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• Boosting my GA with Neural Networks and/or Reinforcement Learning

  - by AlexT

  As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

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• "Hello, WebView" tutorial opens the requested address in Android browser and not in my webview

  - by VitalyB

  Hi everyone, I am using Android emulator with AVD of Android 2.1 and I have the following problem: Trying to load a URL in a WebView using webView.loadUrl causes it to open in the browser instead. Note: I am talking about the initial opening, not the issue in which links from the WebView open in a browser, though, perhaps it is somehow connected. I've tried several things: I've removed <uses-permission android:name="android.permission.INTERNET" /> from the manifest. That actually made it work correctly, i.e, load the html into the webview. However, as one would expect, the only thing it loaded is "unable to connect the internet" error page. I've tried downloading a real sample project ("Hello Android" book source files, project - BrowserView). However, it didn't work just the same. I've created a new project and followed the directions at Google's official tutorial of using WebView and got the same result. I haven't find anyone else complaining about it. Why does it happen? Thanks, Vitaly

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• EDM -> POCO -> WCF (.NET4) But transferring Collections causes IsReadOnly set to TRUE

  - by Gary B

  Ok, this may sound a little 'unorthodox', but...using VS2010 and the new POCO t4 template for Entity Framework (http://tinyurl.com/y8wnkt2), I can generate nice POCO's. I can then use these POCO's (as DTO's) in a WCF service essentially going from EDM all the way through to the client. Kinda what this guys is doing (http://tinyurl.com/yb4bslv), except everything is generated automatically. I understand that an entity and a DTO 'should' be different, but in this case, I'm handling client and server, and there's some real advantages to having the DTO in the model and automatically generated. My problem is, that when I transfer an entity that has a relationship, the client generated collection (ICollection) has the read-only value set, so I can't manipulate that relationship. For example, retrieving an existing Order, I can't add a product to the Products collection client-side...the Products collection is read-only. I would prefer to do a bunch of client side 'order-editing' and then send the updated order back rather than making dozens of server round trips (eg AddProductToOrder(product)). I'd also prefer not to have a bunch of thunking between Entity and DTO. So all-in-all this looks good to me...except for the read-only part. Is there a solution, or is this too much against the SOA grain?

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• Extjs Dynamic Grid

  - by rkenshin

  Hi, I'm trying to create a dynamic grid using Extjs. The grid is built and displayed when a click event is fired then an ajax request is sent to the server to fetch the columns, records and records definition a.k.a Store Fields. Each node could have different grid structure and that depends on the level of the node in the tree. The only way i came up with so far is function showGrid(response, request) { var jsonData = Ext.util.JSON.decode(response.responseText); var grid = Ext.getCmp('contentGrid'+request.params.owner); if(grid) { grid.destroy(); } var store = new Ext.data.ArrayStore({ id : 'arrayStore', fields : jsonData.recordFields, autoDestroy : true }); grid = new Ext.grid.GridPanel({ defaults: {sortable:true}, id:'contentGrid'+request.params.owner, store: store, columns: jsonData.columns, //width:540, //height:200, loadMask: true }); store.loadData(jsonData.records); if(Ext.getCmp('tab-'+request.params.owner)) { Ext.getCmp('tab-'+request.params.owner).show(); } else { grid.render('grid-div'); Ext.getCmp('card-tabs-panel').add({ id:'tab-'+request.params.owner, title: request.params.text, iconCls:'silk-tab', html:Ext.getDom('grid-div').innerHTML, closable:true }).show(); } } The function above is called when a click event is fired 'click': function(node) { Ext.Ajax.request({ url: 'showCtn', success: function(response, request) { alert('Success'); showGrid(response,request); }, failure: function(results, request) { alert('Error'); }, params: Ext.urlDecode(node.attributes.options); } The problem i'm getting with this code is that a new grid is displayed each time the showGrid function is called. The end user sees the old grids and the new one. To mitigate this problem, I tried destroying the grid and also removing the grid element on each request, and that seems to solve the problem only that records never get displayed this time. if(grid) { grid.destroy(true); } The behavior i'm looking for is to display the result of a grid within a tab and if that tab exists replaced the old grid. Any help is appreciated. Thank you

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• kanban scrumish tool(s) to get started

