mkleczek

16 ms·

181.
by mkleczek 4y ago
“Complexity is the business we are in, and complexity is what limits us.” Yet, just as Turski recognized, some people seem to be philosophically offended by this notion, and try to fight the proven limitations. They are under the impression
182.
by mkleczek 4y ago
Here in Poland it is 30 CAD.
183.
by mkleczek 4y ago
No. From the fact that we know how to write programs that halt you cannot deduce we know how to write programs with arbitrary (or even just useful) property, because there is no general procedure to do that. In other words: you cannot use t
184.
by mkleczek 4y ago
Actually it's the other way around: In reality most interesting programs accept Turing complete languages - albeit not formally specified :)
185.
by mkleczek 4y ago
> People create wholly deterministic state machines all the damn time. What do you mean by "wholly deterministic"?
186.
by mkleczek 4y ago
> Every time you're about to write code with a bug, don't. Write that same code but without the bug. This procedure (algorithm) is ill-defined (is not realisable by a TM) as it would require verifying two things: a) the code yo
187.
by mkleczek 4y ago
> You must be misunderstanding the work if you believe that what is being done routinely is impossible. Quite possibly I don't understand what you mean by "work". If by "work" you mean creating provably correct s
188.
by mkleczek 4y ago
My point is that it is _theoretically_ not possible: there is no algorithm that would allow you to build a TM implementing arbitrary requirements. You have to use ad-hoc methods but then it is not possible to know your ad-hoc method is corr
189.
by mkleczek 4y ago
> It is in fact extremely common to build wholly deterministic machines out of the same parts as our unreliable computers, that are correct by construction. It is neither common nor easy but actually provably impossible. Please read this
190.
by mkleczek 4y ago
See above - there is no reliable procedure (algorithm) that would allow you to build a TM with arbitrary properties (ie. implementing arbitrary requirements).
191.
by mkleczek 4y ago
> It suffices that we can reliably construct machines that perform a desired function and have the desired property. See above - there is no reliable procedure (algorithm) that would allow you to do that.
192.
by mkleczek 4y ago
Just having a language that allows you to prove things does not mean it is possible to prove them. We still don't know if it is possible to build a provably correct multi-tasking OS or a web browser without security vulnerabilities. If
193.
by mkleczek 4y ago
> Because this statement uses "exists" on the property, it does not rule out the existence of a y which works for most properties P that we'd care about. It only rules out one that works for all properties. Translated: the
194.
by mkleczek 4y ago
There are two problems with this: 1. Even for as weak computational model as FSM the problem of verifying its correctness is intractable (NP-hard). And modularisation does not help. 2. We don't know any weaker computational model that
195.
by mkleczek 4y ago
> Rice's Theorem isn't as strong as you say it is It is very strong: its corollary is there is no general algorithm to build Turing Machines with arbitrary non-trivial properties (if there was such an algorithm we could use it
196.
by mkleczek 4y ago
> Rice’s theorem tells you you can’t prove you’ve built a flawless system, not that you can’t build a flawless system. If you think about it - it is the same: how do you know the system you just built is flawless?
197.
by mkleczek 4y ago
Actually building such a computer is provably impossible: https://en.wikipedia.org/wiki/Rice%27s_theorem I highly recommend this talk on the subject: https://pron.github.io/posts/correctness-and-co
198.
by mkleczek 4y ago
Indeed - a filesystem is a form of DBMS and provides data sharing capabilities. These capabilities are very poor though - especially its data model (or rather lack of one) makes data sharing difficult as applications cannot rely on it and i
199.
by mkleczek 4y ago
This opinion is quite popular nowadays but IMHO it is caused by misunderstanding what a database and database management system is and what it is for. DBMS (and in particular) RDBMS is not a merely persistence medium for an application - DB
200.
by mkleczek 4y ago
I guess I am in minority here now but... Embedding an SQL database in the application is really missing the point of having RDBMS. The goal of RDBMS is not merely to persist application data but to _share_ data between different application
201.
by mkleczek 5y ago
And this is the root problem as that's equivalent to running software as root.
202.
by mkleczek 5y ago
Any JEE code that uses container provided resources. So a lot...
203.
by mkleczek 5y ago
This is actually worse than log4j. Any code accessing JNDI using URIs from external data is vulnerable. Script injection (aka XSS) at its finest. Looks like a good use case for running under SecurityManager with a restrictive policy. Maybe
204.
by mkleczek 7y ago
In my opinion the main issue with OSGi class loading is that the spec couples three separate concerns: peer class loading (as opposed to hierarchical) dependency resolution dependency specification and module (bundle) packaging This makes O
205.
by mkleczek 7y ago
(Micro)services and separate codebases are orthogonal. You can have multiple separate components (libraries) implemented in different codebases and linked as a single executable (which is actually really common). You can have (micro)service