Operation icons, also called process icons, denote operations and are usually context-dependent. Figure 2 illustrates a content-sensitive visual sentence for TimeMan. Figure 3 illustrates a time-sensitive visual sentence that changes its meaning with time. Operators Icons are combined using operators. In other words, the meaning part x m1 and x m2 are combined using the logical operator op m , and the physical part x p1 and x p2 are combined using the physical operator op p .
Operators can be visible or invisible.
But if we look at Figure 2, the cat is a visible operator denoting a process to be applied to the fish in the fish tank. An operation icon can be regarded as a visible operator. The invisible icon operators are spatial operators and apply only to icons or ticons. The spatial composition of two icons or ticons is a complex icon. Grammar Visual languages can handle temporal as well as spatial operators.