  - by Davide

  After investigating a little bit scrum and kanban, I finally read this answer and decided to start using kanban, picking something from scrum (note that I'm working mostly by myself, and I do have read this question and its answers). Now, my question is: which tool would be best to get started? whiteboard and postit agilezen.com JIRA with greenhopper a spreadsheet (possibly on Google Docs) brightgreenprojects.com Agilo Target Process something else (please specify) Notes about each: I would lean towards the whiteboard, but there are several drawbacks (e.g. cannot make automatic charts, time measurements, metrics, and sometimes I work from home - where I need it most - and it's not convenient to carry :-) I don't want to remember another username/password (I promised to myself to signup only to OpenID-enabled services) My employer has JIRA but my group doesn't use it - I might ask for an account (it shouldn't require another password) and maybe later involve the rest of the group. But I don't know if they are using greenhopper and if it's a big deal installing it. I generally hate spreadsheets maybe overkill? I'd be happy to have a localhost instance, but it could be problematic to give access to the whole group (per network/firewalls) - not a deal-breaker but surely a concern What I'd like to get from this? being more productive tracking how much time I spend in any given task, possibly discussing the issue with my supervisor tracking what "blocks" me most often immediately see where I am compared to my schedule manage in a better way my long todo list (e.g. answering faster to the "what I should do next?" question) Do you have any suggestion? Note on the scrumish tag: read the Henrik Kniberg's PDF. He first introduced the definition of scrumish on page 9.

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• Moving from ClearCase to Mercurial: your top tips?

  - by Robusto

  We will soon start replacing ClearCase with Mercurial. I hear this is a good thing. The change model vs. the version model. Wave of the future. I'm prepared to believe this. Still, it kind of frightens me. Hey, it took Joel Spolsky a while to grok the difference and how to get maximum advantage out of Mercurial, so I'm betting I will run into conceptual traps and pitfalls. Does anyone have any real-world "how to grok Mercurial" tips? Anything specific suggestions that will help me bridge the conceptual gap. Any warnings about things not to do? I'd appreciate hearing them. I've already read the closest questions on SO related to this topic, as well as the Mercurial tour and a number of other blogs. I'm mainly interested in any gotchas or uh-ohs I may encounter. Any wisdom you can impart will be appreciated.

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• Server socket programming in Android 1.5, most power efficient way?

  - by Antek

  Hello people, I am doing a project where I have too develop an application that listens for incoming events by a service. The device that has to listen too events is an Android phone with Android SDK 1.5 on it. Currently the services that call events only implement communication trough UDP or TCP sockets. I can solve my problem by setting up a ServerSocket, but i doubt that's the most power efficient way. This application will be running most of the time, with Wi-Fi on, and I'd like too reach an long battery duration. I've been looking for options on the internet for my question for a while but i couldn't get a real answer. I've got the following questions: What is the most efficient way too listen to incoming events? Should I make an ServerSocket? or what are my options? Are there any other implementations that are more power efficient? Ive been also thinking of implementing communication trough XMPP. Not sure if this is the best way. I'm not forced too an specific implementation. All suggestions are welcome! Thanks for the help, Antek

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• load jquery function from a href onclick

  - by QuBaR

  I have a html table with a column per row with this html code inside the tags: <a onclick="modalDialog(this); return false;" href="javascript:void(0)">17795</a> <div style="display: none;" class="MessageDataDiv"> some text to show up in my jquery modal window when function modaldialog is clicked. </div> And the jquery function that is called when onclick is fired within the a href link function modalDialog(event) { $('a.message').click(function () { var div = new $(this).closest("td").find(".MessageDataDiv").clone(); div.show().dialog(); event.preventDefault(); }); } Can anyone help me with some advice how to write the jquery function more correct so the function only fires one time when the linked is clicked. I need to have the jquery function modalDialog as a separate function because the html table use ajax partial rendering... The problem is when i click the a href link first time nothing happens, second click on the links gives med two modal dialog and third click gives me three modal dialog and so on...

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• Advice for last year college graduates

  - by Tomh

  Hey guys, I know there are many "advice" questions around this site. But I wanted to to narrow mine down to last year college students, in my case my last year as Master student in computer science. So far is a list of things I've done during my time in college (which I can recommend others to do aswell): Code a lot I've written several hobby projects, had part time jobs, entered the Imagine cup from Microsoft, took programming extensive courses and did freelance gigs. Read a lot I've bought most top books from the recommended book topics here, to be honest I have not read them all. learn different languages I've tried several languages including Haskell, Java, Python, Ruby, Lisp, Prolog, C#, PHP, JS, AS3 and possibly some more I forgot. Tried to start a blog Joel recommends to learn how to write, I tried starting a couple of blogs to improve upon this, I gave up on all instances after writing about three posts. It was just not my thing... Have a portfolio of launched projects/programs I'm busy with this, have a couple of finished, working projects I worked on to show to people. So this is my last year. Is there anything else you can recommend a last year college student to do before hitting the job market? Personally I'm tempted to spend my time on the following: Practice algorithm design Learn and memorize the usage of the low level API's of your favorite language Polish your portfolio Why? Because those first two will make sure you pass the majority of the interviews, here in Holland (I could be wrong). I rather not spend my time on those first two points, but I have to be realistic and thats just my experience on what kind of questions you'll get when you apply. The third point is my hope that I won't have to answer questions about the amount of standard types in c# for example if they can see I get projects done and launched. But I'm still graduating, so I don't know anything :), and many of you might be hiring grads on a recent base and could tell me and other interested people what you wish that the recent grads you interviewed would have done before they applied.

