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• PCI Encryption Key Management

  - by Unicorn Bob

  (Full disclosure: I'm already an active participant here and at StackOverflow, but for reasons that should hopefully be obvious, I'm choosing to ask this particular question anonymously). I currently work for a small software shop that produces software that's sold commercially to manage small- to mid-size business in a couple of fairly specialized industries. Because these industries are customer-facing, a large portion of the software is related to storing and managing customer information. In particular, the storage (and securing) of customer credit card information. With that, of course, comes PCI compliance. To make a long story short, I'm left with a couple of questions about why certain things were done the way they were, and I'm unfortunately without much of a resource at the moment. This is a very small shop (I report directly to the owner, as does the only other full-time employee), and the owner doesn't have an answer to these questions, and the previous developer is...err...unavailable. Issue 1: Periodic Re-encryption As of now, the software prompts the user to do a wholesale re-encryption of all of the sensitive information in the database (basically credit card numbers and user passwords) if either of these conditions is true: There are any NON-encrypted pieces of sensitive information in the database (added through a manual database statement instead of through the business object, for example). This should not happen during the ordinary use of the software. The current key has been in use for more than a particular period of time. I believe it's 12 months, but I'm not certain of that. The point here is that the key "expires". This is my first foray into commercial solution development that deals with PCI, so I am unfortunately uneducated on the practices involved. Is there some aspect of PCI compliance that mandates (or even just strongly recommends) periodic key updating? This isn't a huge issue for me other than I don't currently have a good explanation to give to end users if they ask why they are being prompted to run it. Question 1: Is the concept of key expiration standard, and, if so, is that simply industry-standard or an element of PCI? Issue 2: Key Storage Here's my real issue...the encryption key is stored in the database, just obfuscated. The key is padded on the left and right with a few garbage bytes and some bits are twiddled, but fundamentally there's nothing stopping an enterprising person from examining our (dotfuscated) code, determining the pattern used to turn the stored key into the real key, then using that key to run amok. This seems like a horrible practice to me, but I want to make sure that this isn't just one of those "grin and bear it" practices that people in this industry have taken to. I have developed an alternative approach that would prevent such an attack, but I'm just looking for a sanity check here. Question 2: Is this method of key storage--namely storing the key in the database using an obfuscation method that exists in client code--normal or crazy? Believe me, I know that free advice is worth every penny that I've paid for it, nobody here is an attorney (or at least isn't offering legal advice), caveat emptor, etc. etc., but I'm looking for any input that you all can provide. Thank you in advance!

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• Resolving collisions between dynamic game objects

  - by TheBroodian

  I've been building a 2D platformer for some time now, I'm getting to the point where I am adding dynamic objects to the stage for testing. This has prompted me to consider how I would like my character and other objects to behave when they collide. A typical staple in many 2D platformer type games is that the player takes damage upon touching an enemy, and then essentially becomes able to pass through enemies during a period of invulnerability, and at the same time, enemies are able to pass through eachother freely. I personally don't want to take this approach, it feels strange to me that the player should receive arbitrary damage for harmless contact to an enemy, despite whether the enemy is attacking or not, and I would like my enemies' interactions between each other (and my player) to be a little more organic, so to speak. In my head I sort of have this idea where a game object (player, or non player) would be able to push other game objects around by manner of 'pushing' each other out of one anothers' bounding boxes if there is an intersection, and maybe correlate the repelling force to how much their bounding boxes are intersecting. The problem I'm experiencing is I have no idea what the math might look like for something like this? I'll show what work I've done so far, it sort of works, but it's jittery, and generally not quite what I would pass in a functional game: //Clears the anti-duplicate buffer collisionRecord.Clear(); //pick a thing foreach (GameObject entity in entities) { //pick another thing foreach (GameObject subject in entities) { //check to make sure both things aren't the same thing if (!ReferenceEquals(entity, subject)) { //check to see if thing2 is in semi-near proximity to thing1 if (entity.WideProximityArea.Intersects(subject.CollisionRectangle) || entity.WideProximityArea.Contains(subject.CollisionRectangle)) { //check to see if thing2 and thing1 are colliding. if (entity.CollisionRectangle.Intersects(subject.CollisionRectangle) || entity.CollisionRectangle.Contains(subject.CollisionRectangle) || subject.CollisionRectangle.Contains(entity.CollisionRectangle)) { //check if we've already resolved their collision or not. if (!collisionRecord.ContainsKey(entity.GetHashCode())) { //more duplicate resolution checking. if (!collisionRecord.ContainsKey(subject.GetHashCode())) { //if thing1 is traveling right... if (entity.Velocity.X > 0) { //if it isn't too far to the right... if (subject.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height)) || subject.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = entity.CollisionRectangle.Right - subject.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the left, and thing2 to the right. entity.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //if thing1 is traveling left... if (entity.Velocity.X < 0) { //if thing1 isn't too far left... if (entity.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height)) || entity.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = subject.CollisionRectangle.Right - entity.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the right, and thing2 to the left. entity.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //Make record that thing1 and thing2 have interacted and the collision has been solved, so that if thing2 is picked next in the foreach loop, it isn't checked against thing1 a second time before the next update. collisionRecord.Add(entity.GetHashCode(), subject.GetHashCode()); } } } } } } } } One of the biggest issues with my code aside from the jitteriness is that if one character were to land on top of another character, it very suddenly and abruptly resolves the collision, whereas I would like a more subtle and gradual resolution. Any thoughts or ideas are incredibly welcome and helpful.

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• Resolving bounding box collision detection

  - by ndg

  I'm working on a simple collision detection and resolution method for a 2d tile-based bounding box system. Collision appears to work correctly, but I'm having issues with resolving a collision after it has happened. Essentially what I'm attempting to do is very similar to this approach. The problem I'm experiencing is that because objects can be traveling with both horizontal and vertical velocity, my resolution code causes the object to jump incorrectly. I've drawn the following annotation to explain my issue. In this example, because my object has both horizontal and vertical velocity, my object (which is heading upwards and collides with the bottom of a tile) has it's position altered twice: To correctly adjust it's vertical position to be beneath the tile. To incorrectly adjust it's horizontal position to be to the left of the tile. Below is my collision/resolution code in full: function intersects(x1, y1, w1, h1, x2, y2, w2, h2) { w2 += x2; w1 += x1; if (x2 > w1 || x1 > w2) return false; h2 += y2; h1 += y1; if (y2 > h1 || y1 > h2) return false; return true; } for(var y = 0; y < this.game.level.tiles.length; y++) { for(var x = 0; x < this.game.level.tiles[y].length; x++) { var tile = this.game.level.getTile(x, y); if(tile) { if( this.velocity.x > 0 && intersects(this.position.x+dx+this.size.w, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)-this.size.w); hitSomething = true; break; } else if( this.velocity.x < 0 && intersects(this.position.x+dx, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)+tileSize); hitSomething = true; break; } if( this.velocity.y > 0 && intersects(this.position.x+dx, this.position.y+dy+this.size.h, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)-this.size.h); hitSomething = true; break; } else if( this.velocity.y < 0 && intersects(this.position.x+dx, this.position.y+dy, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)+tileSize); hitSomething = true; break; } } } } if(hitSomething) { this.velocity.x = this.velocity.y = 0; dx = dy = 0; this.setJumping(false); }

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• Migrating VB6 to HTML5 is not a fiction - Customer success story

