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• Randomly generate directed graph on a grid

  - by Talon876

  I am trying to randomly generate a directed graph for the purpose of making a puzzle game similar to the ice sliding puzzles from Pokemon. This is essentially what I want to be able to randomly generate: http://bulbanews.bulbagarden.net/wiki/Crunching_the_numbers:_Graph_theory. I need to be able to limit the size of the graph in an x and y dimension. In the example given in the link, it would be restricted to an 8x4 grid. The problem I am running into is not randomly generating the graph, but randomly generating a graph, which I can properly map out in a 2d space, since I need something (like a rock) on the opposite side of a node, to make it visually make sense when you stop sliding. The problem with this is that sometimes the rock ends up in the path between two other nodes or possibly on another node itself, which causes the entire graph to become broken. After discussing the problem with a few people I know, we came to a couple of conclusions that may lead to a solution. Including the obstacles in the grid as part of the graph when constructing it. Start out with a fully filled grid and just draw a random path and delete out blocks that will make that path work. The problem then becomes figuring out which ones to delete to avoid introducing an additional, shorter path. We were also thinking a dynamic programming algorithm may be beneficial, though none of us are too skilled with creating dynamic programming algorithms from nothing. Any ideas or references about what this problem is officially called (if it's an official graph problem) would be most helpful. Here are some examples of what I have accomplished so far by just randomly placing blocks and generating the navigation graph from the chosen start/finish. The idea (as described in the previous link) is you start at the green S and want to get to the green F. You do this by moving up/down/left/right and you continue moving in the direction chosen until you hit a wall. In these pictures, grey is a wall, white is the floor, and the purple line is the minimum length from start to finish, and the black lines and grey dots represented possible paths. Here are some bad examples of randomly generated graphs: http://i.stack.imgur.com/9uaM6.png Here are some good examples of randomly generated (or hand tweaked) graphs: i.stack.imgur.com/uUGeL.png (can't post another link, sorry) I've also seemed to notice the more challenging ones when actually playing this as a puzzle are ones which have lots of high degree nodes along the minimum path.

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• .Net Application & Database Modularity/Reuse

  - by Martaver

  I'm looking for some guidance on how to architect an app with regards to modularity, separation of concerns and re-usability. I'm working on an application (ASP.Net, C#) that has distinctly generic chunks of functionality, that I'd love to be able to lift out, all layers, into re-usable components. This means the module handles the database schema, data access, API, everything so that the next time I want to use it I can just register the module and hook into it. Developing modules of re-usable functionality is a no-brainer, but what is really confusing me is what to do when it comes to handling a core re-usable database schema that serves the module's functionality. In an ideal world, I would register a module and it would ensure that the associated database schema exists in the DB. I would code on the assumption that the tables exist, calling the module's functionality through the DLL, agnostic of the database layer. Kind of like Enterprise Library's Caching/Logging Application Block, which can create a DB schema in the target DB to use as a data store. My Questions is: What do you think is the best way to achieve this, firstly, in terms design architecture, and secondly solution structure. What patterns/frameworks do you know that exist & support this kind of thing? My thoughts so far: I mostly use Entity Framework and SQL Server DB Projects. I thought about a 'black box' approach to modules of functionality. I could use use a code-first approach in EF4, and use the ObjectContext to create a database when the module is initialized. However this means that all of the entities that my module encapsulates would be disconnected from the rest of the application because they belonged to an abstracted ObjectContext. Further - Creating appropriate indexes and references between domain entities and the module's entities would be impossible to do practically. I've thought of adopting Enterprise Library and creating my own Application Blocks. I'm not sure how this would play nice with Entity Framework (if at all) though. I like the idea of building on proven patterns & practices to encapsulate established, reusable functionality. I thought of abandoning Entity Framework for the Module, and just creating a separate DB schema for the module with its own set of stored procedures & ADO.Net. Then deploying the script at run-time if interrogation shows that it doesn't exist. But once again, for application developing outside of the application, I would want to use Entity Framework and I would have to use the module separately, disconnected from the domain ObjectContext. Has anyone had experience developing these sorts of full-stack modules? What advice can you offer? Am I biting off more than I can chew?