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• Windows services with windows forms in the same process

  - by andrecarlucci

  Hello, I have a c# application that runs as a windows service controlling socket connections and other things. Also, there is another windows forms application to control and configure this service (systray with start, stop, show form with configuration parameters). I'm using .net remoting to do the IPC and that was fine, but now I want to show some real traffic and other reports and remoting will not meet my performance requirements. So I want to combine both applications in one. Here is the problem: When I started the form from the windows service, nothing happened. Googling around I've found that I have to right click the service, go to Log on and check the "Allow service to interact with desktop" option. Since I don't want to ask my users to do that, I got some code googling again to set this option in the user's regedit during installation time. The problem is that even setting this option, it doesn't work. I have to open the Log On options of the service (it is checked), uncheck and check again. So, how to solve that? How is the best way to have a windows service with a systray control in the same process, available to any user logging in? UPDATE: Thanks for the comments so far, guys. I agree it is better to use IPC and I know that it is bad to mix windows services and user interfaces. Even though, I want to know how to do that.

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• Eigenvector computation using OpenCV

  - by Andriyev

  Hi I have this matrix A, representing similarities of pixel intensities of an image. For example: Consider a 10 x 10 image. Matrix A in this case would be of dimension 100 x 100, and element A(i,j) would have a value in the range 0 to 1, representing the similarity of pixel i to j in terms of intensity. I am using OpenCV for image processing and the development environment is C on Linux. Objective is to compute the Eigenvectors of matrix A and I have used the following approach: static CvMat mat, *eigenVec, *eigenVal; static double A[100][100]={}, Ain1D[10000]={}; int cnt=0; //Converting matrix A into a one dimensional array //Reason: That is how cvMat requires it for(i = 0;i < affnDim;i++){ for(j = 0;j < affnDim;j++){ Ain1D[cnt++] = A[i][j]; } } mat = cvMat(100, 100, CV_32FC1, Ain1D); cvEigenVV(&mat, eigenVec, eigenVal, 1e-300); for(i=0;i < 100;i++){ val1 = cvmGet(eigenVal,i,0); //Fetching Eigen Value for(j=0;j < 100;j++){ matX[i][j] = cvmGet(eigenVec,i,j); //Fetching each component of Eigenvector i } } Problem: After execution I get nearly all components of all the Eigenvectors to be zero. I tried different images and also tried populating A with random values between 0 and 1, but the same result. Few of the top eigenvalues returned look like the following: 9805401476911479666115491135488.000000 -9805401476911479666115491135488.000000 -89222871725331592641813413888.000000 89222862280598626902522986496.000000 5255391142666987110400.000000 I am now thinking on the lines of using cvSVD() which performs singular value decomposition of real floating-point matrix and might yield me the eigenvectors. But before that I thought of asking it here. Is there anything absurd in my current approach? Am I using the right API i.e. cvEigenVV() for the right input matrix (my matrix A is a floating point matrix)? cheers

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• How to handle payment types with varying properties in the most elegant way.

  - by Byron Sommardahl

  I'm using ASP.NET MVC 2. Keeping it simple, I have three payment types: credit card, e-check, or "bill me later". I want to: choose one payment type display some fields for one payment type in my view run some logic using those fields (specific to the type) display a confirmation view run some more logic using those fields (specific to the type) display a receipt view Each payment type has fields specific to the type... maybe 2 fields, maybe more. For now, I know how many and what fields, but more could be added. I believe the best thing for my views is to have a partial view per payment type to handle the different fields and let the controller decide which partial to render (if you have a better option, I'm open). My real problem comes from the logic that happens in the controller between views. Each payment type has a variable number of fields. I'd like to keep everything strongly typed, but it feels like some sort of dictionary is the only option. Add to that specific logic that runs depending on the payment type. In an effort to keep things strongly typed, I've created a class for each payment type. No interface or inherited type since the fields are different per payment type. Then, I've got a Submit() method for each payment type. Then, while the controller is deciding which partial view to display, it also assigns the target of the submit action. This is not elegant solution and feels very wrong. I'm reaching out for a hand. How would you do this?

