Lecture 4: From ER Diagrams to Relational Models

Now that we have both the high-level visual language of ER diagrams and the more formal structures of the relational model, this lecture presented some recipes for translating from the first into the second. This isn’t always an exact match, and for any particular ER diagram we might go back to its original source to decide how to best represent it as a relational model. Even so, this kind of step-by-step staging towards a fully formal representation is an effective route to capturing the subtleties of real-world systems.

Also, there were a few references to increasingly wild estimates of how much data is created and processed worldwide year-by-year: exabytes, petabytes and yottabytes of it.

“These numbers are impressive, but still miniscule compared to the order of magnitude at which nature handles information”

Martin Hilbert, quoted in Science Daily

Link: Slides for Lecture 4; Video of Lecture 4


Tutorial exercise sheet 1: bring your solutions, on paper, to your tutorial group meeting next week. If you have any difficulties, or questions about it, ask on Piazza.


Data Never Sleeps Infographic Data Never Sleeps
How Much Data is Created Every Minute?
Image collating information on the rate of online activity of particular kinds.

Link: Domo blog article

Screenshot of Cisco web page How Much is That?
Cisco Visual Networking IP Traffic Chart
Table giving examples of various magnitudes of data, from petabytes to yottabytes.

Link: Cisco Traffic Chart

Screenshot of Science Daily web page How Much Information is the in the World?
Science Daily 2011-02-11
Report on a study carried out at the University of Southern California

Link: Science Daily article; Research report

Cartoon image of punched card What if?
Google’s Datacenters on Punch Cards
If all digital data were stored on punch cards, how big would Google’s data warehouse be?

Link: What if?

Screenshot of Mail Online web page Mail Online: Information Overload
There could soon be no words to describe how much data is stored in the world
Pinpoints the nightmare scenario ahead. Illustrated with a picture of The Count from Sesame Street. (Yes, really, go look.)

Link: Mail Online article