Showing papers by "Peter Buneman published in 2013"

Annotations are relative

Abstract: Most systems that have been developed for annotation of data assume a two-level structure in which annotation is superimposed on, and separate from, the data. However there are many cases in which an annotation may itself be annotated. For example threads in e-mail and newsgroups allow the imposition of one comment on another; belief annotations can be compounded; and valid time, regarded as an annotation can be freely mixed with belief annotations (at time t1, B1 believed that at time t2, B2 believed that...).In this paper we describe a hierarchical model of annotation in which there is no absolute distinction between annotation and data. First, we introduce a term model for annotations and, in order to express the fact that an annotation may apply to two or more data values with some shared structure, we provide a simple schema for annotation hierarchies. We then look at how queries can be applied to such hierarchies; in particular we ask the usual question of how annotations should propagate through queries. We take the view that the query together with schema describes a level in the hierarchy: everything below this level is treated as data to which the query should be applied; everything above it is annotation which should, according to certain rules, be propagated with the query. We also examine the representation of annotation hierarchies in conventional relational structures and describe a technique for annotating datalog programs.

The providence of provenance

Abstract: For many years and under various names, provenance has been modelled, theorised about, standardised and implemented in various ways; it has become part of mainstream database research. Moreover, the topic has now infected nearly every branch of computer science: provenance is a problem for everyone. But what exactly is the problem? And has the copious research had any real effect on how we use databases or, more generally, how we use computers. This is a brief attempt to summarise the research on provenance and what practical impact it has had. Although much of the research has yet to come to market, there is an increasing interest in the topic from industry; moreover, it has had a surprising impact in tangential areas such as data integration and data citation. However, we are still lacking basic tools to deal with provenance and we need a culture shift if ever we are to make full use of the technology that has already been developed.