An Initial Homophily Indicator to Reinforce Context-Aware Semantic

ComputingA. Rivero-Rodriguez, P. Pileggi, O. Nykänen

Tampere University of TechnologyTampere, Finland

June 3, 2015Riga, LatviaCICSyN 2015: Computational Intelligence, Communication Systems and Networks

This talk describes the benefits of using social network analysis, in particular homophily, in context-aware systems

Context SNA/Homophily Indicators

2

3.6.2015

What is context?

Context is any information that can be used to characterize the situation of an entity, where an entity can be a person, places, or physical or computational object1.

Context is the sum total of what is known about an individual along with what he or she is currently experiencing.

3

3.6.20157th International Conference CICSyN 2015

Context

Context-aware system can be found everywhere, even in your phone…

4

3.6.20157th International Conference CICSyN 2015

Context

Social Network Analysis

Social Network Analysis (SNA) focuses on the discovery and evolution of relations among entities (people, organizations, activities, etc.) [21].

We want to use SNA techniques to understand existing systems. It can be used for modelling for link prediction etc.

SNA is not solely useful for understanding a system, but for others tasks such as Prediction, Recommendation, etc. For example, Amazon’s recommender system.

5

3.6.2015

SNA

Homophily states that connections between similar people happens at a higher rate than among dissimilar people

6

3.6.2015

SNA

Network that exhibits homophily

Homophily is ubiquitous in social systems.

Network of romantic relationships in a highschool exhibits:inverse homophily according to genderdirect homophily according to age

Two mechanisms underlying homophilySelectionSocial influence (socialization)

7

3.6.2015

SNA

Measuring Homophily in social network

8

3.6.2015

Indicator

n number of present edges in G.p number of possible edges in G.Proportion of edges in the network

Proportion of homophily edges.

Proportion of heterophily edges.

Comparison of homophily indicators

Existing affinity indicator Our homophily indicator

9

3.6.2015

Indicator

+1

-1

0

Homophily

Heterophily+1

∞

0Heterophily

Homophily

Difficult to interpret and utilizeWhat is aff value for a system with only homophilic connections?

Easier to interpret.Homophily and heterophily are equally important.

Experimenting with hom indicators. Description of the nodobo dataset

Smartphone social interaction data27 senior high-school studentsData collected for 5 months: Sep’10 – Feb’11 (only considered 105 days with data)We used the bluetooth data and build a graph G

• Each user is a node in G• There is a link between two users if they have been in

proximity for more than 60 min a day. (preanalysos)

10

3.6.2015

Indicator

Experiment settings

Homophily conditions: Two users are expected to be connected if they have more than f friends in common

We have discretize the 105 days of data into W periods of lenght L, so that

11

3.6.2015

Indicator

Experiment settings

Homophily conditions: Two users are expected to be connected if they have more than f friends in common

We have discretize the 105 days of data into W periods of lenght L, so that

Several experiments, such as:• Experiment A: W=15, f=2• Experiment B: W=5, f=3

12

3.6.2015

Indicator

System parameters

Results & Observations13

3.6.2015

Indicator

Figure 2. Aff and Hom indicator values reported for Experiment A.

Figure 3. Aff and Hom indicator values reported for Experiment B.

Conclusions & Future Work

We propose an homophily indicator that overcomes the weaknesses of others proposed in the literature. It is easier to understand and interpret, potentially useful in existing context-aware systems.

Future work includes• the extension of the indicator to account for time periods, • the development of model driven solutions based for

context inference based on our Hom indicator.

14

3.6.2015

Indicator

Alejandro Riveroalejandro.rivero@tut.fi