In this paper, we provide a systematic characterization of finite BZMVdM-algebra by using semi-tensor product of matrices. The abstract operation law about logic of the finite algebra is transformed into the simple operation of concrete logical matrices. In addition, we study some properties of BZMVdM-algebra, such as homomorphism, isomorphism, and the product of the BZMVdM-algebra. Through logical matrix operation, the direct verifiable conditions for detecting the above properties are given.
BZMVdM-algebra was firstly proposed by Gattaneo, Giuntini and Pilla in 1997 [1]. It is both an MV-algebra and a distributive de Morgan BZ-lattice. MV-algebra have been introduced by Chang [2] in order to provide an adequate semantic characterization for Lukasiewicz multi-valued logics. Brouwer-Zadeh lattices, first investigated in [3], give rise to fuzzy forms of quantum logics. The defination of BZMVdM-algebra is completely equational, which will be very useful for application to multi-valued logics and their algebraic semanties. Gattaneo, Giuntini and Pilla [1] studied the structure and sketched the main properties of BZMVdM-algebra and prove that BZMVdM-algebra are same as the Stonian MV-algebra. Gattaneo and Ciucci [4] used BZMVdM-algebra as an abstract environment to describe both shadowed and fuzzy set, in such structure it is possible to algebraically define an operator which given a fuzzy set returns a particular induced shadowed set. Gao, Deng and Liu [5] showed that BZMVdM-algebra can induce a quasi-lattice implication algebra, FI algebra, lattice implication algebra and weak algebra.
In the process of concrete research on BZMVdM-algebra, it is not easy to find the finite algebra satisfying the conditions, judge the homomorphism and isomorphism, and obtain the operator operation law of the product of two algebras. Therefore, by using the semi-tensor product (STP) of matrices, the abstract logic operation law is transformed into a simple operation of concrete logic matrix and the operators satisfying the conditions in finite BZMVdM-algebra are characterized by structural matrix. STP was first proposed by researcher Daizhan Cheng as a new matrix product, which has been used in many fields, including complex k-valued logic operations, Boolean networks, fuzzy control, etc [6–8]. It also can be applied for the analysis and control of dynamic systems [9], which can be used to represent the logical variables in a matrix form to realize logic reasoning processes. This paper concerns only finite BZMVdM-algebra, the matrix expression of finite BZMVdM-algebra will be proposed by using STP.
The main contribution of this paper include: (i) The BZMVdM-algebra is systematically characterized by STP method; (ii) Using matrix expressions, the abstract operation law about logic is transformed into the simple operation of concrete logical matrices; (iii) The isomorphism classification problem of finite BZMVdM-algebra is solved, which has not been solved completely before.
This paper is organized as follows. In Section 2, we recall STP and the matrix expression of k-valued logical functions which will be used in this paper. In Section 3, we consider the matrix expression of finite BZMVdM-algebra. In Section 4, Using the structure matrices, the homomorphism and isomorphism of the BZMVdM-algebras are investigated. In Section 5, the product of the algebra is considered. Finally, some conclusions are put in Section 6.
In this paper, we adopt the following notations.
• stands for the set of all real column vectors with order n. stands for the set of all m × n real matrices.
•Col (A) (Row (A)) stand for the set of columns (rows) of A; Coli (A) (Rowi (A)) stand for the i-th column (row) of matrix A.
•In represents the unit matrix with order n. represents the k-th column of In.
•1k represents the k-dimensional column vector whose elements are all one.
•
• represents the set , in particular .
•. And any matrix is called a logical matrix.
•If , then it is expressed and briefly denoted as and L = δn [i1, i2, ⋯, ir].
•The symbol ⋉ and ⊗ are the semi-tensor product and Kronecker product of matrices, respectively.
Preliminary
This section provides a brief survey on STP of matrices and the algebraic expression of k-valued logical functions. First, we give the definition of the STP of matrices as follows.
Definition 2.1. [6] Let is the least common multiple of n and p. Then, the semi-tensor product of A and B is defined as
When n = p, A⋉B = AB. The semi-tensor product of matrices is a generalization of conventional matrix product.
In STP of matrices, it cannot achieve the general commutativity, but also has the following properties.
Proposition 2.2. [6] Let , for any arbitrary real matrix A, we have
Proposition 2.3. [11] Let, then
in which
is called swap matrix.
