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• What is the difference between Java 6 and PHP 5.4? [closed]

  - by Mashael

  First of all, let me explain the matter. I'm in a class where we learn Java 6 OOP fundamentals. However, my goal is to learn PHP (the last version) next. So, my question: Is there a big difference between PHP and Java 6 in OOP concepts? Meaning that after I finish the OOP class in Java will I find a lot of things that need to be learned in PHP regarding OOP? Update: *My goal of learning PHP next is to build dynamic sites* (I'm not sure of other options) and to follow OOP.

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• Using machine learning to aim mirrors in a solar array?

  - by Buttons840

  I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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• Materialized View does not import properly when importing on a second instance of a database

  - by marinus

  When I import a database with materialized view mv_mt in just one database (Oracle) everything is ok. create materialized view mv_mt refresh complete next trunc( sysdate ) + 1 as SELECT sysdate, media_type.* from media_type; But when I try to import the same database to a copy in another schema I get the following errors: IMP-00017: following statement failed with ORACLE error 1: "BEGIN DBMS_JOB.ISUBMIT(JOB=438,WHAT='dbms_refresh.refresh(''"ALEXANDRA"" "."MV_MT"'');',NEXT_DATE=TO_DATE('2012-07-02:14:22:36','YYYY-MM-DD:HH24:MI:" "SS'),INTERVAL='sysdate + 1 / 24 / 60 / 6 ',NO_PARSE=TRUE); END;" IMP-00003: ORACLE error 1 encountered ORA-00001: unique constraint (SYS.I_JOB_JOB) violated ORA-06512: at "SYS.DBMS_JOB", line 100 ORA-06512: at line 1 IMP-00017: following statement failed with ORACLE error 23421: "BEGIN dbms_refresh.make('"ALEXANDRA"."MV_MT"',list=null,next_date=null," "interval=null,implicit_destroy=TRUE,lax=FALSE,job=438,rollback_seg=NUL" "L,push_deferred_rpc=TRUE,refresh_after_errors=FALSE,purge_option = 1,par" "allelism = 0,heap_size = 0); END;" IMP-00003: ORACLE error 23421 encountered ORA-23421: job number 438 is not a job in the job queue ORA-06512: at "SYS.DBMS_SYS_ERROR", line 86 ORA-06512: at "SYS.DBMS_IJOB", line 793 ORA-06512: at "SYS.DBMS_REFRESH", line 86 ORA-06512: at "SYS.DBMS_REFRESH", line 62 ORA-06512: at line 1 IMP-00017: following statement failed with ORACLE error 23410: "BEGIN dbms_refresh.add(name='"ALEXANDRA"."MV_MT"',list='"ALEXANDRA"."MV" "_MT"',siteid=0,export_db='ORCL01'); END;" IMP-00003: ORACLE error 23410 encountered ORA-23410: materialized view "ALEXANDRA"."MV_MT" is already in a refresh group ORA-06512: at "SYS.DBMS_SYS_ERROR", line 95 ORA-06512: at "SYS.DBMS_IREFRESH", line 484 ORA-06512: at "SYS.DBMS_REFRESH", line 140 ORA-06512: at "SYS.DBMS_REFRESH", line 125 ORA-06512: at line 1 Anyone any ideas? Regards, Marinus

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• Should I use both WCF and ASP.NET Web API

  - by Mithir

  We already have a WCF API with basichttpbinding. Some of the calls have complex objects in both the response and request. We need to add RESTful abilities to the API. at first I tried adding a webHttp endpoint, but I got At most one body parameter can be serialized without wrapper elements If I made it Wrapped it wasn't pure as I need it to be. I got to read this, and this (which states "ASP.NET Web API is the new way to build RESTful service on .NET"). So my question is, should I make 2 APIs(2 different projects)? one for SOAP with WCF and one RESTful with ASP.NET Web API? is there anything wrong architecturally speaking with this approach?

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• Something confusing about Single Responsibility Principle

  - by user1483278

  1) In fact if two responsibilities are always expected to change at the same time you arguably should not separate them into different classes as this would lead, to quote Martin, to a "smell of Needless Complexity". The same is the case for responsibilities that never change - the behavior is invariant, and there is no need to split it. I assume even if non-related responsibilities are always expected to change for the same reason ( or if they never change ), we still shouldn't put them in the same class, since this would still violate high cohesion principle? 2) I've found two quite different definitions for SRP: Single Responsibility Principle says that a subsystem, module, class, or even a function, should not have more than one reason to change. and There should never be more than one reason for a class to change Doesn't the latter definition narrow SRP to a class level? If so, isn't first quote wrong by claiming that SRP can also be applied at subsystem, module and function levels? thank you

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• What are the downsides of implementing a singleton with Java's enum?

