diff --git a/latex/yssymbols.sty b/latex/yssymbols.sty
index feeccf6..5e12000 100644
--- a/latex/yssymbols.sty
+++ b/latex/yssymbols.sty
@@ -40,7 +40,8 @@
 
 
 \def\dom{\mathcal D}
-\def\sem#1#2{{\mathcal {V}}_{#2}(#1)}
+\def\sem#1#2{{\left\lbr#1\right\rbr}_{#2}}
+\NewNegationCommand\models{\mathrel{\notaccent\models}}
 
 \def\metab#1{\ensuremath{\langle #1\rangle}}
 \def\metasyn#1{\metab{\tmit{#1}}}