Proposition 2.4. [11] The swap matrix is invertible and
In order to use STP of matrices to deal with logical problems, it is a key to express logical relations in matrix form. First, we use vectors to represent logical variables.
Definition 2.5. [12] Suppose , then the vector form expression of is denoted as
Similar to classical logic, the vector form expression can also be used at multi-valued logic. Consider k-valued logic, let .
Under the vector form expression, k-valued logical variables x ∈ Δk.
Lemma 2.6. [12] Let F: be an n-ary k-valued logical function. Using vector form expression, F can be expressed as f: Δkn → Δk. There exists a unique logical matrix , MF is the structure matrix of F, such that
in which .
Example 2.7. Considering 3-valued logical (k=3), let , so the vector form expression Δ3. In other word, . Let .
Consider the logical operator negation “¬”, ¬ξ = 1 - ξ. Denote the structure matrice of “¬” as Mn. By Lemma 2.6,
It follows that Mn = δ3 [3, 2, 1].
Proposition 2.8. [13] Suppose x ∈ Δk, the power reducing matrix is defined as , then we have the following formula,
Remark 2.9. In this paper, the traditional matrix product is assumed to be STP, so the symbol “⋉” is mostly omitted for convenience. Supplementary information of properties about STP of matrices is included in the Appendix.
Matrix expression of finite BZMVdM-algebra
In this section, we introduce the BZMVdM-algebra and give the matrix expression of finite BZMVdM-algebra.
Definition 3.1. [1] A BZMVdM-algebra is a system 〈A, ⊕, ¬, ∼, 0〉, where A is a non-empty set of elements, 0 is a constant element of A, ¬ and ∼ are unary operations on A, ⊕ is a binary operation on A, obeying the following axioms:
(x ⊕ y) ⊕ z = (y ⊕ z) ⊕ x,
x ⊕ 0 = x,
¬ (¬ x) = x,
¬ (¬ x ⊕ y) ⊕ y = ¬ (x ⊕ ¬ y) ⊕ x,
∼x ⊕ ∼∼x = ¬0,
x ⊕ ∼∼x = ∼∼x,
∼¬ [¬ (x ⊕ ¬ y) ⊕ ¬ y] = ¬ (∼∼x ⊕ ¬ ∼∼y) ⊕¬∼∼y.
Consider a finite set A = {b1, b2, ⋯, bk}, k < ∞. We convert the elements of A into vector form as . Assume M⊕ (k), Mn (k) and MB (k) (briefly denoted by M⊕, MnandMB) are structure matrices of ⊕, ¬ and ∼, respectively, then we have the following new definition of equivalent algebraic conditions for BZMVdM-algebra.
Definition 3.2. Assume |A| = k < ∞, 〈A, ⊕, ¬, ∼, 0〉 is a BZMVdM-algebra, obeying the following axioms,
M⊕2 = M⊕2W[k2,k],
Mn2 = Ik,
(M⊕Mn) 2 (Ik ⊗ PRk)
= M⊕MnM⊕ (Ik ⊗ MnW[k,k]) PRk,
M⊕ (Ik ⊗ MB2) PRk = MB2,
(Ik ⊗ PRk).
Proof. We only prove (4), other items can be proved similarly. Expressing ¬ (¬ x ⊕ y) ⊕ y = ¬ (x ⊕ ¬ y) ⊕ x into algebraic form, we have
according to Proposition 2.2 and 2.8, the left hand side of Equation (1) is
By Proposition 2.2, 2.3, 2.8 and 7.2, the right hand side of Equation (1) is
Since x, y, z ∈ Δk are arbitrary, (4) follows.□
Through the conditions of the Definition 3.2, we can construct the structure matrix of BZMVdM-algebra. The following example is used to illustrate the construction of the structure matrix.