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• Drawing lots of tiles with OpenGL, the modern way

  - by Nic

  I'm working on a small tile/sprite-based PC game with a team of people, and we're running into performance issues. The last time I used OpenGL was around 2004, so I've been teaching myself how to use the core profile, and I'm finding myself a little confused. I need to draw in the neighborhood of 250-750 48x48 tiles to the screen every frame, as well as maybe around 50 sprites. The tiles only change when a new level is loaded, and the sprites are changing all the time. Some of the tiles are made up of four 24x24 pieces, and most (but not all) of the sprites are the same size as the tiles. A lot of the tiles and sprites use alpha blending. Right now I'm doing all of this in immediate mode, which I know is a bad idea. All the same, when one of our team members tries to run it, he gets very bad frame rates (~20-30 fps), and it's much worse when there are more tiles, especially when a lot of those tiles are the kind that are cut into pieces. This all makes me think that the problem is the number of draw calls being made. I've thought of a few possible solutions to this, but I wanted to run them by some people who know what they're talking about so I don't waste my time on something stupid: TILES: When a level is loaded, draw all the tiles once into a frame buffer attached to a big honking texture, and just draw a big rectangle with that texture on it every frame. Put all the tiles into a static vertex buffer when the level is loaded, and draw them that way. I don't know if there's a way to draw objects with different textures with a single call to glDrawElements, or if this is even something I'd want to do. Maybe just put all the tiles into a big giant texture and use funny texture coordinates in the VBO? SPRITES: Draw each sprite with a separate call to glDrawElements. Use a dynamic VBO somehow. Same texture question as number 2 above. Point sprites? This is probably silly. Are any of these ideas sensible? Is there a good implementation somewhere I could look over?

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• MSFT new trick to promote IE9 by kill IE6 first.

  - by anirudha

  Every developer know every issue on development for IE6 whenever they know things more. they are frustrated whenever they spent time in IE6 for making application cross browser compatible. not long time ago MSFT make a campaign save IE6 you can find the reference http://blogs.msdn.com/b/anna/archive/2009/04/01/save-internet-explorer-6.aspx and the webstite is here http://www.saveie6.com/ well they really make joke see what they write on the page. well why website maked in PHP whenever they can make them in asp.net or any other technology who reflect the Microsoft technology see here  http://www.saveie6.com/compare.php High security (many updates) :- you can find IE6 is how much secure you can also read Wikipedia for know. well i can say IE6 is very easily to hack. wikipedia tell you about that here http://en.wikipedia.org/wiki/Internet_Explorer_6 and for know about the security watch here http://www.google.co.in/webhp?hl=en#sclient=psy&hl=en&site=webhp&q=ie6+security+issues Lightweight (no support for silly PNG transparency, etc) :- well they tell PNG silly but tell me about the best format on internet. their is no better option as png or SVG. More screen space thanks to no tabs:-  they tell this nonsense without think anything. if they really care about more screen space why they make tab  in 7,8,9. conclusion:- IE team make a research on how to promote IE9 better then they can beat chrome and Firefox. because IE9 not have anything good like customization , plug-in ,add-ons , personas , themes and many other thing like chrome and Firefox provided perhaps IE is outdated thing even everyone their can writing about these days that IE9 have this, have performance better then this… the main problem in IE is IE6. many developer hate them because many of their time goes for making site cross browser compatible. in 2009 they still have no blah like IE9 who they have today so they make a campaign for save IE6. the list they make is a joke. they show that everything in IE6 is perfect even everyone know the truth. they listed IE6 is high security. in 2011 their is a problem for IE9 promotion called IE6. because developer hate IE6 how they can promote IE9 very well. so destroy IE6 is only option for IE9 make promote better. so you can see they make two different different campaign and both are opposite of other. well  how we can believe in IE9. thanks for reading this post. what you thinking on it. have a idea or feedback reported them.

