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Search found 1451 results on 59 pages for 'theory'.

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• Chris Date on "SQL and Relational Theory - How to Write Accurate SQL Code"

  - by MartinBell

  The importance of relational theory......(read more)

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• Theory Of A Weird Thought - Forms Submission

  - by user2738336

  In theory, if you were to open two computers that were perfectly synced together on a website that has a form. This form has fields where say for example the username has to be unique. Assuming both computers have the same information on the form, and in theory let's say that the submit button was pressed at the same time, and that these two computers have the exact same build and internet speed and the same response time from the server, whose information would be submitted to the database and whose information would be denied knowing the username field is unique.

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• category theory based language

  - by pagoda_5b

  It may sound naive, but is there any programming language, or research thereof, based entirely on category theory? I mean this as opposed to embedding CT concepts as an additional feature (like for Haskell or scala). Would it be too abstract or too complex as an approach, or are there any known reasons that makes it impossible or impractical? I have only a relative understanding of the theory as related to programming, so please give me some explanation if the question doesn't makes sense at all

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• Color schemes generation - theory and algorithms

  - by daniel.sedlacek

  Hi I will be generating charts and diagrams and I am looking for some theory on color schemes and algorithm examples. Example questions: How to generate complementary or analogous colors? How to generate pastel, cold and warm colors? How to generate any number of random but distinct colors? How to translate all that to the hex triplet (web color)? My implementation will be in AS3 but any examples in metacode are welcome.

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• Subsumption architecture vs. perceptual control theory

  - by Yasir G.

  I'm a new person to AI field and I have to research and compare 2 different architectures for a thesis I'm writing. Before you scream (homework thread), I've been reading on these 2 topics only to find that I'm confusing myself more.. let me first start with stating briefly what I know so far. Subsumption is based on the fact that targets of a system are different in sophistication, thus that requires them to be added as layers, each layer can suppress (modify) the command of the layers below it, and there are inhibitors to stop signals from execution lets say. PCT stresses on the fact that there are nodes to handle environmental changes (negative feedback), so the inputs coming from an environment go through a comparator node and then an action is generated by that node, HPCT or (Hierarchical PCT) is based on nesting these cycles inside each other so a small cycle to avoid crashing would be nested in a more sophisticated cycle that targets a certain location for example. My questions, am I getting this the right way? am I missing any critical understanding about these 2 models? also any idea where I can find simplified explanations for each theory (so far been struggling trying to understand the papers from Google scholar :< ) /Y

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• Operating systems theory -- using minimum number of semaphores

  - by stackuser

  This situation is prone to deadlock of processes in an operating system and I'd like to solve it with the minimum of semaphores. Basically there are three cooperating processes that all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. Semaphores should be used to synchronize: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'm sure that any kernel programmers that happen on this can knock this out in a minute or 2. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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• How do you deal with translating theory into practice?

  - by Mr. Shickadance

  Hello all! Being a computer scientist in a research field I am often tasked with working alongside professionals outside of the software domain (think math people, electrical engineer etc), and then translating their theories and ideas into real-world implementations. I often find it difficult when they present a theoretical problem which appears to be somewhat disconnected from reality. I am not saying that the theory is bogus, only that it is difficult to translate into real-world situations. For example, recently I have been working with software defined radios. We are exploring many different areas, but often the math specialists in my group would present a problem which is heavily grounded in theory (signal processing, physics, whatever). I often struggle at times where it is hard to draw direct parallels between the theory and the real-world implementation that I need to develop. Say we are working on an energy detector, the theory person in my group would say "you need to measure the noise variance with no signal present." This leads me to think "how the hell do I isolate noise from a signal in reality?" There are many examples, but I hope you see where I am going. So, my question is how does one deal with implementation of theoretical concepts when the theory seems detached from reality? Or at least when the connections are not so clear. Or perhaps, the person with the 'theory' may be ignorant of real restrictions? Note: I found this to be a hard question to ask - hopefully you are following me. If you have suggestions on how I could improve it, by all means let me know! Thanks for looking! EDIT: To be a bit more clear, I understand in situations like this that I must learn that specific domain myself to an extent (i.e. signal processing), but I am more concerned with when those theoretical concepts do not appear to be as grounded in practice as one would like.

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• Are there any formalized/mathematical theories of software testing?

