I would like to restrict this topic to the discussion of how, in general terms product attributes should or will be dealt with in osC 3.0
To kick off…
Point 1
Product attributes have come up at various times and the simple example is how you deal with Tshirts that come in different sizes and different colours.
The point has been made that, if you want to keep track of stock, then each combination of style, colour and size must be a different product with a different ID.
Also that this is the only way you can use barcodes.
To underline the sense of this I would like to point out that this issue has already been tackled on a global scale. The GTIN (Global Trade Identification Number) is a globally agreed system for allocating ID numbers to traded products – particularly those which cross a point of sale. The GTIN numbers are controlled by a network of “GS1” organisations. These guys spend all their time considering and developing the global system of GTIN numbers and have developed a whole system which is pretty much agreed throughout the world. If you are interested in how it all works, go to http://www.gs1.org.
The rules are roughly this – any item which is distinguishable by a customer from another item must have a different GTIN (for example see p34-35 of this document http://www.gs1uk.org/EANUCC/WORD_Files/GS_...n_2-1_V7.1.doc)
So it's clear for a number of reasons, not least that it is the way that items are identified at most points of sale, that every every different style, colour and size combination of a T shirt should have a different ID number (which can be represented by the GTIN or can have a one-to-one relationship with the GTIN if one exists).
Point 2
The term 'product attributes' used in these forums might mislead thinking in this respect. It implies, of course, that you have a particular product with different properties. But it might be better to think of a series of different items which are grouped together for presentational purposes. It this way of thinking, the problem is just an extension of the categories system.
Rather than thinking of a Style of Tshirt as a product with different colours and sizes. Think of each individual colour/size/style combination and how you then group them together.
An XL red style A Tshirt would normally be grouped with other sizes as red style A Tshirts. Blue style A Tshirts would join them in the Style A T shirt group. Style B Tshirts would join these in the Tshirts group. Long sleeve shirts might join these in the Shirts Group ... for some reason in the existing system, we would now call this a category - or a sub-category of the Clothing category.
The advantage of this way of thinking is that you can group your items in any way you want. You could, if you has a themed shop, groups all red items together and then subgroup these into clothes and accessories, then group the clothes into shirts and socks and then into sizes.
Best of all, you can embrace the GTIN and barcode system and maintain the ability to keep track of stock.
I'm not sure how well I've explained this and maybe this has all been sorted out already.