Modeling and Analysis of Tagging Networks in Stack Exchange Communities

TL;DR

This paper investigates the structure of tagging networks across multiple Stack Exchange communities, revealing consistent patterns and proposing a generative model that captures key statistical properties of tag co-occurrence.

Contribution

It provides the first comprehensive analysis of tagging networks in Stack Exchange, and introduces a simple generative model that reproduces observed statistical features.

Findings

Tagging structures are similar across different communities.

The proposed model accurately reproduces the tag frequency distribution.

The model captures key properties of the co-tagging graph.

Abstract

Large Question-and-Answer (Q&A) platforms support diverse knowledge curation on the Web. While researchers have studied user behavior on the platforms in a variety of contexts, there is relatively little insight into important by-products of user behavior that also encode knowledge. Here, we analyze and model the macroscopic structure of tags applied by users to annotate and catalog questions, using a collection of 168 Stack Exchange websites. We find striking similarity in tagging structure across these Stack Exchange communities, even though each community evolves independently (albeit under similar guidelines). Using our empirical findings, we develop a simple generative model that creates random bipartite graphs of tags and questions. Our model accounts for the tag frequency distribution but does not explicitly account for co-tagging correlations. Even under these constraints, we demonstrate empirically and theoretically that our model can reproduce a number of statistical properties of the co-tagging graph that links tags appearing in the same post.