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• Commerce, Anyway You Want It

  - by David Dorf

  I believe our industry is finally starting to realize the importance of letting consumers determine how, when, and where to interact with retailers.  Over the last few months I've seen several articles discussing the importance of removing the barriers between existing channels. Paula Rosenblum of RSR first brought the term omni-channel to my attention back in September. She stated, "omni-channel retail isn’t the merging of channels – rather, it’s the use of all possible channels (present and future) to enhance the customer experience in a profitable way." I added to her thoughts in this blog posting in which I said, "For retailers to provide an omni-channel experience, there needs to be one logical representation of products, prices, promotions, and customers across all channels. The only thing that varies is the presentation of the content based on the delivery mechanism (e.g. shelf labels, mobile phone, web site, print, etc.) and often these mechanisms can be combined in various ways." More recently Brian Walker of Gartner suggested we stop using the term multi-channel and begin thinking more about consumer touch-points. "It is time for organizations to leave their channel-oriented ways behind, and enter the era of agile commerce--optimizing their people, processes and technology to serve today's empowered, ever-connected customers across this rapidly evolving set of customer touch points." Now Jason Goldberg, better known as RetailGeek, says we should start breaking down the channel silos by re-casting the VP of E-Commerce as the VP of Digital Marketing, and change his/her focus to driving sales across all channels using digital media. This logic is based on the fact that consumers switch between channels, or touch-points as Brian prefers, as part of their larger buying process. Today's smart consumer leverages the Web, mobile, and stores to provide the best shopping experience, so retailers need to make this easier. Regardless of what we call it, the key take-away is that "multi-channel" is not only an antiquated term but also an idea who's time has passed.  Today, retailers must look at e-commerce, m-commerce, f-commerce, catalogs, and traditional store sales collectively and through the consumers' eyes.  The goal is not to drive sales through each channel but rather to just drive sales -- using whatever method the customer prefers.  There really should be just one cart.

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• How to properly do weapon cool-down reload timer in multi-player laggy environment?

  - by John Murdoch

  I want to handle weapon cool-down timers in a fair and predictable way on both client on server. Situation: Multiple clients connected to server, which is doing hit detection / physics Clients have different latency for their connections to server ranging from 50ms to 500ms. They want to shoot weapons with fairly long reload/cool-down times (assume exactly 10 seconds) It is important that they get to shoot these weapons close to the cool-down time, as if some clients manage to shoot sooner than others (either because they are "early" or the others are "late") they gain a significant advantage. I need to show time remaining for reload on player's screen Clients can have clocks which are flat-out wrong (bad timezones, etc.) What I'm currently doing to deal with latency: Client collects server side state in a history, tagged with server timestamps Client assesses his time difference with server time: behindServerTimeNs = (behindServerTimeNs + (System.nanoTime() - receivedState.getServerTimeNs())) / 2 Client renders all state received from server 200 ms behind from his current time, adjusted by what he believes his time difference with server time is (whether due to wrong clocks, or lag). If he has server states on both sides of that calculated time, he (mostly LERP) interpolates between them, if not then he (LERP) extrapolates. No other client-side prediction of movement, e.g., to make his vehicle seem more responsive is done so far, but maybe will be added later So how do I properly add weapon reload timers? My first idea would be for the server to send each player the time when his reload will be done with each world state update, the client then adjusts it for the clock difference and thus can estimate when the reload will be finished in client-time (perhaps considering also for latency that the shoot message from client to server will take as well?), and if the user mashes the "shoot" button after (or perhaps even slightly before?) that time, send the shoot event. The server would get the shoot event and consider the time shot was made as the server time when it was received. It would then discard it if it is nowhere near reload time, execute it immediately if it is past reload time, and hold it for a few physics cycles until reload is done in case if it was received a bit early. It does all seem a bit convoluted, and I'm wondering whether it will work (e.g., whether it won't be the case that players with lower ping get better reload rates), and whether there are more elegant solutions to this problem.

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• Using HBase or Cassandra for a token server

