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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• Makefile; mirroring a growing tree through a process

  - by Martineau

  I would like to periodically mirror a growing tree, say, from $in to $out, doing a process in between (saving the only file header). As; #!/bin/bash in=./segd out=./db for f in `find $in -name "*.segd"`;do # Deduct output (dir + name) d=`dirname $f|perl -pe 's!'$in'!'$out'!'` n=`basename $f|perl -pe 's!$!_hdr!'` if [ ! -e $d/$n ]; then [ ! -d $d ] && mkdir -p $d; printf "From %s now build %s\n" $f "$d/$n" # Do something, whathever. For example e.g; dd if=$f bs=32 count=1 conv=swab 2>/dev/null|od -x > $d/$n fi done That is about fair. However; to be more robust, for a better synchronization (say if a source file did change or whatever), I would like to use a Makefile, as in; HDR := $(patsubst ./segd/%.segd,./db/%.segd_hdr,$(wildcard ./segd/*.segd)) all: ${HDR} db/%.segd_hdr: ./segd/%.segd echo "Doing" dd if=$< bs=32 count=1 conv=swab 2>/dev/null|od -x > $@ My problem; I cannot code this Makefile to "dive" more deeply within the source ./segd tree. How can we do it and is there a way ? Many thanks for your kind recommendations. PS: The idea will be to later rsync the (smaller) destination tree over a sat connection.

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• Java "Pool" of longs or Oracle sequence with reusable values

  - by Anthony Accioly

  Several months ago I implemented a solution to choose unique values from a range between 1 and 65535 (16 bits). This range is used to generate unique Route Targets suffixes, which for this customer massive network (it's a huge ISP) are a very disputed resource, so any free index needs to become immediately available to the end user. To tackle this requirement I used a BitSet. Allocate on the RT index with set and deallocate a suffix with clear. The method nextClearBit() can find the next available index. I handle synchronization / concurrency issues manually. This works pretty well for a small range... The entire index is small (around 10k), it is blazing fast and can be easy serialized into a Blob field. The problem is, some new devices can handle RTs of 32 bits (range 1 / 4294967296). Which can't be managed with a BitSet (it would, by itself, consume around 600Mb, plus be limited to int range). Even with this massive range available, the client still wants to free available Route Targets for the end user, mainly because the lowest ones (up to 65535) - which are compatible with old routers - are being heavily disputed. Before I tell the customer that this is impossible and he will have to conform with my reusable index for lower RTs (up to 65550) and use a database sequence for the other ones (which means that when the user frees a Route Target, it will not become available again). Would anyone shed some light? Maybe some kind soul already implemented a high performance number pool for Java (6 if it matters), or I am missing a killer feature of Oracle database (11R2 if it matters)... Wishful thinking. Thank you very much in advance.

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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• How to write a "thread safe" function in C ?

  - by Andrei Ciobanu

  Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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• How to Implement Rich Document Editor for iPhone

  - by benjismith

  I'm just getting started on a new iPhone/iPad development project, and I need to display a document with rich styled text (potentially with embedded images). The user will touch the document, dragging to highlight individual words or multiline text spans. When the text is highlighted, a context menu will appear, letting them change the color of highlighting or add margin notes (or other various bits of structured metadata). If you're familiar with adding comments to a Word document (or annotating a PDF), then this is the same sort of thing. But in my case, the typical user will spend many many hours within the app, adding thousands (in some cases, tens of thousands) of small annotations to the central document. All of those bits of metadata will be stored locally awaiting synchronization with a remote web service. I've read other pieces of advice, where developers suggest creating a UIWebView control and passing it an HTML string. But that seems kind of clunky, especially with all the context-sensitivity that I want to include. Anyhow, I'm brand new to iPhone development and Objective-C, though I have ten years of software development experience, using a variety of languages on many different platforms, so I'm not worried about getting my hands dirty writing new functionality from scratch. But if anyone has experience building a similar kind of component, I'm interested in hearing strategies for enabling that kind of rich document markup and annotation.

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• efficient thread-safe singleton in C++

  - by user168715

  The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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• Locking database edit by key name

  - by Will Glass

  I need to prevent simultaneous edits to a database field. Users are executing a push operation on a structured data field, so I want to sequence the operations, not simply ignore one edit and take the second. Essentially I want to do synchronized(key name) { push value onto the database field } and set up the synchronized item so that only one operation on "key name" will occur at a time. (note: I'm simplifying, it's not always a simple push). A crude way to do this would be a global synchronization, but that bottlenecks the entire app. All I need to do is sequence two simultaneous writes with the same key, which is rare but annoying occurrence. This is a web-based java app, written with Spring (and using JPA/MySQL). The operation is triggered by a user web service call. (the root cause is when a user sends two simultaneous http requests with the same key). I've glanced through the Doug Lea/Josh Bloch/et al Concurrency in Action, but don't see an obvious solution. Still, this seems simple enough I feel there must be an elegant way to do this.

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• Is it safe to use a boolean flag to stop a thread from running in C#

  - by Lirik

  My main concern is with the boolean flag... is it safe to use it without any synchronization? I've read in several places that it's atomic. class MyTask { private ManualResetEvent startSignal; private CountDownLatch latch; private bool running; MyTask(CountDownLatch latch) { running = false; this.latch = latch; startSignal = new ManualResetEvent(false); } // A method which runs in a thread public void Run() { startSignal.WaitOne(); while(running) { startSignal.WaitOne(); //... some code } latch.Signal(); } public void Stop() { running = false; startSignal.Set(); } public void Start() { running = true; startSignal.Set(); } public void Pause() { startSignal.Reset(); } public void Resume() { startSignal.Set(); } } Is this a safe way to design a task? Any suggestions, improvements, comments? Note: I wrote my custom CountDownLatch class in case you're wondering where I'm getting it from.

