E-commerce variables (example UDO variables like product_id, order_id, product_category etc...) can be filled technically anytime you choose.
There are tags (in the tips section) which let you know when and how they pick up these variables automatically. With other tags you have to use mapping for the tag to pick up the values.
As an example, on a product detail page you can fill out all the array variables having to do with the product such as product_id, product_price and other product related values. Again, there are tags that will pick this information up automatically if they are mapped in the e-commerce extension from the base _cXX variables to variables in your UDO. This set of variables relating to product information generally corresponds to the right side of the e-commerce section. You could fill out product information on a search or category page as well.
When a customer completes a transaction, then you would fill out the order related information such as order_id, order_total and variables such as these. This set of variables corresponds to the left side of the e-commerce extension.
Hope this helps guide you in the right direction!
Thank you! My understanding then is that utag_data can be populated with product information as products are added to cart. Once the order data is populated then the transaction is considered completed.
You are very welcome Duane;
Yes the concept of production information (on your cart page load) and a transaction being considered complete (on your receipt and/or confirmation page) from the perspective of utag_data is a good way of thinking of a transaction being complete and the general flow of user purchases.