  - by crippy

  I've been trying to figure out how to use HBase/Cassandra for a token system we're re-implementing. I can probably squeeze quite a lot more from MySQL, but it just seems it has come to clinging on to the wrong tool for the task just because we know it well. Eventually will hit a wall (like happened to us in other areas). Naturally I started looking into possible NoSQL solutions. The prominent ones (at least in terms of buzz) are HBase and Cassandra. The story is more or less like this: A user can send a gift other users. Each gift has a list of recipients or is public in which case limited by number or expiration date For each gift sent we generate some token that uniquely identifies that gift. For each gift we track the list of potential recipients and their current status relating to that gift (accepted, declinded etc). A user can request to see all his currently pending gifts A can request a list of users he has sent a gift to today (used to limit number of gifts sent) Required the ability to "dump" or "ignore" expired gifts (x day old gifts are considered expired) There are some other requirements but I believe the above covers the essentials. How would I go and model that using HBase or Cassandra? Well, the wall was performance. A few 10s of millions of records per day over 2 tables kept for 2 weeks (wish I could have kept it for more but there was no way). The response times kept getting slower and slower until eventually we had to start cutting down number of days we kept data. Caching helps here but it's not an ideal solution since a big part of the ops are updates. Also, as I hinted in my original post. We use MySQL extensively. We know exactly what it can and can't do both in naive implementations followed by native partitioning and finally by horizontally sharding our dataset on the application level to reside on multiple DB nodes. It can be done, but that's not really what I'm trying to get from this. I asked a very specific question about designing a solution using a NoSQL solution since it's very hard to find examples for designs out there. Brainlag, not trying to come off as rude. I actually appreciate it a lot that you are the only one who even bothered to respond. but I see it over and over again. People ask questions and others assume they have no idea what they're talking about and give an irrelevant answer. Ignore RDBMS please. The question is about nosql.

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• What are some reasonable stylistic limits on type inference?

  - by Jon Purdy

  C++0x adds pretty darn comprehensive type inference support. I'm sorely tempted to use it everywhere possible to avoid undue repetition, but I'm wondering if removing explicit type information all over the place is such a good idea. Consider this rather contrived example: Foo.h: #include <set> class Foo { private: static std::set<Foo*> instances; public: Foo(); ~Foo(); // What does it return? Who cares! Just forward it! static decltype(instances.begin()) begin() { return instances.begin(); } static decltype(instances.end()) end() { return instances.end(); } }; Foo.cpp: #include <Foo.h> #include <Bar.h> // The type need only be specified in one location! // But I do have to open the header to find out what it actually is. decltype(Foo::instances) Foo::instances; Foo() { // What is the type of x? auto x = Bar::get_something(); // What does do_something() return? auto y = x.do_something(*this); // Well, it's convertible to bool somehow... if (!y) throw "a constant, old school"; instances.insert(this); } ~Foo() { instances.erase(this); } Would you say this is reasonable, or is it completely ridiculous? After all, especially if you're used to developing in a dynamic language, you don't really need to care all that much about the types of things, and can trust that the compiler will catch any egregious abuses of the type system. But for those of you that rely on editor support for method signatures, you're out of luck, so using this style in a library interface is probably really bad practice. I find that writing things with all possible types implicit actually makes my code a lot easier for me to follow, because it removes nearly all of the usual clutter of C++. Your mileage may, of course, vary, and that's what I'm interested in hearing about. What are the specific advantages and disadvantages to radical use of type inference?

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• Isometric layer moving inside map