Example 3.3. (i) Let k = 2, M⊕ (2) = δ2 [a1, a2, a3, a4], Mn (2) = δ2 [b1, b2], MB (2) = δ2 [c1, c2], according to (2) of Definition 3.2, we have a2 = 1, a4 = 2. Then
According to (3) of Definition 3.2, we have b1 ≠ b2. There are two Kleene orthocomplementations “ ¬ ″, which are
The unary operation “∼” have four possibilities, which are
Using the exhaustive method to test, it easy to figure out that there only one BZMVdM-algebra follows the algebraic conditions in Definition 3.2, which is
The BZMVdM-algebra 〈 {a, 0}, ⊕, ¬, ∼, 0〉 is characterized by the tables:
¬
∼
a
0
0
0
a
a
⊕
a
a
a
a
0
a
0
a
a
0
0
0
(ii) Let k = 3, similar calculations show that there are two BZMVdM-algebras, which are
and
Let A = {a, b, 0}, . The BZMVdM-algebra 〈A, ⊕ i, ¬ i, ∼i, 0〉, i = 1, 2 is characterized by the tables:
¬1
∼1
¬2
∼2
a
0
0
a
0
b
b
0
0
0
0
a
a
b
b
⊕1
⊕2
a
a
a
b
a
b
a
b
a
0
a
a
b
a
a
b
b
b
a
b
b
0
b
b
0
a
a
a
0
b
b
b
0
0
0
0
(iii) Let k = 4, similar calculations show as follows:
Namely, when k = 4, there are nine kinds of BZMVdM algebras satisfying Definition 3.2.
Using BZMVdM-algebra structure, we define several new operations:
Assume M⊙, Md and Mc are structure matrices of ⊙, ∨ and ∧, respectively. Similarly, the matrix expression is
Example 3.4. Let A = {1, a, 0}, . According to (ii) in Example 3.3, the structure matrix of operators ⊕, ¬, ∼, ⊙, ∨ and ∧ are expressed as follows:
Using Equation (8)–(10), we have
The properties satisfied by the BZMVdM-algebra can be transformed into the corresponding algebraic form through matrix expression, as follows.
Proposition 3.5.If A is a BZMVdM-algebra, M⊕, Mn and MB are structure matrices of ⊕, ¬ and ∼, then the following results are true:
M⊕ = M⊕W[k,k],
M⊕2 = M⊕ (Ik ⊗ M⊕),
,
,
M⊕MnM⊕ (Ik ⊗ MB2) (Ik2 ⊗ MB2) PRk2
,
Mc (Ik ⊗ MB2) PRk = Ik,
MnMB = MB2,
MBMc = Md (MB ⊗ MB),
MBMd = Mc (MB ⊗ MB),
MB = MB3,
M⊕ (MB ⊗ MB) PRk = MB,
Proof. Recalling the Proposition 7.5 in Gattaneo [1], the corresponding algebraic form can be obtained. We only prove (6), other items can be proved similarly. Expressing ¬x ⊕ ∼∼ x = 1 into algebraic form, we have
the left hand side is
Since x ∈ Δk are arbitrary, (6) follows.□
Connectives ∨ and ∧ are the algebraic realization of logical disjunction and conjunction of a distributive lattice. Then the order is induced as follows.
Definition 3.6. [4] An order “≤” is defined as x ≤ y if and only if x ∨ y = y (equivalently x ∧ y = x), as the notation x < y usually means that x ≤ y and x ≠ y.
BZMVdM-algebra has the following relationship.
Theorem 3.7. [1] Let be a BZMVdM-algebra, the substructure is an MV-algebra. The substructure ∼, 0〉 is a distributive BZ-lattice.
The unary operation ¬ : A ↦ A is a Kleene (or Zadeh) orthocomplementation (negation). It satisfies the properties: (K1) ¬ (¬ a) = a, (K2) ¬ (a ∨ b) = ¬ a ∧ ¬ b, (K3) a ∧ ¬ a ≤ b ∨ ¬ b.
The unary operation ∼ : A ↦ A is a Brouwer orthocomplement (negation). It satisfies the properties: (B1) a ∧ ∼∼ a = a, (a ≤ ∼∼ a), (B2) ∼ (a ∨ b) = ∼ a ∧ ∼ b, (B3) a ∧ ∼ a = 0.
Now we introduce some equivalent conditions of BZMVdM-algebra. According to Proposition 7.6 in the Appendix, the following result is straightforward verifiable.
Proposition 3.8.Assume 〈A, ⊕, ¬, ∼, 0〉 is a BZMVdM-algebra with |A| = k< ∞, for any x, y, z ∈ Δk the following holds:
With M⊕PRkx = x, then Mc (Ik ⊗ Mn) xy = x,
⇔
MBM⊕ = M⊙ (MB ⊗ MB).
Homomorphism and isomorphism
In this section, we study the homomorphism and isomorphism of the BZMVdM-algebra by using the matrix expression method. Moreover, the direct verifiable conditions for detecting homomorphism are obtained by logical matrix operation.
Homomorphism
This subsection gives the necessary and sufficient conditions for algebra homomorphism.