  - by Webgui

  All of you VB developers in the present or past would probably find it hard to believe that the old VB code can be migrated and modernized into the latest .NET based HTML5 without having to rewrite the application. But we have been working on such tools for the past couple of years and already have several real world applications that were fully 'transposed' from VB6. The solution is called Instant CloudMove and its main tool is called the TranspositionStudio. It is a unique solution that relies on the concept of transposition. Transposition comes from mathematics and music and refers to exchanging elements while everything else remains the same or moving an element as is from one environment to another. This means that we are taking the source code and put it in a modern technological environment with relatively few adjustments.The concept is based on a set of Mapping Expressions which are basically links between an element in the source environment and one in the target environment that has the same functionality. About 95% of the code is usually mapped out-of-the-box and the rest is handled with easy-to-use mapping tools designed for Visual Studio developers providing them with a familiar environment and concepts for completing the mapping and allowing them to extend and customize existing mapping expressions. The solution is also based on a circular workflow that enables developers to make any changes as required until the result is satisfying.As opposed to existing migration solutions that offer automation are usually a “black box” to the user, the transposition concept enables full visibility, flexibility and control over the code and process at all times allowing to also add/change functionalities or upgrade the UI within the process and tools.This is exactly the case with our customer’s aging VB6 PMS (Property Management System) which needed a technological update as well as a design refresh. The decision was to move the VB6 application which had about 1 million lines of code into the latest web technology. Since the application was initially written 13 years ago and had many upgrades since the code must be very patchy and includes unused sections. As a result, the company Mihshuv Group considered rewriting the entire application in Java since it already had the knowledge. Rewrite would allow starting with a clean slate and designing functionality, database architecture, UI without any constraints. On the other hand, rewrite entitles a long and detailed specification work as well as a thorough QA and this translates into a long project with high risk and costs.So the company looked for a migration solution as an alternative; the research lead to Gizmox and after examining the technology it was decided to perform a hybrid project which would include an automatic transposition of the core of the VB6 application (200,000 lines of code) while they redesigning the UI, adding new functionality, deleting unused code and rewriting about 140 reports with Crystal Reports will be done manually using Visual WebGui development tools.The migration part of the project was completed in 65 days by 3 developers from Mihshuv Group guided by Gizmox migration experts while the rewrite and UI upgrade tasks took about the same. So in only a few months period Mihshuv Group generated an up-to-date product, written in the latest Web technology with modern, friendly UI and improved functionality. Guest selection screen of the original VB6 PMS Guest selection screen on the new web–based PMS Compared to the initial plan to rewrite the entire application in Java, the hybrid migration/rewrite approach taken by Mihshuv Group using Gizmox technology proved as a great decision. In terms of time and cost there were substantial savings; from a project that was priced for at least a year (without taking into account the huge risk and uncertainty) it became a few months project only. More about this and other customer stories can be found here

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• MySQL Server 5.6 defaults changes

  - by user12626240

  We're improving the MySQL Server defaults, as announced by Tomas Ulin at MySQL Connect. Here's what we're changing:  Setting  Old  New  Notes back_log  50  50 + ( max_connections / 5 ) capped at 900 binlog_checksum  off  CRC32  New variable in 5.6 binlog_row_event_max_size  1k  8k flush_time  1800  Windows changes from 1800 to 0  Was already 0 on other platforms host_cache_size  128  128 + 1 for each of the first 500 max_connections + 1 for every 20 max_connections over 500, capped at 2000  New variable in 5.6 innodb_autoextend_increment  8  64  Now affects *.ibd files. 64 is 64 megabytes innodb_buffer_pool_instances  0  8. On 32 bit Windows only, if innodb_buffer_pool_size is greater than 1300M, default is innodb_buffer_pool_size / 128M innodb_concurrency_tickets  500  5000 innodb_file_per_table  off  on innodb_log_file_size  5M  48M  InnoDB will always change size to match my.cnf value. Also see innodb_log_compressed_pages and binlog_row_image innodb_old_blocks_time 0  1000 1 second innodb_open_files  300  300; if innodb_file_per_table is ON, higher of table_open_cache or 300 innodb_purge_batch_size  20  300 innodb_purge_threads  0  1 innodb_stats_on_metadata  on  off join_buffer_size 128k  256k max_allowed_packet  1M  4M max_connect_errors  10  100 open_files_limit  0  5000  See note 1 query_cache_size  0  1M query_cache_type  on/1  off/0 sort_buffer_size  2M  256k sql_mode  none  NO_ENGINE_SUBSTITUTION  See later post about default my.cnf for STRICT_TRANS_TABLES sync_master_info  0  10000  Recommend: master_info_repository=table sync_relay_log  0  10000 sync_relay_log_info  0  10000  Recommend: relay_log_info_repository=table. Also see Replication Relay and Status Logs table_definition_cache  400  400 + table_open_cache / 2, capped at 2000 table_open_cache  400  2000   Also see table_open_cache_instances thread_cache_size  0  8 + max_connections/100, capped at 100 Note 1: In 5.5 there was already a rule to make open_files_limit 10 + max_connections + table_cache_size * 2 if that was higher than the user-specified value. Now uses the higher of that and (5000 or what you specify). We are also adding a new default my.cnf file and guided instructions on the key settings to adjust. More on this in a later post. We're also providing a page with suggestions for settings to improve backwards compatibility. The old example files like my-huge.cnf are obsolete. Some of the improvements are present from 5.6.6 and the rest are coming. These are ideas, and until they are in an official GA release, they are subject to change. As part of this work I reviewed every old server setting plus many hundreds of emails of feedback and testing results from inside and outside Oracle's MySQL Support team and the many excellent blog entries and comments from others over the years, including from many MySQL Gurus out there, like Baron, Sheeri, Ronald, Schlomi, Giuseppe and Mark Callaghan. With these changes we're trying to make it easier to set up the server by adjusting only a few settings that will cause others to be set. This happens only at server startup and only applies to variables where you haven't set a value. You'll see a similar approach used for the Performance Schema. The Gurus don't need this but for many newcomers the defaults will be very useful. Possibly the most unusual change is the way we vary the setting for innodb_buffer_pool_instances for 32-bit Windows. This is because we've found that DLLs with specified load addresses often fragment the limited four gigabyte 32-bit address space and make it impossible to allocate more than about 1300 megabytes of contiguous address space for the InnoDB buffer pool. The smaller requests for many pools are more likely to succeed. If you change the value of innodb_log_file_size in my.cnf you will see a message like this in the error log file at the next restart, instead of the old error message: [Warning] InnoDB: Resizing redo log from 2*64 to 5*128 pages, LSN=5735153 One of the biggest challenges for the defaults is the millions of installations on a huge range of systems, from point of sale terminals and routers though shared hosting or end user systems and on to major servers with lots of CPU cores, hundreds of gigabytes of RAM and terabytes of fast disk space. Our past defaults were for the smaller systems and these change that to larger shared hosting or shared end user systems, still with a bias towards the smaller end. There is a bias in favour of OLTP workloads, so reporting systems may need more changes. Where there is a conflict between the best settings for benchmarks and normal use, we've favoured production, not benchmarks. We're very interested in your feedback, comments and suggestions.

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• Can you/should you develop components for ASP.NET MVC?

  - by Vilx-

  Following from the previous question I've started to wonder - is it possible to implement "Components" in ASP.NET MVC (latest version)? And should you? Let's clarify what I mean with a "component". With that I mean a "control" (aka "widget"), similar to those that ASP.NET webforms is built upon. A gridview might be a good example. In webforms I can place on my form a datasource component (one line of code), a gridview component (another line of code) and bind them together (specify an attribute on the gridview). In the codebehind file I fill the datasource with data (a few lines of DB-querying code), and I'm all set. At this point the gridview is a fully functional standalone component. I can open the form, and I'll see all the data. I can sort it by clicking on the column headers; it is split into several pages; I can drag the column headers around and rearrange columns; I can turn on "grouping" mode; etc. And I don't need to write another line of code for any of it. The gridview, as a component, already has all the code tucked away in its classes and assemblies. I just place it on the form, initialize it, and it Just Works. At some times (like sorting or navigation to a different page) it will also perform ajax callbacks to the server, but those too will be handled internally, with my code having no knowledge at all about it. And then there are also events that I can attach if I want to get notified when something happens. In MVC I cannot see a way of doing this cleanly. Sure, there are the partial views, but those only handle half of the problem - they render the initial HTML. Some more can be achieved with client-side Javascript (like column re-arranging), but when the grid needs to do an ajax callback (say, to fetch the next page of data), my code will have to get involved and process that request. At best I guess I can provide some helper methods to process it, but I'll have to write the code that calls them, and also provide a controller method with signature matching the arguments of that callback. I guess that I could make some hacks with global events or special routes or something, but that just seems... hackish. Unelegant. Perhaps this is not the MVC way? Although I've completed one project in it, I'm still far from being an MVC expert. But then what is? In the intranet application that we're building there are dozens upon dozens of such grids. Naturally I want them all to have a unified look & behavior, and I don't want to repeat the same code all over the place. So what's the "MVC" approach to this problem?

