Friday, August 27, 2010

Data Modeling

One of the things I learned to do while working at USDA was data modeling: specifically to figure out how different data items should relate.  In the old old days of 80-character punch cards, we knew each farmer/producer had a social security number, a name, and an address, with the latter fields restricted in length.  By the 1990's we knew a customer could have multiple ID numbers at different times and multiple addresses. 

Today I had my nose rubbed in the fact private corporations still have difficulty with data modeling.  Because there some security breach somewhere in their system, my credit card issuer sent replacement cards, with new numbers.  So I faced the problem of going through all the people with whom I do business online and updating my credit card number. So I had to go through 20 or so accounts, trying to change my credit card number.

Some companies, like Amazon, set up an account which can contain one or more credit cards.  Their modeling allows you to go in, delete the old card and add the new card.  I suspect this makes it easier for them to maintain their historical data.  Others allow you to change the card number,which works fine for the user, maybe not so much for data integrity.

The most aggravating companies are those, such as magazine publishers and my alma mater, which tie the credit card data to the end of the transaction for renewing a subscription.  Presumably they programmed a quick and dirty way: when you login to renew the subscription, the old record is copied to the new record and displayed.  What that means is I can't update the number today.  When it comes time to renew I'll either have to remember to change it then (not likely, not at my age) or rely on the company's validation process for credit card numbers.

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