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• A specific data structure

  - by user550413

  Well, this question is a bit specific but I think there is some general idea in it that I can't get it. Lets say I got K servers (which is a constant that I know its size). I have a program that get requests and every request has an id and server id that will handle it. I have n requests - unknown size and can be any number. I need a data structure to support the next operations within the given complexity: GetServer - the function gets the request ID and returns the server id that is supposed to handle this request at the current situation and not necessarily the original server (see below). Complexity: O(log K) at average. KillServer - the function gets as input a server id that should be removed and another server id that all the requests of the removed server should be passed to. Complexity: O(1) at the worst case. -- Place complexity for all the structure is O(K+n) -- The KillServer function made me think using a Union-Find as I can do the union in O(1) as requested but my problem is the first operation. Why it's LogK? Actually, no matter how I "save" the requests if I want to access to any request (lets say it's an AVL tree) so the complexity will be O(log n) at the worst case and said that I can't assume Kn (and probably K Tried thinking about it a couple of hours but I can't find any solution. Known structures that can be used are: B+ tree, AVL tree, skip list, hash table, Union-Find, rank tree and of course all the basics like arrays and such.

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• Handling primary key duplicates in a data warehouse load

  - by Meff

  I'm currently building an ETL system to load a data warehouse from a transactional system. The grain of my fact table is the transaction level. In order to ensure I don't load duplicate rows I've put a primary key on the fact table, which is the transaction ID. I've encountered a problem with transactions being reversed - In the transactional database this is done via a status, which I pick up and I can work out if the transaction is being done, or rolled back so I can load a reversal row in the warehouse. However, the reversal row will have the same transaction ID and so I get a primary key violation. I've solved this for now by negating the primary key, so transaction ID 1 would be a payment, and transaction ID -1 (In the warehouse only) would be the reversal. I have considered an alternative of generating a BIT column, where 0 is normal and 1 is reversal, then making the PK the transaction ID and the BIT column. My question is, is this a good practice, and has anyone else encountered anything like this? For reference, this is a payment processing system, so values will not be modified, so there will only ever be transactions and reversals.

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• Deleting object in NSMutableSet Core Data

  - by Luke

  Hi I am having trouble deleting an object in an NSMutableSet using core Data... I am trying to delete a "player" object in the second section of my tableview. I am getting the error Invalid update: invalid number of rows in section 1. The number of rows contained in an existing section after the update (6) must be equal to the number of rows contained in that section before the update (6), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out Take a look at my code. - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { if (indexPath.section==0){ }else{ Player *p = [self.fetchedResultsController.fetchedObjects objectAtIndex: indexPath.section]; [_team removePlayersObject:p]; [_team.players removeObject:p]; AppDelegate *delegate = [[UIApplication sharedApplication] delegate]; _managedObjectContext = delegate.managedObjectContext; [_managedObjectContext deleteObject:p]; [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationTop]; } } } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { switch(section){ case 0: return 7; case 1: return [self.fetchedResultsController.fetchedObjects count]; } return 0; }

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• HTTP 401.3 when PUT, DELETE to ADO.NET Data Service (.svc)

  - by Nate

  I have an ADO.NET Data Service (we'll call it service.svc). When I deploy it to an IIS 6 site with Integrated Windows Authentication turned on, all requests (GET, POST, PUT, and DELETE) work fine for me, because I am an administrator on the box. However, when a non-admin user hits the service, only GET and POST requests work. When they try a PUT or DELETE request, they get an HTTP 401.3 "Access is Denied" error: "Error message 401.3: You do not have permission to view this directory or page using the credentials you supplied (access denied due to Access Control Lists). Ask the web server's administrator to give you access to '...\service.svc'." If I give the "Authenticated Users" local group write access to the .svc file, everything works as it should, but I really don't want to do this (and don't think I should have to do this to get this to work). In fact, I'm confused as to why changing the file permissions would affect this at all, but it definitely seems to be the problem. I've found a couple of different suggestions to fix somewhat similar problems in the Microsoft forums (Here, and I would post more links, but am being told that new users can only post one link in a post), but none of the solutions help. Any help is much appreciated. I am certainly no IIS expert, and this one has got me stumped.

