2. The method of claim 1 further comprising receiving, as input into a document set of the workflow instance, one or more documents from an input activity, the input comprising: document metadata associated with the one or more documents comprising the document set; selecting, by an output activity of the workflow instance, the one or more documents from the document set for input by designating the document metadata corresponding to the one or more documents; and selecting, by a processing activity of the workflow instance, the one or more documents from the document set to input by designating the corresponding document metadata.
2. The method of claim 1 further comprising receiving, as input into a document set of the workflow instance, one or more documents from an input activity, the input comprising: document metadata associated with the one or more documents comprising the document set; selecting, by an output activity of the workflow instance, the one or more documents from the document set for input by designating the document metadata corresponding to the one or more documents; and selecting, by a processing activity of the workflow instance, the one or more documents from the document set to input by designating the corresponding document metadata. 4. The method of claim 2 further comprising: filtering, by a processing activity of the workflow instance, the one or more documents from the document set by executing instructions to remove unwanted retrieved documents.