  - by gronzzz

  i'm created isometric map and now trying to limit layer moving. Main idea, that i have left bottom, right bottom, left top, right top points, that camera can not move outside, so player will not see map out of bounds. But i can not understand algorithm of how to do that. It's my layer scale/moving code. - (void)touchBegan:(UITouch *)touch withEvent:(UIEvent *)event { _isTouchBegin = YES; } - (void)touchMoved:(UITouch *)touch withEvent:(UIEvent *)event { NSArray *allTouches = [[event allTouches] allObjects]; UITouch *touchOne = [allTouches objectAtIndex:0]; CGPoint touchLocationOne = [touchOne locationInView: [touchOne view]]; CGPoint previousLocationOne = [touchOne previousLocationInView: [touchOne view]]; // Scaling if ([allTouches count] == 2) { _isDragging = NO; UITouch *touchTwo = [allTouches objectAtIndex:1]; CGPoint touchLocationTwo = [touchTwo locationInView: [touchTwo view]]; CGPoint previousLocationTwo = [touchTwo previousLocationInView: [touchTwo view]]; CGFloat currentDistance = sqrt( pow(touchLocationOne.x - touchLocationTwo.x, 2.0f) + pow(touchLocationOne.y - touchLocationTwo.y, 2.0f)); CGFloat previousDistance = sqrt( pow(previousLocationOne.x - previousLocationTwo.x, 2.0f) + pow(previousLocationOne.y - previousLocationTwo.y, 2.0f)); CGFloat distanceDelta = currentDistance - previousDistance; CGPoint pinchCenter = ccpMidpoint(touchLocationOne, touchLocationTwo); pinchCenter = [self convertToNodeSpace:pinchCenter]; CGFloat predictionScale = self.scale + (distanceDelta * PINCH_ZOOM_MULTIPLIER); if([self predictionScaleInBounds:predictionScale]) { [self scale:predictionScale scaleCenter:pinchCenter]; } } else { // Dragging _isDragging = YES; CGPoint previous = [[CCDirector sharedDirector] convertToGL:previousLocationOne]; CGPoint current = [[CCDirector sharedDirector] convertToGL:touchLocationOne]; CGPoint delta = ccpSub(current, previous); self.position = ccpAdd(self.position, delta); } } - (void)touchEnded:(UITouch *)touch withEvent:(UIEvent *)event { _isDragging = NO; _isTouchBegin = NO; // Check if i need to bounce _touchLoc = [touch locationInNode:self]; } #pragma mark - Update - (void)update:(CCTime)delta { CGPoint position = self.position; float scale = self.scale; static float friction = 0.92f; //0.96f; if(_isDragging && !_isScaleBounce) { _velocity = ccp((position.x - _lastPos.x)/2, (position.y - _lastPos.y)/2); _lastPos = position; } else { _velocity = ccp(_velocity.x * friction, _velocity.y *friction); position = ccpAdd(position, _velocity); self.position = position; } if (_isScaleBounce && !_isTouchBegin) { float min = fabsf(self.scale - MIN_SCALE); float max = fabsf(self.scale - MAX_SCALE); int dif = max > min ? 1 : -1; if ((scale > MAX_SCALE - SCALE_BOUNCE_AREA) || (scale < MIN_SCALE + SCALE_BOUNCE_AREA)) { CGFloat newSscale = scale + dif * (delta * friction); [self scale:newSscale scaleCenter:_touchLoc]; } else { _isScaleBounce = NO; } } }

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• Is Infiniband going to get squeezed by iWARP and external QPI?

  - by andy.grover

  The Inquirer certainly thinks so.However, I'm not so sure it makes sense to compare Infiniband to an as-yet-unannounced optical external QPI. QPI is currently a processor interconnect. CPUs, RAM, and devices connected by it are conceptually part of the same machine -- they run a single OS, for example. They are both "networks" or "fabrics" but they have very different design trade-offs.Another widely-used bus in the system is closer to Infiniband than QPI -- PCI Express. Isn't it more likely that PCIe could take on IB? There are companies already who have solutions that use external PCI Express for cluster interconnect, but these have not gained significant market share. Why would QPI, a technology whose sweet spot is even further from Infiniband's than PCIe, be able to challenge Infiniband? It's hard to speculate without much information, but right now it doesn't seem likely to me.The other prediction made in the article is that Intel's 10GbE iWARP card could squeeze IB on the low end, due to its greater compatibility and lower cost.It's definitely never a good idea to bet against Ethernet when it comes to mass-market, commodity networking. Ethernet will win. 10GbE will win. But, there are now two competing ways to implement the low-latency RDMA Verbs interface on top of Ethernet. iWARP is essentially RDMA over TCP/IP over Ethernet. The new alternative is IBoE (Infiniband over Ethernet, aka RoCEE, aka "Rocky"). This encapsulates the IB packet protocol directly in the Ethernet frame. It loses the layer 3 routability of iWARP, but better maintains software compatibility with existing apps that use IB, and is simpler to implement in both software and hardware. iWARP has a substantial head start, but I believe that IBoE silicon will eventually be cheaper, and more likely to be implemented in commodity Ethernet hardware.I think IBoE is going to take low-end market share from traditional IB, but I think this is a situation IB hardware vendors have no problem accepting. Commoditized IBoE NICs invite greater use of RDMA features, and when higher performance is needed, customers can upgrade to "real" IB, maintaining IB's justification for higher prices. (IB max interconnect speeds have historically been 2-4x higher than Ethernet, and I don't see that changing.)(ObDisclosure: My current employer now sells IB hardware. I previously also worked at Intel. My opinions are my own, duh.)

