• From: Michael Kay <mike@s...>
• To: Roger L Costello <costello@m...>
• Date: Tue, 31 Aug 2021 23:45:22 +0100

The term "mapping" is generally used to mean an operation in which the same function f(x) is applied to every item x in some set (or sequence) of items X.

The term "filtering" is generall used to mean an operation in which some predicate (boolean function) f(x) is applied to every item x in some set of items X, such that x is included in the result if f(x) is true, and excluded if it is false. Filtering using a function p(x) is equivalent to mapping using the function (if (p(x)) then x else ()).

I'm not aware of any mathematically precise use of the term "transformation". An XSLT transformation is of course a function from input documents to output documents.

Michael Kay
Saxonica

> On 31 Aug 2021, at 18:53, Roger L Costello <costello@m...> wrote:
> 
> Hi Folks,
> 
> How do you define those terms? Are they synonymous? Is one a subset of another?
> 
> By "mapping" I mean populating XML instances of one data standard with data from another data standard. For example, I am currently mapping a military air navigation data standard to a civilian air navigation data standard.
> 
> By "filtering" I mean performing actions on data such as redacting, fuzzing, and zeroing. One could think of these actions as mapping: if I fuzz a lat/long location, I am essentially mapping the location to another location.
> 
> By "transforming" I mean all the kinds of things you can do with XSLT.
> 
> Is filtering a subset of mapping? Is mapping a subset of transforming?
> 
> /Roger
> 
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• References:
  • What is the relationship between transforming, mapping, andfiltering?
    • From: Roger L Costello <costello@m...>