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• Problems with MediaRecorder class setting audio source - setAudioSource() - unsupported parameter

  - by arakn0

  Hello everybody, I'm new in Android development and I have the next question/problem. I'm playing around with the MediaRecorder class to record just audio from the microphone. I'm following the steps indicated in the official site: http://developer.android.com/reference/android/media/MediaRecorder.html So I have a method that initializes and configure the MediaRecorder object in order to start recording. Here you have the code: this.mr = new MediaRecorder(); this.mr.setAudioSource(MediaRecorder.AudioSource.MIC); this.mr.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP); this.mr.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB); this.mr.setOutputFile(this.path + this.fileName); try { this.mr.prepare(); } catch (IllegalStateException e) { Log.d("Syso", e.toString()); e.printStackTrace(); } catch (IOException e) { Log.d("Syso", e.toString()); e.printStackTrace(); } When I execute this code in the simulator, thanks to logcat, I can see that the method setAudioSource(MediaRecorder.AudioSource.MIC) gives the next error (with the tag audio_ipunt) when it is called: ERROR/audio_input(34): unsupported parameter: x-pvmf/media-input-node/cap-config-interface;valtype=key_specific_value ERROR/audio_input(34): VerifyAndSetParameter failed And then when the method prepare() is called, I get the another error again: ERROR/PVOMXEncNode(34): PVMFOMXEncNode-Audio_AMRNB::DoPrepare(): Got Component OMX.PV.amrencnb handle If I start to record bycalling the method start()... I get lots of messages saying: AudioFlinger(34):RecordThread: buffer overflow Then...after stop and release,.... I can see that a file has been created, but it doesn't seem that it been well recorderd. Anway, if i try this in a real device I can record with no problems, but I CAN'T play what I just recorded. I gues that the key is in these errors that I've mentioned before. How can I fix them? Any suggestion or help?? Thanks in advanced!!

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• Suppress "No Source Available" pane in 2010

  - by Jason

  Arg! I have a custom "harness" executable running my class library project. Every time I step into the harness's code, I get that "No Source Available" pane popping up. As I know there is no source available, and that this is completely expected, I don't want this very intrusive and useless pane popping up every time. How can I suppress it completely? I can make it smaller at least by making that window part of another smaller pane-set, such as with the watches/locals. It remembers its location from run to run, but its still useless. There might be a more general answer to this question - how can I suppress any particular pane/window from showing at all? I have a VSX package, originally built for VS 2008 (and must keep that compatibility) but I just don't know what command to run to do it. (I had the package commissioned, so I have the source, but not the know-how. This seems like a one/two liner). Thanks!

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• Development process for an embedded project with significant hardware changes

  - by pierr

  I have a good idea about Agile development process but it seems it does not fit well with a embedded project with significant hardware changes. I will describe below what we are currently doing (Ad-hoc way, no defined process yet). The changes are divided into three categories and different processes are used for each of them: complete hardware change example : use a different video codec IP a) Study the new IP b) RTL/FPGA simulation c) Implement the legacy interface - go to b) d) Wait until hardware (tape out) is ready f) Test on the real hardware hardware improvement example : enhance the image display quality by improving the underlying algorithm a) RTL/FPGA simulation b) Wait until hardware and test on the hardware Minor change example : only change hardware register mapping a) Wait until hardware and test on the hardware The worry is it seems we don't have too much control and confidence about software maturity for the hardware changes as the bring-up schedule is always very tight and the customer desired a seamless change when updating to a new version of hardware. How did you manage this kind of hardware change? Did you solve that by a Hardware Abstraction Layer (HAL)? Did you have a automatic test for the HAL layer? How did you test when the hardware platform is not even ready? Do you have well-documented processes for this kind of change?

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• How do I install LFE on Ubuntu Karmic?

  - by karlthorwald

  Erlang was already installed: $dpkg -l|grep erlang ii erlang 1:13.b.3-dfsg-2ubuntu2 Concurrent, real-time, distributed function ii erlang-appmon 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP application monitor ii erlang-asn1 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP modules for ASN.1 support ii erlang-base 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP virtual machine and base applica ii erlang-common-test 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP application for automated testin ii erlang-debugger 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP application for debugging and te ii erlang-dev 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP development libraries and header [... many more] Erlang seems to work: $ erl Erlang R13B03 (erts-5.7.4) [source] [64-bit] [smp:2:2] [rq:2] [async-threads:0] [hipe] [kernel-poll:false] Eshell V5.7.4 (abort with ^G) 1> I downloaded lfe from github and checked out 0.5.2: git clone http://github.com/rvirding/lfe.git cd lfe git checkout -b local0.5.2 e207eb2cad $ configure configure: command not found $ make mkdir -p ebin erlc -I include -o ebin -W0 -Ddebug +debug_info src/*.erl #erl -I -pa ebin -noshell -eval -noshell -run edoc file src/leex.erl -run init stop #erl -I -pa ebin -noshell -eval -noshell -run edoc_run application "'Leex'" '"."' '[no_packages]' #mv src/*.html doc/ Must be something stupid i missed :o $ sudo make install make: *** No rule to make target `install'. Stop. $ erl -noshell -noinput -s lfe_boot start {"init terminating in do_boot",{undef,[{lfe_boot,start,[]},{init,start_it,1},{init,start_em,1}]}} Crash dump was written to: erl_crash.dump init terminating in do_boot () Is there an example how I would create a hello world source file and compile and run it?