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• WPF: issue updating UI from background thread

  - by Ted Shaffer

  My code launches a background thread. The background thread makes changes and wants the UI in the main thread to update. The code that launches the thread then waits looks something like: Thread fThread = new Thread(new ThreadStart(PerformSync)); fThread.IsBackground = true; fThread.Start(); fThread.Join(); MessageBox.Show("Synchronization complete"); When the background wants to update the UI, it sets a StatusMessage and calls the code below: static StatusMessage _statusMessage; public delegate void AddStatusDelegate(); private void AddStatus() { AddStatusDelegate methodForUIThread = delegate { _statusMessageList.Add(_statusMessage); }; this.Dispatcher.BeginInvoke(methodForUIThread, System.Windows.Threading.DispatcherPriority.Send); } _statusMessageList is an ObservableCollection that is the source for a ListBox. The AddStatus method is called but the code on the main thread never executes - that is, _statusMessage is not added to _statusMessageList while the thread is executing. However, once it is complete (fThread.Join() returns), all the stacked up calls on the main thread are executed. But, if I display a message box between the calls to fThread.Start() and fThread.Join(), then the status messages are updated properly. What do I need to change so that the code in the main thread executes (UI updates) while waiting for the thread to terminate? Thanks.

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• Wake up thread blocked on accept() call

  - by selbie

  Sockets on Linux question I have a worker thread that is blocked on an accept() call. It simply waits for an incoming network connection, handles it, and then returns to listening for the next connection. When it is time for the program to exit, how do I signal this network worker thread (from the main thread) to return from the accept() call while still being able to gracefully exit its loop and handle it's cleanup code. Some things I tried: 1. pthread_kill to send a signal. Feels kludgy to do this, plus it doesn't reliably allow the thread to do it's shutdown logic. Also makes the program terminate as well. I'd like to avoid signals if at all possible. pthread_cancel. Same as above. It's a harsh kill on the thread. That, and the thread may be doing something else. Closing the listen socket from the main thread in order to make accept() abort. This doesn't reliably work. Some constraints: If the solution involves making the listen socket non-blocking, that is fine. But I don't want to accept a solution that involves the thread waking up via a select call every few seconds to check the exit condition. The thread condition to exit may not be tied to the process exiting. Essentially, the logic I am going for looks like this. void* WorkerThread(void* args) { DoSomeImportantInitialization(); // initialize listen socket and some thread specific stuff while (HasExitConditionBeenSet()==false) { listensize = sizeof(listenaddr); int sock = accept(listensocket, &listenaddr, &listensize); // check if exit condition has been set using thread safe semantics if (HasExitConditionBeenSet()) { break; } if (sock < 0) { printf("accept returned %d (errno==%d)\n", sock, errno); } else { HandleNewNetworkCondition(sock, &listenaddr); } } DoSomeImportantCleanup(); // close listen socket, close connections, cleanup etc.. return NULL; } void SignalHandler(int sig) { printf("Caught CTRL-C\n"); } void NotifyWorkerThreadToExit(pthread_t thread_handle) { // signal thread to exit } int main() { void* ptr_ret= NULL; pthread_t workerthread_handle = 0; pthread_create(&workerthread, NULL, WorkerThread, NULL); signal(SIGINT, SignalHandler); sleep((unsigned int)-1); // sleep until the user hits ctrl-c printf("Returned from sleep call...\n"); SetThreadExitCondition(); // sets global variable with barrier that worker thread checks on // this is the function I'm stalled on writing NotifyWorkerThreadToExit(workerthread_handle); // wait for thread to exit cleanly pthread_join(workerthread_handle, &ptr_ret); DoProcessCleanupStuff(); }

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• Using LINQ, need help splitting a byte array on data received from Silverlight sockets

  - by gcadmes

  The message packats received contains multiple messages deliniated by a header=0xFD and a footer=0xFE // sample message packet with three // different size messages List<byte> receiveBuffer = new List<byte>(); receiveBuffer.AddRange(new byte[] { 0xFD, 1, 2, 0xFE, 0xFD, 1, 2, 3, 4, 5, 6, 7, 8, 0xFE, 0xFD, 33, 65, 25, 44, 0xFE}); // note: this sample code is without synchronization, // statements, error handling...etc. while (receiveBuffer.Count > 0) { var bytesInRange = receiveBuffer.TakeWhile(n => n != 0xFE); foreach (var n in bytesInRange) Console.WriteLine(n); // process message.. // 1) remove bytes read from receive buffer // 2) construct message object... // 3) etc... receiveBuffer.RemoveRange(0, bytesInRange.Count()); } As you can see, (including header/footer) the first message in this message packet contains 4 bytes, and the 2nd message contains 10 bytes,a and the 3rd message contains 6 bytes. In the while loop, I was expecting the TakeWhile to add the bytes that did not equal the footer part of the message. Note: Since I am removing the bytes after reading them, the header can always be expected to be at position '0'. I searched examples for splitting byte arrays, but non demonstrated splitting on arrays of unknown and fluctuating sizes. Any help will be greatly appreciated. thanks much!