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• Auto-organized / smart inventory system?

  - by VeXe

  for the past week I've been working on an inventory system with Unity3D. At first I got help from the guys at Design3 but it wasn't too long till we split path, because I really didn't like the way they did their code, it didn't have any smell of OOP whatsoever. I took it further steps ahead - items take more than one slot, advanced placement system (items tries their best to find the best close fit), local mouse system (mouse gets trapped in active bag area), etc. Here's a demo of my work. What we would like to have in our game, is an auto-organizing feature - not auto-sort. We want this feature because our inventory's going to be in 'real-time' - not like in Resident Evil 1,2,3 etc where you would pause the game and do things in your inventory. Now imagine your self in a sticky situation surrounded by zombies, and you don't have bullets, you look around, you see that there are bullets nearby on the ground, so you go for them and try to pick them up, but they don't fit! you look at your inventory and find out that if you reorganize some of the items, it will fit! - now the player - in that situation doesn't have time to reorganize because he's surrounded with zombies and will die if he stops and organizes the inventory to make space (remember inventory in real-time, no pausing) - wouldn't it be nice for that to happen automatically? - Yes! (I believe this has been implemented in some games like Dungeon siege or something, so sure it's doable) take a look at this picture for example: Yes, so if you auto-sort the issue you will get your spaces but it's bad because: 1- Expensive: it doesn't need a whole sort operation to free those spaces, in the first picture, just slide the red item at the bottom to the very left, and you get the same spaces that you got from the auto-sort. 2- It's annoying to the player: "Who the F told you to re-order my stuff?" I'm not asking for "How to write the code" for this, I'm just asking for some guidance, where to look, what algorithms are involved? Is this something related to graphs and shortest path stuff? I hope not cuz I didn't manage to continue my college studies :/ But even if it is, just tell me and I will learn the stuff related. Notice there could be more than just one solution. So I guess the first thing I have to do is figure out if the situation is 'solvable' - if I know how to determine if a situation is solvable or not, then I can 'solve' it. I just need to know the conditions that makes it 'solvable'. And I believe there must be some algorithm/data structure for this. Here's a pic for more than one solution of trying to fit a 1x3 item: The arrows show just one of the solutions, but if you look you will find more than one. This is what I ultimately not auto-sorting but find a solution and applying it. Note that if I spend time on it I will come up with a way to solve it, but it wouldn't be the best way, it's like, holding a car wheel with your feet instead of your hands! XD Or just like trying to solve an issue that requires arrays, but you're not yet aware of their existence! So what is the right approach to this? Hope somebody helps, thanks a lot in advance :)

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• How to layout class definition when inheriting from multiple interfaces

  - by gabr

  Given two interface definitions ... IOmniWorkItem = interface ['{3CE2762F-B7A3-4490-BF22-2109C042EAD1}'] function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); // procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; end; IOmniWorkItemEx = interface ['{3B48D012-CF1C-4B47-A4A0-3072A9067A3E}'] function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); // property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; ... what are your ideas of laying out class declaration that inherits from both of them? My current idea (but I don't know if I'm happy with it): TOmniWorkItem = class(TInterfacedObject, IOmniWorkItem, IOmniWorkItemEx) strict private FData : TOmniValue; FOnWorkItemDone : TOmniWorkItemDoneDelegate; FOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; FResult : TOmniValue; FUniqueID : int64; strict protected procedure FreeException; protected //IOmniWorkItem function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); protected //IOmniWorkItemEx function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); public constructor Create(const data: TOmniValue; uniqueID: int64); destructor Destroy; override; public //IOmniWorkItem procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; public //IOmniWorkItemEx property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; As noted in answers, composition is a good approach for this example but I'm not sure it applies in all cases. Sometimes I'm using multiple inheritance just to split read and write access to some property into public (typically read-only) and private (typically write-only) part. Does composition still apply here? I'm not really sure as I would have to move the property in question out from the main class and I'm not sure that's the correct way to do it. Example: // public part of the interface interface IOmniWorkItemConfig = interface function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; end; // private part of the interface IOmniWorkItemConfigEx = interface ['{42CEC5CB-404F-4868-AE81-6A13AD7E3C6B}'] function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end; // implementing class TOmniWorkItemConfig = class(TInterfacedObject, IOmniWorkItemConfig, IOmniWorkItemConfigEx) strict private FOnExecute : TOmniBackgroundWorkerDelegate; FOnRequestDone : TOmniWorkItemDoneDelegate; FOnRequestDone_Asy: TOmniWorkItemDoneDelegate; public constructor Create(defaults: IOmniWorkItemConfig = nil); public //IOmniWorkItemConfig function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; public //IOmniWorkItemConfigEx function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end;

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• Using Private Extension Galleries in Visual Studio 2012

  - by Jakob Ehn

  Note: The installer and the complete source code is available over at CodePlex at the following location: http://inmetavsgallery.codeplex.com   Extensions and addins are everywhere in the Visual Studio ALM ecosystem! Microsoft releases new cool features in the form of extensions and the list of 3rd party extensions that plug into Visual Studio just keeps growing. One of the nice things about the VSIX extensions is how they are deployed. Microsoft hosts a public Visual Studio Gallery where you can upload extensions and make them available to the rest of the community. Visual Studio checks for updates to the installed extensions when you start Visual Studio, and installing/updating the extensions is fast since it is only a matter of extracting the files within the VSIX package to the local extension folder. But for custom, enterprise-specific extensions, you don’t want to publish them online to the whole world, but you still want an easy way to distribute them to your developers and partners. This is where Private Extension Galleries come into play. In Visual Studio 2012, it is now possible to add custom extensions galleries that can point to any URL, as long as that URL returns the expected content of course (see below).Registering a new gallery in Visual Studio is easy, but there is very little documentation on how to actually host the gallery. Visual Studio galleries uses Atom Feed XML as the protocol for delivering new and updated versions of the extensions. This MSDN page describes how to create a static XML file that returns the information about your extensions. This approach works, but require manual updates of that file every time you want to deploy an update of the extension. Wouldn’t it be nice with a web service that takes care of this for you, that just lets you drop a new version of your VSIX file and have it automatically detect the new version and produce the correct Atom Feed XML? Well search no more, this is exactly what the Inmeta Visual Studio Gallery Service does for you :-) Here you can see that in addition to the standard Online galleries there is an Inmeta Gallery that contains two extensions (our WIX templates and our custom TFS Checkin Policies). These can be installed/updated i the same way as extensions from the public Visual Studio Gallery. Installing the Service Download the installler (Inmeta.VSGalleryService.Install.msi) for the service and run it. The installation is straight forward, just select web site, application pool and (optional) a virtual directory where you want to install the service.   Note: If you want to run it in the web site root, just leave the application name blank Press Next and finish the installer. Open web.config in a text editor and locate the the <applicationSettings> element Edit the following setting values: FeedTitle This is the name that is shown if you browse to the service using a browser. Not used by Visual Studio BaseURI When Visual Studio downloads the extension, it will be given this URI + the name of the extension that you selected. This value should be on the following format: http://SERVER/[VDIR]/gallery/extension/ VSIXAbsolutePath This is the path where you will deploy your extensions. This can be a local folder or a remote share. You just need to make sure that the application pool identity account has read permissions in this folder Save web.config to finish the installation Open a browser and enter the URL to the service. It should show an empty Feed page:   Adding the Private Gallery in Visual Studio 2012 Now you need to add the gallery in Visual Studio. This is very easy and is done as follows: Go to Tools –> Options and select Environment –> Extensions and Updates Press Add to add a new gallery Enter a descriptive name, and add the URL that points to the web site/virtual directory where you installed the service in the previous step   Press OK to save the settings. Deploying an Extension This one is easy: Just drop the file in the designated folder! :-)  If it is a new version of an existing extension, the developers will be notified in the same way as for extensions from the public Visual Studio gallery: I hope that you will find this sever useful, please contact me if you have questions or suggestions for improvements!

