$\models$ vice-versa as semantically equivalent

Question

How to get the $\models$-symbol vice-versa to form a symbol for semantically equivalent like the following: =||=

Answer 1

\models in the standard fonts is a made up symbol

\DeclareRobustCommand
  \models{\mathrel{|}\joinrel\Relbar}

So you could do a matching combination:

\documentclass{article}


%\DeclareRobustCommand
%  \models{\mathrel{|}\joinrel\Relbar}
\DeclareRobustCommand
  \sledommodels{\Relbar\joinrel\mathrel{\|}\joinrel\Relbar}

\begin{document}

\[A \models B\]
\[A \sledommodels B\]

\end{document}

Answer 2

If you are in a LaTeX-only environment (for example, MathJax), consider this:

\newcommand{\rmodels}{\ensuremath{\mathrel{=\!\!\!|}}}

Semantic equivalence can, for example, look like this:

\newcommand{\semeq}{\ensuremath\mathrel{\rmodels\!\models}}}

The result (pdflatex):

Depending on your context of conventions, \models\rmodels might be what you want: