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(1)

V P Tsvetov1

1Samara National Research University, Moskovskoe Shosse 34А, Samara, Russia, 443086

e-mail: [email protected]

Abstract. Algebras of finitary relations naturally generalize the algebra of binary relations with the left composition. In this paper, we consider some properties of such algebras. It is well known that we can study the hypergraphs as finitary relations. In this way the results can be applied to graph and hypergraph theory, automatons and artificial intelligence.

1. Introduction

It is obvious that graphs and binary relations are closely related. We often use the facts of the binary relations theory in graph theory to solve some algorithmic problems. In the same way, we can consider hypergraphs as finitary relations. This could be a good idea for IT and AI, especially for pattern recognition and machine learning [1-13].

By now it has become common to use universal algebras [14] in various applications [15].

Algebraic methods can also be efficiently applied in graph theory. For example, the shortest path problem can be solved by transitive closure algorithm for binary relation [16].

In this way, and following by [17], we are going to study hypergraphs as elements of algebraic structures.

At first, we define a (n-uniform) hypergraph as a finitary relation on finite set U, in other words, as a subset of Un. In case of n=2 this leads to graph as a binary relation. Boolean algebras

( )

2U U× , ∪ ∩ ∅, , , ,U U× and 2 ,Un

(

∪ ∩ ∅, , , ,Un

)

are well known to us.

It is less trivial to define the inverse operation and the left composition for finitary relations. We have to start from inverse operation, left and right compositions for binary relations:

( ) ( )

{ }

1

2, 1 | 1, 2

R = u u u uR , (1)

( ) ( ) ( )

{ }

1 2 1, 2 | 0 1, 0 1 0, 2 2

RR = u uu u uRu uR , (2) R1R2 = R2◦R1 = {(u1,u2) |Ǝ u0(u0,u2)ЄR1^(u1,u0) Є R2} (3) Note that are isomorphic monoids, where I is identity relation on U. By the way, we can define operations

1

1 1 2 1 2

RR =RR , (4)

(5)

1

1 2 2 1 2

RR =RR , (6)

(2)

(7)

1 1

1 3 2 1 2

RR =RR , (8)

(9) This makes it possible to set the following pairs of isomorphic magmas.

(

1

) (

1

)

2U U× , ,I  2U U× , ,I are isomorphic magmas with left identity elements.

(

2

) (

2

)

2U U× ,  ,I  2U U× , ,I are isomorphic magmas with right identity elements.

( )

3

( )

3

2U U× ,   2U U× ,  are isomorphic magmas without identity elements.

It is easy to see that in the symmetric case R=R1 all of monogenic monoids

{ }

Rn n=0, ,

( )

I ,

{ }

Rn n=0, ,

( )

I ,

{ }

Rn n=0,

(

i,I

)

,

{ }

Rn n=0,

(

i,I

)

(i1..3) are equal.

The monogenic monoid

{ }

Rn n=0, ,

( )

I and distributive algebraic structure

{ }

Rn n=0, , , ,

(

∪ ∅I

)

are useful to treat all-pairs shortest path problem [16]. We are going to define and study hypergraph operations similar to (1)-(9).

2. Algebras of finitary relations

Let us consider the underlying set of finitary relations 2Un, and define the following unary and binary operations for ij

( ) ( )

{ }

(ij) (ji)

1,.., j,.., ,..,i n | 1,.., ,..,i j,.., n

R =R = u u u u u u u uR , (10)

( ) ( ) ( )

{ }

1 ij 2 1,.., ,..,i j,.., n | 0 1,.., 0,.., j,.., n 1 1,.., ,..,i 0,.., n 2

RR = u u u uu u u u u ∈ ∧R u u u uR . (11)

Obviously, the operation (10) is an involution.

( )

R(ij) (ij)=R. (12)

Moreover,

1 ij 2 2 ji 1

RR =RR . (13)

It is easy to prove that operation (11) is associative. Actually,

(

u1,.., ,..,ui uj,..,un

)

R1ij

(

R2ij R3

)

⇔ ∃u0

(

u1,..,u0,..,uj,..,un

)

R1

(

u1,.., ,..,ui u0,..,un

)

R2ij R3

( ) ( ( ) ( ) )

0 1,.., 0,.., j,.., n 1 0 1,.., 0,.., 0,.., n 2 1,.., ,..,i 0,.., n 3

u u u u u R uu uu u R u u uu R

⇔ ∃ ∈ ∧ ∃ ∈ ∧ ∈ ⇔

( ) ( )

( ) ( )

0 0 1,.., 0,.., j,.., n 1 1,.., 0,.., 0,.., n 2 1,.., ,..,i 0,.., n 3

uu u u u u R u uu u R u u uu R

⇔ ∃ ∃ ∈ ∧ ∈ ∧ ∈ ⇔

( ) ( )

0 1,.., 0,.., j,.., n 1 ij 2 1,.., ,..,i 0,.., n 3

uu uu u R R u u uu R

⇔ ∃ ∈  ∧ ∈ ⇔

(

u1,.., ,..,ui uj,..,un

) (

R1 ij R2

)

ij R3

⇔ ∈   .