  - by Erik Allik

  Googling "software testing theory" only seems to give theories in the soft sense of the word; I have not been able to find anything that would classify as a theory in the mathematical, information theoretical or some other scientific field's sense. What I'm looking for is something that formalizes what testing is, the notions used, what a test case is, the feasibility of testing something, the practicality of testing something, the extent to which something should be tested, formal definition/explanation of code coverage, etc. UPDATE: Also, I'm not sure, intuitively, about the connection between formal verification and what I asked, but there's clearly some sort of connection.

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• Why do some programmers think there is a contrast between theory and practice?

  - by Giorgio

  Comparing software engineering with civil engineering, I was surprised to observe a different way of thinking: any civil engineer knows that if you want to build a small hut in the garden you can just get the materials and go build it whereas if you want to build a 10-storey house you need to do quite some maths to be sure that it won't fall apart. In contrast, speaking with some programmers or reading blogs or forums I often find a wide-spread opinion that can be formulated more or less as follows: theory and formal methods are for mathematicians / scientists while programming is more about getting things done. What is normally implied here is that programming is something very practical and that even though formal methods, mathematics, algorithm theory, clean / coherent programming languages, etc, may be interesting topics, they are often not needed if all one wants is to get things done. According to my experience, I would say that while you do not need much theory to put together a 100-line script (the hut), in order to develop a complex application (the 10-storey building) you need a structured design, well-defined methods, a good programming language, good text books where you can look up algorithms, etc. So IMO (the right amount of) theory is one of the tools for getting things done. So my question is why do some programmers think that there is a contrast between theory (formal methods) and practice (getting things done)? Is software engineering (building software) perceived by many as easy compared to, say, civil engineering (building houses)? Or are these two disciplines really different (apart from mission-critical software, software failure is much more acceptable than building failure)?

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• What types of programming require practical category theory?

  - by Alexander Gruber

  Category theory has applications in theoretical computer science and obviously is central to abstract mathematics. I have heard that it also has direct practical applications in programming and software development. What type of programming is practical category theory necessary for? What do programmers use category theory to accomplish? Please note my use of "necessary" and "require" in this post. I realize that in some sense most programmers will benefit from having experience in different types of theories, but I am looking for direct applications where the usage of category theory is essential, i.e. if you didn't know category theory, you probably couldn't do it. Also, I'd like to clarify that by "what type of programming," I am hoping less for a broad answer like "functional programming," and more for specific applications like "writing bank software" or "making operating systems."

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• Why does NUnit ignore datapoints when using generics in a theory

  - by The Chairman

  I'm trying to make use of the TheoryAttribute, introduced in NUnit 2.5. Everything works fine as long as the arguments are of a defined type: [Datapoint] public double[,] Array2X2 = new double[,] { { 1, 0 }, { 0, 1 } }; [Theory] public void TestForArbitraryArray(double[,] array) { // ... } It does not work, when I use generics: [Datapoint] public double[,] Array2X2 = new double[,] { { 1, 0 }, { 0, 1 } }; [Theory] public void TestForArbitraryArray<T>(T[,] array) { // ... } NUnit gives a warning saying No arguments were provided. Why is that?

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• Is there a good example of the difference between practice and theory?

  - by a_person

  There has been a lot of posters advising that the best way to retain knowledge is to apply it practically. After ignoring said advice for several years in a futile attempt to accumulate enough theoretical knowledge to be prepared for every possible case scenario, the process which lead me to assembling a library that's easily worth ~6K, I finally get it. I would like to share my story in the hopes that others will avoid taking the same route that was taken by me. I've selected graphical format (photos with caption to be exact) as my media. Help me with your ideas, maybe a fragment of code, or other imagery that would convey a message of the inherent difference between practice and theory.

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• Is it possible to test a theory?

  - by user363295

  We are a group of students who are working on a theory in software engineering (talking about the theory takes a lot of time so I just skip that). Implementing the theory is impossible, due to technical limitations, but it can be proven on a paper logically. We've been pushed to do a testing on it, so it can be proved that way too (although we bleieve that's not possible!), now: Basically, is it possible to test something like this? If it is, what type of testing should we use? I heard,its possible to handout a brief about it to some experts and asking about their opinion (not sure if that's true), is that a testing method? if it is, what does it called? and how exactly can be done?