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• Returning Meaningful Exceptions from a WCF Project

  - by MissingLinq

  I am pretty new to WCF in general. What little experience I have comes from using fairly simple .SVC services in ASP.NET web applications. I tried experimenting with using a WCF Project for the first time, and ran into a major show-stopper. As I’m sure most are aware, for some strange reason, in a web application in which the customErrors mode is set to On , services (both .ASMX and .SVC) will not return exception details to the client. Instead, the exception and stack trace are emptied, and the message always reads “There was an error processing the request”, which is not at all helpful. When services are directly hosted inside the web application itself, it’s easy to work around this restriction by placing the services in a dedicated folder, and setting for that folder. However, I’m running into this same issue with exceptions not being returned from services that live in a separate WCF project. Thing is, I don’t know how to work around that. In a nutshell: I need to get my WCF Project services to bubble REAL exceptions to the client – or at least, the original exception message, instead of “There was an error processing the request”.

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• C# Winforms TabControl elements reading as empty until TabPage selected

  - by Geo Ego

  I have Winform app I am writing in C#. On my form, I have a TabControl with seven pages, each full of elements (TextBoxes and DropDownLists, primarily). I pull some information in with a DataReader, populate a DataTable, and use the elements' DataBindings.Add method to fill those elements with the current values. The user is able to enter data into these elements, press "Save", and I then set the parameters of an UPDATE query using the elements' Text fields. For instance: updateCommand.Parameters.Add("@CustomerName", SqlDbType.VarChar, 100).Value = CustomerName.Text; The problem I have is that once I load the form, all of the elements are apparently considered empty until I select each tab manually. Thus, if I press "Save" immediately upon loading the form, all of the fields on the TabPages that I have not yet selected try to UPDATE with empty data (not nice). As I select each TabPage, those elements will now send their data along properly. For the time being, I've worked out a (very) ugly workaround where I programmatically select each TabPage when the data is populated for the first time, but that's an unacceptable long-term solution. My question is, how can I get all of the elements on the TabPages to return their data properly before the user selects that TabPage?

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• cookieless sessions with ajax

  - by thezver

  ok, i know you get sick from this subject. me too :( I've been developing a quite "big application" with PHP & kohana framework past 2 years, somewhat-successfully using my framework's authentication mechanism. but within this time, and as the app grown, many concerning state-preservation issues arisen. main problems are that cookie-driven sessions: can't be used for web-service access ( at least it's really not nice to do so.. ) in many cases problematic with mobile access don't allow multiple simultaneous apps on same browser ( can be resolved by hard trickery, but still.. ) requires many configurations and mess to work 100% right, and that's without the --browser issues ( disabled cookies, old browsers bugs & vulnerabilities etc ) many other session flaws stated in this old thread : http://lists.nyphp.org/pipermail/talk/2006-December/020358.html After a really long research, and without any good library/on-hand-solution to feet my needs, i came up with a custom solution to majority of those problems . Basically, i'ts about emulating sessions with ajax calls, with additional security/performance measures: state preserved by interchanging SID(+hash) with client on ajax calls. state data saved in memcache(or equivalent), indexed by SID security achieved by: appending unpredictible hash to SID egenerating hash on each request & validating it validating fingerprint of client on each request ( referrer,os,browser etc) (*)condition: ajax calls are not simultaneous, to prevent race-condition with session token. (hopefully Ext-Direct solves that for me) From the first glance that supposed to be not-less-secure than equivalent cookie-driven implementation, and at the same time it's simple, maintainable, and resolves all the cookies flaws.. But i'm really concerned because i often hear the rule "don't try to implement custom security solutions". I will really appreciate any serious feedback about my method, and any alternatives. also, any tip about how to preserve state on page-refresh without cookies would be great :) but thats small technical prob. Sorry if i overlooked some similar post.. there are billions of them about sessions . Big thanks in advance ( and for reading until here ! ).

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• Silverlight and Encryption, how to store/generate they key/iv pair?