Definition 4.1. [1] Let 〈A, ⊕ 1, ¬ 1, ∼ 1, 01〉 and 〈B, ⊕ 2, ¬2, ∼ 2, 02〉 be two BZMVdM-algebras. We say that the function φ : A → B is a homomorphism of A onto B if
If φ is a homomorphic mapping, we have
Assume |A| = p, |B| = q. Express Then φ : A → B can be expressed in a matrix form as
where is the structure matrix of φ.
Proposition 4.2.Let 〈A, ⊕ 1, ¬ 1, ∼ 1, 01〉 and 〈B, ⊕ 2, ¬2, ∼ 2, 02〉 be two BZMVdM-algebras, |A| = p < ∞, |B| = q< ∞, and φ : A → B. Then φ is a homomorphism, if and only if,
If φ is a homomorphic mapping, we have
Proof. It is sufficient to prove that each formula in the Definition 4.1 is equivalent to the formula in this proposition, so we consider the first formula
the matrix form is
So, we have .□
Isomorphism
In this subsection, we discuss the properties of isomorphism and give some examples.
Definition 4.3. [1] Let 〈A, ⊕ 1, ¬ 1, ∼ 1, 01〉 and 〈B, ⊕ 2, ¬2, ∼ 2, 02〉 be two BZMVdM-algebras. φ : A → B is a homomorphism. If the function φ is one-to-one and onto, then φ is called isomorphism.
Remark 4.4. If φ is an isomorphism, then φ-1 is also an isomorphism.
When the mapping and operations are expressed as concrete logical matrix operations, the isomorphism satisfies the following conditions.
Proposition 4.5.Assume 〈A, ⊕ 1, ¬ 1, ∼ 1, 01〉 and 〈B, ⊕ 2, ¬ 2, ∼ 2, 02〉 with |A| = |B| = p be two BZMVdM-algebras.
(1) φ : A → B is an isomorphism, then
i) The structure matrix of φ is a permutation matrix, and .
ii) The corresponding structure matrices of
satisfies
(2) A and B is isomorphism if and only if exist φ satisfied Mφ is a permutation matrix and such that Equation (11)–(13) established.
Proof. We just prove Equation (11), the others are similar. According to the Proposition 7.2 and 4.2,
□
Here are two examples of determining the isomorphism between finite BZMVdM-algebras.
Example 4.6. When k=3, the only non-trivial isomorphism, which keep 0 unchanged, is Mφ = δ3 [2, 1, 3].
Recall Example 3.3, it is easy to see that and satisfy the Equation (11)–(13). Hence, we have isomorphic BZMVdM-algebra as is isomorphic to .
Example 4.7. Recall Example 3.3. When k=4, there are five non-trivial isomorphisms, which keep 0 unchanged, they are
We can see that . If φj : Ap → Aq is an isomorphism, then φj : Aq → Ap is also an isomorphism. Similarly, , if φ3 (φ4) : Ap → Aq is an isomorphism, then φ4 (φ3) : Aq → Ap is also an isomorphism.
We set , it is easy to verify that the following mappings are isomorphisms:
In conclusions
According to isomorphism, this finite BZMVdM-algebra is divided into two classes.
Product of BZMVdM-algebras
This section mainly discusses the cartesian product of BZMVdM-algebras, and gives the calculation method of the structure matrix of its operator. First, we give the definition of the product BZMVdM-algebras.
Definition 5.1. Let Li = 〈Ai, ⊕ i, ¬ i, ∼ i, 0i〉, i = 1, 2 be two BZMVdM-algebras. Their product can be defined as L = 〈A, ⊕, ¬, ∼, 0〉, where A = A1 × A2 is the cartesian (or direct) product of A1 and A2. Let (x1, x2), (y1, y2) ∈ A1 × A2, define the operator on A as follows:
⊕ : = ⊕ 1 × ⊕ 2,
¬ : = ¬ 1 × ¬ 2,
∼ : = ∼ 1 × ∼ 2,
0 : = (01, 02).
Remark 5.2. According to the Definition 5.1, the product of BZMVdM-algebras is a BZMVdM-algebra. The cartesian product of a finite number of algebras can be similarly defined, and the product is also a BZMVdM-algebra.
Next, consider how to calculate the structure matrix of the operator of product BZMVdM-algebras.