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• Validation and authorization in layered architecture

  - by SonOfPirate

  I know you are thinking (or maybe yelling), "not another question asking where validation belongs in a layered architecture?!?" Well, yes, but hopefully this will be a little bit of a different take on the subject. I am a firm believer that validation takes many forms, is context-based and varies at each level of the architecture. That is the basis for the post - helping to identify what type of validation should be performed in each layer. In addition, a question that often comes up is where authorization checks belong. The example scenario comes from an application for a catering business. Periodically during the day, a driver may turn in to the office any excess cash they've accumulated while taking the truck from site to site. The application allows a user to record the 'cash drop' by collecting the driver's ID, and the amount. Here's some skeleton code to illustrate the layers involved: public class CashDropApi // This is in the Service Facade Layer { [WebInvoke(Method = "POST")] public void AddCashDrop(NewCashDropContract contract) { // 1 Service.AddCashDrop(contract.Amount, contract.DriverId); } } public class CashDropService // This is the Application Service in the Domain Layer { public void AddCashDrop(Decimal amount, Int32 driverId) { // 2 CommandBus.Send(new AddCashDropCommand(amount, driverId)); } } internal class AddCashDropCommand // This is a command object in Domain Layer { public AddCashDropCommand(Decimal amount, Int32 driverId) { // 3 Amount = amount; DriverId = driverId; } public Decimal Amount { get; private set; } public Int32 DriverId { get; private set; } } internal class AddCashDropCommandHandler : IHandle<AddCashDropCommand> { internal ICashDropFactory Factory { get; set; } // Set by IoC container internal ICashDropRepository CashDrops { get; set; } // Set by IoC container internal IEmployeeRepository Employees { get; set; } // Set by IoC container public void Handle(AddCashDropCommand command) { // 4 var driver = Employees.GetById(command.DriverId); // 5 var authorizedBy = CurrentUser as Employee; // 6 var cashDrop = Factory.CreateCashDrop(command.Amount, driver, authorizedBy); // 7 CashDrops.Add(cashDrop); } } public class CashDropFactory { public CashDrop CreateCashDrop(Decimal amount, Employee driver, Employee authorizedBy) { // 8 return new CashDrop(amount, driver, authorizedBy, DateTime.Now); } } public class CashDrop // The domain object (entity) { public CashDrop(Decimal amount, Employee driver, Employee authorizedBy, DateTime at) { // 9 ... } } public class CashDropRepository // The implementation is in the Data Access Layer { public void Add(CashDrop item) { // 10 ... } } I've indicated 10 locations where I've seen validation checks placed in code. My question is what checks you would, if any, be performing at each given the following business rules (along with standard checks for length, range, format, type, etc): The amount of the cash drop must be greater than zero. The cash drop must have a valid Driver. The current user must be authorized to add cash drops (current user is not the driver). Please share your thoughts, how you have or would approach this scenario and the reasons for your choices.

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• Can someone explain the true landscape of Rails vs PHP deployment, particularly within the context of Reseller-based web hosting (e.g., Hostgator)?

  - by rcd

  Currently, I have a reseller account with the company HostGator. I design websites, which up until now have occasionally been wrapped in Wordpress CMSs and the like (PHP applications). I then sell hosting (of the site I've designed) to the client, which is pretty simple, in that I can simply click a button and add a new shared hosting account/site with whatever settings I want. Furthermore, I then utilize WHMCS to automate billing and account management. It's a nice package and pretty simple. I pay something like $25 a month, and can sell a hundred accounts under this (because my clients bandwidth requirements are low). Now I am finding the need to develop more customized applications, including a minimalist CMS and several proprietary things. I soon anticipate developing these apps for clients as well. Thus, I've spent the past few months learning Rails, and it's coming along well now. The thing that has nagged at me all along, though, is the deployment issue. I can't wrap my brain around it. It seems like all of the popular options (Heroku, etc) have nice automation with git and are set up in the "Rails Way". I get that (sort of). But it's terribly expensive... a single dyno, a helper, and the cheapest database (which they say is mainly suitable for testing) that isn't limited to 5MB runs $51. This is for ONE app!!! Throw in a "production" DB and you're over $200. This is like... the same prices as getting a server somewhere, right? Meanwhile, going back to what I guess is a "traditional" hosting environment with Hostgator, their server only has Ruby 1.8.7 and Rails 2.3.5... No Rails 3. AND, no Passenger (not that I really understand the difference in CGI or mod_rails or whatever, but they say Passenger is the simplest). So I'm to understand that if I build an app in Rails 3, it won't run at all on this host? But damn, I already have these accounts under my reseller account there, all running static html and/or PHP stuff, right? So what now? How do I get all of this under one simple (and affordable) roof? Forgive my ignorance, but I just don't get it. Managing a VPS is cool and all, but entails learning server admin stuff and security... And it's expensive. I get that a shared and/or reseller "server-based" (forgive the terminology) may be inadequate for large-scale apps that use a lot of bandwidth... But what about for those of us who are building real (but small and low bandwidth) apps (with Rails) and who want to deploy them simply, cheaply, using the same conceptual approach as PHP? Even after learning all of this Ruby and Rails stuff for months, I'm questioning whether it's worth it when it comes to deployment. I want to build a small app, upload it to my home directory on a shared server account, and just make it run. Why should that be so hard? Am I just choosing the wrong language/framework? Forgive my ignorance in the subject; these questions are not rhetorical; just trying to learn here. So: 1) I'd appreciate if someone could give me a good rundown of how to understand deployment in Rails vs. PHP. 2) I'd appreciate if someone could address my issue with running a hosting/web business around reseller hosting (Hostgator) while also being able to host Rails apps. Can it be done? And how can a company like Hostgator completely ignore what's current in Rails/Ruby? Thanks.

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• Cloud Fact for Business Managers #3: Where You Data Is, and Who Has Access to It Might Surprise You

  - by yaldahhakim

  Written by: David Krauss While data security and operational risk conversations usually happen around the desk of a CCO/CSO (chief compliance and/or security officer), or perhaps the CFO, since business managers are now selecting cloud providers, they need to be able to at least ask some high-level questions on the topic of risk and compliance.  While the report found that 76% of adopters were motivated to adopt cloud apps because of quick access to software, most of these managers found that after they made a purchase decision their access to exciting new capabilities in the cloud could be hindered due to performance and scalability constraints put forth  by their cloud provider.  If you are going to let your business consume their mission critical business applications as a service, then it’s important to understand who is providing those cloud services and what kind of performance you are going to get.  Different types of departments, companies and industries will all have unique requirements so it’s key to take this also into consideration.   Nothing puts a CEO in a bad mood like a public data breach or finding out the company lost money when customers couldn’t buy a product or service because your cloud service provider had a problem.  With 42% of business managers having seen a data security breach in their department associated directly with the use of cloud applications, this is happening more than you think.   We’ve talked about the importance of being able to avoid information silos through a unified cloud approach and platform.  This is also important when keeping your data safe and secure, and a key conversation to have with your cloud provider.  Your customers want to know that their information is protected when they do business with you, just like you want your own company information protected.   This is really hard to do when each line of business is running different cloud application services managed by different cloud providers, all with different processes and controls.   It only adds to the complexity, and the more complex, the more risky and the chance that something will go wrong. What about compliance? Depending on the cloud provider, it can be difficult at best to understand who has access to your data, and were your data is actually stored.  Add to this multiple cloud providers spanning multiple departments and it becomes very problematic when trying to comply with certain industry and country data security regulations.  With 73% of business managers complaining that having cloud data handled externally by one or more cloud vendors makes it hard for their department to be compliant, this is a big time suck for executives and it puts the organization at risk. Is There A Complete, Integrated, Modern Cloud Out there for Business Executives?If you are a business manager looking to drive faster innovation for your business and want a cloud application that your CIO would approve of, I would encourage you take a look at Oracle Cloud.  It’s everything you want from a SaaS based application, but without compromising on functionality and other modern capabilities like embedded business intelligence, social relationship management (for your entire business), and advanced mobile.  And because Oracle Cloud is built and managed by Oracle, you can be confident that your cloud application services are enterprise-grade.  Over 25 Million users and 10 thousands companies around the globe rely on Oracle Cloud application services everyday – maybe your business should too.  For more information, visit cloud.oracle.com. Additional Resources •    Try it: cloud.oracle.com•    Learn more: http://www.oracle.com/us/corporate/features/complete-cloud/index.html•    Research Report: Cloud for Business Managers: The Good, the Bad, and the Ugly

