What is the meaning of the $\int$ symbol in Giancarlo Guizzardi's PhD thesis?

Question

I am reading Giancarlo Guizzardi's PhD thesis Ontological Foundations for Structural Conceptual Models. On p.218 there is an expression I cannot understand. It is

$\forall x,y\ \operatorname{Substantial}(x) \land \operatorname{Substantial}(y) \land (x\mathrel{\int} y)\rightarrow \operatorname{indep}(x,y)$

I believe this is the first time in the thesis the symbol $\int$ has been used in this manner. What does it mean in this context?

Answer 1

This symbol is defined on page 145 of the linked document.

$( x \mathrel{\int} y ) =_{\text{def}}\neg(x\bullet y)$

On the previous page, $x\bullet y$ is defined by

$(x\bullet y)=_{\text{def}} \exists z(z\leq x\land z\leq y)$

In words, $x\int y$ means that there is no element that is less than or equal to both $x$ and $y$. To use some terminology from comparability theory, it means that the "cones below" $x$ and $y$ (the sets of all points less than or equal to $x$ and $y$ respectively) are disjoint.

Answer 2

The symbol is defined first on page 145 of the document that you linked.

$x\mathrel{\int}y$ is defined as $\lnot(x\mathrel{\bullet}y)$. And you can track back the definition of $\bullet$ in the few pages before p. 145.