Theorem 5.3. Let Li = 〈Ai, ⊕ i, ¬ i, ∼ i, 0i〉, i = 1, 2 be two BZMVdM-algebras, |A1| = p and |A2| = q. The structure matrices of the operators ⊕i, ¬ i, ∼ i are expressed as and Then, the structural matrices of the corresponding operators of product BZMVdM-algebras are denoted as . It can be calculated as follows:
Proof. Firstly, the elements x ∈ A1 are expressed in vector form as , y ∈ A2 can be expressed as . Similarly, z ∈ A = A1 × A2 can be expressed as . In particular, if , then
in which i = 1, ⋯, p ; j = 1, ⋯, q. Under this expression, we have
We just prove Equation (17), the others are similar. Let x1, y1 ∈ Δp, x2, y2 ∈ Δq. Then we know that
which is equivalent to
□ An example of solving the product of BZMVdM-algebras is given below.
Example 5.4. Let Li = 〈Ai, ⊕ i, ¬ i, ∼ i, 0i〉, i = 1, 2 be two BZMVdM-algebras. |A1|=2, |A2|=3. Recall Example 3.3, let the structure matrices of L1 be Equation (2)-(4), the structure matrices of L2 be Equation (5), according to Equation (17)–(19) we can get
Let the structure matrices of L2 be Equation (6), then
According to Definition 3.2, it is easy to check that the product of L1 and L2 is also a BZMVdM-algebra.
Conclusions
BZMVdM-algebra is a general “fuzzy environment” which can be successfully applied to a number of different fuzzy situations. On the basis of the matrix expression, the finite BZMVdM-algebra and its related properties are transformed into the semi-tensor product operation of concrete logic matrices. Using this expression method, the homomorphism and isomorphism can be easily determined. Isomorphism classification between finite BZMVdM-algebras is realized. At the same time, the operation law of cartesian product of two algebras can also be calculated. Therefore, this method is very convenient, which avoids complex abstract operations, and the examples also illustrate its efficiency.
Acknowledgments
The authors are very indebted to the editors and the anonymous referees for valuable comments and suggestions, which greatly improve the original manuscript of this paper. This research is supported by the Natural Science Foundation of Shandong Province (No. ZR2020MA053).
Appendix
The relevant properties of the STP and Kronecker product of matrices are supplemented as follows.
Proposition 7.1. [6] Let A, B, C be real matrix with proper dimensions, then
The definition of the structure matrix in the multilinear mapping is as follows.
Definition 7.4. [6] Let Wi (i = 0, 1, 2, ⋯, n) be vector spaces, the mapping is a multilinear mapping.
If dim (Wi) = ki, i = 0, 1, ⋯, n, and the base of Wi is , denote
jt = 1, ⋯, kt, t = 1, ⋯, n. Then is called structural constants of the mapping F. Arranging the structural constants as a matrix
MF is called structural matrix of F. Generally, the structural matrix MF of F is called the algebraic expression of F.
According to the definition of BZMVdM-algebra, the following operation law can be deduced.
Proposition 7.5. [1] If A is a BZMVdM-algebra, then the following results are true:
x ⊕ y = y ⊕ x,
(x ⊕ y) ⊕ z = x ⊕ (y ⊕ z),
x ⊕ 1 =1,
x ⊕ ¬ x = 1,
¬ (x ⊕ ∼∼ x) ⊕ ∼∼ x = 1,
¬x ⊕ ∼∼ x = 1,
x ∧ ∼∼ x = x,
¬x ∼ x = ∼∼ x,
∼ (x ∧ y) = ∼ x ∨ ∼ y,
∼ (x ∨ y) = ∼ x ∧ ∼ y,
x ∧ ∼ x = 0,
∼x = ∼∼ ∼ x,
∼x ⊕ ∼ x = ∼ x,
¬0 = ∼1.
Proposition 7.6. [1] Let A be a BZMVdM-algebra, ∀x, y, z ∈ A, then we have
x ∧ y = 0 iff y ≤ ∼ x (x ≤ ∼ y),
withx ⊕ x = x, x ∧ y = 0 iff x ≤ ¬ y,
∼∼ x = x iff ∼ x ⊕ x = 1 iff x ⊕ x = x,
(x ⊕ y) ∧ z = 0 iff x ∧ z = 0 andy ∧ z = 0,
(x ⊕ y) ∧ z = 0 iff z ≤ ∼ x ⊙ ∼ y,
∼ (x ⊕ y) = ∼ x ⊙ ∼ y.
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