  - by irreputable

  Traditionally, a singleton is usually implemented as public class Foo1 { private static final Foo1 INSTANCE = new Foo1(); public static Foo1 getInstance(){ return INSTANCE; } private Foo1(){} public void doo(){ ... } } With Java's enum, we can implement a singleton as public enum Foo2 { INSTANCE; public void doo(){ ... } } As awesome as the 2nd version is, are there any downsides to it? (I gave it some thoughts and I'll answer my own question; hopefully you have better answers)

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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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• Immutable Method Java

  - by Chris Okyen

  In Java, there is the final keyword in lieu of the const keyword in c and c++. In the latter languages their is mutable and immutable methods such as stated in one answer by Johannes Schaub - litb the question how-many-and-which-are-the-uses-of-const-in-ce Use const to tell others methods won't change the logical state of this object. struct SmartPtr { int getCopies() const { return mCopiesMade; } }ptr1; ... int var = ptr.getCopies(); // returns mCopiesMade and is specified that to not modify objects state. How is this performed in Java?

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• Evaluating Scrum - is it okay to have people with multiple roles in a Scrum team?

  - by Wayne M

  I'm evaluating some Agile-style methodologies for possible introduction to my team. With Scrum, is it allowable to have the same person perform multiple roles? We have a small team of four developers and a web designer; we don't really have a lead (I fulfill this role), QA testers or business analysts, and all of our development tasks come from the CIO. Automated testing is seen as a total waste of time, and everything focuses on speed and not quality. What will happen is the CIO will come up with a development task (whether a feature or a bug) and give it to a developer (not to the whole team, to an individual, often in private or out of the blue) who is then expected to get it completed. The CIO doesn't gather requirements beyond the initial idea (and this has bitten us before as we'll implement something only to find out that none of the end users can use the feature, because they weren't consulted or even informed about it before we developed it, and in a panic we'll be told to revert the change) but requires say in/approval of everything that we do. First things first, is a Scrum style something to consider to introduce some standards and practices? From reading, Scrum seems to rely on a bit more trust and communication and focuses more on project management than on development, which is something we are completely devoid of as we don't have any semblance of project management at present. Second, if it can work is it unreasonable for someone, let's say myself, to act as both ScrumMaster and a developer? Or for a developer to also be the Product Owner (although chances are this will be the CIO, who isn't a developer)? I realize the Scrum Master and the Product Owner should be different people but at the same time I don't think we have anyone who has the qualities of a Product Owner (chances are it would turn into a "I need all these stories, I don't care how but get it done" type of deal and/or any freeze would be unfrozen on a whim). It seems to me that I might need to pick and choose pieces of Scrum/XP/Lean to compensate for how things are done currently, as it's highly unlikely that the mentality can be changed; for instance Pair Programming would never fly (seen as a waste, you get half the tasks done if you need two people for everything), TDD would be a hard sell, but short cycles would be welcomed.

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• Is an 'if password == XXXXXXX' enough for minimum security?

  - by Morgan Herlocker

  If I create a login for an app that has middle to low security risk (in other words, its not a banking app or anything), is it acceptable for me to verify a password entered by the user by just saying something like: if(enteredPassword == verifiedPassword) SendToRestrictedArea(); else DisplayPasswordUnknownMessage(); It seems to easy to be effective, but I certainly would not mind if that was all that was required. Is a simple check on username/password combo enough? Update: The particular project happens to be a web service, the verification is entirely server side, and it is not open-source. Does the domain change how you would deal with this?

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• In this slow Job Market, I have no choice to take a Job that uses VB.NET and is going to use C#. Advice?

  - by Xaisoft

  I really don't want to do VB.NET, but I need a Job and I need a Job Fast. The two positions I am looking at both have existing apps in VB.NET, but are looking to convert them to C# and do new development in C#, but as well all know, sometimes this doesn't happen for a while and you get stuck with the main language. My background is in C# and after looking at VB.NET, my head is hurting. Any advice as I tackle a Job like this. As I said, I preferably want stick with C#, but today, one may have no choice, so I have to just take what I get. I am looking for advice on this for those who have experienced it, are experiencing it, and those who have not.