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• Bind data of interface properties only

  - by nivpenso

  I am new in all the Entity Framework models and the data bindings. I created an interface and generated a model class from my Candidate table in the db. public interface ICandidate { String ID { get; set; } string Name { get; set; } string Mail { get; set; } } i created a partial class to the generated Candidate model so i will be able to implement the ICandidate interface without changing any generated code. public partial class Candidates : ICandidate { string ICandidate.ID { get { return this.PK; } set { _PK = value; } } string ICandidate.Name { get{ return this._Name; } set { _Name = value; } } string ICandidate.Mail { get { return this._Email; } set { this._Email = value; } } } Of course, the generated class has more properties than the interface has (Like IsDeleted field that is not necessary for the interface). I want to display in a DataGridView all the candidates from the db. But I want that only the interface's properties will be shown as columns in the DataGridView. Is there a way bind only the interface's properties the the DataGridView? In my DB there is a table called Candidate_To_Company with these columns: PK, Candidate_FK, Company_FK, Insertion_Date I would like to bind this table to DataGridView. but instead of displaying Candidate_FK i would like to display the candidate name from ICandidate. Is this possible?

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• Core Data to-many relationship in code

  - by Jan Bezemer

  I have three entities: Session, User and Test. A session has 0-many users and a user can perform 0-6 tests. (I say 0 but in the real application always at least 1 is required, at least 1 user for a session and at least 1 test for a user. But I say 0 to express an empty start.) All entities have their own specific data attributes too. A user has a name, A session has a name, a test has six values to be filled in by the user, and so on. But my issue is with the relationships. How do I set multiple users and have them added to one session (same goes for multiple tests for one user). How do I show the content in a right way? How do I show a session that has multiple users and these users having completed multiple tests? Here's my code so far with regard to issue 1: Session *session = [NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:context]; session.name = @"Session 1"; User *users = [NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:context]; users.age = [NSNumber numberWithInt:28]; users.session = session; //sessie.users = users; [sessie addUserObject:users]; With regard to issue 2: I can log the session, but I can't get the user(s) logged from a session. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Session" inManagedObjectContext:context]; [fetchRequest setEntity:entity]; NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error]; for (Session *info in fetchedObjects) { NSLog(@"Name: %@", info.name); NSLog(@"Having problems with this: %@",info.user); //User *details = info.user; //NSLog(@"User: %@", details.age); }

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• Best way to store data in database when you don't know the type

  - by stiank81

  I have a table in my database that represents datafields in a custom form. The DataField gives some representation of what kind of control it should be represented with, and what value type it should take. Simplified you can say that I have 2 entities in this table - Textbox taking any string and Textbox only taking numbers. Now I have the different values stored in a separate table, referencing the datafield definition. What is the best way to store the data value here, when the type differs? One possible solution is to have the FieldValue table hold one field per possible value type. Now this would certainly be redundant, but at least I would get the value stored in its correct form - simplifying queries later. FieldValue ---------- Id DataFieldId IntValue DoubleValue BoolValue DataValue .. Another possibility is just storing everything as String, and casting this in the queries. I am using .Net with NHibernate, and I see that at least here there is a Projections.Cast that can be used to cast e.g. string to int in the query. Either way in these two solutions I need to know which type to use when doing the query, but I will know that from the DataField, so that won't be a problem. Anyway; I don't think any of these solutions sounds good. Are they? Or is there a better way?