Then we set

( )

{

1,.., ,.., ,.., | 1..

}

2Un

ij i j n k j i

I = u u u u kn∧ ∈ ∧u U u =u ∈ . (14) It is easy to see

(

u1,.., ,..,ui uj,..,un

)

Iijij R⇔ ∃u0

(

u1,..,u0,..,uj,..,un

)

∈ ∧Iij

(

u1,.., ,..,ui u0,..,un

)

∈ ⇔R

( ) ( )

0 1,.., ,..,i 0,.., n j 0 1,.., ,..,i j,.., n

u u u u u R u u u u u u R

⇔ ∃ ∈ ∧ = ⇔ ∈ ,

and similarly

(

u1,.., ,..,ui uj,..,un

)

Rij Iij ⇔ ∃u0

(

u1,..,u0,..,uj,..,un

)

∈ ∧R

(

u1,.., ,..,ui u0,..,un

)

Iij

( ) ( )

0 1,.., 0,.., j,.., n i 0 1,.., ,..,i j,.., n

u u u u u R u u u u u u R

⇔ ∃ ∈ ∧ = ⇔ ∈ .

Thus,

(3)

ij ij ij ij

IR=RI =R. (15)

Hence we have just proved the

Lemma 1. 2 ,Un

(

ij,Iij

)

is a monoid.

Note that

(

u1,.., ,..,ui uj,..,un

) (

R1ij R2

)

(ij)

(

u1,..,uj,.., ,..,ui un

)

R1ijR2

( ) ( )

0 1,.., 0,.., ,..,i n 1 1,.., j,.., 0,.., n 2

u u u u u R u u u u R

⇔ ∃ ∈ ∧ ∈ ⇔

( )

(ij)

( )

(ij)

0 1,.., ,..,i 0,.., n 1 1,.., 0,.., j,.., n 2

u u u u u R u u u u R

⇔ ∃ ∈ ∧ ∈ ⇔

(

u1,.., ,..,ui uj,..,un

)

R1(ij) jiR2(ij)

(

u1,.., ,..,ui uj,..,un

)

R2(ij) ijR1(ij)

⇔ ∈  ⇔ ∈  .

In that way

(

R1ijR2

)

(ij) =R1(ij)ji R2(ij)=R2(ij)ijR1(ij). (16) Hence the bijective function f R

( )

:=R(ij) is an isomorphism of monoids 2 ,Un

(

ij,Iij

)

and

( )

2 ,Unji,Iji . Moreover,

(

u1,.., ,..,ui uk,..,uj,..,un

)

(

R1ik R2

)

(ij)

(

u1,..,uj,..,uk,.., ,..,ui un

)

R1ik R2

( ) ( )

0 1,.., 0,.., k,.., ,..,i n 1 1,.., j,.., 0,.., ,..,i n 2

u u u u u u R u u u u u R

⇔ ∃ ∈ ∧ ∈ ⇔

( )

(ij)

( )

(ij)

0 1,.., ,..,i k,.., 0,.., n 1 1,.., ,..,i 0,.., j,.., n 2

u u u u u u R u u u u u R

⇔ ∃ ∈ ∧ ∈ ⇔

(

u1,.., ,..,ui uj,..,un

)

R1(ij) jkR2(ij)

(

u1,.., ,..,ui uj,..,un

)

R2(ij) kjR1(ij)

⇔ ∈  ⇔ ∈  .

From which we obtain

(

R1ikR2

)

(ij) =R1(ij)jk R2(ij)=R2(ij)kjR1(ij). (17) Hence we have proved the

Lemma 2. Monoids 2 ,Un

(

ik,Iik

)

and 2 ,Un

(

jk,Ijk

)

are isomorphic, as well as monoids

( )

2 ,Unij,Iij and 2 ,Un

(

ji,Iji

)

.

