Template-based wrappers in the TSIMMIS system

TLDR

Accessing heterogeneous information sources requires translating queries and data between data models, a task performed by source wrappers that convert queries and transform results into application‑friendly formats. The TSIMMIS project produced hard‑coded wrappers for various sources, but most of the code is generic and could be expressed declaratively, highlighting the need for template‑based wrappers to accelerate new source integration.

Abstract

In order to access information from a variety of heterogeneous information sources, one has to be able to translate queries and data from one data model into another. This functionality is provided by so-called (source) wrappers [4,8] which convert queries into one or more commands/queries understandable by the underlying source and transform the native results into a format understood by the application. As part of the TSIMMIS project [1, 6] we have developed hard-coded wrappers for a variety of sources (e.g., Sybase DBMS, WWW pages, etc.) including legacy systems (Folio). However, anyone who has built a wrapper before can attest that a lot of effort goes into developing and writing such a wrapper. In situations where it is important or desirable to gain access to new sources quickly, this is a major drawback. Furthermore, we have also observed that only a relatively small part of the code deals with the specific access details of the source. The rest of the code is either common among wrappers or implements query and data transformation that could be expressed in a high level, declarative fashion.