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• Scientific Data processing (Graph comparison and interpretation)

  - by pinkynobrain

  Hi stackoverflow friends, I'm trying to write a program to automate one of my more boring and repetitive work tasks. I have some programming experience but none with processing or interpreting large volumes of data so I am seeking your advice (both suggestions of techniques to try and also things to read to learn more about doing this stuff). I have a piece of equipment that monitors an experiment by taking repeated samples and displays the readings on its screen as a graph. The input of experiment can be altered and one of these changes should produce a change in a section of the graph which I currently identify by eye and is what I'm looking for in the experiment. I want to automate it so that a computer looks at a set of results and spots the experiment input that causes the change. I can already extract the results from the machine. Currently they results for a run are in the form of an integer array with the index being the sample number and the corresponding value being the measurement. The overall shape of the graph will be similar for each experiment run. The change I'm looking for will be roughly the same and will occur in approximately the same place every time for the correct experiment input. Unfortunately there are a few gotchas that make this problem more difficult. There is some noise in the measuring process which mean there is some random variation in the measured values between different runs. Although the overall shape of the graph remains the same. The time the experiment takes varies slightly each run causing two effects. First, the a whole graph may be shifted slightly on the x axis relative to another run's graph. Second, individual features may appear slightly wider or narrower in different runs. In both these cases the variation isn't particularly large and you can assume that the only non random variation is caused by the correct input being found. Thank you for your time, Pinky

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• Same Data Appear only once.

  - by friendishan

  I have the following code which produces following output:- <? $tablaes = mysql_query("SELECT * FROM members where id='$order[user_id]'"); $user = mysql_fetch_array($tablaes); $idsd=$user['id']; $rPaid=mysql_query("SELECT SUM(`price`) AS total FROM order_history WHERE type!='rent_referral' AND date>'" . strtotime($time1) . "' AND date<'" . strtotime($time2) . "'"); $hdPaid = mysql_fetch_array($rPaid); $sPaid=mysql_query("SELECT SUM(`price`) AS total FROM order_history WHERE user_id='$idsd' AND type!='rent_referral' AND date>'" . strtotime($time1) . "' AND date<'" . strtotime($time2) . "'"); while ($hPaid = mysql_fetch_array($sPaid)) { ?> <td><?=$user['username']?></td> <td><?=$hPaid['total']?></td> <? } ?> </tr> It appears like this http://dl.dropbox.com/u/14384295/darrenan.jpg I want same data to appear only once.. Like Username: Vegas and price with him only once.

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• A good(elegant) way to retrieve records with counts.

  - by user93422

  Context: ASP.NET MVC 2.0, C#, SQL Server 2007, IIS7 I have 'scheduledMeetings' table in the database. There is a one-to-many relationship: scheduledMeeting - meetingRegistration So that you could have 10 people registered for a meeting. meetingRegistration has fields Name, and Gender (for example). I have a "calendar view" on my site that shows all coming events, as well as gender count for each event. At the moment I use Linq to Sql to pull the data: var meetings = db.Meetings.Select( m => new { MeetingId = m.Id, Girls = m.Registrations.Count(r => r.Gender == 0), Boys = m.Registrations.Count(r=>r.Gender == 1) }); (actual query is half-a-page long) Because there is anonymous type use going on I cant extract it into a method (since I have several different flavors of calendar view, with different information on each, and I dont want to create new class for each). Any suggestions on how to improve this? Is database view is the answer? Or should I go ahead and create named-type? Any feedback/suggestions are welcome. My DataLayer is huge, I want to trim it, just dont know how. Pointers to a good reading would be good too.

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• Would you re-design completely under .Net?

  - by dboarman

  A very extensive application began as an Access-based system (for database storage). Forms were written in VB5 and/or VB6. As .Net became a fixture in the development community, certain modules have been rewritten. This seems very awkward and potentially costly just to maintain because of the cross-technologies and extra work to keep the two technologies happy with each other. Of course, the application uses a mix of ODBC OleDb and MySql. Would you think spending the time and resources to completely re-develop the application under .Net would be more cost effective? In an effort to develop a more stable application, wouldn't it make sense to use .Net? Or continue chasing Access bugs, adding new features in .Net (which may or may not create new bugs between .Net and Access), and rewriting old Access modules into .Net modules under time constraints that prevent proper design and development? Update The application uses OleDb and MySql - I corrected my previous statement. Also, to lend further support to rewriting: I have since found out that when the "porting" to .Net began, the VBA/VB6 code that existed was basically translated to the .Net equivalent. From my understanding, nothing was done to improve performance, or take advantage of new libraries or technologies. In my opinion, this creates a very fragile and unstable application. With every new update, this becomes more and more visible. As a help desk technician, I have noticed an increase in problems reported. The customers using the software have noticed an increase in problems and are commenting on it.