  - by cmaduro

  I have a Silverlight app that connects to a php webservice. I want to encrypt the communication between the webservice and the Silverlight client. I'm not relying on SSL. I'm encrypting/decrypting the POST string myself using AES 256bit Key and IV. The big questions then are: How do I generate a random unique key/iv pair in PHP. How do I share this key/iv pair between the web service and silverlight client in a secure way. It seems impossible without having some kind of hard coded key or iv on the client. Which would compromise security. This is a public website, there are no logins. Just the requirement of secure communication. I can hard code the seed for the key/iv (which is hashed with SHA256 with a time stamp salt and then assigned as the key or iv) in PHP source code, that's on the server so that is pretty safe. However on the client the seed for the key/iv pair would be visible, if it is hard coded. Further more using a time stamp as the basis for uniqueness/randomness is definitely not ok, since timestamps are predictable. It does however provide a common factor between the C# code and the PHP code. The only other option that I can think of would be to have a 3rd service involved that provides the key/iv to the Silverlight client, as well as the php webservice. This of course start the cycle anew, with the question of how to store the credentials for accessing the key/iv distribution service on the Silverlight client. Sounds like the solution is then asymmetric encryption, since sensitive data will be viewed only on the administrative back end of the website. Unfortunately Silverlight has no asymmetric encryption classes. The solution? Roll my own Diffie-Hellman key exchange! Plug that key into AES256!

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• How to handle ViewModel and Database in C#/WPF/MVVM App

  - by Mike B

  I have a task management program with a "Urgency" field. Valid values are Int16 currently mapped to 1 (High), 2 (Medium), 3 (Low), 4 (None) and 99 (Closed). The urgency field is used to rank tasks as well as alter the look of the items in the list and detail view. When a user is editing or adding a new task they select or view the urgency in a ComboBox. A Converter passes Strings to replace the Ints. The urgency collection is so simple I did not make it a table in the database, instead it is a, ObservableCollection(Int16) that is populated by a method. Since the same screen may be used to view a closed task the "Closed" urgency must be in the ItemsSource but I do not want the user to be able to select it. In order to prevent the user from being able to select that item in the ComboBox but still be able to see it if the item in the database has that value should I... Manually disable the item in the ComboBox in code or Xaml (I doubt it) Change the Urgency collection from an Int16 to an Object with a Selectable Property that the isEnabled property of the ComboBoxItem Binds to. Do as in 2 but also separate the urgency information into its own table in the database with a foreign key in the Tasks table None of the above (I suspect this is the correct answer) I ask this because this is a learning project (My first real WPF and first ever MVVM project). I know there is rarely one Right way to do something but I want to make sure I am learning in a reasonable manner since it if far harder to Unlearn bad habits Thanks Mike

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• Weblogic is slow to start (11mins) under VM (VirtualBox and VMware)