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• Graph theory in python

  - by Dan

  I was wondering how people deal with graph theory in python? How is a graph stored? Are there libraries for this? For example how would I input a graph and then find its Chromatic polynomial? Or its girth? Or the number of unique spanning trees? How about problems that involve edge weight like salesman problems? I don't need all of these answered, I'm just looking for a method or tool set that will be able to help me approach solve problems like this. Thanks, Dan

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• What is the relaxation condition in graph theory

  - by windopal

  Hi, I'm trying to understand the main concepts of graph theory and the algorithms within it. Most algorithms seem to contain a "Relaxation Condition" I'm unsure about what this is. Could some one explain it to me please. An example of this is dijkstras algorithm, here is the pseudo-code. 1 function Dijkstra(Graph, source): 2 for each vertex v in Graph: // Initializations 3 dist[v] := infinity // Unknown distance function from source to v 4 previous[v] := undefined // Previous node in optimal path from source 5 dist[source] := 0 // Distance from source to source 6 Q := the set of all nodes in Graph // All nodes in the graph are unoptimized - thus are in Q 7 while Q is not empty: // The main loop 8 u := vertex in Q with smallest dist[] 9 if dist[u] = infinity: 10 break // all remaining vertices are inaccessible from source 11 remove u from Q 12 for each neighbor v of u: // where v has not yet been removed from Q. 13 alt := dist[u] + dist_between(u, v) 14 if alt < dist[v]: // Relax (u,v,a) 15 dist[v] := alt 16 previous[v] := u 17 return dist[] Thanks

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• Set Theory and .NET

  - by MasterMax1313

  Recently I came across a situation where set theory and set math fit what I was doing to the letter (granted there was an easier way to accomplish what I needed - i.e. LINQ - but I didn't think of that at the time). However I didn't know of any generic set libraries. Granted IEnumerables provide some set operations (Union, etc.), but nothing like Intersection or set comparison. Can anyone point out something that fits here? Something that implements set math using a generic type?

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• Is there a theory for "transactional" sequences of failing and no-fail actions?

  - by Ross Bencina

  My question is about writing transaction-like functions that execute sequences of actions, some of which may fail. It is related to the general C++ principle "destructors can't throw," no-fail property, and maybe also with multi-phase transactions or exception safety. However, I'm thinking about it in language-neutral terms. My concern is with correctly designing error handling in C++ functions that must be reliable. I would like to know what the concepts below are called so that I can learn more about them. I'm sorry that I can't ask the question more directly. Since I don't know this area I have provided an example to explain my question. The question is at the end. Here goes: Consider a sequence of steps or actions executed sequentially, where actions belong to one of two classes: those that always succeed, and those that may fail. In the examples below: S stands for an action that always succeeds (called "no-fail" in some settings). F stands for an action that may fail (for example, it might fail to allocate memory or do I/O that could fail). Consider a sequences of actions (executed sequentially from left to right): S->S->S->S Since each action in the sequence above succeeds, the whole sequence succeeds. On the other hand, the following sequence may fail because the last action may fail: S->S->S->F So, claim: a sequence has the no-fail (S) property if and only if all of its actions are no-fail. Now, I'm interested in action sequences that form "atomic transactions", with "failure atomicity," i.e. where either the whole sequence completes successfully, or there is no effect. I.e. if some action fails, the earlier ones must be rolled back. This requires that any successfully executed actions prior to a failing action must always be able to be rolled back. Consider the sequence: S->S->S->F S<-S<-S In the example above, the first row is the forward path of the transaction, and the second row are inverse actions (executed from right to left) that can be used to roll back if the final top row actions fails. It seems to me that for a transaction to support failure atomicity, the following invariant must hold: Claim: To support failure atomicity (either completion or complete roll-back on failure) all actions preceding the latest failable (F) action on the forward path (marked * in the example below) must have no-fail (S) inverses. The following is an example of a sequence that supports failure atomicity: * S->F->F->F S<-S<-S Further, if we want the transaction to be able to attempt cancellation mid-way through, but still guarantee either full completion or full rollback then we need the following property: Claim: To support failure atomicity and cancellation mid-way through execution, in the face of errors in the inverse (cancellation) path, all actions following the earliest failable (F) inverse on the reverse path (marked *) must be no-fail (S). F->F->F->S->S S<-S<-F<-F * I believe that these two conditions guarantee that an abortable/cancelable transaction will never get "stuck". My questions are: What is the study and theory of these properties called? are my claims correct? and what else is there to know? UPDATE 1: Updated terminology: what I previously called "robustness" is called atomicity in the database literature. UPDATE 2: Added explicit reference to failure atomicity, which seems to be a thing.

