Graph Classification
Classification Outline
• Introduction, Overview
• Classification using Graphs
– Graph classification – Direct Product Kernel
• Predictive Toxicology example dataset
– Vertex classification – Laplacian Kernel
• WEBKB example dataset
• Related Works
Example: Molecular Structures
Known
Toxic
Non-toxic
BB
AA
CC
DD
CC
BB
AA
DD
EE
Task: predict whether molecules are
toxic, given set of known examples
Unknown
BB
CC
AA
EE
CC
BB
AA
DD
DD
EE
FF
Solution: Machine Learning
• Computationally discover and/or predict
properties of interest of a set of data
• Two Flavors:
– Unsupervised: discover discriminating properties among
groups of data (Example: Clustering)
Data
–
Property
Discovery,
Partitioning
Clusters
– Supervised: known properties, categorize data with unknown
properties (Example: Classification)
Training
Data
Build Classification
Model
Predict Test
Data
Classification
• Classification: The task of assigning class labels in a discrete
class label set Y to input instances in an input space X
• Ex: Y = { toxic, non-toxic }, X = {valid molecular structures}
Misclassified
data
instance
(test error)
Unclassified
data
instances
Training the classification model
using the training data
Assignment of the unknown (test) data to
appropriate class labels using the model
Classification Outline
• Introduction, Overview
• Classification using Graphs,
– Graph classification – Direct Product Kernel
• Predictive Toxicology example dataset
– Vertex classification – Laplacian Kernel
• WEBKB example dataset
• Related Works
Classification with Graph Structures
• Graph classification
• Vertex classification
(between-graph)
– Each full graph is
assigned a class label
• Example: Molecular
graphs
(within-graph)
– Within a single graph,
each vertex is assigned
a class label
• Example: Webpage
(vertex) / hyperlink
(edge) graphs
BB
AA
EE
CC
Toxic
DD
NCSU domain
Faculty
Course
Student
Relating Graph Structures to Classes?
• Frequent Subgraph Mining (Chapter 7)
– Associate frequently occurring subgraphs with classes
• Anomaly Detection (Chapter 11)
– Associate anomalous graph features with classes
• *Kernel-based methods (Chapter 4)
– Devise kernel function capturing graph similarity, use vector-
based classification via the kernel trick