Assume $P_1$ and $P_2$ are tnvarants of a system $S$. Prove that $\left(P_1 \vee P_2\right)$ and $\left(P_1 \wedge P_2\right)$ are invariants.
Assume $P_1$ and $P_2$ are $Q$-derivates of a system $S$. Prove that $\left(P_1 \vee P_2\right)$ and $\left(P_1 \wedge P_2\right)$ are $Q$-derivates of a system $S$.
Transition systems with the same set of configuratious and initial configurations can be composed by combining their transition relations. Thus, the parallel composition of $S_1=\left(\mathcal{C}, \rightarrow_1, \mathcal{I}\right)$ and $S_2=\left(\mathcal{C}, \rightarrow_2, I\right)$ is the system $S=(\mathcal{C}, \rightarrow, I)$, where $\rightarrow=(\rightarrow 1 \cup \rightarrow 1)$.