Explicitly Representing Superimposed Information in a Conceptual Model

Superimposed information

(SI) refers to new information such as annotations and summaries overlaid on fragments of existing

base information

(BI) such as web pages and PDF documents. Each BI fragment is referenced using an encapsulated address called a

mark

. Based on the widespread applicability of SI and wide range of superimposed applications (SAs) that can be built, we consider here how to represent marks explicitly in a conceptual model for an SA. The goal of this work is to facilitate the development of SAs by making it easy to model SI (including the marks) and to exploit the middleware and query capability that we have developed for managing marks and interacting with the base applications. The contribution of this paper is a general-purpose framework to make marks explicit in a conceptual (ER) model. We present conventions to associate marks with entities, attributes, and relationships; and to represent that an attribute’s value is the same as the excerpt obtained from a mark. We also provide procedures to automatically convert ER schemas expressed using our conventions to relational schemas, and show how a resulting relational schema supports SQL queries over the combination of SI, the associated marks and the excerpts associated with the marks.