Stock-control puzzle: how products are related to each other

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Shopping cart software and stock control.
How are products related to each other?

Programmers see products and attributes in a different way to shopkeepers.
Programmers use language to describe the subtleties, but I don't think there is any standard way of using words to describe

• different ways that programmers relate data, and

• different ways that shopkeepers relate stock

Programmers see a product, and a variation to make a 2D table, and another variation to make a 3D table, and a third to become something you can't draw. Programmers take that product and add more to it at the checkout stage, when shipping zones and such are attached.

Shopkeepers see products in a way that has probably built-up over the years from experience, rudely interrupted each time their systems are automated. I'm thinking of small-scale self-employed shopkeepers and stall-holders and people who sell things online with DIY shopping cart software. People who work in logistics at Tesco are probably ahead of me in their analysis. They don't need to read the relationships below, which are customer expectation, ability to alter the product after an order has come-in, and then some relationships further-up the supply chain. These can be whether a product has a minimum, such as five reams of paper in a carton, or a minimum per type of product, such as any choice of sizes of green slipper from the slipper manufacturer, or any choice of products from the slipper shoe and boot wholesaler.

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Customer expectation about stock?

I can have nearly identical products from different suppliers within one family.
To a programmer they can share a photograph and an ordering system.
To the customer they are T shirts in small medium or large sizes.
As long as the customer doesn't mind, I can have blue T shirts from one supplier and red T shirts from another supplier, and they are all just a T shirt range to the customer. The link is that the customer is likely to look for T shirts and then think about size, unless a shopping cart persuades a customer to state a size while browsing. People with specialist clothes shops particularly want a full size range. They don't want a customer to make a special journey one Saturday, think they have seen a product available, and then discover that it's not.

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Can stock be altered on-site, after an order comes-in?

Shopkeepers are used to altering the address and delivery costs after an order comes in. They may offer gift wrapping or first class postage. I could probably turn a white T shirt into a blue T shirt, but I am not sure if the dye would be fast or cheap or that I could do it quickly enough for it to be worth the time. Maybe a specialist T shirt printer would know. I couldn't turn a blue T shirt into a white T shirt. I can turn a long belt into a short belt and that's quite common in belt shops. I specialise more in belts. I can keep kits of parts and make belts to any length up to a maximum.

If a shopkeeper can turn one product into another as with belt length or gift-wrapping, that's one relation between products; if not, I think of them as separate products within a family. Maybe that's why Americans keep using the term "SKU" or "Stock Keeping Unit", or maybe that's just a bit of jargon they like to use in America.

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Is stock separated from other products back-up the supply chain? 

I cannot turn a size 8 into a size 9 by stretching. I cannot make shoes after an order comes-in.

Shopkeepers see a product as something that comes from up the supply chain.
Products have family relations to each other. Just as sheep are used to living in herds, shoes are used to living in size ranges. They go-about in pairs, like pidgeons, but before they are sold they also like to have a hurd like sheep or cows. A full size range has a higher vaue because it matches customer expectations. Sizes are linked further-up the supply chain in the way that the size range is available. Complexity lurks, un-stated, as something that I just worked-out as I went along last time I organised the way I do business.

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Is stock linked to other products by supplier minimum orders?

One of my suppliers can send anything in the catalogue, whatever size it is, from whatever range, if I make a minimum order value. So the sizes are linked by customer expectation - the wish to see a choice of sizes - and by a wider family of goods from one supplier, and their minimum order for cheap delivery which takes two or three working days. That contradicts my statement that I can't alter a shoe after the order comes-in. If the wholesaler will send quickly enough or send direct to the customer, then the stock-keeping task is to know what's in their warehouse as well as my small stock room. I can advertise a product as in stock - perhaps with an asterisk to say that delivery is subject to confirmation and will take a few days, or with simpler software I can just mark it in stock and take a chance.

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Is stock linked to other products by supplier constraints within an order?

One of my suppliers makes shoes in sizes. They will make 12 of a style - any size combinations - within a minimum order for free delivery which is 24. So the relations are style for a minimum order per style, and supplier for a minimum order per free delivery. There's also a 2-3 month lead time.

One supplier that I don't use sells shoes in pre-paks. So-many size 3, so-many size 4, more size 5 and 6, less size 7 and so many size 8. These are ordered as one product; they can't come in any other size ratio, but they are separate in their ability to be out of stock. Some combination of stock should persuade a shopkeeper to order another carton. I'm not sure how it goes.

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Is stock linked to other products by supplier rules?

If I sold food or stationary, it would be normal for a supplier to sell things in minimums within the minimum order for free delivery. They would be packed in sixes and twelves and crates and boxes. The rule us that a supplier will not break-open a pack in order to reduce picking and packing costs; a wholesaler sells the whole pack. Hence the name. The rule can relate to a real pack, or it can be applied arbitarilly by the supplier.

I'm still confused but at least I have written the problem down.
I have not written a neat summery or solution.
I think programmers are confused in how to present their software as well; I haven't seen standard language used or explained.

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the author sells vegan shoes online at Veganline.com , a UK online vegan shoe shop
related post: Free Fast and Pretty - which shopping cart?