Dynamic native advertisment insertion

A system comprising at least one or more processors and a memory storing instructions that, when executed by the one or more processors, implement:

• a distribution component, configured to distribute item insertion initiating instructions to clients at which documents will be displayed, the item insertion initiating instructions configured to cause the clients to send requests to a server to insert supplemental items into the documents;
• a template cache configured to store, in one or more memories, supplemental item templates for use in generating new content for insertion into the documents;
• a template loader component, at the server, configured to select particular supplemental item templates from the template cache based on document identifying information associated with the requests, different templates being selected from the template cache for different documents;
• a repository of supplemental items configured to store supplemental item descriptive metadata for each of the supplemental items;
• an item selector component, at the server, configured to select, from the repository of supplemental items, particular supplemental items to insert in the documents based on the requests;
• one or more supplemental item renderers configured to generate rendered supplemental items from the particular supplemental item templates selected by the template loader component and the particular supplemental items selected by the item selector component, the rendered supplemental items generated by causing particular descriptive metadata items of the particular supplemental items to be inserted into template elements to which the particular descriptive metadata items have been mapped in corresponding templates of the particular supplemental item templates;
• one or more item insertion components configured to insert the rendered supplemental items into the documents.

One or more non-transitory computer-readable media storing instructions that, when executed by one or more computing devices,

• cause performance of:
• receiving a first request comprising document information that identifies a particular document;
• analyzing markup element code within the particular document to identify different types of structures that are repeated multiple times within corresponding groups of content items within the particular document;
• selecting, from the identified types of structures, a target repeated structure type, the target repeated structure type being an arrangement of one or more of:
• markup tags or markup attributes, the arrangement repeated multiple times in the particular document;
• based on the arrangement of the one or more of the markup tags or markup attributes of the selected target repeated structure type, generating a template for use in generating new content for insertion into the particular document, the template conforming to the target repeated structure type;
• causing a new content item to be generated from the template by causing descriptive metadata items that describe the new content item to be inserted into template elements to which the descriptive metadata items have been mapped, the new content item also conforming to the target repeated structure type;
• causing the new content item to be inserted in the particular document at an insertion point before or after a particular content item that also conforms to the target repeated structure type.