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• Single Responsibility Principle Implementation

  - by Mike S

  In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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• links for 2010-12-22

  - by Bob Rhubart

  @hajonormann: BPM: Top Seven Architectural Topics in 2010 Oracle ACE Director Hajo Normann offers details on how to design a BPM/SOA solution including: modeling human interaction, improving BPM models, orchestrating composed services, central task management, new approaches for business-IT alignment, solutions for non-deterministic processes, and choreography. (tags: oracle otn soasymposium infoq soa bpm) InfoQ: Simplicity, The Way of the Unusual Architect Dan North talks about the tendency developers-becoming-architects have to create bigger and more complex systems. Without trying to be simplistic, North argues for simplicity, offering strategies to extract the simple essence from complex situations. (tags: ping.fm) Fun with Sun Ray, 3D, Oracle VM x86 and SRIOV (Wim Coekaerts Blog) "One of the things I like about my job is that I get to play around with stuff and make use of the technologies we work on in my teams. Sort of my own little playground." - Wim Coekaerts (tags: oracle otn virtualization oraclevm) Oracle VM VirtualBox 4.0.0 Released! (Oracle's Virtualization Blog) And you were worried about what to get that special someone for Christmas... (tags: oracle otn virtualization virtualbox) Virtual Developer Day: Oracle WebLogic Server & Java EE (#OTNVDD) (Oracle Technology Network Blog (aka TechBlog)) "Virtual Developer Day is back with a vengeance! On Feb. 1, login to learn how Oracle WebLogic Server enables a whole new level of productivity for enterprise developers." Registration is open. (tags: oracle otn events webinar java) New Coherence 3.6 Oracle University Course (Cristóbal Soto's Blog) Cristóbal Soto shares information on the "Oracle Coherence 3.6: Share and Manage Data in Clusters" course now available through Oracle University. (tags: oracle otn grid coherence) The Aquarium: Oracle WebLogic Server & Java EE developer day "Oracle WebLogic is well on its way to contribute to the general Java EE 6 momentum and the OTN Blog has just announced a Virtual Developer Day for Oracle WebLogic." (tags: oracle otn weblogic java) Enterprise 2.0 Use Cases for Semantic Web (Reiser 2.0) "How can an enterprise improve the efficiency and effectiveness of their Knowledge and Community model leveraging semantic technologies and social networking dynamics?" - Peter Reiser (tags: oracle otn enterprise2.0 semanticweb) John Gøtze: European Interoperability Framework 2.0 "This week, the European Commission announced an updated interoperability policy in the EU. The Commission has committed itself to adopt a Communication that introduces the European Interoperability Strategy (EIS) and an update to the European Interoperability Framework (EIF)..." - John Gøtze (tags: entarch Interoperability) Andy Mulholland: Maybe Web 3.0 is quite understandable – and a natural result "The idea of Web 1.0 = content, Web 2.0 = people and Web 3.0 = services has a nice symmetrical feel to it, in fact it feels basically right as such a definition would include the two other major definitions as well. So if we put these things all together what picture do we see?" - Andy Mulholland (tags: web2.0 web3.0) Ken Downs: A Working Definition of Business Logic, with Implications for CRUD Code "The Wikipedia entry on 'Business Logic' has a wonderfully honest opening sentence stating that 'Business logic, or domain logic, is a non-technical term...'"  (tags: businesslogic crud)

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• SQL: empty string vs NULL value

  - by Jacek Prucia

  I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the difference between NULL and empty string is. So they tell stories about surprising results with joins/aggregates and generally do a bit more advanced SQL lessons. By doing this, they absolutely miss the whole point and are therefore useless for me. So hopefully this question and all answers will move subject a bit forward. Let's suppose I have a table with personal information (name, birth, etc) where one of the columns is an email address with varchar type. We assume that for some reason some people might not want to provide an email address. When inserting such data (without email) into the table, there are two available choices: set cell to NULL or set it to empty string (''). Let's assume that I'm aware of all the technical implications of choosing one solution over another and I can create correct SQL queries for either scenario. The problem is even when both values differ on the technical level, they are exactly the same on logical level. After looking at NULL and '' I came to a single conclusion: I don't know email address of the guy. Also no matter how hard i tried, I was not able to sent an e-mail using either NULL or empty string, so apparently most SMTP servers out there agree with my logic. So i tend to use NULL where i don't know the value and consider empty string a bad thing. After some intense discussions with colleagues i came with two questions: am I right in assuming that using empty string for an unknown value is causing a database to "lie" about the facts? To be more precise: using SQL's idea of what is value and what is not, I might come to conclusion: we have e-mail address, just by finding out it is not null. But then later on, when trying to send e-mail I'll come to contradictory conclusion: no, we don't have e-mail address, that @!#$ Database must have been lying! Is there any logical scenario in which an empty string '' could be such a good carrier of important information (besides value and no value), which would be troublesome/inefficient to store by any other way (like additional column). I've seen many posts claiming that sometimes it's good to use empty string along with real values and NULLs, but so far haven't seen a scenario that would be logical (in terms of SQL/DB design). P.S. Some people will be tempted to answer, that it is just a matter of personal taste. I don't agree. To me it is a design decision with important consequences. So i'd like to see answers where opion about this is backed by some logical and/or technical reasons.