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• Java - System design with distributed Queues and Locks

  - by sunny

  Looking for inputs to evaluate a design for a system (java) which would have a distributed queue serving several (but not too many) nodes. These nodes would process objects present in the distributed queue and on occasion require a distributed lock across the cluster on an arbitrary (distributed) data structures. These (distributed) data structures could potentially lie in a distributed cache. Eliminating Terracotta (DSO),Hazelcast and Akka what could be alternative choices. Currently considering zookeeper as a distributed locking mechanism. Since the recommendation of a znode is not to exceed the 1M size , the understanding is that zookeeper should not be used a distributed queue. And also from Netflix curator tech note 4. So should a distributed cache, say like memcached, or redis be used to emulate a distributed queue ? i.e. The distributed queue will be stored in the caches and will be locked cluster-wide via zookeeper. Are there potential pitfalls with this high-level approach. The objects don't need to be taken off the queue. The object will pass through a lifecycle which will determine its removal from the queue. There would be about 10k+ objects in a queue at a given time changing states and any node could service one stage of the object's lifecycle. (Although not strictly necessary .. i.e. one node could serve the entire lifecycle if that is more efficient.) Any suggestions/alternatives ? sidenote: new to zookeeper ; redis etc.

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• Design pattern for procedural terrain assets

  - by Alex

  I'm developing a procedural terrain class at the moment and am stuck on the correct design pattern. The terrain is 2D and is constructed from a series of (x,y) points. I currently have a method that just randomly adds points to an array of points to generate a random spread of points. However I need a more elaborate system for generating the terrain. The terrain will be built form a series of re-accuring terrain structures eg. a pit, jump, hill etc. Each structure will have some randomness assigned to it, each height of hill will be random, pit size will be random etc. Each terrain structure will have: A property detailing the number of points making up that structure A method for generating the points (not absolutely necessary) My current thinking is to have a class for each terrain structure, create a fixed amount of terrain elements ahead of the player, loop over these and add the corresponding points to the game. What is the best way to create these procedural terrain structures when they are ultimately just a set of functions for generating terrain elements? Is a class for each terrain element excessive? I'm developing the game for iphone so any objective-c related answers would be welcome.

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• Design and Print Your Own Christmas Cards in MS Word, Part 2: How to Print

  - by Eric Z Goodnight

  Creating greeting cards can be a lot of DIY fun around the holidays, but printing them can often be a nightmare. This simple How-To will show you how to figure out how to perfectly print your half fold card. Last week we showed you how to create a simple, attractive greeting card in Microsoft Word using Creative Commons images and basic fonts. If you missed out, it is still available, and the Word template used here can still be downloaded. If you have already made your Christmas card and are struggling to get it printed right, then this simple How-To is for you Latest Features How-To Geek ETC The How-To Geek Guide to Learning Photoshop, Part 8: Filters Get the Complete Android Guide eBook for Only 99 Cents [Update: Expired] Improve Digital Photography by Calibrating Your Monitor The How-To Geek Guide to Learning Photoshop, Part 7: Design and Typography How to Choose What to Back Up on Your Linux Home Server How To Harmonize Your Dual-Boot Setup for Windows and Ubuntu Hang in There Scrat! – Ice Age Wallpaper How Do You Know When You’ve Passed Geek and Headed to Nerd? On The Tip – A Lamborghini Theme for Chrome and Iron What if Wile E. Coyote and the Road Runner were Human? [Video] Peaceful Winter Cabin Wallpaper Store Tabs for Later Viewing in Opera with Tab Vault

