You can include the following element tags as part of the RSS feed, to extend the information that you want to appear in recommendations.
For these Optimizely Personalization namespace tags, default RSS 2.0 tags also exist. You can use either for these elements, but if you are using the Optimizely Personalization namespace tags, you must also include the default tag in the feed but leave it empty.
## Attribute elements
In addition to the standard product details, make sure every product in your feed includes any \<p:attribute> information that you want to use in the product recommendation process (algorithms and/or filters). For example, if you place importance on attributes such as gender or material, those products in your catalog must have these attributes defined.
Maintain consistency throughout the feed, using the same terms when referring to an attribute. For example, if you refer to an attribute of _collar_, do not also refer to it as _neck_ or _collar\_sizes_.
Where multiple size or color variants exist for an item, variant items can be created (see Variant elements).
Attribute names cannot contain spaces.
## Variant elements
You can provide product variant entries in the Optimizely feed format with the \<p:variant> element. This element contains variants in a product's attributes. If omitted, the variant properties are taken from the corresponding property of the main item. You should provide variant data if you want to track the variants individually in merchandising rules, reports, and so on.