Sure, it's concise, but I'd hardly describe ncatlab as introduction. It's more of a reference. I'd dare say the Wikipedia entry on category theory (and related links) makes a better introduction for the uninitiated.
To actually learn it, Mac Lane & Saunders "Categories for the Working Mathematician." seems to enjoy continued popularity.
MacLane is still the standard for working mathematicians, but for those with less background, Steve Awodey's book is very good. He also has some YouTube lectures. While you're on YouTube, the Catsters channel has many excellent 10-minute category theory videos.
I can second the Catsters channel. As a complete category theory newbie watching those videos was nevertheless enjoyable because of the upbeat and cheerful attitude with which the material was covered.
I actually found MacLane's book to be more approachable than Awodey's. Although I'm not sure this is good advice because it took me several years casually feeling my way through the field to start to gain an understanding into it (ie YMMV).
Interesting category theory historical fact! Checkout MacLane's wikipedia page and you will find one of his students was in fact Steve Awodey.
> To actually learn it, Mac Lane & Saunders "Categories for the Working Mathematician." seems to enjoy continued popularity.
This is the best way I've found so far, and I had been semi-supplementing with MacLane and Birkhoff's "Algebra", just to get a feeling for the vocabulary; bringing myself from the space I typically mathematically exist in, to the space of category theory. Nothing else really has come close in composing the correct thought direction. It is dense, but I enjoy it very much. It is very beautiful math.
I have always sworn by Borceux' Handbook of Categorical Algebra. It progresses smoothly all the way from first principles up to (if you buy all three volumes) sheaves and topoi, but it is kind of expensive.
It probably is. Sure they have a good R&D department. But it's still a collection of many books on just one device. Good for ecological reasons and so on. But if you just think about it, it's still fun to have a physical overview of all the books that you have bought and read. I can see a future where paper books will have no place. Or am i wrong about that?
If you want the joy of owning a physical book, which looks nice, advertises its presence to you every time you walk past and shows off how educated you are, then a physical book is actually the optimum solution to the problem. Like vinyl records, they offer a different experience of media consumption that some people consider superior, as well as showing off that you're a connoisseur and filling your shelves with nice artwork. So paper books will always have a niche, even if it's a fairly small one when it comes to novels.
What you're proposing though is like inventing a particularly-complex-to-manufacture CD... after the iPod.
If you want the convenience of something that not only has resizeable, searchable text but also weighs very little, then any current generation reader offers the exact experience you're looking to replicate, except you only have to buy and carry around one of them.
Even if and when we get to the point where e-ink screens can be manufactured for a dollar, I don't see much of a market for one-book readers.
I'm not saying that URLs are superfluous. But I think their function is exaggerated. Especially when it comes to Web Apps, but even in the case of articles in which hyperlinks are really useful and used a lot. They often seem like C pointers on which you better don't do any arithmetics. But unlike C pointers, often I cannot dereference them. ;)
Around '99 I did not rely on bookmarks, instead I saved interesting articles to my hard drive because links would break so often. Even today the problem remains and I don't even dare to say whether it got better or worse.
Maybe there are smarter concepts than HTTP-style URLs that we are not aware of yet. Might be also interesting regarding privacy, because many people actually do not want static hyperlinks to their personal information that last a million years.
SELinux. This kind of stuff would be where it really shines. A correctly configured installation would block and report access to files the application is not supposed to access. Maintaining it, especially for individual applications, is work, but it seems to me that on the scale of Google it may well be worthwhile.