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• definition of wait-free (referring to parallel programming)

  - by tecuhtli

  In Maurice Herlihy paper "Wait-free synchronization" he defines wait-free: "A wait-free implementation of a concurrent data object is one that guarantees that any process can complete any operation in a finite number of steps, regardless the execution speeds on the other processes." www.cs.brown.edu/~mph/Herlihy91/p124-herlihy.pdf Let's take one operation op from the universe. (1) Does the definition mean: "Every process completes a certain operation op in the same finite number n of steps."? (2) Or does it mean: "Every process completes a certain operation op in any finite number of steps. So that a process can complete op in k steps another process in j steps, where k != j."? Just by reading the definition i would understand meaning (2). However this makes no sense to me, since a process executing op in k steps and another time in k + m steps meets the definition, but m steps could be a waiting loop. If meaning (2) is right, can anybody explain to me, why this describes wait-free? In contrast to (2), meaning (1) would guarantee that op is executed in the same number of steps k. So there can't be any additional steps m that are necessary e.g. in a waiting loop. Which meaning is right and why? Thanks a lot, sebastian

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• Java - Display % of upload done

  - by tr-raziel

  I have a java applet for uploading files to server. I want to display the % of data sent but when I use ObjectOutputStream.write() it just writes to the buffer, does not wait until the data has actually been sent. How can I achieve this. Perhaps I need to use thread synchronization or something. Any clues would be most helpful. This is the code I'm using right now: try{ for(File file : ficheiros){ FileInputStream stream = new FileInputStream (file); int bytesRead1 = 0;; int off1 = 0; int len1 = 100000; if(file.length() < 100000) len1 = new Long(file.length()).intValue(); byte[] bytes1 = new byte[len1]; while (off1 < file.length()) { bytes1 = new byte[len1]; if((file.length() - off1) < len1){ len1 = (new Long(file.length()).intValue() - off1); bytes1 = new byte[len1]; } if((bytesRead1 = stream.read(bytes1)) != -1){ //I want this to block until all data has been sent outputToServlet.write(bytes1, 0, bytesRead1 ); System.out.println("off1: " + off1); off1 = off1 + len1; outputToServlet.flush(); } sent += len1; if(sent>totalLength) sent = (int)totalLength; updateFeedback(sent,totalLength,false);//calls method to display % } updateFeedback(-1,-1,true); } }catch(Exception e){ e.printStackTrace(); } Thanks

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• Parallelism in .NET – Part 20, Using Task with Existing APIs

  - by Reed

  Although the Task class provides a huge amount of flexibility for handling asynchronous actions, the .NET Framework still contains a large number of APIs that are based on the previous asynchronous programming model.  While Task and Task<T> provide a much nicer syntax as well as extending the flexibility, allowing features such as continuations based on multiple tasks, the existing APIs don’t directly support this workflow. There is a method in the TaskFactory class which can be used to adapt the existing APIs to the new Task class: TaskFactory.FromAsync.  This method provides a way to convert from the BeginOperation/EndOperation method pair syntax common through .NET Framework directly to a Task<T> containing the results of the operation in the task’s Result parameter. While this method does exist, it unfortunately comes at a cost – the method overloads are far from simple to decipher, and the resulting code is not always as easily understood as newer code based directly on the Task class.  For example, a single call to handle WebRequest.BeginGetResponse/EndGetReponse, one of the easiest “pairs” of methods to use, looks like the following: var task = Task.Factory.FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The compiler is unfortunately unable to infer the correct type, and, as a result, the WebReponse must be explicitly mentioned in the method call.  As a result, I typically recommend wrapping this into an extension method to ease use.  For example, I would place the above in an extension method like: public static class WebRequestExtensions { public static Task<WebResponse> GetReponseAsync(this WebRequest request) { return Task.Factory.FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); } } This dramatically simplifies usage.  For example, if we wanted to asynchronously check to see if this blog supported XHTML 1.0, and report that in a text box to the user, we could do: var webRequest = WebRequest.Create("http://www.reedcopsey.com"); webRequest.GetReponseAsync().ContinueWith(t => { using (var sr = new StreamReader(t.Result.GetResponseStream())) { string str = sr.ReadLine();; this.textBox1.Text = string.Format("Page at {0} supports XHTML 1.0: {1}", t.Result.ResponseUri, str.Contains("XHTML 1.0")); } }, TaskScheduler.FromCurrentSynchronizationContext());   By using a continuation with a TaskScheduler based on the current synchronization context, we can keep this request asynchronous, check based on the first line of the response string, and report the results back on our UI directly.

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• Parallelism in .NET – Part 19, TaskContinuationOptions

  - by Reed

  My introduction to Task continuations demonstrates continuations on the Task class.  In addition, I’ve shown how continuations allow handling of multiple tasks in a clean, concise manner.  Continuations can also be used to handle exceptional situations using a clean, simple syntax. In addition to standard Task continuations , the Task class provides some options for filtering continuations automatically.  This is handled via the TaskContinationOptions enumeration, which provides hints to the TaskScheduler that it should only continue based on the operation of the antecedent task. This is especially useful when dealing with exceptions.  For example, we can extend the sample from our earlier continuation discussion to include support for handling exceptions thrown by the Factorize method: // Get a copy of the UI-thread task scheduler up front to use later var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Start our task var factorize = Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }); // When we succeed, report the results to the UI factorize.ContinueWith(task => textBox1.Text = string.Format("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result), CancellationToken.None, TaskContinuationOptions.NotOnFaulted, uiScheduler); // When we have an exception, report it factorize.ContinueWith(task => textBox1.Text = string.Format("Error: {0}", task.Exception.Message), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, uiScheduler); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The above code works by using a combination of features.  First, we schedule our task, the same way as in the previous example.  However, in this case, we use a different overload of Task.ContinueWith which allows us to specify both a specific TaskScheduler (in order to have your continuation run on the UI’s synchronization context) as well as a TaskContinuationOption.  In the first continuation, we tell the continuation that we only want it to run when there was not an exception by specifying TaskContinuationOptions.NotOnFaulted.  When our factorize task completes successfully, this continuation will automatically run on the UI thread, and provide the appropriate feedback. However, if the factorize task has an exception – for example, if the Factorize method throws an exception due to an improper input value, the second continuation will run.  This occurs due to the specification of TaskContinuationOptions.OnlyOnFaulted in the options.  In this case, we’ll report the error received to the user. We can use TaskContinuationOptions to filter our continuations by whether or not an exception occurred and whether or not a task was cancelled.  This allows us to handle many situations, and is especially useful when trying to maintain a valid application state without ever blocking the user interface.  The same concepts can be extended even further, and allow you to chain together many tasks based on the success of the previous ones.  Continuations can even be used to create a state machine with full error handling, all without blocking the user interface thread.

