[FEATURE] Validate a process flow graph

[dbwiddis]

Is your feature request related to a problem?

The result of #17 will be an ordered collection of nodes. However, there may be invalid connections in this sequence.

What solution would you like?

Perform error-handling to identify these invalid connections, throwing verbose exceptions explaining the reason. Validation checks should include:

• Type-checking of output vs. input at at least a high level (text vs. binary data)
• Type-checking of output vs. input at a more detailed level if available (required attributes)
• All nodes have a predecessor and dependent node

Do you have any additional context?

The type checking would ideally tie into Java inheritance concepts.

[minalsha]

This will be covered as part of #88.