Wolfgang Gatterbauer

Towards domain-independent information extraction from web tables

Traditionally, information extraction from web tables has focused on small, more or less homogeneous corpora, often based on assumptions about the use of <table> tags. A multitude of different HTML implementations of web tables make these approaches difficult to scale. In this paper, we approach the problem of domain-independent information extraction from web tables by shifting our attention from the tree-based representation of webpages to a variation of the two-dimensional visual box model used by web browsers to display the information on the screen. The there by obtained topological and style information allows us to fill the gap created by missing domain-specific knowledge about content and table templates. We believe that, in a future step, this approach can become the basis for a new way of large-scale knowledge acquisition from the current Visual Web.

Using visual cues for extraction of tabular data from arbitrary HTML documents

We describe a method to extract tabular data from web pages. Rather than just analyzing the DOM tree, we also exploit visual cues in the rendered version of the document to extract data from tables which are not explicitly marked with an HTML table element. To detect tables, we rely on a variant of the well-known X-Y cut algorithm as used in the OCR community. We implemented the system by directly accessing Mozillas box model that contains the positional data for all HTML elements of a given web page.

Estimating required recall for successful knowledge acquisition from the web

Information on the Web is not only abundant but also redundant. This redundancy of information has an important consequence on the relation between the recall of an information gathering system and its capacity to harvest the core information of a certain domain of knowledge. This paper provides a new idea for estimating the necessary Web coverage of a knowledge acquisition system in order to achieve a certain desired coverage of the contained core information.

Counterexamples to Commonly Held Assumptions on Unit Commitment and Market Power Assessment

This chapter revisits two commonly accepted assumptions about the economics of deregulated electricity markets. It first disproves that, in theory and under the condition of perfect information, decentralized and centralized unit commitment (UC) would lead to the same power quantities traded and the same optimal social welfare. It then shows that a generator owner’s optimum bid sequence for an auction market is generally above marginal cost, even where absolutely no abuse of market power is involved.