PREVIEW 1 Towards Consistency and Complementarity A Multiview Graph Information Bottleneck Approach

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PREVIEW 1
Towards Consistency and Complementarity: A
Multiview Graph Information Bottleneck Approach
Xiaolong Fan, Maoguo Gong, Senior Member, IEEE, Yue Wu, Member, IEEE,
Mingyang Zhang Member, IEEE, Hao Li, and Xiangming Jiang
Abstract—The empirical studies of Graph Neural Networks
(GNNs) broadly take the original node feature and adjacency
relationship as singleview input, ignoring the rich information
of multiple graph views. To circumvent this issue, the mul-
tiview graph analysis framework has been developed to fuse
graph information across views. How to model and integrate
shared (i.e. consistency) and view-specific (i.e. complementarity)
information is a key issue in multiview graph analysis. In
this paper, we propose a novel Multiview Variational Graph
Information Bottleneck (MVGIB) principle to maximize the
agreement for common representations and the disagreement for
view-specific representations. Under this principle, we formulate
the common and view-specific information bottleneck objectives
across multiviews by using constraints from mutual information.
However, these objectives are hard to directly optimize since
the mutual information is computationally intractable. To tackle
this challenge, we derive variational lower and upper bounds of
mutual information terms, and then instead optimize variational
bounds to find the approximate solutions for the information
objectives. Extensive experiments on graph benchmark datasets
demonstrate the superior effectiveness of the proposed method.
Index Terms—Graph data mining, multiview graph represen-
tation learning, graph neural networks, deep neural networks.
I. INTRODUCTION
AS a ubiquitous data structure, graph is capable of mod-
eling real-world systems in numerous domains, ranging
from social network analysis [1, 2], natural language process-
ing [3, 4], computer vision [5, 6], and other domains. In recent
years, as a powerful tool for learning and analyzing graph
data, Graph Neural Networks (GNNs) [7, 8, 9, 10, 11] have
received tremendous research attention and have been widely
employed for graph analysis tasks. The common graph neural
networks broadly follow the message passing framework [9]
which involves a message passing phase and a readout phase.
The message passing first iteratively aggregates the neighbor
representations of each node to generate new node represen-
tations, and then the readout phase capture the global graph
information from node representation space to generate the
graph representation. The success of GNNs can be attributed
to their ability to simultaneously exploit the rich information
X. Fan, M. Gong (corresponding author), M. Zhang, H. Li, and
X. Jiang are with the School of Electronic Engineering, Key Labo-
ratory of Intelligent Perception and Image Understanding, Ministry of
Education, Xidian University, Xi’an, Shaanxi province, China, 710071.
(e-mail: xiaolongfan@outlook.com; gong@ieee.org; haoli@xidian.edu.cn;
myzhang@xidian.edu.cn; xmjiang@xidian.edu.cn)
Y. Wu is with the School of Computer Science and Technol-
ogy, Xidian University, Xi’an, Shaanxi province, China, 710071. (e-mail:
ywu@xidian.edu.cn)
inherent in the singleview graph topology structure and input
node attributes.
However, for real-world applications, graph data are often
manifested as multiple types of sources or different topology
subsets, which can be naturally organized as multiview graph
data. For example, a multiplex network [12, 13] contains mul-
tiple systems of the same set of nodes, and there exists various
types of relationships among nodes, which can be seen as
different topology subsets. Furthermore, existing approaches
may confront challenges, such as difficulty in obtaining labeled
data and generalization bias under the supervised learning
setting [14]. One way to alleviate these issues is unsupervised
representation learning on graph. Therefore, how to integrate
different graph views into low-dimensional representations
for downstream tasks in an unsupervised manner becomes a
fundamental problem for graph representation learning.
Recently, several multiview graph representation learning
approaches have been proposed to effectively explore the
multiview graph data. For instance, Adaptive Multi-channel
Graph Convolutional Networks (AM-GCN) [15] show that
performing graph convolutional operation over both topology
and feature views can improve the performance of node repre-
sentation learning, where the feature view can be generated by
distance based K-Nearest Neighbor algorithm. Note that AM-
GCN works in the supervised learning manner and therefore
may suffer from the challenge of annotating graphs. Con-
trastive Multiview Graph Representation Learning (MVGRL)
[16] presents an unsupervised mutual information maximiza-
tion approach for learning node and graph representations by
contrasting graph views, where the additional graph view is
generated by structural augmentations such as Personalized
PageRank diffusion and heat diffusion strategies. Specifically,
MVGRL maximizes the mutual information between two
views by contrasting node representations from one view with
graph representation from the other view, but neglects to ex-
plicitly distinguish the common and view-specific information
across multiviews. Recent work [17] has shown that explicitly
modeling common and view-specific information can improve
the performance of multiview representation model.
