Data Tiers and Information Architecture

What are Data tiers?

data [dey-tuh, dat-uh, dah-tuh] noun
1.
a pl. of datum.
2.
(used with a plural verb) individual facts, statistics, or items of information: These data represent the results of our analyses. Data are entered by terminal for immediate processing by the computer.
3.
(used with a singular verb) a body of facts; information: Additional data is available from the president of the firm.

(Dictionary.com Unabridged (v 1.1). Retrieved October 03, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/data)


tier [teer] noun
1.
one of a series of rows or ranks rising one behind or above another
2.
one of a number of galleries, as in a theater.
3.
a layer; level; stratum: The wedding cake had six tiers. All three tiers of the firm's management now report to one director.

(Dictionary.com Unabridged (v 1.1). Retrieved October 03, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/tier)


After checking the dictionary definitions, I would simplify the meanings as follows:

Data: Information
Tier: A level within a structure

Therefore Data tiers are:
A) Levels of information within a structure.
B) An informational structure itself.

In yesterdays class, the tutor talked about data tiers and gave examples of ways in which information can be structured (with a database driven ecommerce site in mind). He then demonstrated that running simple 'data tier' tests on paper can identify faults or elements that can be more 'normalised' (reducing the amount of tables fields in a table, to simplify the structure as much as possible.)

Exercise

The tutor set us this exercise:

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Data Tier - Planning exercise
'Homespare' are a small retail chain of 10 locally based stores selling home appliance spares. They have a centrally located warehouse that houses their catalogue of 2000 products, so at least 85% of their goods are availableas an in-stock item.

The owner of the business has decided he wants to put his catalogue online and create a web based online shop.

The online shop is to feature:

The full product catalogue
A category based navigation
A shopping cart system
Order tracking
Product reviews / info
Product images
A search based on manufacturer or product type


Tasks
1) Design the data tier for this system. Be sure to normalise the database as much as possible and describe the table relationships you will use.

2) Run some simple data tier tests - and identify if there are any points in which your data tier demonstrates either a fault or an element that could be more normalised.

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My response to this task is as in the following image. The fields shown in black, within the 5 tables at the top, are the fields i had before running any tests.
I ran 3 queries on paper:

#1-inserting some categories
#2-insert some products
#3-attempt to purchase using the 'cart' and 'checkout' tables.
As I ran the queries, the need for more fields arose(shown in red)

The following image shows how the tables would be populated after the previous tests. I have used coloured arrows to show the relationship between the tables and to show where data is input into the system.

My diagram of the table contents shows that an 'ID' field for each table is essential for creating data tiers as each table is referenced by a number. The further you move through this system the fields eventually contain numbers only. This is good because databases handle numbers faster.