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• Is this over-abstraction? (And is there a name for it?)

  - by mwhite

  I work on a large Django application that uses CouchDB as a database and couchdbkit for mapping CouchDB documents to objects in Python, similar to Django's default ORM. It has dozens of model classes and a hundred or two CouchDB views. The application allows users to register a "domain", which gives them a unique URL containing the domain name that gives them access to a project whose data has no overlap with the data of other domains. Each document that is part of a domain has its domain property set to that domain's name. As far as relationships between the documents go, all domains are effectively mutually exclusive subsets of the data, except for a few edge cases (some users can be members of more than one domain, and there are some administrative reports that include all domains, etc.). The code is full of explicit references to the domain name, and I'm wondering if it would be worth the added complexity to abstract this out. I'd also like to know if there's a name for the sort of bound property approach I'm taking here. Basically, I have something like this in mind: Before in models.py class User(Document): domain = StringProperty() class Group(Document): domain = StringProperty() name = StringProperty() user_ids = StringListProperty() # method that returns related document set def users(self): return [User.get(id) for id in self.user_ids] # method that queries a couch view optimized for a specific lookup @classmethod def by_name(cls, domain, name): # the view method is provided by couchdbkit and handles # wrapping json CouchDB results as Python objects, and # can take various parameters modifying behavior return cls.view('groups/by_name', key=[domain, name]) # method that creates a related document def get_new_user(self): user = User(domain=self.domain) user.save() self.user_ids.append(user._id) return user in views.py: from models import User, Group # there are tons of views like this, (request, domain, ...) def create_new_user_in_group(request, domain, group_name): group = Group.by_name(domain, group_name)[0] user = User(domain=domain) user.save() group.user_ids.append(user._id) group.save() in group/by_name/map.js: function (doc) { if (doc.doc_type == "Group") { emit([doc.domain, doc.name], null); } } After models.py class DomainDocument(Document): domain = StringProperty() @classmethod def domain_view(cls, *args, **kwargs): kwargs['key'] = [cls.domain.default] + kwargs['key'] return super(DomainDocument, cls).view(*args, **kwargs) @classmethod def get(cls, *args, **kwargs, validate_domain=True): ret = super(DomainDocument, cls).get(*args, **kwargs) if validate_domain and ret.domain != cls.domain.default: raise Exception() return ret def models(self): # a mapping of all models in the application. accessing one returns the equivalent of class BoundUser(User): domain = StringProperty(default=self.domain) class User(DomainDocument): pass class Group(DomainDocument): name = StringProperty() user_ids = StringListProperty() def users(self): return [self.models.User.get(id) for id in self.user_ids] @classmethod def by_name(cls, name): return cls.domain_view('groups/by_name', key=[name]) def get_new_user(self): user = self.models.User() user.save() views.py @domain_view # decorator that sets request.models to the same sort of object that is returned by DomainDocument.models and removes the domain argument from the URL router def create_new_user_in_group(request, group_name): group = request.models.Group.by_name(group_name) user = request.models.User() user.save() group.user_ids.append(user._id) group.save() (Might be better to leave the abstraction leaky here in order to avoid having to deal with a couchapp-style //! include of a wrapper for emit that prepends doc.domain to the key or some other similar solution.) function (doc) { if (doc.doc_type == "Group") { emit([doc.name], null); } } Pros and Cons So what are the pros and cons of this? Pros: DRYer prevents you from creating related documents but forgetting to set the domain. prevents you from accidentally writing a django view - couch view execution path that leads to a security breach doesn't prevent you from accessing underlying self.domain and normal Document.view() method potentially gets rid of the need for a lot of sanity checks verifying whether two documents whose domains we expect to be equal are. Cons: adds some complexity hides what's really happening requires no model modules to have classes with the same name, or you would need to add sub-attributes to self.models for modules. However, requiring project-wide unique class names for models should actually be fine because they correspond to the doc_type property couchdbkit uses to decide which class to instantiate them as, which should be unique. removes explicit dependency documentation (from group.models import Group)

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• Using NSpec at various architectural layers

  - by nono

  Having read the quick start at nspec.org, I realized that NSpec might be a useful tool in a scenario which was becoming a bit cumbersome with NUnit alone. I'm adding an OAuth (or, DotNetOpenAuth) to a website and quickly made a mess of writing test methods such as [Test] public void UserIsLoggedInLocallyPriorToInvokingExternalLoginAndExternalLoginSucceedsAndExternalProviderIdIsNotAlreadyAssociatedWithUserAccount() { ... } ... and I wound up with maybe a dozen permutations of this theme, for the user already being logged in locally and not locally, the external login succeeding or failing, etc. Not only were the method names unwieldy, but every test needed a setup that contained parts in common with a different set of other tests. I realized that NSpec's incremental setup capabilities would work great for this, and for a while I was trucking a long wonderfully, with code like act = () => { actionResult = controller.ExternalLoginCallback(returnUrl); }; context["The user is already logged in"] = () => { before = () => identity.Setup(x => x.IsAuthenticated).Returns(true); context["The external login succeeds"] = () => { before = () => oauth.Setup(x => x.VerifyAuthentication(It.IsAny<string>())).Returns(new AuthenticationResult(true, providerName, "provideruserid", "username", new Dictionary<string, string>())); context["External login already exists for current user"] = () => { before = () => authService.Setup(x => x.ExternalLoginExistsForUser(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>())).Returns(true); it["Should add 'login sucessful' alert"] = () => { var alerts = (IList<Alert>)controller.TempData[TempDataKeys.AlertCollection]; alerts[0].Message.should_be_same("Login successful"); alerts[0].AlertType.should_be(AlertType.Success); }; it["Should return a redirect result"] = () => actionResult.should_cast_to<RedirectToRouteResult>(); }; context["External login already exists for another user"] = () => { before = () => authService.Setup(x => x.ExternalLoginExistsForAnyOtherUser(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>())).Returns(true); it["Adds an error alert"] = () => { var alerts = (IList<Alert>)controller.TempData[TempDataKeys.AlertCollection]; alerts[0].Message.should_be_same("The external login you requested is already associated with a different user account"); alerts[0].AlertType.should_be(AlertType.Error); }; it["Should return a redirect result"] = () => actionResult.should_cast_to<RedirectToRouteResult>(); }; This approach seemed to work magnificently until I prepared to write test code for my ApplicationServices layer, to which I delegate viewmodel manipulation from my MVC controllers, and which coordinates the operations of the lower data repository layer: public void CreateUserAccountFromExternalLogin(RegisterExternalLoginModel model) { throw new NotImplementedException(); } public void AssociateExternalLoginWithUser(string userName, string provider, string providerUserId) { throw new NotImplementedException(); } public string GetLocalUserName(string provider, string providerUserId) { throw new NotImplementedException(); } I have no idea what in the world to name the test class, the test methods, or even if I should perhaps include the testing for this layer into the test class from my large code snippet above, so that a single feature or user action could be tested without regard to architectural layering. I can't find any tutorials or blog posts which cover more than simple examples, so I would appreciate any recommendations or pointing in the right direction. I would even welcome "your question is invalid"-type answers as long as some explanation is provided.

