My work is based upon that of Bernard Jancewicz, e.g.: The extended Grassmann algebra of R3. Clifford (geometric) algebras (Banff, AB, 1995), 389--421, Birkhauser Boston, Boston, MA, 1996 Here is a brief description of the relationships between Jancewicz's work and my algebra. I will exhibit a table (in two parts). Here e_x, e_y, and e_z constitute an orthonormal basis of vectors for three-space with a Euclidean metric to be definite. Also where Jancewicz uses the term odd (previously, pseudo-) I use twisted. Similarly, where he uses the term even (previously, no prefix) I use straight. Analogous to the notation of differential geometry I symbolize the unit straight positively-oriented trivector as an upper case Omega = e_xyz = e_x /\ e_y/\ e_z. This table introduces two new representations for directed quantities. Directed | Jancewicz | Differential Quantitiy | (modified) | Geometry ------------------------------------------------------ Straight Scalar | 1 | 1 Twisted Scalar | r | (1, Omega) Straight Vector | e_x | e_x Twisted Vector | r e_x | (e_x, Omega) Straight Bivector | e_xy | e_xy Twisted Bivector | r e_xy | (e_xy, Omega) Straight Trivector | e_xyz | e_xyz Twisted Trivector | r e_xyz | (e_xyz, Omega) Directed | Extremum | Correlated Quantitiy | Grade Form | Grade Form ------------------------------------------------------ Straight Scalar | [1, 1] | [1, 1] Twisted Scalar | [Omega, 1] | [Omega, 1] Straight Vector | [1, e_x] | [e_x, e_x] Twisted Vector | [Omega, e_x] | [e_yz, e_x] Straight Bivector | [1, e_xy] | [e_xy, e_xy] Twisted Bivector | [Omega, e_xy] | [e_z, e_xy] Straight Trivector | [1, Omega] | [Omega, Omaga] Twisted Trivector | [Omega, Omega] | [1, Omega] Let us use the abbreviations EGF and CGF for extremum grade form and correlated grade form, respectively. I use the square brackets to denote that the EGF and CGF are equivalence classes of ordered pairs. Then you will notice that the EGF of twisted multivectors rather directly corresponds to the standard notation of differential geometry except for the reversal of the order of the elements in the ordered pairs (although that notation is usually applied to twisted forms rather than multivectors). The EGF is a symbolic analog of one type of icon that Burk uses to represent twisted multivectors (see, for example, the left hand side of Figure 28.10 of "Applied Differential Geometry"), again with a reversal of the two components of the ordered pair. Now the CGF is a symbolic analog of the other form of icon on the right hand side of Burke's Figure 28.10. Very importantly this icon represents the natural or native geometrical structure of a twisted multivector as it arises in the fundamental measurement procedures of physical theories. For examples from electromagnetism see Tonti, "On the Geometrical Structure of Electromagnetism," Figures 1(c) and (d) and accompanying text (available at http://discretephysics.dic.units.it/papers/TONTI/Electrom%20Algebraic%20Topology.pdf). The order chosen for the components of the EGF and CGF is meant to mimic the familiar placement of the sign (+ or -) in front of a numerical quantity. The first component in these forms is then a generalized sign which represents what Jancewicz has called (following Lounesto) a "direction" comprising an attitude and orientation. I have chosen the second component to be a carrier of both a direction and relative magnitude. Thus, these notations are redundunt. Any extended (straight or twisted) multivector may be represented as a linear combination of basis multivectors in EGF or CGF form. The extremum grade form is so named because its first component is always either of grade zero or the largest grade possible in the space under oonsideration, say, n. The correlated grade form is so named because its two components' grades are correlated so that either they are equal or they sum to n. The interesting thing is that one can define a generalized exterior product among straight and twisted multivectors represented in the CGF. The second components of the CGF multiply as the normal exterior product of straight multivectors. However, one finds that the first components must multiply as the product of the new algebra -- the OC product. The OC product is not only essential to the exterior product of straight and twisted multivectors as represented in the CGF, but also is key to the interconversion of the EGF and CGF. There are a more complications, but I will end here.