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• Correct For Loop Design

  - by Yttrill

  What is the correct design for a for loop? Felix currently uses if len a > 0 do for var i in 0 upto len a - 1 do println a.[i]; done done which is inclusive of the upper bound. This is necessary to support the full range of values of a typical integer type. However the for loop shown does not support zero length arrays, hence the special test, nor will the subtraction of 1 work convincingly if the length of the array is equal to the number of integers. (I say convincingly because it may be that 0 - 1 = maxval: this is true in C for unsigned int, but are you sure it is true for unsigned char without thinking carefully about integral promotions?) The actual implementation of the for loop by my compiler does correctly handle 0 but this requires two tests to implement the loop: continue: if not (i <= bound) goto break body if i == bound goto break ++i goto continue break: Throw in the hand coded zero check in the array example and three tests are needed. If the loop were exclusive it would handle zero properly, avoiding the special test, but there'd be no way to express the upper bound of an array with maximum size. Note the C way of doing this: for(i=0; predicate(i); increment(i)) has the same problem. The predicate is tested after the increment, but the terminating increment is not universally valid! There is a general argument that a simple exclusive loop is enough: promote the index to a large type to prevent overflow, and assume no one will ever loop to the maximum value of this type.. but I'm not entirely convinced: if you promoted to C's size_t and looped from the second largest value to the largest you'd get an infinite loop!

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• Transient VO : Powerful J2EE Design Pattern

  - by Vijay Mohan

  We had a use-case wherein, the communication has to happen between regions residing under differenet taskfows. Essentially, they had a common set of parameters to be used. Initially, we resorted to the  use of pageFlowScope variables, but they are tightly coupled with the individual task flows. So, how the communication has to happen..?Some of the alternatives that we brainstormed into are - 1.usage of adf contextual event - This is a powerful feature indeed for such use-cases, but there is a considerable cost involved with it. So, before resorting to it, you have to make sure that you have good enough reason to use it.It actually does a server roundtrip and also the issue of an event and listening part to it is also something which requires your attention !!2.Use a transientVO with shared data control scope - with shared data control scope, the transient VO rows would be persistent across the task flows in your application. All you have to do is to create the attributes in the transientVO(prefereably with the same names - for the ease of conversion) and create some utility methods in VOImpl for creating row, updating row and deleting a row. You also have to make sure that the vo row is initialized per http request( this you can do in a bookmark method of your index.jspx - residing in adfc-config.xml), else the ui fields binded to the transient vo attributes won't render in UI.Hope, this helps and this should be a common use-case across apps.

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• Regarding sprite design and resolution for tablets and phones

  - by Dimitris P.

  I am about to start working on a game for android devices, in my spare time, to get familiar with android development. I'm more interested in using the best practices possible than getting a quick result, and that is why I need some guidance regarding graphics. I think the game is going to be fully sprite based. Everything is going to be in .bmp form, or something similar, and my question is: Should I design the sprites in a small resolution (ie for phone screens) and scale them up to fit into larger screens (tablet screens), should I do it vice-versa or should I consider a completely different approach? Would designing a different set of sprites for each of the most used resolution settings be worth it or are there simpler solutions to the problem with fewer drawbacks than the ones I mentioned above? (If I follow the first approach, for example, the larger the screen the worse the graphics will get, since every pixel of the original drawing will cover several pixels on the screen). Is there a standard approach for dealing with this kind of problems? If you need me to be more detailed or more clear about something I mentioned (or forgot to) please don't hesitate to ask. Also, excuse me for any inaccurate use of the English language. Thank you in advance for your input.

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• The best way to structure/design game code

  - by Edward

  My question is quite broad and related to the 2D game code design/architecture/structure. Usually the main game consists of the main loop where you update & render your world states. However, it's recommended for many purposes to separate rendering from the game-logic and so on. I am kinda confused about the whole situation. Many game engines/libs/sdks don't follow separation schema. They propagate a way where you define some scenes/stages and they contain some objects and the scene/stage controls the user input and so on. For example, in cocos2d(-x) and libgdx (stage2d) the games are usually done the way that the update logic happens at the same time/place as rendering. Also, the propagated way is to have a structure where an object knows how to draw itself - which is not a separation of updating & rendering. The same with Flash based games, they are usually done the way when an object (class) contains a swf or a texture and some data and holds some update logic itself, or updated from main Scene. And again this object already knows how to draw itself via "addChild". Also, some people recommend to use MVC pattern, which will require to completely obey the structure of those engines/libs/sdks. Maybe I am overthinking everything, but I am totally confused. I would be grateful if somebody could point me to a correct direction with the game code structures. What is your way of doing things in libgdx/cocos2d/flash?

