Multiplying beliefs together

 

Syntax

1. BD>matmult : v(I1,B1,B2)=v(I2,B3,B4)*v(I3,B5,B6)

2. BD>matmult : v(I1,B1,B2)=v(I2,B3,B4)*r(I3,B5,B6)

3. BD>matmult : v(I1,B1,B2)=r(I2,B3,B4)*v(I3,B5,B6)

4. BD>matmult : v(I1,B1,B2)=r(I2,B3,B4)*r(I3,B5,B6)

where I1,I2,I3 are valid belief store numbers, and are the names of bases or elements. In all parts, v(1,B1,B1) may be abbreviated to v(1,B1).

The MATMULT:  command is used to multiply beliefs together. The first form of the syntax essentially defines

where represdent collections, although the numbers involved may not actually be covariances per se. The left hand side of the equality defines the place where the result of the multiplication is to be stored, and the right hand side defines the product to be stored.

The dimensions of the collection must be compatible for the multiplication. Thus, the dimensions of B1 and B3 must match; the dimensions of B2 and B6 must match; and the dimensions of B4 and B5 must match.

The remaining forms of the syntax show how we ask for transformation to correlation form before carrying out the multiplication.

An error will occur when a part of the result of the product is asymmetric, and the intended storage position requires symmetric beliefs. An illustration of the kind of problem that might arise is given in §6.8.5.