xi

Wow, this is truly creative editing. None of your insertions are implied from the context and the quotes you picked up are several minutes apart. In particular, he talks about 1.5 millions of people lacking meaningful job prospects as one of the causes of the unrest (which is true). A few minutes later, when he talks about about killing people, nowhere he implies millions of civilians, in fact, it's obvious he means armed militants.

I'll give you a better explanation: the TV host didn't challenge him because it never happened. The "expert" (another journalist, in fact) never suggested to "physically eliminate about 1.5 million of civilians of Donetsk and Luhansk regions that are not able to fit in Ukrainian Nation" or anything close to it.

Maybe because of them? The article about Timoshenko is written by a serious antisemitic nutjob.

Here is an implementation of `cached_property` I use:

    class cached_property(object):

        def __init__(self, fget):
            self.fget = fget
            self.__name__ = fget.__name__
            self.__module__ = fget.__module__
            self.__doc__ = fget.__doc__

        def __get__(self, obj, objtype=None):
            if obj is None:
                return self
            value = self.fget(obj)
            # For a non-data descriptor (`__set__` is not defined),
            # `__dict__` takes precedence.
            obj.__dict__[self.__name__] = value
            return value

An ant may randomly leave a pheromone trail, which ensures that other, perhaps more attractive food sources are not missed. In general, the stronger the signal, the faster ants move with the less probability of diverging from the path.

This strategy ensures optimal area exploitation under varying conditions. For instance, if the food is concentrated in one or a few locations, you'll see a single column between the nest and the source, but when the food is scattered through the area, the ants would disperse too.

Source: an excellent book "Cells, Embryos and Evolution" where it was used as an example of how complex and seemingly organized and directed behavior could be achieved by a population of identical individuals acting under uniform rules.

Very good point.

In the book pointed out by Matt, Date explicitly states he's not saying ORDER BY is not useful, just that it doesn't return a relation and thus it's not included in the algebra.

My biggest gripe about ORDER BY, LIMIT and relational model is the fact that while Date and others made some attempts to express these operations in terms of relational algebra, they never (AFAIK) tried to do the opposite: alter the relational query model to naturally support them. It's not hard: just replace sets with sequences or arrays. It will gives you natural ORDER and SLICE operators as well as new aggregates FIRST, LAST, NTH. It solves duplicates without having to introduce bags, gives windowing functions for free and probably better represents how modern RDBMS interpret a query. Another hint why sequences may work better than sets is the fact that regular set operations such as INTERSECT and UNION (as opposed to UNION ALL, which becomes concatenation) are so rarely used in real-world queries.

I'm not even arguing that this is a good approach, but I think it deserves some discussion and it appears they never even thought of a possibility of changing the model treating it not as an instrument, but as a sacred scripture.

However you can't do the same trick if I ask you to return the top 3 posts with the largest number of comments; or, to make the query more realistic, ask you to return the percentage of comments generated by the top 10% popular (by the number of comments) posts. Which is my point: pure relational algebra as advocated by Date et al in Tutorial D is less expressive than SQL, which probably explains the cold reception it got from the industry.

Edit: now that I think about it, you could do it without ORDER BY/LIMIT, but still it's harder than necessary.