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• What do you need to know to be a world-class master software developer? [closed]

  - by glitch

  I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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• How to introduce a computer illiterate 50-year old to programming [closed]

  - by sunday

  The other day my dad asked me a question that I would have never expected from him. "How can I learn C++?" My dad is turning 56 this year and computers are a distant concept for him. He doesn't know how to use a phone very well besides calling numbers (no speed dial or contacts); though he has started to learn computers a little better - to the point that he knows how to open the internet (in Windows) and browse around (and has successfully completed several job applications entirely on his own online, of which he was offered positions too). But still, these are too narrow-windowed experiences to mean much, really. While he may not have the background, my dad knows how to read. And I mean reading as a skill, not just an ability. He has little to no college education (financial problems, family, etc.) and was fortunate enough to finish high school, but still taught himself to become a master electrician and has been one for almost 30 years now. He did the same with guitar, learning to play at a very professional level and has been praised for his skill. In high school, he picked up a weight lifting book - and was the only person in his high school at the time to qualify officially as an "athlete" by national standards. In all cases, he just needed something to read. Something to teach him. He absorbs information like a sponge. I have no doubt in my dad's motivation or capability of doing this, so my general goal is simply: Get my dad into the world of computers, and get him on the road to programming. I strongly believe that once I get him through the fundamentals, his drive and reading skill will keep him going on this own. So I'm asking you all: where should I start with all this? And what are the best resources out there? Should I get him to start Linux instead of Windows? Is C++ a bad idea? Remember, he needs to (IMO) learn computers first, and then get that first grasp (the "Hello world" experience) of programming. For money's sake and at top preference, I'd like free online resources that he can read, but by all means any good suggestions in print or paid-for-online are welcome (that I could possibly look into later to purchase). And also, I intend to start him off with C++ (no Python, Java, etc.), because I know it the best and will be able to help him along the way with code. (I have minimal knowledge right now in other languages). Edit: I'm getting a lot of persistent suggestions to use Python. The only reason I wanted to do C++ is that I KNOW it and can be THERE when my dad needs help. My VERY FIRST exposure to programming ever was Java. I learned Java, and I got good at it. I open to other suggestions, but please provide an effective application of your suggestions. EDIT #2: I understand my approach/thinking/knowledge could be lacking here. I'm a sophomore level undergraduate CS major. If you don't agree with anything in my post, tell me why - give me ideas, information - that's why I'm asking in the first place. To narrow down my general goal to specific reachable goals.

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• Concurrent Affairs

  - by Tony Davis

  I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

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• Appropriate design / technologies to handle dynamic string formatting?

  - by Mark W

  recently I was tasked with implementing a way of adding support for versioning of hardware packet specifications to one of our libraries. First a bit of information about the project. We have a hardware library which has classes for each of the various commands we support sending to our hardware. These hardware modules are essentially just lights with a few buttons, and a 2 or 4 digit display. The packets typically follow the format {SOH}AADD{ETX}, where AA is our sentinel action code, and DD is the device ID. These packet specs are different from one command to the next obviously, and the different firmware versions we have support different specifications. For example, on version 1 an action code of 14 may have a spec of {SOH}AADDTEXT{ETX} which would be AA = 14 literal, DD = device ID, TEXT = literal text to display on the device. Then we come out with a revision with adds an extended byte(s) onto the end of the packet like this {SOH}AADDTEXTE{ETX}. Assume the TEXT field is fixed width for this example. We have now added a new field onto the end which could be used to say specify the color or flash rate of the text/buttons. Currently this java library only supports one version of the commands, the latest. In our hardware library we would have a class for this command, say a DisplayTextArgs.java. That class would have fields for the device ID, the text, and the extended byte. The command class would expose a method which generates the string ("{SOH}AADDTEXTE{ETX}") using the value from the class. In practice we would create the Args class as needed, populate the fields, call the method to get our packet string, then ship that down across the CAN. Some of our other commands specification can vary for the same command, on the same version, depending on some runtime state. For example, another command for version 1 may be {SOH}AA{ETX}, where this action code clears all of the modules behind a specific controller device of their text. We may overload this packet to have option fields with multiple meanings like {SOH}AAOC{ETX} where OC is literal text, which tells the controller to only clear text on a specific module type, and to leave the others alone, or the spec could also have an option format of {SOH}AADD{ETX} to clear the text off a a specific device. Currently, in the method which generates the packet string, we would evaluate fields on the args class to determine which spec we will be using when formatting the packet. For this example, it would be along the lines of: if m_DeviceID != null then use {SOH}AADD{ETX} else if m_ClearOCs == true then use {SOH}AAOC{EXT} else use {SOH}AA{ETX} I had considered using XML, or a database to store String.format format strings, which were linked to firmware version numbers in some table. We would load them up at startup, and pass in the version number of the hardwares firmware we are currently using (I can query the devices for their firmware version, but the version is not included in all packets as part of the spec). This breaks down pretty quickly because of the dynamic nature of how we select which version of the command to use. I then considered using a rule engine to possibly build out expressions which could be interpreted at runtume, to evaluate the args class's state, and from that select the appropriate format string to use, but my brief look at rule engines for java scared me away with its complexity. While it seems like it might be a viable solution, it seems overly complex. So this is why I am here. I wouldn't say design is my strongest skill, and im having trouble figuring out the best way to approach this problem. I probably wont be able to radically change the args classes, but if the trade off was good enough, I may be able to convince my boss that the change is appropriate. What I would like from the community is some feedback on some best practices / design methodologies / API or other resources which I could use to accomplish: Logic to determine which set of commands to use for a given firmware version Of those command, which version of each command to use (based on the args classes state) Keep the rules logic decoupled from the application so as to avoid needing releases for every firmware version Be simple enough so I don't need weeks of study and trial and error to implement effectively.

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• Building Enterprise Smartphone App &ndash; Part 1: Why Build Smart Phone Apps

  - by Tim Murphy

  This is part 1 in a series of post based on a talk I gave recently at the Chicago Information Technology Architects Group.  Feel free to leave feedback. Intro Most of us already carry smartphones. We play games on them. We keep up with what is going on with our friends and our favorite teams. We take pictures of our kids at their events. But the question is if that is all they are good for. Many companies have aspects of their business that lend themselves to being performed by mobile devices. Some of them lean toward larger device such as tablets, but many can be executed on smartphones. This and the following articles will discuss some of the possible applications of smartphone technology for businesses, the platforms that are available and the considerations you need to make when building them. I'll take a look at some specific scenarios and wrap up with a couple of capabilities that are just emerging that can be used in the future. Why Build Enterprise Smartphone Applications So what are some of the ways that you can leverage smartphone technology to gain efficiency in your business or a clients business. There are a few major areas that I have seen mobile platforms being an advantage to. Your mobile sales force is a key candidate for leveraging smartphone apps.  They can visit clients in their retail location and place orders on site. It is a more personal approach which can gain you customer loyalty.  A sales person may also gather information about the way a client does business or who their target market is. This allows them you to focus marketing information or build customized support for your customer. You may also have need to track physical inventory in a store. This is something that has historically been done with laser scanners, but with the camera capabilities in today's phones and tablets it is possible to use more general multi-purpose devices.  This can save costs on both hardware and telecommunication contracts. Delivery verification is another area that historically has been the domain of specialized devices but can now be accomplished with smartphones.  This also reduces costs because it is also used for communicating with the driver and other operations.  Add to that the navigation capability of smartphones and you can see how the return on investment increases. Executives are always on the go. They spend most of their time in meetings and yet they need access to decision making information at their finger tips. With a smartphone app they can get alerts when major sales are closed or critical accounting process are completed that may need their attention. They can also answer questions by instantly pulling up BI reports. I have often heard operations support people say that they need things like VPN and RDP from their phones. If they can also have notifications of outages or critical support requests they can be react to situations without needing to be tied to their desks. These are all valid reasons to need smartphone applications.  In the next installment I will discuss platforms and features. del.icio.us Tags: Smartphones,Enterprise Smartphone Apps,Architecture