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• OSI Model

  - by kaleidoscope

  The Open System Interconnection Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer network protocol design. In its most basic form, it divides network architecture into seven layers which, from top to bottom, are the Application, Presentation, Session, Transport, Network, Data Link, and Physical Layers. It is therefore often referred to as the OSI Seven Layer Model. A layer is a collection of conceptually similar functions that provide services to the layer above it and receives service from the layer below it. Description of OSI layers: Layer 1: Physical Layer ·         Defines the electrical and physical specifications for devices. In particular, it defines the relationship between a device and a physical medium. ·         Establishment and termination of a connection to a communications medium. ·         Participation in the process whereby the communication resources are effectively shared among multiple users. ·         Modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. Layer 2: Data Link Layer ·         Provides the functional and procedural means to transfer data between network entities. ·         Detect and possibly correct errors that may occur in the Physical Layer. The error check is performed using Frame Check Sequence (FCS). ·         Addresses is then sought to see if it needs to process the rest of the frame itself or whether to pass it on to another host. ·         The Layer is divided into two sub layers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. ·         MAC sub layer controls how a computer on the network gains access to the data and permission to transmit it. ·         LLC layer controls frame synchronization, flow control and error checking.   Layer 3: Network Layer ·         Provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks. ·         Performs network routing functions, and might also perform fragmentation and reassembly, and report delivery errors. ·         Network Layer Routers operate at this layer—sending data throughout the extended network and making the Internet possible.   Layer 4: Transport Layer ·         Provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. ·         Controls the reliability of a given link through flow control, segmentation/de-segmentation, and error control. ·         Transport Layer can keep track of the segments and retransmit those that fail. Layer 5: Session Layer ·         Controls the dialogues (connections) between computers. ·         Establishes, manages and terminates the connections between the local and remote application. ·         Provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. ·         Implemented explicitly in application environments that use remote procedure calls. Layer 6: Presentation Layer ·         Establishes a context between Application Layer entities, in which the higher-layer entities can use different syntax and semantics, as long as the presentation service understands both and the mapping between them. The presentation service data units are then encapsulated into Session Protocol data units, and moved down the stack. ·         Provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer. Layer 7: Application Layer ·         This layer interacts with software applications that implement a communicating component. ·         Identifies communication partners, determines resource availability, and synchronizes communication. o       When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. o       When determining resource availability, the application layer must decide whether sufficient network or the requested communication exists. o       In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer. Technorati Tags: Kunal,OSI,Networking

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• career in Mobile sw/Application Development [closed]