Let us set an algebraic structure 2 ,Un

(

 ij, ik,Iij,Iik

)

and then we can write the following logical consequences:

(

u1,.., ,..,ui uj,..,uk,..,un

)

R1ij

(

R2ik R3

)

⇔ ∃u0

(

u1,..,u0,..,uj,..,uk,..,un

)

R1

(

u1,.., ,..,ui u0,..,uk,..,un

)

R2 ikR3 u0 u0

(

u1,..,u0,..,uj,..,uk,..,un

)

R1

∧ ∈  ⇔ ∃ ∃ ∈ ∧

(

u1,..,u0′,..,u0,..,uk,..,un

)

R2

(

u1,.., ,..,ui u0,..,u0′,..,un

)

R3

∧ ∈ ∧ ∈ ⇔

( ) ( )

0 0 1,.., 0,.., j,.., k,.., n 1 1,.., 0,.., 0,.., k,.., n 2

uu u u u u u R u uu u u R

∃ ∃ ∈ ∧ ∈ ∧

(

u1,.., ,..,ui u0,..,u0′,..,un

)

R3

∧ ∈ ⇒

( ) ( )

( )

0 0 1,.., 0,.., j,.., k,.., n 1 1,.., 0,.., 0,.., k,.., n 2

uu u u u u u R u uu u u R

∃ ∃ ∈ ∧ ∈ ∧

( )

(

u0 u1,.., ,..,ui u0,..,u0′,..,un R3

)

u0

(

u1,..,u0′,..,uj,..,uk,..,un

)

R1 ij R2

∧ ∃ ∈ ⇔ ∃ ∈  ∧

( ) ( )

(

u0 u1,.., ,..,ui u0,..,u0,..,un R3 u1,..,u0,..,uj,..,u0,..,un 1R

)

∧ ∃ ∈ ∧ ∈ ⇔

( ) ( )

0 1,.., 0,.., j,.., k,.., n 1 ij 2 1,.., ,..,i j,.., 0,.., n 3 ij1R

uu uu u u R R u u u uu R

⇔ ∃ ∈  ∧ ∈  ⇔

(

u1,.., ,..,ui uj,..,uk,..,un

) (

R1 ijR2

) (

ik R3 ij1R

)

⇔ ∈    .

This means that the following Lemma is true.

(4)

Lemma 3. In an ordered algebra 2 ,Un

(

 ij, ik, , Iij,Iik,0 ,1R R

)

, the pseudo distributive law holds

( ) ( ) ( )

1 ij 2 ik 3 1 ij 2 ik 3 ij1R

RRRRRR  . (18)

According to [17], we use the notation 1 :R =Un and 0 :R = ∅. Then look at composition

( ) ( ) ( )

( ) ( )

(ij) (ij)

1 0 1 0 1 0

0 1 0 1 0

,.., ,.., ,.., ,.., ,.., ,.., ,.., ,.., ,..,

,.., ,.., ,.., ,.., ,.., ,.., .

i j n ij j n i n

j n i n

u u u u R R u u u u u R u u u u R

u u u u u R u u u u R

∈ ⇔ ∃ ∈ ∧ ∈ ⇔

⇔ ∃ ∈ ∧ ∈

(19) Definition 1. The finitary relation R is called a function from i-th to j-th argument if

( ) ( )

1,..., ,..,i j, j,.., n 1,.., ,..,i j,.., n 1,.., ,..,i j,.., n j j

u u u uu u u u u R u u uu R u u

∀ ∈ ∧ ∈ → = . (20)

We can obtain from (19) - (20) the following set inclusion

(

u1,.., ,..,ui uj,..,un

)

Rij R(ij)ui=uj

(

u1,.., ,..,ui uj,..,un

)

IijRij R(ij)Iij. (21) Definition 2. The finitary relation R is called a surjection from i-th argument if

( )

1,..., i1, i 1,.., j,.., n 0 1,.., 0,.., j,.., n

u u u+ u u u u u u u R

∀ ∃ ∈ . (22)

From (21) - (22) we can get the reverse set inclusion

(ij)

ij ij

IRR . (23)

Thus, in the case of R is a surjective function from i-th to j-th argument we have the equality

(ij)

ij ij

RR =I . (24)

Similarly, in the case of R is a surjective function from j-th to i-th argument we have the equality

(ij)

ij ij

RR =I . (25)

Let us denote the set of surjective functions from both (i-th to j-th and j-th to i-th) arguments as Fij. It is easy that Fij is closed by ij, and hence we have proved the

Lemma 4. Fij,

(

ij,Iij

)

is a subgroup of the monoid 2 ,Un

(

ij,Iij

)

.