In this paper, we focus on the in-depth analysis of multiview
graph representation learning and aim to answer the question
that how to extract common and view-specific information
in an unsupervised manner for graph representation learning.
Inspired by the idea of mutual information constraints in
information bottlenecks [18, 19, 20, 21], we first formulate
the information bottleneck objective to encourage that the
latent representation contains as much information as possible
arXiv:2210.05676v1 [cs.LG] 11 Oct 2022
PREVIEW 2
about the corresponding input view and as less information as
possible about the other view to explore the complementary
information across multiple graph views. Then, to further
explore the complex associations among different graph views,
we also formulate an information bottleneck objective to retain
as much information as possible about the corresponding input
view and the other view simultaneously. Note that, different
from previous information bottleneck methods [19, 20, 22]
that discard superfluous information for the given task, the
proposed method focuses on using mutual information to
constrain the latent graph representations to model consistency
and complementarity across graph multiviews.
However, the mutual information terms are challenging
to calculate in practice, since they require computing the
intractable posterior distribution. To tackle this challenge, we
follow the variational inference methods [19, 23] and derive
the variational lower bounds of mutual information terms that
need to be maximized. For the mutual information terms that
need to be minimized, we adopt Contrastive Log-ratio Upper
Bound (CLUB) [24] as the upper bound approximation. To
enable the computation of CLUB, a key challenge is to model
the intractable conditional distribution. Here, we employ the
classical graph neural network encoder to variationally approx-
imate conditional distribution. By combining the derived lower
and upper bounds, we can easily optimize the overall objective
by using the stochastic gradient descent algorithm.
Extensive validation experiments on seven graph benchmark
datasets demonstrate the superior effectiveness of the proposed
method. Specifically, we evaluate the proposed method on
the graph classification and graph clustering tasks, and also
perform the ablation study to investigate the performance of
certain components in the proposed method to understand the
contribution to the overall system.
To summarize, we outline the main contributions in this
paper as below:
1. We propose a novel Multiview Variational Graph Infor-
mation Bottleneck (MVGIB) principle to maximize the
agreement for common representations and the disagree-
ment for view-specific representations.
2. We present the variational lower and upper bounds of
the mutual information terms in MVGIB by exploiting
the variational approximation method.
3. Extensive validation experiments and ablation studies on
seven graph benchmark datasets demonstrate the superior
effectiveness of the proposed method.
The rest of this paper is organized as follows. In section II,
we make a brief review of the related works of graph neural
networks and information bottleneck. Section III describes
the preliminaries. Section IV gives the proposed method by
introducing representation model towards complementarity
and consistency, and then discusses the optimize and inference.
Section V evaluates the proposed method with extensive ex-
periments on graph representation benchmark datasets. Finally,
section VI concludes this paper and discusses the future work.
II. RELATED WORK
A. Graph Neural Network
Graph Neural Networks (GNNs) aim to model the non-
Euclidean graph data structure and have been demonstrated to
achieve state-of-the-art performance on graph analysis tasks.
As a unified framework for graph neural networks, graph
message passing neural network [9, 25] generalizes several
existing representative graph neural networks, such as Graph
Convolutional Networks (GCN) [10], Graph Isomorphism
Network (GIN) [11], Deep Hierarchical Layer Aggregation
(DHLA) [26], and others. In recent years, several label-
free contrastive self-supervised graph representation learning
methods have been developed, such as Deep Graph Info-
max (DGI) [27], Contrastive Multiview Graph Representation
Learning (MVGRL) [16], InfoGraph [28], and have achieved
competitive performance, even exceeding supervised graph
representation learning. In this paper, we use the graph iso-
morphism network as graph encoder to generate the graph
representation.
B. Information Bottleneck
The information bottleneck methods for deep neural net-
works [19] are developed to generate a compact but informa-
tive representation. Under this setting, if latent representation
discards information from the input which is not useful for a
given task, it can increase robustness for the downstream tasks.
In recent years, several information bottleneck based graph
representation learning methods have been proposed, such as
Graph Information Bottleneck (GIB) [20], Subgraph Informa-
tion Bottleneck (SIB) [22], and Variational Information Bot-
tleneck for Graph Structure Learning (VIB-GSL) [21]. In this
paper, we follow the idea of mutual information constraints
in information bottlenecks and develop the multiview graph
information bottleneck for graph representation learning.
III. PRELIMINARIES
This section first introduces notations and then discusses the
recent variational information bottleneck method.