  - by pramod

  i m planning to do a course on Wireless & mobile computing.The syllabus are given below.Please check & let me know whether its worth to do.How is the job prospects after that.I m a fresher & from electronic Engg.The modules are- *Wireless and Mobile Computing (WiMC) – Modules* C, C++ Programming and Data Structures 100 Hours C Revision C, C++ programming tools on linux(Vi editor, gdb etc.) OOP concepts Programming constructs Functions Access Specifiers Classes and Objects Overloading Inheritance Polymorphism Templates Data Structures in C++ Arrays, stacks, Queues, Linked Lists( Singly, Doubly, Circular) Trees, Threaded trees, AVL Trees Graphs, Sorting (bubble, Quick, Heap , Merge) System Development Methodology 18 Hours Software life cycle and various life cycle models Project Management Software: A Process Various Phases in s/w Development Risk Analysis and Management Software Quality Assurance Introduction to Coding Standards Software Project Management Testing Strategies and Tactics Project Management and Introduction to Risk Management Java Programming 110 Hours Data Types, Operators and Language Constructs Classes and Objects, Inner Classes and Inheritance Inheritance Interface and Package Exceptions Threads Java.lang Java.util Java.awt Java.io Java.applet Java.swing XML, XSL, DTD Java n/w programming Introduction to servlet Mobile and Wireless Technologies 30 Hours Basics of Wireless Technologies Cellular Communication: Single cell systems, multi-cell systems, frequency reuse, analog cellular systems, digital cellular systems GSM standard: Mobile Station, BTS, BSC, MSC, SMS sever, call processing and protocols CDMA standard: spread spectrum technologies, 2.5G and 3G Systems: HSCSD, GPRS, W-CDMA/UMTS,3GPP and international roaming, Multimedia services CDMA based cellular mobile communication systems Wireless Personal Area Networks: Bluetooth, IEEE 802.11a/b/g standards Mobile Handset Device Interfacing: Data Cables, IrDA, Bluetooth, Touch- Screen Interfacing Wireless Security, Telemetry Java Wireless Programming and Applications Development(J2ME) 100 Hours J2ME Architecture The CLDC and the KVM Tools and Development Process Classification of CLDC Target Devices CLDC Collections API CLDC Streams Model MIDlets MIDlet Lifecycle MIDP Programming MIDP Event Architecture High-Level Event Handling Low-Level Event Handling The CLDC Streams Model The CLDC Networking Package The MIDP Implementation Introduction to WAP, WML Script and XHTML Introduction to Multimedia Messaging Services (MMS) Symbian Programming 60 Hours Symbian OS basics Symbian OS services Symbian OS organization GUI approaches ROM building Debugging Hardware abstraction Base porting Symbian OS reference design porting File systems Overview of Symbian OS Development – DevKits, CustKits and SDKs CodeWarrior Tool Application & UI Development Client Server Framework ECOM STDLIB in Symbian iPhone Programming 80 Hours Introducing iPhone core specifications Understanding iPhone input and output Designing web pages for the iPhone Capturing iPhone events Introducing the webkit CSS transforms transitions and animations Using iUI for web apps Using Canvas for web apps Building web apps with Dashcode Writing Dashcode programs Debugging iPhone web pages SDK programming for web developers An introduction to object-oriented programming Introducing the iPhone OS Using Xcode and Interface builder Programming with the SDK Toolkit OS Concepts & Linux Programming 60 Hours Operating System Concepts What is an OS? Processes Scheduling & Synchronization Memory management Virtual Memory and Paging Linux Architecture Programming in Linux Linux Shell Programming Writing Device Drivers Configuring and Building GNU Cross-tool chain Configuring and Compiling Linux Virtual File System Porting Linux on Target Hardware WinCE.NET and Database Technology 80 Hours Execution Process in .NET Environment Language Interoperability Assemblies Need of C# Operators Namespaces & Assemblies Arrays Preprocessors Delegates and Events Boxing and Unboxing Regular Expression Collections Multithreading Programming Memory Management Exceptions Handling Win Forms Working with database ASP .NET Server Controls and client-side scripts ASP .NET Web Server Controls Validation Controls Principles of database management Need of RDBMS etc Client/Server Computing RDBMS Technologies Codd’s Rules Data Models Normalization Techniques ER Diagrams Data Flow Diagrams Database recovery & backup SQL Android Application 80 Hours Introduction of android Why develop for android Android SDK features Creating android activities Fundamental android UI design Intents, adapters, dialogs Android Technique for saving data Data base in Androids Maps, Geocoding, Location based services Toast, using alarms, Instant messaging Using blue tooth Using Telephony Introducing sensor manager Managing network and wi-fi connection Advanced androids development Linux kernel security Implement AIDL Interface. Project 120 Hours

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• How to convert from amateur web app developer to professional web apper?

  - by Nilesh

  This is more of a practical question on web app development and deployment process. Here is some background information. I use PHP for server side scripting, javascript for client side. I use Netbeans and notepad++. I user Firefox and firebug for debugging and testing. The process I use is very amateurish, I code something in netbeans, something in notepad++ and since there is nothing to compile, I just refresh the firefox browser and test it. This is convenient and faster compared to the Java development enviornment where you would have to atleast compile and deploy the jar files before you could run them. I have been thinking of putting a formal process in my development and find it hard putting it together. There are so many things to do before you can deploy your final web app. I keep hearing jslint, compression, unit testing (selenium), Ant, YUI compressor etc but I am now looking for some steps that I can take to make me more organized. For e.g I use netbeans but don't use any projects within it. I directly update the files. I don't use any source control but use my Iomega backup that saves each save into a different version and at the end of the day I backup the dev directory to my Amazon s3 account. For me development environment is just a DEV directory, TEST is my intermediate stage and PROD is the final directory that gets pushed out to the server. But all these directories are in the same apache home. I have few php scripts that just copies the needed files into the production directory. Thats about it for my development approach. I know I am missing the following - Regression testing (manual or automated ??) - automated testing (selenium ??) - automated deployment (ANT ??) - source control (svn ??) - quality control (jslint ??) Can someone explain what are the missing steps and how to go about filling those steps in order to have more professional approach. I am looking for tools with example tutorials in streamlining the whole development to deployment stage. For me just getting a hang of database, server side and client side development all in synchronization was itself a huge accomplishment. And now I feel there is lot missing before you can produce quality web application. For e.g I see lot of mention about using automated testing but how to put in use with respect to javascript and php. How to use ANT for the deployment etc. Is this all too much for a single or two person development team? Is there a way to automate all the above so that I just keep coding in netbeans and then run a batch file that is configured once and run it everytime to produce the code in the production directory? Lot of these information is scattered on the web and here, if someone can guide I would be happy to consolidate here. Thank you for your patience :)

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• Reduce ERP Consolidation Risks with Oracle Master Data Management

