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Designing Weave Structures Using Boolean Operations, Part 1

Introduction

Basic weave structures interlacementpatterns can be described in many ways, butthey all come down to representing the cross-ings of warp and weft threads. One or the otheris on top. This is represented in drawdowns bya grid in which the cells represent the intersec-tions and (usually) a cell is black if the warpthread is on top but white if the weft thread ison top. See Figure 1.

Figure 1. Drawdown

From a computational point of view, 1sand 0s instead of colors are the natural repre-sentation of interlacement patterns. See Figure

2, which corresponds to the drawdown ofFigure 1. A 1 corresponds to black for the warpthread on top and a 0 corresponds to white forthe weft thread on top.

0100011001100111111001100110001000010011001100101011001100110111011001100110011001100110011001101110110011001101010011001100100001000110011001111110011001100010000100110011001010110011001101111011100110011000000110011001110111101100111011010100100011001000010001100100011111100010011000100001001100010010101101110011011110111000011001100110011000011101111011001110110011001000110010000100011001000110011000100110001000010011000100110011011100110111101110011011100110011101100111010011001100101100110010110011001110011001100001100110000110011001000100110001001100110111001101111011100110111001100111011001110111101100111011001100100011001000010001100100011001100010011000100001001011001100110011001011011110111001101110000001110110011101111011001110110101001000110010000100011001000111111000100110001000010011001100101011001100110111101110011001100000011001100111011110110011001101010011001100100001000110011001111110011001100010110011001100110011001100110011001011100110011000000110011001110111101100110011010100110011001000

Figure 2. Binary Interlacement Pattern

This binary representation suggests theuse of Boolean operations for weave design.

Boolean Operations

George Boole (see the side-bar on the nextpage) invented the mathematical systemnamed after him to describe logical operationson truth values true or false [1].

Although Boole was motivated by logic,his system applies equally well to contexts inwhich there are two mutually exclusive val-ues, such as on and off. In the case ofweave structures, the values are warp ontop and weft on top, or alternatively, it istrue that the warp is on top and it is false thatthe warp is on top. (The choice of warp rather

than weft is arbitrary, as is the choice of 1 and0 to represent truth values.)

In Boolean algebra [2], variables, whichare indicated by x, y , and so forth, can haveonly two values 1 or 0. Boolean operationsproduce values depending on the values of thevariables to which they are applied. The opera-tions, however, are not the familiar arithmeticones, but rather logical operations like and andor.

Boolean operations are described by truth

tables that detail the results depending on thevalue of the variables to which the operatorsare applied. An example is not, also known ascomplementand negation, indicated by the sym-bol ~. This operation has the truth table

not

Other basic Boolean operations are or (+),also known as disjunction , and and (), alsoknown as conjunction. Their truth tables are

or

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and

Note that ~(x +y) = (~x ~y) and ~(xy)= (~x + ~y). These are known as De MorgansLaws, named after the 19th century logicianand mathematician Augustus De Morgan, whopropounded them.

A particularly interesting Boolean opera-tion is exclusive or (), which has the truth table

exclusive or

That is, xy has the value 1 if exactly one ofxandy is 1 it excludes the case that both are.The + operations sometimes is called inclusiveor to distinguish it from exclusive or.

Exclusive or has an interesting and impor-tant property:

(xy) y = x

(xy) x = y

That is, eitherx or y can be extracted from(x y) by applying exclusive or with the other.

The complement ofexclusive or is equiva-lence (), which has the value 1 only if x and yare the same.

equivalence

Another important Boolean operation isimplication (), which is based on modus ponens,one of the foundations of logical argument: Ifx impliesy and x is true, theny is true.

George Boole

George Boolegrew up in povertyin England. Heearly exhibited in-

tellectual powersand showed a spe-cial aptitude formathematics.

He was un-able to pursue aformal education because he had to workto support his parents.

He undertook to learn mathematicson his own and soon began to do originalwork.

His work attracted the attention ofprominent mathematicians and he beganto publish in mathematical journals. Heeventually was awarded a gold medal bythe Royal Society.

He contributed to several areas ofmathematics, but he is best known for hisseminal work on the mathematics of logic.

This work is the foundation for mod-ern computing and information technol-

ogy.Because of his need to work and lack

of formal training in mathematics, hestarted late. Unfortunately, he died early.

He had hereditary lung disease.Caught in a drenching rain and late to alecture, he continued without changing todry clothes. He subsequently contractedpneumonia.

His wife, who thought the only way to

cure a disease was to apply its cause,drenched him with cold water as he layfeverish in bed. He died shortly thereafter.

