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Ingest forms are affiliated with content models. This means that a collection object that subscribes to a given model will make available to users, on ingest, any forms that are associated with the content model. Forms are associated with content models, not collections. A collection will make available all of the forms associated with a content model to which it subscribes The collection has no effect on what forms are offered when someone goes to upload.

When you use Islandora solution packs, the association to a content model (and its default form) are made for you:

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