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• Choosing Technology To Include In Software Design

  How many of us have been forced to select one technology over another when designing a new system? What factors do we and should we consider? How can we ensure the correct business decision is made? When faced with this type of decision it is important to gather as much information possible regarding each technology being considered as well as the project itself. Additionally, I tend to delay my decision about the technology until it is ultimately necessary to be made. The reason why I tend to delay such an important design decision is due to the fact that as the project progresses requirements and other factors can alter a decision for selecting the best technology for a project. Important factors to consider when making technology decisions: Time to Implement and Maintain Total Cost of Technology (including Implementation and maintenance) Adaptability of Technology Implementation Team’s Skill Sets Complexity of Technology (including Implementation and maintenance) orecasted Return On Investment (ROI) Forecasted Profit on Investment (POI) Of the factors to consider the ROI and POI weigh the heaviest because the take in to consideration the other factors when calculating the profitability and return on investments.For a real world example let us consider developing a web based lead management system for a new company. This system can either be hosted on Microsoft Windows based web server or on a Linux based web server. Important Factors for this Example Implementation Team’s Skill Sets Member 1  Skill Set: Classic ASP, ASP.Net, and MS SQL Server Experience: 10 years Member 2  Skill Set: PHP, MySQL, Photoshop and MS SQL Server Experience: 3 years Member 3  Skill Set: C++, VB6, ASP.Net, and MS SQL Server Experience: 12 years Total Cost of Technology (including Implementation and maintenance) Linux Initial Year: $5,000 (Random Value) Additional Years: $3,000 (Random Value) Windows Initial Year: $10,000 (Random Value) Additional Years: $3,000 (Random Value) Complexity of Technology Linux Large Learning Curve with user driven documentation Estimated learning cost: $30,000 Windows Minimal based on Teams skills with Microsoft based documentation Estimated learning cost: $5,000 ROI Linux Total Cost Initial Total Cost: $35,000 Additional Cost $3,000 per year Windows Total Cost Initial Total Cost: $15,000 Additional Cost $3,000 per year Based on the hypothetical numbers it would make more sense to select windows based web server because the initial investment of the technology is much lower initially compared to the Linux based web server.

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• Oracle Advanced Benefits: Plan Design Maintenance for Open Enrollment

  - by Annemarie Provisero

  ADVISOR WEBCAST: Oracle Advanced Benefits: Plan Design Maintenance for Open Enrollment PRODUCT FAMILY: Oracle HCM - Benefits  July 13, 2011 at 1 pm PT, 2 pm MT, 4 pm ET This session AU gives you the information to define new and maintain all Compensation Objects used in your Benefits setup. Course highlights things to consider when getting ready for Open Enrollment or when there is a need to change compensation objects. We will review creating a new or ending an old program, plan, or option. We also review what to do when you need to move from an Unrestricted program to a Restricted one. TOPICS WILL INCLUDE: Adding or Modifying Compensation Objects Ending Compensation Objects Elements and Element Links Standard and Variable Rates Dependents and Beneficiaries Moving from Oracle Standard Benefits to Oracle Advanced Benefits A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. Click here to register for this session ------------------------------------------------------------------------------------------------------------- The above webcast is a service of the E-Business Suite Communities in My Oracle Support. For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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• Class Design - Space Simulator

  - by Peteyslatts

  I have pretty much taught myself everything I know about programming, so while I know how to teach myself (books, internet and reading API's), I'm finding that there hasn't been a whole lot in the way of good programming. So I have two questions: First the broad one: Does anyone have suggestions as to sources for learning about good programming habits and techniques? I'd prefer it if the resource wasn't a 5000 page tome. The more I can read it in installments the better. More specifically: I am finishing up learning the basics of XNA and I want to create a space simulator to test my knowledge. This isn't a full scale simulator, but just something that covers everything I learned. It's also going to be modular so I can build on it, after I get the basics down. One of the early features I want to implement is AI. And I want to take this into account as I'm designing my classes so I can minimize rewriting code. So my question: How should I design ship classes so that both the player and AI can use them? The only idea I have so far is: Create a ship class that contains stats, models, textures, collision data etc. The player and AI would then have the data for position, rotation, health, etc and would base their status off of the ship stats.

