How do we make domain decisions when coding software?

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I stumbled on an interesting discussion over at hacker news about when you have to make a decision in code outside of your domain of expertise.

This is a super interesting topic to me. As the world is more and more powered by computers and algorithms, this seemingly obscure philisophical corner of computing begins to affect us all.

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While many programmers are familiar with the experience of stumbling upon an edge case which wasn’t covered in the spec. The truth is you can’t go back and block on every single tiny detail.

Some of the bigger ones can trigger further discussion, but were it not for Falsehoods programmers believe about X the software would never go out the door.

Here’s some more food for thought…

1. Falsehoods programmers believe about names

o They won’t be a *bad* word. Whose bad? i’m not sure.
o All people have names.
o We only have to work with names from English.
o Names are ordered in a sensible manner.
o A name won’t have to change later.

You get the picture. As you start working with the minutae around names, you realize there is a lot of assumptions. Even when you weed out the big ones, there are still small assumptions.

Ultimately, you can’t get to the bottom. There will always be some assumptions, and as software evolves, changes will be required to match the real world. Living systems grow. Software systems must receive *updates*.

Read: What happened when I offered advice outside my pay grade?

2. Falsehoods programmers believe about selling products

o each product has a price
o each product has one price
o each product is one unit
o two decimal places is enough for all currencies
o all currencies have a unicode symbol

There are many more. The point is once you start digging, everything gets fuzzy. Products can be in stock and not in the warehouse. Single product can have multiple prices. It goes on and on!

Read: What did Matt Ranney discover scaling Uber to 1000 microservices?

3. Falsehoods programmers believe about addresses

o two districts will not have the same number
o postal codes will agree across jurisdictions
o a fixed number of characters will work for every address
o roads have names
o buildings are not numbered zero

Addresses are *really* messy. I remember being surprised when I moved to brooklyn. Streeteasy & Google put me in different neighborhoods. I asked my lawyer why this was. He said DOB and the post office use different databases. And google further samples from one or the other.

Never the twain shall meet!

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