  - by Vladimir Dyuzhev

  (SOLVED! BY FAKING SYSTEM RANDOM GENERATOR, SEE BELOW) I'm setting up a VM image for my dev/build team. Inside that VM a Weblogic domain should be running. I use Ububtu server distro, WLS 9.2MP3 + ALSB. Everything works OK, quite fast, but at the start time the WLS stops twice for a measurable amounts of time. Two stops in total amount to about 10 minutes delay. For tasks where deployment requires server restart it's very annoying. :-( Sleeping time is not constant, sometimes the server starts very fast, sometimes so-so, sometimes 10 minutes or more. Interesting that if I press Enter while looking at the stopped server, it wakes up much faster, sometimes after a few seconds. WLST (Weblogic Jython shell) is also hanging for quite a time when executed in VM. It doesn't react to Enter though. Here must be some developers who run WLS with a VM. I wonder if others have the same problem? Was someone able to solve it? Here's the server output (just for a case): Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_12-b04) Java HotSpot(TM) Client VM (build 1.5.0_12-b04, mixed mode) Starting WLS with line: /shared2/beahome/jdk150_12/bin/java -client -Xmx256m -XX:MaxPermSize=128m -Xverify:none -da -Dplatform.home=/shared2/beahome/weblogic92 -Dwls.home=/shared2/beahome/weblogic92/server -Dwli.home=/shared2/beahome/weblogic92/integration -Dweblogic.management.discover=true -Dwl w.iterativeDev= -Dwlw.testConsole= -Dwlw.logErrorsToConsole= -Dweblogic.ext.dirs=/shared2/beahome/patch_weblogic923/profiles/default/sysext_ manifest_classpath -Dweblogic.management.username=admin -Dweblogic.management.password=wlsadmin -Dweblogic.Name=LOGMGR-admin -Djava.security .policy=/shared2/beahome/weblogic92/server/lib/weblogic.policy weblogic.Server <1-Apr-2010 12:47:22 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000395> <Following extensions directory contents added to the end of the classpath: /shared2/beahome/weblogic92/platform/lib/p13n/p13n-schemas.jar:/shared2/beahome/weblogic92/platform/lib/p13n/p13n_common.jar:/shared2/beahom e/weblogic92/platform/lib/p13n/p13n_system.jar:/shared2/beahome/weblogic92/platform/lib/wlp/netuix_common.jar:/shared2/beahome/weblogic92/pl atform/lib/wlp/netuix_schemas.jar:/shared2/beahome/weblogic92/platform/lib/wlp/netuix_system.jar:/shared2/beahome/weblogic92/platform/lib/wl p/wsrp-common.jar> <1-Apr-2010 12:47:22 o'clock PM GMT-05:00> <Info> <WebLogicServer> <BEA-000377> <Starting WebLogic Server with Java HotSpot(TM) Client VM Ve rsion 1.5.0_12-b04 from Sun Microsystems Inc.> <1-Apr-2010 12:47:23 o'clock PM GMT-05:00> <Info> <Management> <BEA-141107> <Version: WebLogic Server 9.2 MP3 Mon Mar 10 08:28:41 EDT 2008 1096261 > <1-Apr-2010 12:47:25 o'clock PM GMT-05:00> <Info> <WebLogicServer> <BEA-000215> <Loaded License : /shared2/beahome/license.bea> <1-Apr-2010 12:47:25 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to STARTING> <1-Apr-2010 12:47:25 o'clock PM GMT-05:00> <Info> <WorkManager> <BEA-002900> <Initializing self-tuning thread pool> <1-Apr-2010 12:47:25 o'clock PM GMT-05:00> <Notice> <Log Management> <BEA-170019> <The server log file /shared2/wldomains/beaadmd/LOGMGR/ser vers/LOGMGR-admin/logs/LOGMGR-admin.log is opened. All server side log events will be written to this file.> Here we have the first delay, up to 5 mins... <1-Apr-2010 12:53:21 o'clock PM GMT-05:00> <Notice> <Security> <BEA-090082> <Security initializing using security realm myrealm.> <1-Apr-2010 12:53:24 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to STANDBY> <1-Apr-2010 12:53:24 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to STARTING> <1-Apr-2010 12:53:25 o'clock PM GMT-05:00> <Notice> <Log Management> <BEA-170027> <The server initialized the domain log broadcaster success fully. Log messages will now be broadcasted to the domain log.> <1-Apr-2010 12:53:25 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to ADMIN> <1-Apr-2010 12:53:25 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to RESUMING> <1-Apr-2010 12:53:28 o'clock PM GMT-05:00> <Notice> <Security> <BEA-090171> <Loading the identity certificate and private key stored under t he alias adminuialias from the jks keystore file /shared2/wldomains/beaadmd/LOGMGR/CustomIdentity.jks.> And here is the second, again up to 5 mins. <1-Apr-2010 12:58:56 o'clock PM GMT-05:00> <Notice> <Security> <BEA-090169> <Loading trusted certificates from the jks keystore file /shared 2/wldomains/beaadmd/LOGMGR/CustomTrust.jks.> <1-Apr-2010 12:58:57 o'clock PM GMT-05:00> <Notice> <Server> <BEA-002613> <Channel "DefaultSecure" is now listening on 192.168.56.102:7002 f or protocols iiops, t3s, ldaps, https.> <1-Apr-2010 12:58:57 o'clock PM GMT-05:00> <Notice> <Server> <BEA-002613> <Channel "Default" is now listening on 192.168.56.102:8012 for pro tocols iiop, t3, ldap, http.> <1-Apr-2010 12:58:57 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000331> <Started WebLogic Admin Server "LOGMGR-admin" for domain " LOGMGR" running in Development Mode> <1-Apr-2010 12:58:57 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000365> <Server state changed to RUNNING> <1-Apr-2010 12:58:57 o'clock PM GMT-05:00> <Notice> <WebLogicServer> <BEA-000360> <Server started in RUNNING mode> UPDATE I think I've got the track: it must be the randon seed initialization. That may explain why generating keyboard events release the server. I've made the thread dump, and one thread is in runnable state, but waiting: "[STANDBY] ExecuteThread: '1' for queue: 'weblogic.kernel.Default (self-tuning)'" daemon prio=1 tid=0x0a7b06e8 nid=0xeda runnable [0x728a500 0..0x728a6d80] at java.io.FileInputStream.readBytes(Native Method) at java.io.FileInputStream.read(FileInputStream.java:194) at sun.security.provider.NativePRNG$RandomIO.readFully(NativePRNG.java:185) at sun.security.provider.NativePRNG$RandomIO.implGenerateSeed(NativePRNG.java:202) - locked <0x7d928c78> (a java.lang.Object) at sun.security.provider.NativePRNG$RandomIO.access$300(NativePRNG.java:108) at sun.security.provider.NativePRNG.engineGenerateSeed(NativePRNG.java:102) at java.security.SecureRandom.generateSeed(SecureRandom.java:475) at weblogic.security.AbstractRandomData.ensureInittedAndSeeded(AbstractRandomData.java:83) SOLVED Weblogic uses SecureRandom to init security subsystem. SecureRandom by default uses /dev/urandom file. For some reason, reading this file under VM comes to halt quite often. Generating console events helps to create more randomness, and release the WLS. For the test purposes I have changed jre/lib/security/java.security file, property to securerandom.source=file:/tmp/big.random.file. Weblogic now starts in 15 seconds.

