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To assert a proposition, i.e., to tell the SNePS knowledge-representation
and reasoning system something
that you want it to believe, evaluate the SNePSUL command assert. assert can take pairs of arguments: The first
member of each pair is a relation; the second can be a node (or
a list of nodes; see §2.30). assert builds a propositional node that has an arc that is labeled with the
relation and that points to the node that is the second argument.
If there are several such relation-node pairs, then the
propositional node that is built has several arcs, each labeled
with one of the relations, and each pointing to one of the nodes. Finally,
the node that is built is asserted. SNePS automatically generates
an identifier for the node that is built by the assert command.
SNePS marks the fact that this node is asserted with an exclamation mark.
For the details on assert, see UM§§
1.4,
2.7.
Cassie is the computational cognitive agent implemented in SNePS.
She can be thought of as the agent whose memory consists of the
knowledge base represented in SNePS.
(More information about
Cassie and her relationship to SNePS can be found in
Shapiro & Rapaport 1987.
Let's tell Cassie that Clyde is an elephant. There are several
ways this can be represented. For the purposes of this tutorial,
we'll represent it by a node that
analyzes this proposition as: Clyde is a member of the class
of elephants. To do this,
evaluate:
(assert member Clyde class elephant)
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which will build a node with a member
arc pointing to a node with the identifier Clyde and a class arc pointing to a node with the identifier elephant.
SNePS asserts node M1 (which it represents as
`M1!', since it asserted it, and didn't merely build it).
Next: 2.5. Correcting Mistakes, part
Up: 2. BUILDING AND FINDING
Previous: 2.3. EXERCISE: Defining Relations
William J. Rapaport
2003-09-22