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• Color Theory: How to convert Munsell HVC to RGB/HSB/HSL

  - by Ian Boyd

  I'm looking at at document that describes the standard colors used in dentistry to describe the color of a tooth. They quote hue, value, chroma values, and indicate they are from the 1905 Munsell description of color: The system of colour notation developed by A. H. Munsell in 1905 identifies colour in terms of three attributes: HUE, VALUE (Brightness) and CHROMA (saturation) [15] HUE (H): Munsell defined hue as the quality by which we distinguish one colour from another. He selected five principle colours: red, yellow, green, blue, and purple; and five intermediate colours: yellow-red, green-yellow, blue-green, purple-blue, and red-purple. These were placed around a colour circle at equal points and the colours in between these points are a mixture of the two, in favour of the nearer point/colour (see Fig 1.). VALUE (V): This notation indicates the lightness or darkness of a colour in relation to a neutral grey scale, which extends from absolute black (value symbol 0) to absolute white (value symbol 10). This is essentially how ‘bright’ the colour is. CHROMA (C): This indicates the degree of divergence of a given hue from a neutral grey of the same value. The scale of chroma extends from 0 for a neutral grey to 10, 12, 14 or farther, depending upon the strength (saturation) of the sample to be evaluated. There are various systems for categorising colour, the Vita system is most commonly used in Dentistry. This uses the letters A, B, C and D to notate the hue (colour) of the tooth. The chroma and value are both indicated by a value from 1 to 4. A1 being lighter than A4, but A4 being more saturated than A1. If placed in order of value, i.e. brightness, the order from brightest to darkest would be: A1, B1, B2, A2, A3, D2, C1, B3, D3, D4, A3.5, B4, C2, A4, C3, C4 The exact values of Hue, Value and Chroma for each of the shades is shown below (16) So my question is, can anyone convert Munsell HVC into RGB, HSB or HSL? Hue Value (Brightness) Chroma(Saturation) === ================== ================== 4.5 7.80 1.7 2.4 7.45 2.6 1.3 7.40 2.9 1.6 7.05 3.2 1.6 6.70 3.1 5.1 7.75 1.6 4.3 7.50 2.2 2.3 7.25 3.2 2.4 7.00 3.2 4.3 7.30 1.6 2.8 6.90 2.3 2.6 6.70 2.3 1.6 6.30 2.9 3.0 7.35 1.8 1.8 7.10 2.3 3.7 7.05 2.4 They say that Value(Brightness) varies from 0..10, which is fine. So i take 7.05 to mean 70.5%. But what is Hue measured in? i'm used to hue being measured in degrees (0..360). But the values i see would all be red - when they should be more yellow, or brown. Finally, it says that Choma/Saturation can range from 0..10 ...or even higher - which makes it sound like an arbitrary scale. So can anyone convert Munsell HVC to HSB or HSL, or better yet, RGB?

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• Theory of formal languages - Automaton

  - by dader51

  Hi everybody ! I'm wondering about formal languages. I have a kind of parser : It reads à xml-like serialized tree structure and turn it into a multidimmensionnal array. I figured out that i need at least three variables to achieve the job : $tree = array(); // a new array $pTree = array(&$tree); // a new array which the first element points to $tree; $deep = 0; plus the one containing the sentence splitted into words. My point is on the similarities between the algorithm deing used and the differents kinds of automatons ( state machines turing machines stack ... ). The $words variable is the "tape" of the automaton, the test/conditions of the algorithm are transitions, $deep is the state and $tree is the output. I cannont figure what is $pTree. So the question is : which is the automaton I implictly use here, and to which formal languages family does it fit ? And what's about recursion ?

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• Set theory problem - transform one set to another

  - by mwnorman

  Given 2 sets A & B, is there an algorithm that will generate the insert/update/delete operations required to transform set A into set B?