  - by Dain C. Hansen

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} Reducing the Risk of ERP Consolidation starts first and foremost with your Data.This is nothing new; companies with multiple misaligned ERP systems are often putting inordinate risk on their business. It can translate to too much inventory, long lead times, and shipping issues from poorly organized and specified goods. And don’t forget the finance side! When goods are shipped and promises are kept/not kept there’s the issue of accounts. No single chart of counts translates to no accountability. So – I’ve decided. I need to consolidate! Well, you can’t consolidate ERP applications [for that matter any of your applications] without first considering your data. This means looking at how your data is being integrated by these ERP systems, how it is being synchronized, what information is being shared, or not being shared. Most importantly, making sure that the data is mastered. What is the best way to do this? In the recent webcast: Reduce ERP consolidation Risks with Oracle Master Data Management we outlined 3 key guidelines: #1: Consolidate your Product Data#2: Consolidate your Customer, Supplier (Party Data) #3: Consolidate your Financial Data Together these help customers achieve reduced risk, better customer intimacy, reducing inventory levels, elimination of product variations, and finally a single master chart of accounts. In the case of Oracle's customer Zebra Technologies, they were able to consolidate over 140 applications by mastering their data. Ultimately this gave them 60% cost savings for the year on IT spend. Oracle’s Solution for ERP Consolidation: Master Data Management Oracle's enterprise master data management (MDM) can play a big role in ERP consolidation. It includes a set of products that consolidates and maintains complete, accurate, and authoritative master data across the enterprise and distributes this master information to all operational and analytical applications as a shared service. It’s optimized to work with any application source (not just Oracle’s) and can integrate using technology from Oracle Fusion Middleware (i.e. GoldenGate for data synchronization and real-time replication or ODI with its E-LT optimized bulk data and transformation capability). In addition especially for ERP consolidation use cases it’s important to leverage the AIA and SOA capabilities as part of Fusion Middleware to connect these multiple applications together and relay the data into the correct hub. Oracle’s MDM strategy is a unique offering in the industry, one that has common elements across the top and bottom in Middleware, BI/DW, Engineered systems combined with Enterprise Data Quality to enable comprehensive Data Governance at all levels. In addition, Oracle MDM provides the best-in-class capabilities to master all variations of data, including customer, supplier, product, financial data. But ultimately at the center of Oracle MDM is your data, making it more trusted, making it secure and accessible as part of a role-based approach, and getting it to make sense to you in any situation, whether it’s a specific ERP process like we talked about or something that is custom to your organization. To learn more about these techniques in ERP consolidation watch our webcast or goto our Oracle MDM website at www.oracle.com/goto/mdm

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• Oracle OpenWorld Update: Demo Pods and Hands-on Labs

  - by Doug Reid

  0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} Less than one week away until the start of Oracle OpenWorld 2012 and the Data Integration Solutions team is ready to go!  We have an exciting line up for you this year which we have summarized for you in the Oracle OpenWorld Focus on Data Integration Solutions document. In past posts we have discussed session themes and our customer panel, but today I would like to summarize our Hands-on Labs and Demo Pods that we have available for attendees. For Oracle GoldenGate Hands-On Labs we have two labs that we are running this year. Deep Dive into Oracle GoldenGate Thursday October 4th at 11:15AM in the Marriott Marquis Salon 1/2 Oracle GoldenGate provides real-time log-based change data capture and delivery between heterogeneous systems. It enables cost-effective, low-impact, real-time data integration and continuous availability solutions. This session covers Oracle GoldenGate 11g’s internal product architecture and includes a hands-on lab that covers configuration examples for target database instantiation and real-time change data capture and delivery. The participants will configure Oracle GoldenGate to instantiate a secondary database that can be used for disaster recovery or a reporting instance. Come learn how easy it is to use and how this can be a very valuable and easy technology solution for your organization. Introduction to Oracle GoldenGate Veridata Wednesday October 3rd 10:15AM in the Marriott Marquis Sales 1/2 Oracle GoldenGate Veridata compares one set of data with another and identifies data that is out of synchronization. In this hands-on lab, you will be introduced to the key features of this product. Using the Oracle GoldenGate Veridata Web client, you will have the opportunity to configure comparison objects and rules, initiate a comparison, review the status and output of a comparison, and review out-of-sync data. As a bonus this year, we have recorded the labs and made them available on youtube.com/oraclegoldengate. These will be available the day of the labs. Our demo pods are an opportunity for attendees to see our products but more so to meet the product management and development teams. I would like to point out that we have two Oracle GoldenGate 11gR2 demo pods, one in the database camp and the other in the middleware camp. The one in the middleware camp will be focused on all platforms while the one in the database camp will have a focus on the Oracle platform. The other two I would like to point out are the Monitoring Oracle GoldenGate and the Oracle Enterprise Manager demo pods; both of these pods will focus on methods to monitor GoldenGate but the OEM demo pod will have a specific focus on the Oracle GoldenGate Management Pack plug-in for OEM. Below is a list of our demo pods and their locations. Monitoring Oracle GoldenGate for End-to-End Visibility Moscone South, Right - S-241 Oracle Data Integrator and Oracle GoldenGate for Oracle Applications Moscone South, Right - S-240 Oracle GoldenGate 11gR2 New Features Moscone South, Right - S-239 Oracle GoldenGate 11gR2: Real-Time, Transactional Database Replication     Moscone South, Left - S-027 Oracle GoldenGate Veridata and Adapters Moscone South, Right - S-242 Oracle Enterprise Manager Moscone South, Left - S-040 Keep tuned to our blog during the show for news and highlights from the Data Integration Solutions team. See you there.

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• SQL SERVER – How to Roll Back SQL Server Database Changes

