## `Ax::systemRep` -- the axiom of facade domains

#### Introduction

`Ax::systemRep` states that domain elements are represented by elements of built-in domains.

#### Generating the axiom

`Ax::systemRep()`

#### Details

- There are principally two ways to represent the elements of a domain: On the one hand the elements may be created explicitly by the system function `new`, on the other hand one may use the built-in (or basic) domains of MuPAD (like `DOM_INT`) to represent the elements.
- Domains which don't create elements of their own but use elements of basic domains instead are called facade domains.
- The usage of basic domains for the representation has the advantage that system functions may be used directly as methods of the domain without the overhead caused by overloading and procedure calls. But it has some severe limitations, see the domain `Dom::Expression` for details.
- The axiom `Ax::systemRep` is used to state that the elements of a domain are represented by basic domains and are not created by `new`.

#### Changes

- no changes

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