Data Extraction and Ad Hoc Query of an Entity--Attribute--Value Database

TLDR

Entity–attribute–value tables dominate mainstream electronic patient record systems, enabling fast individual patient retrieval but posing challenges for attribute‑centric, cross‑patient queries. The authors present ACT/DB, a clinical‑trial database designed to address attribute‑centric query difficulties. Their solution employs metadata‑driven query front‑end that abstracts the underlying EAV or non‑EAV storage from users. The study concludes that the query problem remains unsolved, highlighting several complex subproblems that require further work.

Abstract

Entity—attribute—value (EAV) tables form the major component of several mainstream electronic patient record systems (EPRSs). Such systems have been optimized for real-time retrieval of individual patient data. Data warehousing, on the other hand, involves cross-patient data retrieval based on values of patient attributes, with a focus on ad hoc query. Attribute-centric query is inherently more difficult when data are stored in EAV form than when they are stored conventionally. The authors illustrate their approach to the attribute-centric query problem with ACT/DB, a database for managing clinical trials data. This approach is based on metadata supporting a query front end that essentially hides the EAV/non-EAV nature of individual attributes from the user. The authors' work does not close the query problem, and they identify several complex subproblems that are still to be solved.