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• Why are we as an industry not more technically critical of our peers? [closed]

  - by Jarrod Roberson

  For example: I still see people in 2011 writing blog posts and tutorials that promote setting the Java CLASSPATH at the OS environment level. I see people writing C and C++ tutorials dated 2009 and newer and the first lines of code are void main(). These are examples, I am not looking for specific answers to the above questions, but to why the culture of accepting sub-par knowledge in the industry is so rampant. I see people posting these same type of empirically wrong suggestions as answers on www.stackoverflow.com and they get lots of up votes and practically no down votes! The ones that get lots of down votes are usually from answering a question that wasn't asked because of lack of reading for comprehension skills, and not incorrect answers per se. Is our industry that ignorant as a whole, I can understand the internet in general being lazy, apathetic and un-informed but our industry should be more on top of things like this and way more critical of people that are promoting bad habits and out-dated techniques and information. If we are really an engineering discipline, why aren't people held to a higher standard as they are in other engineering disciplines? I want to know why people accept bad advice, poor practices as the norm and are not more critical of their peers in the software industry.?

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• Why maven so slow compared to automake?

  - by ???'Lenik

  I have a Maven project consists of around 100 modules. I have reason to decompose the project to so many modules, and I don't think I should merge them in order to speed up the build process. I have read a lot of projects by other people, e.g., the Maven project itself, and Apache Archiva, and Hudson project, they all consists of a lot of modules, nearly 100 maybe, more or less. The problem is, to build them all need so much time, 3 hours for the first time build (this is acceptable because a lot of artifacts to download), and 15 minutes for the second build (this is not acceptable). For automake, things are similarly, the first time you need to configure the project, to prepare the magical config.h file, it's far more complex then what maven does. But it's still fast, maybe 10 seconds on my Debian box. After then, make install requires maybe 10 minutes for the first time build. However, when everything get prepared, the .o object files are generated, they don't have to be rebuild at all for the second time build. (In Maven, everything rebuild at everytime.) I'm very wondering, how guys working for Maven projects can bare this long time for each build, I'm just can't sit down calmly during each time Maven build, it took too long time, really.

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• Is there an easy way to type in common math symbols?

  - by srcspider

  Disclaimer: I'm sure someone is going to moan about easy-of-use, for the purpose of this question consider readability to be the only factor that matters So I found this site that converts to easting northing, it's not really important what that even means but here's how the piece of javascript looks. /** * Convert Ordnance Survey grid reference easting/northing coordinate to (OSGB36) latitude/longitude * * @param {OsGridRef} gridref - easting/northing to be converted to latitude/longitude * @returns {LatLonE} latitude/longitude (in OSGB36) of supplied grid reference */ OsGridRef.osGridToLatLong = function(gridref) { var E = gridref.easting; var N = gridref.northing; var a = 6377563.396, b = 6356256.909; // Airy 1830 major & minor semi-axes var F0 = 0.9996012717; // NatGrid scale factor on central meridian var f0 = 49*Math.PI/180, ?0 = -2*Math.PI/180; // NatGrid true origin var N0 = -100000, E0 = 400000; // northing & easting of true origin, metres var e2 = 1 - (b*b)/(a*a); // eccentricity squared var n = (a-b)/(a+b), n2 = n*n, n3 = n*n*n; // n, n², n³ var f=f0, M=0; do { f = (N-N0-M)/(a*F0) + f; var Ma = (1 + n + (5/4)*n2 + (5/4)*n3) * (f-f0); var Mb = (3*n + 3*n*n + (21/8)*n3) * Math.sin(f-f0) * Math.cos(f+f0); var Mc = ((15/8)*n2 + (15/8)*n3) * Math.sin(2*(f-f0)) * Math.cos(2*(f+f0)); var Md = (35/24)*n3 * Math.sin(3*(f-f0)) * Math.cos(3*(f+f0)); M = b * F0 * (Ma - Mb + Mc - Md); // meridional arc } while (N-N0-M >= 0.00001); // ie until < 0.01mm var cosf = Math.cos(f), sinf = Math.sin(f); var ? = a*F0/Math.sqrt(1-e2*sinf*sinf); // nu = transverse radius of curvature var ? = a*F0*(1-e2)/Math.pow(1-e2*sinf*sinf, 1.5); // rho = meridional radius of curvature var ?2 = ?/?-1; // eta = ? var tanf = Math.tan(f); var tan2f = tanf*tanf, tan4f = tan2f*tan2f, tan6f = tan4f*tan2f; var secf = 1/cosf; var ?3 = ?*?*?, ?5 = ?3*?*?, ?7 = ?5*?*?; var VII = tanf/(2*?*?); var VIII = tanf/(24*?*?3)*(5+3*tan2f+?2-9*tan2f*?2); var IX = tanf/(720*?*?5)*(61+90*tan2f+45*tan4f); var X = secf/?; var XI = secf/(6*?3)*(?/?+2*tan2f); var XII = secf/(120*?5)*(5+28*tan2f+24*tan4f); var XIIA = secf/(5040*?7)*(61+662*tan2f+1320*tan4f+720*tan6f); var dE = (E-E0), dE2 = dE*dE, dE3 = dE2*dE, dE4 = dE2*dE2, dE5 = dE3*dE2, dE6 = dE4*dE2, dE7 = dE5*dE2; f = f - VII*dE2 + VIII*dE4 - IX*dE6; var ? = ?0 + X*dE - XI*dE3 + XII*dE5 - XIIA*dE7; return new LatLonE(f.toDegrees(), ?.toDegrees(), GeoParams.datum.OSGB36); } I found that to be a really nice way of writing an algorythm, at least as far as redability is concerned. Is there any way to easily write the special symbols. And by easily write I mean NOT copy/paste them.