We can only speculate as to what Boolemight have accomplished had he had theopportunity to get a formal education andhad lived longer.

1815 - 1864

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implication

All together there are 16 Boolean opera-tions of two variables, corresponding to the 16possible patterns of 0 and 1 for the four pos-sible combinations of the variable values.

If we use the order of the values ofx andy as given in the truth tables above, we canrepresent the 16 Boolean operations of twovariables by the patterns of the values theyproduce.

For example, or and and have the valuepatterns

1110 or

1000 and

It is possible to use only a smallfunction-ally complete set of Boolean operations fromwhich all 16 can be composed. Two function-ally complete sets are {~, +} and {~, }. Thereare several other small functionally completesets. In fact, there are single operations from

which all others can be composed. See the side-bar Sheffer Strokes.

So far, we have identified Boolean opera-tions by names and operator symbols. We canalso identify them by the hexadecimal charac-ters for their value patterns. For example, orhas the hexadecimal identification e and andhas the hexadecimal identification 8.

The complete list of 2-variable Booleanoperations, with hexadecimal identifications

and names and symbols for common opera-tions is

0000 00001 10010 20011 30100 40101 50110 6 exclusive or xy0111 7

Sheffer Strokes

In a 1913 paper [1], Henry M. Sheffershowed that one of the 16 Boolean opera-tions constitutes a functionally completeset in itself. This operation, called the Sheffer

Stroke and designated by the symbol, hasthe value pattern 0111 and the hexadeci-

mal identification 7. This operation can bedescribed as not bothxandy.

It can be shown that

~x = xy

and

x +y = (xy) (y x)

Since it is well known that {~, +} con-

stitutes a functionally complete set, then{} does also.

The second Sheffer Stoke, designatedby the symbol , has the value pattern 0001and the hexadecimal identification 1. Italso constitutes a functionally completeset.

While it may be interesting to knowthat only one operation is necessary toform all Boolean operations of two vari-

ables, using just one operation is compli-cated and unintuitive. These operationsare, however, good for making up home-work problems.

Reference

1. A Set of Five Independent Postulatesfor Boolean Algebras, with Application toLogical Constants, Transactions of theAmerican Mathematical Society , Vol. 14(1913), pp. 481-488.

1000 8 and x y1001 9 equivalence x y1010 a1011 b implication x y1100 c1101 d1110 e (inclusive) or x + y1111 f

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=

Figure 5. Exclusive OrSpot Weave

Other weaves can be used for the ground.Figure 6 shows a 2/2 twill in place of the plainweave in Figure 5.

=

Figure 6. Twill-Based Spot Weave

Other ApplicationsThe concept of combining figure and

ground implies a fundamental distinction be-tween the two. Boolean operations can, ofcourse, be applied to any two weaves. Thequestion is what kinds of weave and whichoperations produce good results. Figure 7shows the result of combining a 2/2 twill witha basket weave.

+ =

Figure 7. Combining Plain and BasketWeaves

Comments

Boolean operations provide a natural wayto combine two (or more) interlacement pat-

terns to form new ones. As in all matters ofdesign, artistic sense and understanding of thetools used are essential.

There are two potential problems associ-ated with using Boolean operations in weavedesign: long floats and the loom resourcesrequired.

In Boolean operation value patterns, 1stend to add warp floats and 0s tend to add weftfloats.

The balanced Boolean operations, whichhave two 1s and two 0s in their value patternsgenerally cause fewer problems with floatsthan the unbalanced ones. Note that there isonly one balanced operation, exclusive or , inthe functionally complete design set describedearlier.

The problem of loom resources is moreserious and difficult to gauge in design. One ofOelsners examples of diversified weaves has60 ends and 60 picks and would require 60shafts and 60 treadles (the maximum possiblefor a weave of this size). While this weavecould be done on a drawloom, it really is in theprovince of Jacquard weaving.

Advanced Boolean Design

In this article, one Boolean operation hasbeen applied to all the variables in two inter-lacement patterns.

The next article in this series describes theuse of arrays of Boolean operations, in whichdifferent operations can be applied to differentparts of the interlacement patterns.

References:

1. An Investigation of the Laws of Thought on

which are Founded the Mathematical Theoriesof Logic and Probabilities , George Boole, 1854,Dover reprint, 1973.

2. Boolean Algebra and its Applications, J. EldonWhitesitt, Addison-Wesley, 1961

3. A Handbook of Weaves , G. H. Oelsner,Macmillan, 1915. pp. 147.

Ralph E. Griswold

Department of Computer ScienceThe University of Arizona

Tucson, Arizona

2002 Ralph E. Griswold