As well as binary relations, finitary relations have the following properties [17]

( ) ( ) ( )

1 ij 2 3 1 ij 2 1 ij 3

RRR = RRRR , (26)

(

R2R3

)

ij R1=

(

R2ij R1

) (

R3ij R1

)

, (27)

( ) ( ) ( )

1 ij 2 3 1 ij 2 1 ij 3

RRRRRRR , (28)

(

R2R3

)

ijR1

(

R2ijR1

) (

R3ij R1

)

, (29) and so we can set an algebraic structures Fij,

(

ij,Iij

)

, 2 ,Un

(

∪ ∩, , ij, ik,(ij), ,0 ,1 ,R R I Iij, ik

)

that have properties (12)-(18), (24)-(29).

3. Conclusion and examples

We have defined algebraic structures of finitary relations as a common case of well-known algebraic structures of binary relations. We have considered the algebraic structures on an underlying set 2Un and sometimes called a finitary relation R∈2Un by a (n-uniform) hypergraph. The operation ij can be called the “straightening the edges” or “deleting shared intermediate vertices”. Let us take an example.

Example 1 (algebraic). Let us set U =

{

u u u u0, ,1 2, 3

}

, 2 ,U3

(

23,I23

)

, and

( ) ( )

{

1, 0, 3 , 1, 2, 0

}

R= u u u u u u . Now we can get

(5)

( ) ( ) ( ) ( )

( ) ( ) ( ) ( )

( ) ( ) ( ) ( )

( ) ( ) ( ) ( )

0 0 0 0 1 1 0 2 2 0 3 3

1 0 0 1 1 1 1 2 2 1 3 3

23

2 0 0 2 1 1 2 2 2 2 3 3

3 0 0 3 1 1 3 2 2 3 3 3

, , , , , , , , , , , ,

, , , , , , , , , , , ,

, , , , , , , , , , , ,

, , , , , , , , , , ,

u u u u u u u u u u u u u u u u u u u u u u u u

I u u u u u u u u u u u u

u u u u u u u u u u u u

 

 

 

=  

 

 

 

,

( )

{ }

23 1, 2, 3

RR= u u u ,

23 23

RRR= ∅.

Despite its simplicity, operation 23 has some interesting applications. In examples 2, 3 we are going to denote 3-tuple

(

u u ui1, i2, i3

)

as a word

1 2 3

i i i

u u u .

Example 2 (feature selection). Let R=

{

u u u u u u u u u u u u u u u u u u1 0 0, 1 1 0, 1 2 0, 1 2 1, 1 2 3, 1 3 0

}

be a set of words, and Rf =

{

u u u1 0 3

}

, R(23)f =

{

u u u1 3 0

}

are filters. First, apply the filter Rf

{ }

23 1 0 3, 1 1 3, 1 2 3, 1 3 3

RfR= u u u u u u u u u u u u . Then apply the filter R(23)f

{ }

(23)

23 23 1 0 0, 1 1 0, 1 2 0, 1 3 0

f f

RRR= u u u u u u u u u u u u .

Example 3 (crossover). Let R=

{

u u u u u u u u u u u u1 0 0, 1 1 0, 1 2 1, 1 3 2

}

be a population. Let us define the evolution operator Ε

( )

R = ∪R R23R and start a first step of evolution

( ) {

R u u u u u u u u u u u u u u u u u u1 0 0, 1 1 0, 1 2 0, 1 2 1, 1 3 1, 1 3 2

}

Ε = .

In example 4 we are going to denote 3-tuple

(

u u ui1, i2, i3

)

as an implies ui1

(

ui2ui3

)

.

Example 4 (AI). Let R=

{

u1

(

u1u1

)

,u1

(

u1u2

) }

be a base set of AI premises. Let us define the semantic closure of R as

[ ] (

( )23

)

1

k

k

R R R

=

=

, where Rk+1=Rk23R and R1=R. By definition we have

[ ]

R =

{

u1

(

u1u1

)

,u1

(

u1u2

)

,u1

(

u2u1

)

,u1

(

u2u2

) }

.

Note that

( (

u1

(

u0u3

) )

(

u1

(

u2u0

) ) )

(

u1

(

u2u3

) )

is tautology, so the inference rule u1

(

u0u3

)

,u1

(

u2u0

)

ђu1

(

u2u3

)

preserves truth.

We also note that

( ( (

u1u0

)

u3

)

( (

u1u2

)

u0

) )

( (

u1u2

)

u3

)

is tautology, too.

It makes perfect sense to use an indicator function χR:Un

{ }

0,1 for R∈2Un, that is defined as

( ) ( )

( )

1 1

1

1, ,.., ,.., 0, ,..,

n

R n

n

u u R

u u

u u R

χ = 

 ∉ .

