Thanks for the question on EAVs. They are a very controversial topic. I have designed databases that used them for PART of the schema. However, I always use them with some reluctance.

In particular, I used them when I did the data model for LAN Desk for Intel. It was a product that, among other things, had to track the configuration information for systems on the network. Hardware and software had to be modeled, as well as the relationships between components. It got kind of messy when you had to store information about daughter cards mounted on the motherboard that were being used as RAM drives! (Just to name one example.) Plus, the database had to account for all the possible ways that technology would add in new kinds of things to put in a computer, new attributes that you didn't even envision, and new ways for things to be related. It was fun, but it took a lot of time to explain to the developers.

[Fixed typo.]