2.7 Reading arrows
The challengeReading arrows is not easy at first. There are eight combinations of various dimensions that one has to keep track of. However, reading arrows is essential to reading conceptual graphs. Therefore, this page has all of the information you need in order to be able to read arrows.
Equivalence of reading directions
The following two graphs are equivalent:
[A]->(R)->[B] and [B]<-(R)<-[A]
Thus the direction of the arrows on the page is determined by the position of the concept types within the signature, and is otherwise immaterial.
There is also special standard language associated with the direction of an arrow. This language can be divided into two groups:
For each group, it also matters whether we are reading an arrow that points towards or away from a relation.
This can be shown as in the following two tables. The first is when reading from left to right and the second is when reading from right to left:
Now we need examples. Try to follow these examples in the two tables above. The following graph can be read in two ways:
[Bird]<-(Agnt)<-[Sing] "A bird is singing"
can be read:
It is important that you learn to read arrows. Thus it is recommended that you go back and try to match each arrow with each of the four expressions in the two ways of reading the graph.
Language about prepositional relations
This technique does not work very well with relations which are prepositions, such as On and In. In this case, it is better simply to say the preposition, preceded by a form of the verb 'to be', as in:
[Book]->(On)->[Table] "A book is on a table"
Importance of reading arrows
This concludes our discussion of how to read arrows. It is important that you practice reading arrows until you master the technique.
If you wish, you can print out this page and have it lying beside you as a reference.
Prev: 2.6 Special names
Up: 2 Conceptual graphs
Next: 2.8 Quiz: Conceptual graphs