Restructure introduction to specification

[harisood]

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⤴️ Summary

Refactor the introduction to the specification with our current version of the architecture, including visualisations

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[harisood]

Is this the right kind of thing?

If so work to come out of this:

• Update the principles as in line with @machintim 's latest architecture doc
• Refactor capabilities to match visualisations (e.g. for IG there are now only 4 capabilities, but in the specification there are 6 and the titles do not match)

[harisood]

FYI this diagram is a refactor of @machintim 's original based on my understanding/what I think might be a bit clearer!

[jemrobinson]

LGTM subject to questions inline

[harisood]

@jemrobinson made edits, will leave open for a little bit to see if others have thoughts. Feel free to merge without me if not done today!

[JimMadge]

As @harisood is away I will make the changes I've suggested above. However, please do say if you disagree because those are just my opinions after all.

[jemrobinson]

If we want to restructure into three capabilities, shouldn't we also renumber the sections below?

[JimMadge]

If we want to restructure into three capabilities, shouldn't we also renumber the sections below?

Yes. Do you think it is in scope for this PR?

Longer term, do we think that part will be on a separate page?
It would be nice if we could use automatic numbering so that the references can come out like "Capability 1.3.4".

[jemrobinson]

If we want to restructure into three capabilities, shouldn't we also renumber the sections below?

Yes. Do you think it is in scope for this PR?

I'm happy to do this in a follow-on PR.