Big congrats! that’s a major achievement!
Or should that be a “Captain achievement”?
heck, just celebrate!
Many thanks all.
Strangely, both. I expected the “general questions” about my field to be routine, and the picking apart of my thesis to be harder, as there’s some design choices we made that aren’t at all obvious (and possibly aren’t justified too well in my thesis). Instead, I got hard questions about my field and its relationship with my work, and the “going through each chapter of my thesis” part was routine and relatively quick.
Standard three months, I think, although from the sounds of it my internal examiner thinks this is pretty flexible. There’s no use me telling you not to worry as you will anyway (many people told me it’s a piece of piss, yet I still worried) but it really is only a sanity check, and making sure you wrote the thesis and not your examiners.
I have an infamous ability to be unable to describe what I do in layman’s terms amongst my friends, but, here goes: I study calculi of metavariables (where a metavariable is like a “hole in a term”). These appear all over computer science, mathematics, and logic, yet are almost always kept implicit, and never studied formally. If you’ve studied calculus, then you will have been introduced to the notion of “metavariable” without having realised it, for instance. Of course, if you study these things formally (i.e. incorporate them into a formal calculus), then you can get extremely nice systems: adding explicit metavariables to a typed lambda-calculus (the canonical syntax for describing functions in computer science) gives you a notion of proof term for incomplete derivations, as normally seen in type-theory based proof assistants (programs that check mathematics proofs, like Coq or Matita). Similarly, extending the lambda-calculus with metavariables and with the ability to lambda-abstract over metavariables gives you a “context calculus”, which are interesting from a programming language design viewpoint (static checking of Lisp-like macros, metaprogramming, module systems, etc.)
I bet you’re glad you asked!
The words seem to be English…so, why are you hanging around with us idjits again? 
… so how is a metavariable used in calculus, and what kind of system would it be a hole in? And how come that googling metavariable talks about metalanguage? Is that a branch of math (logic?)? Me no comprende rien de zip. And what the heck is lambda-calculus?
You need to get the elevator speech version of that, Captain 
Not just small words, but in a way that makes sense to us laymen, although it won’t be as precise as whatever it was you said there; right now I don’t even know if you studied math, computer science or paleonthology (well, probably not this one). When I tell people I’m a consultant, they ask “doing what?” “companies that want to start using this program I’m an expert in hire us to teach them how to use it. So, I teach people how to do their jobs.” Trying to explain MRP vs ERP wouldn’t do me, or them, any good.
I have a Masters Degree in Mechanical Engineering and Mathematics minor with my BS in Mechanical Engineering and I still had problems with that; like I only got about 30% of it. Good job adding to the knowledge though.
Congratulations! Here’s hoping you gave yourself one hell of a hangover last night. You’ve earned it.
There’s very likely no elevator speech forthcoming. Research in a given subfield of math/computer science is pretty much unintelligible to specialists in other subfields, although we might be able to pick up some high-level details. It’s a very rare problem that can be summarized for a lay audience in any way that’s not a complete lie, and the solutions are even more complicated.