Things I used to be Wrong about – Part 1

I get very annoyed about politicians being held to account for admitting they were wrong, rather than forcefully challenged when they were wrong in the first place. Unless they lied, if someone was wrong and admits it, they should be congratulated. They have grown as a human being.

I am about to do something very similar. I’m going to start confessing some wrong things I used to think, that the world has come to agree with me about. I feel I should congratulate you all.

You can’t design a Database without knowing how it will be used

I was taught at university that you could create a single abstract data model of an organisation’s data. “The word database has no plural”, I was told. I tried to create a model of all street furniture (signs and lighting) in Staffordshire, in my second job. I couldn’t do it. I concluded that it was impossible to know what was entities and what was attributes. I now know this is because models are always created for a purpose. If you aren’t yet aware of that purpose, you can’t design for it. My suspicion was confirmed in a talk at Wolverhampton University by Michael ‘JSD’ Jackson. The revelation seemed a big shock to the large team from the Inland Revenue. I guess they had made unconscious assumptions about likely processes.

Relations don’t understand time

(They would probably say the same about me.) A transaction acting across multiple tables is assumed to be instantaneous. This worried me. A complex calculation requiring reads could not be guaranteed to be consistent unless all accessed tables are locked against writes, throughout the transaction. Jackson also confirmed that the Relational Model has no concept of time. A dirty fix is data warehousing which achieves consistency without locking by the trade-off of guaranteeing the data is old.

The Object Model doesn’t generalise

I’d stopped developing software by the time I heard about the Object Oriented Programming paradigm. I could see a lot of sense in OOP for simulating real-world objects. Software could be designed to be more modular when the data structures representing the state of a real-world object and the code which handled state-change were kept in a black box with a sign on that said “Beware of the leopard”. I couldn’t grasp how people filled the space between the objects with imaginary software objects that followed the same restrictions, or why they needed to.

A new wave of Functional Programming has introduced immutable data structures. I have recently learned through Clojure author Rich Hickey’s videos that reflecting state-change by mutating the value of variables is now a sin punishable by a career in Java programming. Functional Programmers have apparently always agreed with me that not all data structures belong in an object

There are others I’m still waiting for everyone to catch up on:

The Writable Web is a bad idea

The Web wasn’t designed for this isn’t very good at it. Throwing complexity bombs at an over-simplified model rarely helps.

Rich Hickey’s Datomic doesn’t appear to have fixed my entity:attribute issue

Maybe that one is impossible.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s