
Datomic 2013 Recap - joeyespo
http://blog.datomic.com/2014/01/datomic-2013-recap.html
======
cgag
Glad to hear things are going well. I'm using datomic for a side project and
loving it. Writing queries in datalog is easier than sql, and having the
queries be composed of data structures instead of strings is so so nice.

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juliangamble
I'm a big fan of Datomic and am interested to see how people will apply it.

One thing that fascinates me is that Datalog (the query language of Datomic
and a precursor to SQL) doesn't have negation. (ie in an SQL query you can use
the NOT operator in your WHERE clause - but you don't have the equivalent in
Datomic datalog at present). It seems to be a low priority feature.

[https://groups.google.com/forum/#!topic/datomic/UBWzp4nYOMk](https://groups.google.com/forum/#!topic/datomic/UBWzp4nYOMk)

They very gently touch on this in the rationale page: _Datalog with negation
is of equivalent power to relational algebra with recursion._ Which seems to
suggest you don't need it.

[http://www.datomic.com/rationale.html](http://www.datomic.com/rationale.html)

~~~
jamii
Negation is a pretty common addition to datalog, along with group-by, max, min
and other non-monotonic operators. It merely requires stratification.

[http://webdam.inria.fr/Alice/pdfs/Chapter-15.pdf](http://webdam.inria.fr/Alice/pdfs/Chapter-15.pdf)

~~~
cgag
This looks cool, I'll have to check this book out. For people who are
interested, this is from Foundations of Databases
([http://www.amazon.com/Foundations-Databases-The-Logical-
Leve...](http://www.amazon.com/Foundations-Databases-The-Logical-
Level/dp/0201537710/ref=cm_lmf_tit_11)) and is available for free at the root
url from jamii's link.

edit: realized it's a referral link, it's not mine, it's because I got there
through Rich Hickey's list of books that influenced clojure:
[http://www.amazon.com/Clojure-
Bookshelf/lm/R3LG3ZBZS4GCTH](http://www.amazon.com/Clojure-
Bookshelf/lm/R3LG3ZBZS4GCTH)