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• What to include in metadata?

  - by shyam

  I'm wondering if there are any general guidelines or best practices regarding when to split data into a metadata format, as oppose to directly embedding it within the data. (Specific example below). My understanding of metadata is that it describes data (without the need to actually look at the data), allowing for data to be quickly search/filtered for easy access. Let's take for example a simple 3D model format. The actual data file itself is a binary file containing vertices and colors. Things like creation date, modified data and author name would be things that describe the binary data, so I would say these belong as metadata (outside of the binary file). But what if the application had no need to search or filter by these fields? Would it be acceptable to embed these fields directly into the binary data itself? Could they be duplicated in both the binary data and the meta data, or would this be considered bad practice? What about more ambiguous fields such as the model name, which could be considered part of the data itself, but also as data describing the binary data?... How do you decide which data to embed in the actual binary file, as opposed to separating into a more flexible metadata format? Thanks!

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• Hadoop and Object Reuse, Why?

  - by Andrew White

  In Hadoop, objects passed to reducers are reused. This is extremely surprising and hard to track down if you're not expecting it. Furthermore, the original tracker for this "feature" doesn't offer any evidence that this change actually improved performance (unless I missed it). It would speed up the system substantially if we reused the keys and values [...] but I think it is worth doing. This seems completely counter to this very popular answer. Is there some credence to the Hadoop developer's claim? Is there something "special" about Hadoop that would invalidate the notion of object creation being cheap?

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• Optimistic work sharing on sparsely distributed systems

  - by Asti

  What would a system like BOINC look like if it were written today? At the time BOINC was written, databases were the primary choice for maintaining a shared state and concurrency among nodes. Since then, many approaches have been developed for tasking with optimistic concurrency (OT, partial synchronization primitives, shared iterators etc.) Is there an optimal paradigm for optimistically distributing units of work on sparsely distributing systems which communicate through message passing? Sorry if this is a bit vague. P.S. The concept of Tuple-spaces is great, but locking is inherent to its definition. Edit: I already have a federation system which works very well. I have a reactive OT system is implemented on top of it. I'm looking to extend it to get clients to do units of work.

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• Replicate GAE Datastore On A Server LAN in Java

  - by Franz Noel

  There may be instances wherein one Company Client may not have internet connection on their vicinity. Either their Internet Service Provider currently experience a down time or there are some other problems involving the network, but not their LAN. GAE seems to be needing a connection at all times in the internet. I only need GAE Datastore. I'm thinking about a different application. Creating a Java Swing Client, for instance, and connecting to the Office Server via HRD of GAE Datastore. When I tried to check on the solutions for Java, it does not say anything about uploading all data and I do not need the App. I just need the GAE Datastore. In Java GAE, only indexes can be able to be manipulated. So, is there any tricks/ideas that you can use HRD with GAE Datastore on Java with an Internal Office Server combined? This way, it may provide service even during network down times. (Can somebody create me a tag of gae-datastore, please.)