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• Best way to process a queue in C# (PDF treatment)

  - by Bartdude

  First of all let me expose what I would like to do : I already dispose of a long-time running webapp developed in ASP.NET (C#) 2.0. In this app, users can upload standard PDF files (text+pics). The app is running in production on a Windows Server 2003 and has a dedicated database server (SQL server 2008) also running Windows Server 2003. I myself am a quite experienced web developer, but never actually programmed anything non-web (or at least nothing serious). I plan on adding a functionality to the webapp for which I would need a jpg snapshot of each page of the PDF. Creating these "thumbnails" isn't the big deal as such, I already do it inside my webapp using ghostscript. I've only done it on 1 page documents for now though, and the new functionality will need to process bigger documents. In order for this process to be transparent aswell for the admins as the final users, I would like to implement some kind of queue to delay the processing of the thumbnails. There again, no problem to create the queue, it will consist of records in a table, with enough info to find the pdf document back. Then I will need to process this queue, and that's were my interrogations start. Obviously the best solution to process it isn't an ASP script or so, so I will have to get out of my known environment. No problem, but I have no idea which direction to go. Therefore, a few questions : What should I develop ? I presumably need something that is "standby" on the server, runs when needed, then returns to idle state until further notice.Should I be looking into Windows service ? Is there another more appropriate type of project ? Depending on the first answer, what will be the approach ? Should I have somehow SQL server "tell" the program/service/... to process the queue, or should I have that program/service/... periodically check the state of the queue and treat new items. In both case, which functionality can I use ? we're not talking about hundreds of PDF a day (max 50 maybe), I can totally afford to treat the queue 1 item at a time. Can you confirm I don't have to look much further on threads and so ? (I found a lot of answers talking about threads in queue treatment, but it looks quite overkill for my needs) Maybe linked to the previous question : what about concurrent call to the program, whatever it is ? Let's suppose it is currently running, and a new record comes in the queue, what should be the behaviour ? I don't need much detailed answers and would already be happy with answers like "You can do the processing with a service, and yes it's possible to have sqlserver on machine A trigger a service start on machine B" or "You have to develop xxx and then use the scheduler to run it every xxx minutes". I don't mind reading articles and so, but I can hardly afford to spend too much time learning stuff to finally realize I went the wrong way for this project, so basically I'm trying to narrow down the scope of matters I need to investigate. Thanks for reading me, I hope I'll find some helping hands on here :-)

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• Partitioning recommendations for a Proxmox VM Server (OpenVZ)

  - by luison

  We are new to virtualization and we are planning to turn our online server into a virualized one, mainly for maintenance, backup and recovery improvements. Initially we would only have one real virtual system with load plus 1-3 copys for testing and recovering and maybe a small centralized syslog virtual machine. We would like, if possible the host machine to include an iptables plus rsync to back up to other machines and some other global security systems. Due to this and the offerings of our hosting supplier we are mainly considering Proxmox for its simplicity (we like the idea of its web admin panel) and as I also understand that the container approach of OpenVMZ systems may fit well resource wise with our setup. The base system comes with debian so we can personalise it to our requirements. Proxmox installations default installs an LVM partition for the VMs. Our doubts are with the fact of what would be the best partition structure for this considering that: we would like to have a mirror of the root partition we could boot from if required (our provider supports booting the system from another partition via control panel) we ideally would like to have a partition that could be shared among the VM systems. We still don't know if this is possible directly with OpenVMZ containers, otherwise we are considering doing this by sharing it via NFS on the host machine. we want to use the backup system available on the proxmox host administrator to programme VMs backups and then rsync it to another machine. With this based on a Linux Raid of aprox (750Gb) we are considering something like: ext3_1/ - (20Gb) ext3_2/bak_root - (20Gb) mostly unmounted, root partition sync LVM_1 /var/lib/vz - (390Gb) partition for virtual images LVM_2 /shared_data - (30Gb) LVM_3 /backups - (300Gb) where all backups would be allocated Our initial tests with Proxmox seem to have issues with snapshots backups like this, perhaps caused by the fact that they can not be done to another LVM partition (error: command 'lvcreate --size 1024M --snapshot --name vzsnap-ns204084.XXX.net-0 /dev/pve/LV' failed with exit code 5) in which case we might have to use a standart ext3 partition (but unsure if we can do this with the 4 primary partition limitations). Does this makes more or less sense? Would it be mad to for example write VMs /var/logs to a NFS mounted partition (on the host system)? Are their any other easier ways to mount host system partitions (or folders) to the VMs?

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• Can't install new database in OpenLDAP 2.4 with BDB on Debian

  - by Timothy High

  I'm trying to install an openldap server (slapd) on a Debian EC2 instance. I have followed all the instructions I can find, and am using the recommended slapd-config approach to configuration. It all seems to be just fine, except that for some reason it can't create my new database. ldap.conf.bak (renamed to ensure it's not being used): ########## # Basics # ########## include /etc/ldap/schema/core.schema include /etc/ldap/schema/cosine.schema include /etc/ldap/schema/nis.schema include /etc/ldap/schema/inetorgperson.schema pidfile /var/run/slapd/slapd.pid argsfile /var/run/slapd/slapd.args loglevel none modulepath /usr/lib/ldap # modulepath /usr/local/libexec/openldap moduleload back_bdb.la database config #rootdn "cn=admin,cn=config" rootpw secret database bdb suffix "dc=example,dc=com" rootdn "cn=manager,dc=example,dc=com" rootpw secret directory /usr/local/var/openldap-data ######## # ACLs # ######## access to attrs=userPassword by anonymous auth by self write by * none access to * by self write by * none When I run slaptest on it, it complains that it couldn't find the id2entry.bdb file: root@server:/etc/ldap# slaptest -f ldap.conf.bak -F slapd.d bdb_db_open: database "dc=example,dc=com": db_open(/usr/local/var/openldap-data/id2entry.bdb) failed: No such file or directory (2). backend_startup_one (type=bdb, suffix="dc=example,dc=com"): bi_db_open failed! (2) slap_startup failed (test would succeed using the -u switch) Using the -u switch it works, of course. But that merely creates the configuration. It doesn't resolve the underlying problem: root@server:/etc/ldap# slaptest -f ldap.conf.bak -F slapd.d -u config file testing succeeded Looking in the database directory, the basic files are there (with right ownership, after a manual chown), but the dbd file wasn't created: root@server:/etc/ldap# ls -al /usr/local/var/openldap-data total 4328 drwxr-sr-x 2 openldap openldap 4096 Mar 1 15:23 . drwxr-sr-x 4 root staff 4096 Mar 1 13:50 .. -rw-r--r-- 1 openldap openldap 3080 Mar 1 14:35 DB_CONFIG -rw------- 1 openldap openldap 24576 Mar 1 15:23 __db.001 -rw------- 1 openldap openldap 843776 Mar 1 15:23 __db.002 -rw------- 1 openldap openldap 2629632 Mar 1 15:23 __db.003 -rw------- 1 openldap openldap 655360 Mar 1 14:35 __db.004 -rw------- 1 openldap openldap 4431872 Mar 1 15:23 __db.005 -rw------- 1 openldap openldap 32768 Mar 1 15:23 __db.006 -rw-r--r-- 1 openldap openldap 2048 Mar 1 15:23 alock (note that, because I'm doing this as root, I had to also change ownership of some of the files created by slaptest) Finally, I can start the slapd service, but it dies in the attempt (text from syslog): Mar 1 15:06:23 server slapd[21160]: @(#) $OpenLDAP: slapd 2.4.23 (Jun 15 2011 13:31:57) $#012#011@incagijs:/home/thijs/debian/p-u/openldap-2.4.23/debian/build/servers/slapd Mar 1 15:06:23 server slapd[21160]: config error processing olcDatabase={1}bdb,cn=config: Mar 1 15:06:23 server slapd[21160]: slapd stopped. Mar 1 15:06:23 server slapd[21160]: connections_destroy: nothing to destroy. I manually checked the olcDatabase={1}bdb file, and it looks fine to my amateur eye. All my specific configs are there. Unfortunately, syslog isn't reporting a specific error in this case (if it were a file permission error, it would say). I've tried uninstalling and reinstalling slapd, changing permissions, Googling my wits out, but I'm tapped out. Any OpenLDAP genius out there would be greatly appreciated!

