where you cant combine the two feature.

do_work(bool feature1, bool feature2)
{
  if(not feature1 and feature 2)
  { //... do this }

  else if(feature1 and not feature2)
  { // do work }

  // else impossible or different behavior
  // etc..
}