  - by Pinal Dave

  In a perfect scenario, no unexpected and unplanned changes occur. There are no unpleasant surprises, no inadvertent changes. However, even with all precautions and testing, there is sometimes a need to revert a structure or data change. One of the methods that can be used in this situation is to use an older database backup that has the records or database object structure you want to revert to. For this method, you have to have the adequate full database backup and a tool that will help you with comparison and synchronization is preferred. In this article, we will focus on another method: rolling back the changes. This can be done by using: An option in SQL Server Management Studio T-SQL, or ApexSQL Log The first two solutions have been described in this article The disadvantages of these methods are that you have to know when exactly the change you want to revert happened and that all transactions on the database executed in a specific time range are rolled back – the ones you want to undo and the ones you don’t. How to easily roll back SQL Server database changes using ApexSQL Log? The biggest challenge is to roll back just specific changes, not all changes that happened in a specific time range. While SQL Server Management Studio option and T-SQL read and roll forward all transactions in the transaction log files, I will show you a solution that finds and scripts only the specific changes that match your criteria. Therefore, you don’t need to worry about all other database changes that you don’t want to roll back. ApexSQL Log is a SQL Server disaster recovery tool that reads transaction logs and provides a wide range of filters that enable you to easily rollback only specific data changes. First, connect to the online database where you want to roll back the changes. Once you select the database, ApexSQL Log will show its recovery model. Note that changes can be rolled back even for a database in the Simple recovery model, when no database and transaction log backups are available. However, ApexSQL Log achieves best results when the database is in the Full recovery model and you have a chain of subsequent transaction log backups, back to the moment when the change occurred. In this example, we will use only the online transaction log. In the next step, use filters to read only the transactions that happened in a specific time range. To remove noise, it’s recommended to use as many filters as possible. Besides filtering by the time of the transaction, ApexSQL Log can filter by the operation type: Table name: As well as transaction state (committed, aborted, running, and unknown), name of the user who committed the change, specific field values, server process IDs, and transaction description. You can select only the tables affected by the changes you want to roll back. However, if you’re not certain which tables were affected, you can leave them all selected and once the results are shown in the main grid, analyze them to find the ones you to roll back. When you set the filters, you can select how to present the results. ApexSQL Log can automatically create undo or redo scripts, export the transactions into an XML, HTML, CSV, SQL, or SQL Bulk file, and create a batch file that you can use for unattended transaction log reading. In this example, I will open the results in the grid, as I want to analyze them before rolling back the transactions. The results contain information about the transaction, as well as who and when made it. For UPDATEs, ApexSQL Log shows both old and new values, so you can easily see what has happened. To create an UNDO script that rolls back the changes, select the transactions you want to roll back and click Create undo script in the menu. For the DELETE statement selected in the screenshot above, the undo script is: INSERT INTO [Sales].[PersonCreditCard] ([BusinessEntityID], [CreditCardID], [ModifiedDate]) VALUES (297, 8010, '20050901 00:00:00.000') When it comes to rolling back database changes, ApexSQL Log has a big advantage, as it rolls back only specific transactions, while leaving all other transactions that occurred at the same time range intact. That makes ApexSQL Log a good solution for rolling back inadvertent data and schema changes on your SQL Server databases. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: ApexSQL

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• Oracle MDM Maturity Model

  - by David Butler

  A few weeks ago, I discussed the results of a survey conducted by Oracle’s Insight team. The survey was based on the data management maturity model that the Oracle Insight team has developed over the years as they analyzed customer IT organizations to help them get more out of everything they already have. I thought you might like to learn more about the maturity model itself. It can help you figure out where you stand when it comes to getting your organizations data management act together. The model covers maturity levels around five key areas: Profiling data sources; Defining a data strategy; Defining a data consolidation plan; Data maintenance; and Data utilization. Profile data sources: Profiling data sources involves taking an inventory of all data sources from across your IT landscape. Then evaluate the quality of the data in each source system. This enables the scoping of what data to collect into an MDM hub and what rules are needed to insure data harmonization across systems. Define data strategy: A data strategy requires an understanding of the data usage. Given data usage, various data governance requirements need to be developed. This includes data controls and security rules as well as data structure and usage policies. Define data consolidation strategy: Consolidation requires defining your operational data model. How integration is to be accomplished. Cross referencing common data attributes from multiple systems is needed. Synchronization policies also need to be developed. Data maintenance: The desired standardization needs to be defined, including what constitutes a ‘match’ once the data has been standardized. Cleansing rules are a part of this methodology. Data quality monitoring requirements also need to be defined. Utilize the data: What data gets published, and who consumes the data must be determined. How to get the right data to the right place in the right format given its intended use must be understood. Validating the data and insuring security rules are in place and enforced are crucial aspects for full no-risk data utilization. For each of the above data management areas, a maturity level needs to be assessed. Where your organization wants to be should also be identified using the same maturity levels. This results in a sound gap analysis your organization can use to create action plans to achieve the ultimate goals. Marginal is the lowest level. It is characterized by manually maintaining trusted sources; lacking or inconsistent, silo’d structures with limited integration, and gaps in automation. Stable is the next leg up the MDM maturity staircase. It is characterized by tactical MDM implementations that are limited in scope and target a specific division.  It includes limited data stewardship capabilities as well. Best Practice is a serious MDM maturity level characterized by process automation improvements. The scope is enterprise wide. It is a business solution that provides a single version of the truth, with closed-loop data quality capabilities. It is typically driven by an enterprise architecture group with both business and IT representation.   Transformational is the highest MDM maturity level. At this level, MDM is quantitatively managed. It is integrated with Business Intelligence, SOA, and BPM. MDM is leveraged in business process orchestration. Take an inventory using this MDM Maturity Model and see where you are in your journey to full MDM maturity with all the business benefits that accrue to organizations who have mastered their data for the benefit of all operational applications, business processes, and analytical systems. To learn more, Trevor Naidoo and I have written the Oracle MDM Maturity Model whitepaper. It’s free, so go ahead and download it and use it as you see fit.