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• Java game design question (graphical objects)

  - by vemalsar

  Hello Guys, I'm beginner in game development, in Java and here on this site too and I have a game design question. Please comment my idea: I have a main loop which call update and draw method. I want to use an ArrayList which store graphical objects, they have coordinate and image or text to draw and my game objects extends this class. In update, I can choose which objects should be put in the array and in draw method I'll display the elements of array on the screen. I'm using a buffer and draw first there, but it is not important now I guess...Here is a simple (not full) code, only the logic: public class GamePanel extends JPanel implements KeyListener { ArrayList<graphicalObjects> graphArray = new ArrayList<graphicalObjects>(); public void update() { //change the game scene, update the graphArray, process input etc. } public void draw() { //draws every element of graphArray to a JPanel } public static main(String[] args) { while(true) { update(); draw(); } } } My questions: Should have I use interface or abstract class for graphicalObjects? graphicalObjects class and the ArrayList really needs or there is some better solution? How to draw objects? They draw themself with their own method or in the draw method I have to draw manually based on graphicalObjects variables (x,y coordinates, image etc.)? If this conception is wrong, please suggest another one! All comments are welcome and sorry if this is dumb question, thanks!

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• Issue with dynamic array Queue data structure with void pointer

  - by Nazgulled

  Hi, Maybe there's no way to solve this the way I'd like it but I don't know everything so I better ask... I've implemented a simple Queue with a dynamic array so the user can initialize with whatever number of items it wants. I'm also trying to use a void pointer as to allow any data type, but that's the problem. Here's my code: typedef void * QueueValue; typedef struct sQueueItem { QueueValue value; } QueueItem; typedef struct sQueue { QueueItem *items; int first; int last; int size; int count; } Queue; void queueInitialize(Queue **queue, size_t size) { *queue = xmalloc(sizeof(Queue)); QueueItem *items = xmalloc(sizeof(QueueItem) * size); (*queue)->items = items; (*queue)->first = 0; (*queue)->last = 0; (*queue)->size = size; (*queue)->count = 0; } Bool queuePush(Queue * const queue, QueueValue value, size_t val_sz) { if(isNull(queue) || isFull(queue)) return FALSE; queue->items[queue->last].value = xmalloc(val_sz); memcpy(queue->items[queue->last].value, value, val_sz); queue->last = (queue->last+1) % queue->size; queue->count += 1; return TRUE; } Bool queuePop(Queue * const queue, QueueValue *value) { if(isEmpty(queue)) return FALSE; *value = queue->items[queue->first].value; free(queue->items[queue->first].value); queue->first = (queue->first+1) % queue->size; queue->count -= 1; return TRUE; } The problem lies on the queuePop function. When I call it, I lose the value because I free it right away. I can't seem to solve this dilemma. I want my library to be generic and modular. The user should not care about allocating and freeing memory, that's the library's job. How can the user still get the value from queuePop and let the library handle all memory allocs/frees?

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• Migration Core Data error code 134130

