Author
W. H. Inmon
1 reading card from 1 book · 1992.
1 card
Building the Data Warehouse · 1992
Subject-oriented, integrated, time-variant, nonvolatile: four adjectives, one architecture.
Inmon's four adjectives are really four design decisions. Subject-oriented: data is organised by customer, product, order — not by the applications that produced it. Integrated: the same country codes, the same units, the same keys, however many sources sit behind them; integration is the most expensive part of the work and the reason the warehouse exists at all. Time-variant: every row is a dated snapshot, and history is kept rather than overwritten. Nonvolatile: data is loaded and read; it is not corrected in place the way a transactional system corrects it. The production system answers "what is this customer's address now?". The warehouse answers "how has order value moved across regions over the last five years?". The first question wants one row, fast and consistent. The second wants millions of rows that can be compared with each other. They are two different jobs, and the lessons that follow show why the same engine does not do both well.
“A data warehouse is a subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management's decision making process.”