Question
How does the Data Splitter Workflow node and the Data Collector work?
How to use the Data Splitter and Data Collector Workflow nodes?
Answer
Data Splitter
Use the Data Splitter workflow node if you want the next steps in the workflow to process each document individually.
Example (click to enlarge):

In the example above, three files are attached when the workflow starts. They appear as a group (one token) on the output pin of the Start node. Click the output pin to see all the other members of the group in light-blue. When you check the output pin of the Data Splitter - Legal Approvals node, only one document is highlighted: the Data Splitter has "split" the group to process each document separately in the next steps: three tasks are created for Legal Comments - Patent, one for each document. The same happens for Legal Comments - Trademark.
Data Collector
Use the Data Collector workflow control to:
- Collect all documents that travel separately in the workflow and then send them all together to the next step.
- Wait for all previous steps before continuing the workflow.
Example 1 (click to enlarge):

When the workflow from the previous example illustrating the Data Splitter continues a bit, two of the Legal Comments - Patent tasks are already completed and one of the Legal Comments - Trademark tasks. The Data Collector - Legal Approvals waits for the remaining three tasks to be completed, before continuing with a merged group of documents. This only works if the upper branch is a separate workflow (see further for the Legal Approvals Run Example), but in this case it will even wait longer because of the second condition: 'it waits for all previous steps before continuing the workflow', see below.
Example 2 (click to enlarge):

The Data Collector makes an analysis of all possible paths from where tokens can still arrive. It waits until these arrive before continuing. In the example above, the Graphic Coordinator Approve or Reject and the Proofreading Approve or Reject Router nodes have a loop back via the task Upload Revised Graphic Items to the beginning of the workflow. The Data Collector - Legal Approvals can still receive tokens from these paths, so it waits for them as well. One possible workaround for this problem is to split up your workflow in smaller pieces. The above workflow can be replaced with the workflows below:
Alternative to Example 1 and 2 (click to enlarge):

The upper branch is replaced with a sub workflow Legal Approvals.
Legal Approvals Run Example (click to enlarge):

The Data Collector above waits for both Legal Comments tasks to be completed before continuing with the document.