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• EPM 11.1.2.2 Architecture: Financial Performance Management Applications

  - by Marc Schumacher

   Financial Management can be accessed either by a browser based client or by SmartView. Starting from release 11.1.2.2, the Financial Management Windows client does not longer access the Financial Management Consolidation server. All tasks that require an on line connection (e.g. load and extract tasks) can only be done using the web interface. Any client connection initiated by a browser or SmartView is send to the Oracle HTTP server (OHS) first. Based on the path given (e.g. hfmadf, hfmofficeprovider) in the URL, OHS makes a decision to forward this request either to the new Financial Management web application based on the Oracle Application Development Framework (ADF) or to the .NET based application serving SmartView retrievals running on Internet Information Server (IIS). Any requests send to the ADF web interface that need to be processed by the Financial Management application server are send to the IIS using HTTP protocol and will be forwarded further using DCOM to the Financial Management application server. SmartView requests, which are processes by IIS in first row, are forwarded to the Financial Management application server using DCOM as well. The Financial Management Application Server uses OLE DB database connections via native database clients to talk to the Financial Management database schema. Communication between the Financial Management DME Listener, which handles requests from EPMA, and the Financial Management application server is based on DCOM.  Unlike most other components Essbase Analytics Link (EAL) does not have an end user interface. The only user interface is a plug-in for the Essbase Administration Services console, which is used for administration purposes only. End users interact with a Transparent or Replicated Partition that is created in Essbase and populated with data by EAL. The Analytics Link Server deployed on WebLogic communicates through HTTP protocol with the Analytics Link Financial Management Connector that is deployed in IIS on the Financial Management web server. Analytics Link Server interacts with the Data Synchronisation server using the EAL API. The Data Synchronization server acts as a target of a Transparent or Replicated Partition in Essbase and uses a native database client to connect to the Financial Management database. Analytics Link Server uses JDBC to connect to relational repository databases and Essbase JAPI to connect to Essbase.  As most Oracle EPM System products, browser based clients and SmartView can be used to access Planning. The Java based Planning web application is deployed on WebLogic, which is configured behind an Oracle HTTP Server (OHS). Communication between Planning and the Planning RMI Registry Service is done using Java Remote Message Invocation (RMI). Planning uses JDBC to access relational repository databases and talks to Essbase using the CAPI. Be aware of the fact that beside the Planning System database a dedicated database schema is needed for each application that is set up within Planning.  As Planning, Profitability and Cost Management (HPCM) has a pretty simple architecture. Beside the browser based clients and SmartView, a web service consumer can be used as a client too. All clients access the Java based web application deployed on WebLogic through Oracle HHTP Server (OHS). Communication between Profitability and Cost Management and EPMA Web Server is done using HTTP protocol. JDBC is used to access the relational repository databases as well as data sources. Essbase JAPI is utilized to talk to Essbase.  For Strategic Finance, two clients exist, SmartView and a Windows client. While SmartView communicates through the web layer to the Strategic Finance Server, Strategic Finance Windows client makes a direct connection to the Strategic Finance Server using RPC calls. Connections from Strategic Finance Web as well as from Strategic Finance Web Services to the Strategic Finance Server are made using RPC calls too. The Strategic Finance Server uses its own file based data store. JDBC is used to connect to the EPM System Registry from web and application layer.  Disclosure Management has three kinds of clients. While the browser based client and SmartView interact with the Disclosure Management web application directly through Oracle HTTP Server (OHS), Taxonomy Designer does not connect to the Disclosure Management server. Communication to relational repository databases is done via JDBC, to connect to Essbase the Essbase JAPI is utilized.

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• database design help for game / user levels / progress

  - by sprugman

  Sorry this got long and all prose-y. I'm creating my first truly gamified web app and could use some help thinking about how to structure the data. The Set-up Users need to accomplish tasks in each of several categories before they can move up a level. I've got my Users, Tasks, and Categories tables, and a UserTasks table which joins the three. ("User 3 has added Task 42 in Category 8. Now they've completed it.") That's all fine and working wonderfully. The Challenge I'm not sure of the best way to track the progress in the individual categories toward each level. The "business" rules are: You have to achieve a certain number of points in each category to move up. If you get the number of points needed in Cat 8, but still have other work to do to complete the level, any new Cat 8 points count toward your overall score, but don't "roll over" into the next level. The number of Categories is small (five currently) and unlikely to change often, but by no means absolutely fixed. The number of points needed to level-up will vary per level, probably by a formula, or perhaps a lookup table. So the challenge is to track each user's progress toward the next level in each category. I've thought of a few potential approaches: Possible Solutions Add a column to the users table for each category and reset them all to zero each time a user levels-up. Have a separate UserProgress table with a row for each category for each user and the number of points they have. (Basically a Many-to-Many version of #1.) Add a userLevel column to the UserTasks table and use that to derive their progress with some kind of SUM statement. Their current level will be a simple int in the User table. Pros & Cons (1) seems like by far the most straightforward, but it's also the least flexible. Perhaps I could use a naming convention based on the category ids to help overcome some of that. (With code like "select cats; for each cat, get the value from Users.progress_{cat.id}.") It's also the one where I lose the most data -- I won't know which points counted toward leveling up. I don't have a need in mind for that, so maybe I don't care about that. (2) seems complicated: every time I add or subtract a user or a category, I have to maintain the other table. I foresee synchronization challenges. (3) Is somewhere in between -- cleaner than #2, but less intuitive than #1. In order to find out where a user is, I'd have mildly complex SQL like: SELECT categoryId, SUM(points) from UserTasks WHERE userId={user.id} & countsTowardLevel={user.level} groupBy categoryId Hmm... that doesn't seem so bad. I think I'm talking myself into #3 here, but would love any input, advice or other ideas. P.S. Sorry for the cross-post. I wrote this up on SO and then remembered that there was a game dev-focused one. Curious to see if I get different answers one place than the other....

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