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• HT Link Sync Error after Ubuntu 10.04 LTS Installation

  - by marklab

  Update 1 I just assembled an exact replica of this server, and successfully installed Ubuntu 10.04 LTS in a RAID10 configuration. The success was confirmed by a login to the initial account. There must be a hardware component that is faulty. Since the error mentions HT, which I believe to be Hyper Threading, I will start with the CPUs. Please indicate if this error is more strongly associated with any other piece of hardware. Or make a recommendation of another approach that would be good for this issue. Issue I was attempting to install Ubuntu 10.04 LTS on this system with the board RAID10 configured. However, the installation failed at the partitioning stage by rebooting the system. Upon reboot, there is an error report after POST listing the following: Node0: NB WatchDog Timer Error Node1: HT Link Sync Error Node2: HT Link Sync Error ... Node7: HT Link Sync Error Press F1 to continue/resume. After pressing F1 the system will boot from the Ubuntu 10.04 LTS installation disc. However, it will fail at the same stage, and go through the same process from there. Hardware CPU: AMD OPTERON X12 6172 G34 2.1G 18MB Motherboard: Supermicro H8QG6-F HDD: WD Caviar Green 2TB 5.4K RPM Troubleshooting I disabled RAID10 on the system, and installed the Ubuntu on a single drive. It installed successfully. I then went back to a RAID10 setup and attempted to install on the system again, and was able to make it through the partitioning stage. However, upon reboot, the system reported: Error: file not found, and then booted me into the Grub Rescue console. I feel I have aggravated the problem at this point because when I attempted to install from the boot disc again, the system reboots upon hitting enter to even start the installation process. It does the same thing when trying to boot from an Ubuntu 11 disc. I have not been able to find any information on this HT Link Sync Error, which I feel may have started the problems I am experiencing now with the installation of the OS. I am also aware that Ubuntu is said not to be supported by the motherboard according to Supermicro's site. However, since I was able to install it successfully on a single drive, I do not believe it is incompatible. I would like to know a reason for why it's failing to install on/off.

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• Moving windows-2003 hdd into virtual machine - with HDD shrink

  - by jm666

  Before you vote to close as exact duplicate, please read the full question. I was already read: Can I make a virtual machine out of a Windows XP physical machine? Disk2vhd,convert my PC to Hyper-V Virtual Machine Creating a Windows Virtual PC image from a Physical machine physical machine to virtual machine and place into VirtualBox BSOD trying to migrate Windows XP from a physical to a virtual machine http://en.wikipedia.org/wiki/Physical-to-Virtual and all other similiar questions here and several external sites too Unfortunately, don't find answer for my problem. I have an physical machine with 500GB HDD, on what is installed old Windows-2003 server with one server application. The application is like the windows itself, too old, no support for it today, haven't installation media and so on.. ;( On the HDD it is used only approx. 100MB (maybe less when will delete all unnecessary files). Want convert the the machine into the VirtualBox, and the VirtualBox should run on the same machine. Is possible to do this with the next steps? I can attach another HDD (via USB or internally) Boot an live Linux from CD, mount HDDs Run "something" on the Linux (the above wikipedia article have many pointer for the SW) for the conversion and store the image on the USB HDD - unfortunately, many of tools uses some specialty what exists in Windows-XP and above. No informations about Windows-2003 server, so what is an working solution for Windows-2003? try boot the virtual image with VirtualBox when it will run ok, remove the old installation, install Linux on the old 500GB hdd, copy the image and run.. The above should works (i hope), but the problems: i currently have only 320GB external USB hdd. (ofc, i can remove it from a box and enter it as internal HDD too) so, for the conversion I looking for the on the fly HDD shrink, so while moving the physical 500GB HDD need shrink it into smaller HDD - as i told above, only 100MB is used Exists something for this? (free) - or the only way is buying and larger 1TB hdd and using it for the conversion? Another question are: is anybody have real experience with windows-2003 conversion into VirtualBox? Looking for an answer from someone who really doing it and can figure out real pitfalls. (googling can do myself). exists here better approach for the solution?

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• How Do I Restrict Repository Access via WebSVN?

  - by kaybenleroll

  I have multiple subversion repositories which are served up through Apache 2.2 and WebDAV. They are all located in a central place, and I used this debian-administration.org article as the basis (I dropped the use of the database authentication for a simple htpasswd file though). Since then, I have also started using WebSVN. My issue is that not all users on the system should be able to access the different repositories, and the default setup of WebSVN is to allow anyone who can authenticate. According to the WebSVN documentation, the best way around this is to use subversion's path access system, so I looked to create this, using the AuthzSVNAccessFile directive. When I do this though, I keep getting "403 Forbidden" messages. My files look like the following: I have default policy settings in a file: <Location /svn/> DAV svn SVNParentPath /var/lib/svn/repository Order deny,allow Deny from all </Location> Each repository gets a policy file like below: <Location /svn/sysadmin/> Include /var/lib/svn/conf/default_auth.conf AuthName "Repository for sysadmin" require user joebloggs jimsmith mickmurphy </Location> The default_auth.conf file contains this: SVNParentPath /var/lib/svn/repository AuthType basic AuthUserFile /var/lib/svn/conf/.dav_svn.passwd AuthzSVNAccessFile /var/lib/svn/conf/svnaccess.conf I am not fully sure why I need the second SVNParentPath in default_auth.conf, but I just added that today as I was getting error messages as a result of adding the AuthzSVNAccessFile directive. With a totally permissive access file [/] joebloggs = rw the system worked fine (and was essentially unchanged), but as I soon as I start trying to add any kind of restrictions such as [sysadmin:/] joebloggs = rw instead, I get the 'Permission denied' errors again. The log file entries are: [Thu May 28 10:40:17 2009] [error] [client 89.100.219.180] Access denied: 'joebloggs' GET websvn:/ [Thu May 28 10:40:20 2009] [error] [client 89.100.219.180] Access denied: 'joebloggs' GET svn:/sysadmin What do I need to do to get this to work? Have configured apache wrong, or is my understanding of the svnaccess.conf file incorrect? If I am going about this the wrong way, I have no particular attachment to my overall approach, so feel free to offer alternatives as well. UPDATE (20090528-1600): I attempted to implement this answer, but I still cannot get it to work properly. I know most of the configuration is correct, as I have added [/] joebloggs = rw at the start and 'joebloggs' then has all the correct access. When I try to go repository-specific though, doing something like [/] joebloggs = rw [sysadmin:/] mickmurphy = rw then I got a permission denied error for mickmurphy (joebloggs still works), with an error similar to what I already had previously [Thu May 28 10:40:20 2009] [error] [client 89.100.219.180] Access denied: 'mickmurphy' GET svn:/sysadmin Also, I forgot to explain previously that all my repositories are underneath /var/lib/svn/repository UPDATE (20090529-1245): Still no luck getting this to work, but all the signs seem to be pointing to the issue being with path-access control in subversion not working properly. My assumption is that I have not conf

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