In the case of finite set U =

{

u1,..,um

}

, we can use this function to define a join-vertices logical array ψR: 1..

(

m

)

n

{

false true,

}

for (n-uniform) hypergraph. Let f : 1..mU be a total bijection and R∈2Un. We define

( ) ( ( ) ( ) )

( ) ( )

( )

1

1 1

1

,.., 1 1 1

1

, ,.., 1

,..,

, ,.., 0

n

R n

R R

k k n

R n

true f k f k

k k

false f k f k

ψ ψ χ

χ

 =

= = 

 = .

Let us denote

{

false true,

}

as D and a set of logical array defined above as D(1..m)n.

(6)

We also can set a logical algebra that generalized adjacency matrices algebra. In this way we define a binary operation ∗ij on (1.. )

mn

D

1 1 1 1 1 1 1 1

1 2 1 2

,.., ,.., ,.., , , ,.., ,.., ,.., ,.., , , ,.., 1

n n i i j n i j j n

m

k k ij k k k k s k k k k k k s k k

s

ψ ψ ψ + ψ +

=

∗ =

.

By our construction semigroups 2 ,Un

( )

ij and D(1..m)n,

( )

ij are isomorphic.

More interesting is the case of algebraic structures on an underlying set

12Un

n

= and operations from 2Un to 2Um. For example, let us define the operations “gluing edges” g and “replacing chains”

r.

( ) ( ) ( )

{ }

1 g 2 1,.., m 1, 2,.., n | 0 1,.., m 1, 0 1 0, 2,.., n 2

RR = u u uu′ ∃u u u uRu uu′ ∈R ,

( ) ( ) ( )

{ }

1 r 2 1,.., i 1, j1,.., n | 0 1,.., i 1, 0,.., m 1 1,.., 0, j1,.., n 2

RR = u u u+ u′ ∃ ∃ ∃u i j u u u u ∈ ∧R uu u+ u′ ∈R . For the finitary relation R=

{ (

u u u1, 0, 3

) (

, u u u1, 2, 0

) }

from Example 1 we can get

( ) ( )

{ }

(13)

3, 0, 1 , 0, 2, 1

R = u u u u u u ,

( ) ( )

{ }

(13)

1, 0, 0, 1 , 1, 2, 2, 1

RgR = u u u u u u u u ,

( ) ( ) ( ) ( ) ( ) ( ) ( )

{

1 , 0, 3 , 1, 0 , 1, 2 , 1, 3 , 2, 0 , 1, 2, 3

}

RrR= u u u u u u u u u u u u u u .

It is clear that even in the case of finite set U we would never make a finite representation for such algebraic structures. But in particular cases, maybe we can. This case is of interest.

4. References

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[3] Louis A 2015 Hypergraph markov operators, eigenvalues and approximation algorithms Proceedings of the Forty-Seventh Annual ACM on Symposium on Theory of Computing 713-722

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[7] Panagopoulos A, Wang C, Samaras D and Paragios N 2013 Simultaneous cast shadows, illumination and geometry inference using hypergraphs IEEE Transactions on Pattern Analysis and Machine Intelligence 35(2) 437-449

[8] Wang M, Wu X 2015 Visual classification by l1-hypergraph modeling IEEE Transactions on Knowledge and Data Engineering 27(9) 2564-2574

[9] Zhou D, Huang J and Scholkopf B 2007 Learning with Hypergraphs: Clustering, Classification, and Embedding Advances in Neural Information Processing Systems: Proceedings of the 2006 Conference 19 1601-1608

[10] Ghoshdastidar D, Ambedkar D 2014 Consistency of Spectral Partitioning of Uniform Hypergraphs under Planted Partition Model Advances in Neural Information Processing Systems 27: Annual Conference on Neural Information Processing Systems 397-405

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[11] Ghoshdastidar D, Ambedkar D 2015 A Provable Generalized Tensor Spectral Method for Uniform Hypergraph Partitioning Proceedings of the 32nd International Conference on Machine Learning, ICML 400-409

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[14] Mal’tsev A I 1973 Algebraic systems (Springer) p 319

[15] Chernov V M 2018 Ternary number systems in finite fields Computer Optics 42(4) 704-711 DOI: 10.18287/2412-6179-2018-42-4-704-711

[16] Tsvetov V P 2014 On a syntactic algorithm on graphs Proceedings of the International Conference Advanced Information Technologies and Scientific Computing (Samara, Russia) 235-238

[17] Tsvetov V P 2018 Dual ordered structures of binary relations Proceedings of the International Conference Information Technology and Nanotechnology. Session Data Science (Samara, Russia) 2635-2644

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