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• StackOverflow in VB.NET SQLite query

  - by Majgel

  I have an StackOverflowException in one of my DB functions that I don't know how to deal with. I have a SQLite database with one table "tblEmployees" that holds records for each employees (several thousand posts) and usually this function runs without any problem. But sometimes after the the function is called a thousand times it breaks with an StackOverflowException at the line "ReturnTable.Load(reader)" with the message: An unhandled exception of type 'System.StackOverflowException' occurred in System.Data.SQLite.dll If I restart the application it has no problem to continue with the exact same post it last crashed on. I can also make the exactly same DB-call from SQLite Admin at the crash time without no problems. Here is the code: Public Function GetNextEmployeeInQueue() As String Dim NextEmployeeInQueue As String = Nothing Dim query As [String] = "SELECT FirstName FROM tblEmployees WHERE Checked=0 LIMIT 1;" Try Dim ReturnTable As New DataTable() Dim mycommand As New SQLiteCommand(cnn) mycommand.CommandText = query Dim reader As SQLiteDataReader = mycommand.ExecuteReader() ReturnTable.Load(reader) reader.Close() If ReturnTable.Rows.Count > 0 Then NextEmployeeInQueue = ReturnTable.Rows(0)("FirstName").ToString() Else MsgBox("No more employees found in queue") End If Catch fail As Exception MessageBox.Show("Error: " & fail.Message.ToString()) End Try If NextEmployeeInQueue IsNot Nothing Then Return NextEmployeeInQueue Else Return "No more records in queue" End If End Function When crashes, the reader has "Property evaluation failed." in all values. I assume there is some problem with allocated memory that isn't released correctly, but can't figure out what object it's all about. The DB-connection opens when the DB-class object is created and closes on main form Dispose. Should I maybe dispose the mycommand object every time in a finally block? But wouldn't that result in a closed DB-connection?

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• JSON-RPC and Json-rpc service discovery specifications

  - by Artyom

  Hello, I'm going to implement JSON-PRC web service. I need specifications for this. So far I had found only one resource that can be called as real specifications: JSON-RPC 1.0 http://json-rpc.org/wiki/specification Proposal of JSON-PRC 2.0: http://groups.google.com/group/json-rpc/web/json-rpc-2-0 (why is it on google groups?) However I've seen that JavaScript frameworks like Dojo actively use JSON-RPC SMD Service Mapping Description proposal But it requires JSON Schema specifications, but it redirects to incorrect URL as reference. So far I had found following: http://tools.ietf.org/html/draft-zyp-json-schema-02 And it is still draft... Can anybody point me to some actual specifications... At least something official updated? Because it looks like that implementing JSON-RPC 1.0 as is may be not enough, at least for frameworks like Dojo. Or am I wrong? Questions: Would implementation of JSON-RPC 1.0 specifications be enough to provide JSON-RPC service for most of modern clients, and how many clients there (if at-all) that actually support beyond JSON-RPC 1.0 capabilities (SMD, Schema, 2.0)? Because it looks like that JSON-RPC 1.0 is only one that has official specifications (and not draft) If I should implement SMD, or it is recommended can somebody point to official, most recent specifications of Json Schema and Service Mapping Description or links I found are really "the specifications?" Are JSON-RPC 2.0, SMD and JSON-Schema drafts stable enough to implement them? Note: do not suggest existing JSON-RPC service implementations. Anybody?

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• Is Rails Metal (& Rack) a good way to implement a high traffic web service api?

  - by Greg

  I am working on a very typical web application. The main component of the user experience is a widget that a site owner would install on their front page. Every time their front page loads, the widget talks to our server and displays some of the data that returns. So there are two components to this web application: the front end UI that the site owner uses to configure their widget the back end component that responds to the widget's web api call Previously we had all of this running in PHP. Now we are experimenting with Rails, which is fantastic for #1 (the front end UI). The question is how to do #2, the back serving of widget information, efficiently. Obviously this is much higher load than the front end, since it is called every time the front page loads on one of our clients' websites. I can see two obvious approaches: A. Parallel Stack: Set up a parallel stack that uses something other than rails (e.g. our old PHP-based approach) but accesses the same database as the front end B. Rails Metal: Use Rails Metal/Rack to bypass the Rails routing mechanism, but keep the api call responder within the Rails app My main question: Is Rails/Metal a reasonable approach for something like this? But also... Will the overhead of loading the Rails environment still be too heavy? Is there a way to get even closer to the metal with Rails, bypassing most of the environment? Will Rails/Metal performance approach the perf of a similar task on straight PHP (just looking for ballpark here)? And... Is there a 'C' option that would be much better than both A and B? That is, something before going to the lengths of C code compiled to binary and installed as an nginx or apache module? Thanks in advance for any insights.

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