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• Theory: "Lexical Encoding"

  - by _ande_turner_

  I am using the term "Lexical Encoding" for my lack of a better one. A Word is arguably the fundamental unit of communication as opposed to a Letter. Unicode tries to assign a numeric value to each Letter of all known Alphabets. What is a Letter to one language, is a Glyph to another. Unicode 5.1 assigns more than 100,000 values to these Glyphs currently. Out of the approximately 180,000 Words being used in Modern English, it is said that with a vocabulary of about 2,000 Words, you should be able to converse in general terms. A "Lexical Encoding" would encode each Word not each Letter, and encapsulate them within a Sentence. // An simplified example of a "Lexical Encoding" String sentence = "How are you today?"; int[] sentence = { 93, 22, 14, 330, QUERY }; In this example each Token in the String was encoded as an Integer. The Encoding Scheme here simply assigned an int value based on generalised statistical ranking of word usage, and assigned a constant to the question mark. Ultimately, a Word has both a Spelling & Meaning though. Any "Lexical Encoding" would preserve the meaning and intent of the Sentence as a whole, and not be language specific. An English sentence would be encoded into "...language-neutral atomic elements of meaning ..." which could then be reconstituted into any language with a structured Syntactic Form and Grammatical Structure. What are other examples of "Lexical Encoding" techniques? If you were interested in where the word-usage statistics come from : http://www.wordcount.org

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• Discrete problem of probability theory [closed]

  - by calejero

  A jury consists of 12 persons each of which has, before the trial started, a probability of 0.4 to vote in favor of the defendant's innocence. During the trial, the lawyer has a probability of 0.6 to change the mind of each juror who was biased against the accused. How likely is the defendant to be acquitted if he needs 10 votes in favor?

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• A Grand Unified Theory of AI

  A new approach unites two prevailing but often opposed strains in the history of AI research Artificial intelligence - Physics - Alternative - Quantum Mechanics - Quantum Field Theory

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• The theory of evolution applied to software

  - by Michel Grootjans

  I recently realized the many parallels you can draw between the theory of evolution and evolving software. Evolution is not the proverbial million monkeys typing on a million typewriters, where one of them comes up with the complete works of Shakespeare. We would have noticed by now, since the proverbial monkeys are now blogging on the Internet ;-) One of the main ideas of the theory of evolution is the balance between random mutations and natural selection. Random mutations happen all the time: millions of mutations over millions of years. Most of them are totally useless. Some of them are beneficial to the evolved species. Natural selection favors the beneficially mutated species. Less beneficial mutations die off. The mutated rabbit doesn't have to be faster than the fox. It just has to be faster than the other rabbits.   Theory of evolution Evolving software Random mutations happen all the time. Most of these mutations are so bad, the new species dies off, or cannot reproduce. Developers write new code all the time. New ideas come up during the act of writing software. The really bad ones don't get past the stage of idea. The bad ones don't get committed to source control. Natural selection favors the beneficial mutated species Good ideas and new code gets discussed in group during informal peer review. Less than good code gets refactored. Enhanced code makes it more readable, maintainable... A good set of traits makes the species superior to others. It becomes widespread A good design tends to make it easier to add new features, easier to understand the current implementations, easier to optimize for performance...thus superior. The best designs get carried over from project to project. They appear in blogs, articles and books about principles, patterns and practices.   Of course the act of writing software is deliberate. This can hardly be called random mutations. Though it sometimes might seem that code evolves through a will of its own ;-) Does this mean that evolving software (evolution) is better than a big design up front (creationism)? Not necessarily. It's a false idea to think that a project starts from scratch and everything evolves from there. Everyone carries his experience of what works and what doesn't. Up front design is necessary, but is best kept simple and minimal, just enough to get you started. Let the good experiences and ideas help to drive the process, whether they come from you or from others, from past experience or from the most junior developer on your team. Once again, balance is the keyword. Balance design up front with evolution on a daily basis. How do you know what balance is right? Through your own experience of what worked and what didn't (here's evolution again). Notes: The evolution of software can quickly degenerate without discipline. TDD is a discipline that leaves little to chance on that part. Write your test to describe the new behavior. Write just enough code to make it behave as specified. Refactor to evolve the code to a higher standard. The responsibility of good design rests continuously on each developers' shoulders. Promiscuous pair programming helps quickly spreading the design to the whole team.

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• Resources on concepts/theory behind GUI development?

  - by ShrimpCrackers

  I was wondering if there were any resources that explain concepts/theory behind GUI development. I don't mean a resource that explains how to use a GUI library, but rather how to create your own widgets. For example a resource that explains different methods on how to implement scrollable listboxes. I ask because I have an idea for a game tool where I would like to create my own widgets and let users drag and drop them onto some kind of form. How do GUI libraries usually draw widgets? I'm not sure if reskinning widgets from a GUI library fits my needs, since widget behavior needs to be dynamic based on user interaction.

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