It is evident to me that the chart conveys that Section 5 (Management Responsibility), Section 6 (Resource Management), Section 7 (Product Realization) and Section 8 (Monitoring, Measuring, and Analysis) interact to produce Continual Improvement. It show those main elements of the standard and how they interrelate to each other. It is by the application of them that Continual Improvement is achieved.
I think the model missed Section 4 and somehow should show Document Control in the mix.
The thick curvy arrows mainly signify "information" to me. This information must be valid and that covers clause 4.2.3 for me (valid information available where required).
I am not sure about any connection between those thick curvy arrows and 4.2.3. If they wanted to show possible flow of some "information", why wouldn't they use the very same dashed arrows that are marked "information flow" in the legend?
Yes, those thick curvy arrows are obviously an attempt (IMHO, an extremely awkward one) to convey something like "processes in four groups
somehow interact to achieve the ultimate goal of continual improvement". But how exactly do they interact? What's the nature of those interactions? They do not interact in a way that is usually designated by "control flow" or "information flow". Hence those fancy arrows with extremely vague meaning.
The result - a lot of confusion and, worse yet, some misleading like here
Hi Jane,
Thanks for pointing out that the model in ISO 9000/1/4 is not a PDCA. It merely lulls you into thinking it is...
or here
That chart is also called the "Deming Wheel". ...
or at the beginning of my own learning curve.
This "help" from ISO is a classic example of what we call "a bear's favour" in Russia (which means "a well-intended favour that is made in such a clumsy way that it does more harm than good").
If they wanted to say that "processes interact to provide continual improvement" they would be better off
writing just that somewhere,
in plain English, as a comment. (And better not make "continual improvement" itself look like another group of processes!

)
Interestingly enough, there are no such arrows between "extended" groups of processes in the current draft of ISO 9004:2009...
BTW, from what I see in numerous document samples posted at Cove, many authors do realize that something is wrong with this "sample" provided by ISO. As a result, they elaborate only on interactions between product realization processes. Interactions with/between other processes are either being omitted or described in the same vague way as ISO "sample" does it. That's sad because those "other" interactions are very important to understand clearly...