So I may have just had an epiphany. At least I hope this is the case concerning the concept of practices in ITIL Version 4.
It is my understanding that Service Value Chains consist of Service Value Streams which in turn consist of Practices. The Practices produce the outputs which together make up the service for the stream.
Is this accurate? Thanks in advance
Hi Ralph,
Difficult answer, but yes and no.
The service Value system refers to Service Management as entirety within an organisation (including project management).
The Service Value Chain is generic to an organisation and lays out all of the processes and activities required to deliver services (so just a specific portion of the Service Value System referring to activities).
A Service Value Stream starts with a business / customer outcome and then details all of the practices (processes, capabilities, and resources) required just facilitate the co-creation of that outcome.
Each Service Value Stream will be unique to the specific outcome and will pull elements from the Service Value Chain. Each Stream may use different elements from the Chain, but of course the Stream contains much more than just the activities found in the Chain.
Does that make sense?
Thanks
Jo
Yes Jo it makes sense 
Thanks again