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• Why Adobe Air is so underrated for building mobile apps?

  - by Marcelo de Assis

  I worked with Adobe Flash related technologies for the last 5 years, although not being a big fan of Adobe. I see some little bugs happening in some apps, but I cannot imagine why a lot of big companies do not even think to use use Adobe Air as a good technology for their mobile apps. I see a lot of mobile developer positions asking for experts in Android or iOS , but very much less positions asking for Adobe Air, even when Adobe Air apps have the advantage of being multi-plataform, with the same app working in Blackberry, iOS and Android. Is so much easier to develop a game using Flash, than using Android SDK, for example. It really have flaws (that I never saw) or it is just some kind of mass prejudgement? I also would like to hear what a project manager or a indie developer takes when choosing a plataform for building apps.

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• Looking for a Python UI library comparable with Windows Forms [on hold]

  - by Mitten

  I am looking for a Python UI library which I could use to develop a desktop GUI comparable to what can be done with .NET Windows Forms. I have no previous experience programming UI in Python, so I would rather choose (if there is a choice) something simple. The application I am building would be a document oriented - rich texts, lists and grids, I don't expect to use much graphics - mostly formatted texts. Any pointers, and if there is more than one major GUI library available for Python - how could I quickly test them to see which one is a better fit for my needs?

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• what is need for a handler in general

  - by nish

  I have been searching for a definition for handler. basics i've understood that "A handler is a piece of code that is called when something happens, and usually takes some action, like generating a response." - (from http://stackoverflow.com/questions/3246200/what-is-an-handler ). But that can be a trigger or a callback. Also in specific an event handler on a low-level , often works by polling a device and waiting for a hardware response. So, what is the specific role of a handler ( that makes it unique from a trigger or a callback or any other such function ). Do all handlers have similar role ( event handler, file handler , exception handler, error handler )...

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• Has any hobbyist attempted to make a simple VGA-graphics based operating system in machine code?

  - by Bigyellow Bastion

  I mean real bare bones, bare machine here(no Linux kernel, pre-existing kernel, or any bootloader). I mean honestly write the bootloading software in direct microarchitecture-specific machine opcode, host the operating system, interrupts, I/O, services, and graphical software and all hardware interaction, computation, and design entirely in binary. I know this is quite the leap here, but I was thinking to practice first in x86 assembly (not binary) 16-bit style. Any ideas?

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• Using XNA to learn to build a game, but wanna move on [closed]

  - by Daniel Ribeiro

  I've been building a 2D isometric game (with learning purposes) in C# using XNA. I found it's really easy to manage sprite sheets loading, collision, basic physics and such with the XNA api. The thing is, I want to move on. My real goal is to learn C++ and develop a game using that language. What engine/library would you guys recommend for me to keep going on that same 2D isometric game direction using pretty much sprite sheets for the graphical part of the game?

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• How to choose the right web development language for my app without much programming experience?

  - by twinbornJoint

  I have my own idea for a web application, and I am not a programmer. The application will work similar to Facebook and Twitter, profiles and feeds. I have learned some computer science theory, all the way up to OOP, but have no practical experience. Without any experience, is there a way I can evaluate the different language and platform choices available to me? What kind of things should I be looking at? Ease of setup? How many followers it has? How can I evaluate whether a language will have the capabilities I need?

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• Licensing approach for .NET library that might be used desktop / web-service / cloud environment

  - by Bobrovsky

  I am looking for advice how to architect licensing for a .NET library. I am not asking for tool/service recommendations or something like that. My library can be used in a regular desktop application, in an ASP.NET solution. And now Azure services come into play. Currently, for desktop applications the library checks if the application and company names from the version history are the same as the names the key was generated for. In other cases the library compares hardware IDs. Now there are problems: an Azure-enabled web-application can be run on different hardware each time (AFAIK) sometimes the hardware ID for the same hardware changes unexpectedly checking the hardware ID or version info might not be allowed in some circumstances (shared hosting for example) So, I am thinking about what approach I can take to architect a licensing scheme that: is friendly to customers (I do not try to fight piracy, but I do want to warn the customer if he uses the library on more servers than he paid for) can be used when there is no internet connection can be used on shared hosting What would you recommend?

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