  - by magichero

  I want to do migration with 2 core database. I have read apple developer document. For the first database, I add some attributes (string, integer and date properties) to new version database. And follow all steps, I have done migration successfully with the first once. But the second database, I also add attributes (string, integer, date, transformable and binary-data properties) to new version database. And follow all steps (like the first database) but system return an error (134130). Here is the code: if (persistentStoreCoordinator_) { PMReleaseSafely(persistentStoreCoordinator_); } // Notify NSNotificationCenter *nc = [NSNotificationCenter defaultCenter]; [nc postNotificationName:GCalWillMigrationNotification object:self]; // NSString *sourceStoreType = NSSQLiteStoreType; NSString *dataStorePath = [PMUtility dataStorePathForName:GCalDBWarehousePersistentStoreName]; NSURL *storeURL = [NSURL fileURLWithPath:dataStorePath]; BOOL storeExists = [[NSFileManager defaultManager] fileExistsAtPath:dataStorePath]; // NSError *error = nil; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel]; [persistentStoreCoordinator_ addPersistentStoreWithType:sourceStoreType configuration:nil URL:storeURL options:options error:&error]; if (error != nil) { abort(); } error is not nil and below is log: Error Domain=NSCocoaErrorDomain Code=134130 "The operation couldn\u2019t be completed. (Cocoa error 134130.)" UserInfo=0x856f790 {URL=file://localhost/Users/greensun/Library/Application%20Support/iPhone%20Simulator/5.0/Applications/D10712DE-D9FE-411A-8182-C4F58C60EC6D/Library/Application%20Support/Promise%20Mail/GCalDBWarehouse.sqlite, metadata={type = immutable dict, count = 7, entries = 2 : {contents = "NSStoreModelVersionIdentifiers"} = {type = immutable, count = 1, values = ( 0 : {contents = ""} )} 4 : {contents = "NSPersistenceFrameworkVersion"} = {value = +386, type = kCFNumberSInt64Type} 6 : {contents = "NSStoreModelVersionHashes"} = {type = immutable dict, count = 2, entries = 0 : {contents = "SyncEvent"} = {length = 32, capacity = 32, bytes = 0xfdae355f55c13fbd0344415fea26c8bb ... 4c1721aadd4122aa} 1 : {contents = "ImportEvent"} = {length = 32, capacity = 32, bytes = 0x7676888f0d7eaff4d1f844343028ce02 ... 040af6cbe8c5fd01} } 7 : {contents = "NSStoreUUID"} = {contents = "51678BAC-CCFB-4D00-AF5C-8FA1BEDA6440"} 8 : {contents = "NSStoreType"} = {contents = "SQLite"} 9 : {contents = "_NSAutoVacuumLevel"} = {contents = "2"} 10 : {contents = "NSStoreModelVersionHashesVersion"} = {value = +3, type = kCFNumberSInt32Type} }, reason=Can't find model for source store} I try a lot of solutions but it does not work. I just add more attributes to 2 new version database, and succeed in migrating once. Thanks for reading and your help.

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• Multiple views and source list in a Core Data app

  - by Ellie P.

  I'm working on my first major Cocoa app for an undergraduate research project. The application is document-based and uses Core Data. One of the entities is an abstract entity, Page. Page is parent of several types of pages: ie PageWithHeaderAndFooter, PageWithTwoColumns, BasicPage etc. Page has attributes, such as title and author, that all pages have in common. Each specific type of page has a certain number of layout blocks (PageWithHeaderAndFooter has three: header, footer, body. BasicPage has one: body. etc.) Additionally, all Page subclasses define layout-specific implementations of certain methods. The other relevant entity is Style, which defines the visual look of a Page. (Think of Pages as HTML and Style as CSS.) I would like my app to have an iTunes/Mail-like source list with sections. (One section would be Pages, the other would be Styles.) I have a pretty good idea how to do the sectioned source list (this was a great help). However, after hours of headbanging and fruitless googling, here's what I can't figure out: Pages and Styles listed in the source list, and when you select one of them, all of the relevant fields for that object appear at the right (mostly NSTextViews, pop up menus, etc). I laid that out and did all of the bindings in Interface Builder. The problem is, if my source list contains different types of pages, how do I get a different view to display at the right depending on the type of page selected? For example, if a BasicPage is selected, I want just what you see above: the general page stuff and one NSTextView that corresponds to the one field body of BasicPage. But if I select a PageWithHeaderAndFooter, I want to display the general page stuff plus three NSTextViews (one for header, body, and footer.) If I have a Style selected, I want to display various pop up menus, color wells, etc. For the pages at least, we're only talking about one or more NSTextViews, each of which corresponds to a String attribute of the respective entity. How would you do this? Thank you for your help!

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