A. Notations
We first introduce the notations throughout this paper. Let
G= (V,E)be a graph with Vand Edenoting the node
set and edge set, respectively. The nodes are described by
the adjacency matrix ARn×nwith the number of nodes
nwhere Aij = 1 if the edge between i-th node and j-th
node exists and else Aij = 0, and the node feature matrix
XRn×dwith the number of feature dper node. Under the
multiview graph input setting, suppose the number of graph
views is r, the graph contains a set of adjacency matrices,
i.e., A={A1, A2, ..., Ar}, and a set of node features, i.e.,
X={X1, X2, ..., Xr}. Following the frequent notations in
information theory, we use H(x) = Ep(x)log p(x)denoting
Shannon entropy, H(p, q) = Eq(x)log p(x)denoting cross
entropy, I(x;y) = Ep(x,y)log p(x,y)
p(x)p(y)denoting mutual infor-
mation, and DKL(pkq) = Ep(x)log p(x)
q(x)denoting Kullback-
Leiber divergence.
PREVIEW 3
Encoder
Encoder
Encoder
Encoder
InputInput
1 1 2 1
max ( ; ) ( ; )I h I h
22
()|q h
22
()|q c
21
()|q c
21
()|q c
11
()|q c
11
()|q h
11
()|ph
11
()|pc
22
()|pc
22
()|ph
1
View
2
View
2 2 1 2
max ( ; ) ( ; )I h I h
1 1 2 1
max ( ; ) ( ; )I c I c
+
2 2 1 2
max ( ; ) ( ; )I c I c
+
Fig. 1. The overall framework of the proposed approach. Here, G1with (A1, X)and G2with (A2, X)to be two input graph views. To extract consistent
relationships between multiview graphs, the proposed approach maximizes the mutual information between input graph and the common representation, while
maximizing the mutual information between G2and the common representation c1. To extract complementarity relationships between multiview graphs, the
proposed approach maximizes the mutual information between G1and h1, while minimizing the mutual information between G2and h1.
B. Information Bottleneck
The Information Bottleneck (IB) method [18] is introduced
as an information theoretic principle for extracting compact
but informative representations. Given the input data x, rep-
resentation z, and predict label y, the IB method maximizes
the mutual information between representation zand predicted
label y, while constraining the mutual information between
representation zand input data x, i.e.,
max I(z;y)s.t. I(x;z)Ic(1)
where Icdenotes the information constraint. By introducing
Lagrange multiplier α, Equation 1 can be transformed as
max I(z;y)αI(x;z).(2)
Intuitively, the first term of Equation 2 encourages zto be
predictive of yand the second term encourages zto forget
x, resulting in the minimal but sufficient encoding zfor
predicting y. However, due to the computational challenge
of mutual information, the IB objective is hard to directly
optimized. To compensate for this, recent work [19] proposes
a feasible way to approximate IB objective by incorporating
variational inference in form of
Ep(x,y)Ep(z|x)log q(y|z)αEp(x)Ep(z|x)log p(z|x)
r(z)(3)
where q(y|z)and r(z)are the variational approximations to
p(y|z)and marginal distribution p(z), respectively.
IV. PROPOSED APPROACH
As a motivating example, suppose G1with (A1, X1)and G2
with (A2, X2)to be two input graph views. Without loss of
generality, we assume that the different graph views differ only
in their adjacency relationship, i.e., X1=X2. To extract con-
sistent relationship and complementary information between
multiview graph data, we propose Multiview Variational Graph
Information Bottleneck (MVGIB) by extending the informa-
tion bottleneck principle to the unsupervised multiview graph
representation setting. The overall framework of MVGIB is
shown in Figure 1.
A. Towards Complementarity
Given two input graph views G1and G2of graph G,
complementarity principle aims to generate the view-specific
representation h1and h2for the given graph views G1and
G2, respectively. Taking fenc :G1h1as an example, we
expect to maximize the mutual information between G1and
h1, while minimizing the mutual information between G2and
h1, i.e.,
max I(G1;h1)δI(G2;h1)(4)
where δis the trade-off parameter to balance I(G1;h1)and
I(G2;h1). Analogously, we can formulate the information
bottleneck objective for fenc :G2h2, i.e.,
max I(G2;h2)ηI(G1;h2)(5)
where ηis the trade-off parameter. Intuitively, maximizing
Equation 4 and Equation 5 encourage representation h1and
h2to maximally express the input graph views generated
from, while maximally compressing the other graph views, i.e.,
towards complementarity. However, the mutual information
is computationally intractable since it requires computing the
intractable posterior distribution, resulting in these objectives
being hard to optimize. To tackle this challenge, we introduce
the variational inference approach [19] to derive the variational
摘要:

PREVIEW1TowardsConsistencyandComplementarity:AMultiviewGraphInformationBottleneckApproachXiaolongFan,MaoguoGong,SeniorMember,IEEE,YueWu,Member,IEEE,MingyangZhangMember,IEEE,HaoLi,andXiangmingJiangAbstract—TheempiricalstudiesofGraphNeuralNetworks(GNNs)broadlytaketheoriginalnodefeatureandadjacencyrela...

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