{"id":1329,"date":"2026-03-24T09:00:32","date_gmt":"2026-03-24T16:00:32","guid":{"rendered":"https:\/\/www.kenwalger.com\/blog\/?p=1329"},"modified":"2026-05-05T07:11:27","modified_gmt":"2026-05-05T14:11:27","slug":"designing-a-schema-for-physical-objects","status":"publish","type":"post","link":"https:\/\/www.kenwalger.com\/blog\/data-engineering\/designing-a-schema-for-physical-objects\/","title":{"rendered":"The Backyard Quarry, Part 2: Designing a Schema for Physical Objects"},"content":{"rendered":"

In the first post of this series<\/a> we set the stage for the Backyard Quarry<\/strong> project.<\/p>\n

Once you decide every rock in the yard should have a record, the next question appears immediately:<\/p>\n

What exactly should we record?<\/p>\n

It\u2019s a deceptively simple question. And like most simple questions in engineering, it opens the door to a surprisingly large number of decisions.<\/p>\n

The First Attempt<\/h2>\n

The most straightforward approach is to keep things minimal.<\/p>\n

Each rock gets an identifier and a few attributes.<\/p>\n

Something like:<\/p>\n

rock_id\nsize\nprice\n<\/code><\/pre>\n
At first glance, this seems reasonable.<\/p>\n
We can identify the rock. We can describe it in some vague way. We can assign a price.<\/p>\n
But this model breaks down almost immediately.<\/p>\n
\u201cSize\u201d is ambiguous. Is that weight? Volume? Longest dimension? All of the above?<\/p>\n
Two rocks of the same \u201csize\u201d might behave very differently when you try to move them.<\/p>\n
And more importantly, this model doesn\u2019t capture anything about the rock beyond its most basic characteristics.<\/p>\n
It\u2019s enough to sell a rock.<\/p>\n
It\u2019s not enough to understand one.<\/p>\n
Expanding the Model<\/h2>\n
To make the system more useful, we need to be more explicit.<\/p>\n
A slightly richer model might look like this:<\/p>\n
rock_id\nweight_lb\nlength_cm\nwidth_cm\nheight_cm\ncolor\nrock_type\nlocation_found\nstatus\n<\/code><\/pre>\n
Now we\u2019re getting somewhere.<\/p>\n
We can distinguish between rocks that look similar but behave differently.<\/p>\n
We can track where each rock came from.<\/p>\n
We can start to answer questions like:<\/p>\n