Application of inter-item category constraint for uncategorized content items

A system, comprising:

• one or more processors and corresponding memory configured to implement a service configured to:
• prepare, responsive to receipt of responses comprising indications of supplemental content items from first and second supplemental content servers, a response to a request from a content provider including supplemental content items from both the first supplemental content server and the second supplemental content server, wherein prepare the response comprises:
• analyze, based at least in part on logic for inferring categories of supplemental content items, response metadata or the indicated supplemental content items from the responses from the first and second supplemental content servers to infer categories for the at least some of the indicated supplemental content items;
• and
• apply an inter-item category constraint using the inferred categories for the indicated supplemental content items to select a plurality of the indicated supplemental content items for inclusion in the response to the content provider, wherein said apply the inter-item category constraint using the inferred categories reduces a likelihood of any two supplemental content items included in the response having a same category;
• and
• transmit the response to the content provider.

A method, comprising:

• preparing, responsive to receipt of responses comprising indications of supplemental content items from first and second supplemental content servers, a response to a request from a content provider including supplemental content items from both the first supplemental content server and the second supplemental content server, wherein preparing comprises:
• analyzing, based at least in part on logic for inferring categories of supplemental content items, response metadata or the indicated supplemental content items from the responses from the first and second supplemental content servers to infer categories for the at least some of the indicated supplemental content items;
• and
• applying an inter-item category constraint using the inferred categories for the indicated supplemental content items to select a plurality of the indicated supplemental content items for inclusion in the response to the content provider, wherein said applying the inter-item category constraint using the inferred categories reduces a likelihood of any two supplemental content items included in the response having a same category;
• and
• sending, over a network, the response to the content provider.

One or more non-transitory computer-readable media storing program instructions executable on or across one or more processors to perform:

• preparing, responsive to receipt of responses comprising indications of supplemental content items from first and second supplemental content servers, a response to a request from a content provider including supplemental content items from both the first supplemental content server and the second supplemental content server, wherein preparing comprises:
• analyzing, based at least in part on logic for inferring categories of supplemental content items, response metadata or the indicated supplemental content items from the responses from the first and second supplemental content servers to infer categories for the at least some of the indicated supplemental content items;
• and
• dropping one or more of the indicated supplemental content items that remain uncategorized after said analyzing, wherein said dropping reduces a likelihood of any two supplemental content items included in the response having a same category;
• or
• applying frequency information indicating a frequency of one or more of the indicated supplemental content items or of the inferred categories for the indicated supplemental content items to select a plurality of the indicated supplemental content items for inclusion in the response to the content provider, wherein said applying frequency information indicating a frequency of one or more of the indicated items or of the inferred categories reduces a likelihood of any two supplemental content items included in the response having a same category;
• and
• responding to the content provider with the response.