glued(${\it es}$; $B$; $f$; ${\it Ia}$; ${\it Ib}$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\exists$$g$:E(${\it Ib}$)$\rightarrow$E. glues(${\it es}$; $B$; $g$; $f$; ${\it Ia}$; ${\it Ib}$)