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• C++ and SDL resource management for 2D game

  - by KuruptedMagi

  My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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• Cron job running successfully suddenly reports script is not found

  - by Ted B

  What might cause cron to suddenly report a file it is supposed to run is "not found," when the file hasn't been touched, and in fact, the entire system hasn't been touched since it last ran successfully? I have a cronjob schedule I define by doing sudo crontab -e In it, I have dozens of cron jobs that run successfully.. I do not have a PATH specified, and I use absolute paths to call all my scheduled scripts, setting the PATH in them as needed. I do not specify a SHELL in the crontab. All scripts identify the shell as their first line. Without me touching the system, a particular job defined in the middle of other jobs will suddenly stop running. To debug this, I added an output redirection to a log file. In that, the output clearly shows the output of the script successfully running time after time for weeks, and then suddenly the following appears: /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found If I do the ls command, copying and pasting that exact path from the error message, it clearly reports the file is still there (no surprise). Yet the log continues to report that file is "not found" until I take action. I can run the script manually and it runs just fine. If I do sudo crontab -e and save the file, the job runs on the next scheduled time, putting its output in the log, no longer reporting the script is "not found". It seems to me the contents of the script trying to be run are irrelevant since cron doesn't even process the file because it is "not found". I have a job scheduled below the one that is encountering this problem that I know is continuing to run, because I have its output mailed to me. So I know cron is running and continues to run at least one other job, even after it suddenly reports this job's script is "not found". All my lines end with a newline. I had no periods in the crontab until I added the redirection to a log file. I have now added a PATH specification, but left the absolute paths in the jobs. Unfortunately, I have no idea if and when this problem will occur. It will likely be weeks from now. By the way, I am running a script to syncronize the clock, and I see the time is exactly what it should be.

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• How to move a website and domain name without experiencing downtime for emails or site?

  - by user4842

  Okay, I have a pretty complex problem, so I'll get right to it. I'm a designer who built a new website for my client. Their old site is hosted at GoDaddy, as well as their email. Problem is, the guy who built the original site decided to put the original domain name and hosting under HIS personal GoDaddy account. Well, that turned out to be a bad move for several reasons. Here's how it's all tied together. The original domain name, www.domainoriginal.com, was actually purchased at Network Solutions. The original web designer pointed the nameservers from Network Solutions to his GoDaddy account, where the email and hosting is setup. The new domain name, www.domainnew.com, was purchased under a new and separate GoDaddy account belonging to the company, and the new website was built under a 3rd party platform (Big Commerce). So, the www.domainnew.com is already pointed to the new website using A records at new GoDaddy account. All is fine there. However, they still need www.domainoriginal.com to point to the NEW website as well. (The old one can simply be deleted, it is NOT important). AND, they want to keep their old email addresses intact and working as well, but under the NEW GoDaddy account. Obviously, I have no DNS control at Network Solutions, and I have no idea what kind of control I have at GoDaddy under the old account because the web designer will not let me see inside his account. But, he and GoDaddy both tell me nothing can be done other than to repoint the nameservers to Network Solutions, and then repoint the A record to my new website, www.domainnew.com, and point the MX Records to GoDaddy. I'm told the downtime would be 24-48 hours if I do this. Ideally, we'd like to do a domain name transfer and get www.domainoriginal.com in the new GoDaddy account created by the company. But, I'm told this could take up to 7 days. Does this mean the site and email will be down for 7 days? And any emails sent during this time, would they be lost forever? If I do this, how long could I expect the site and email to go down? And, will the emails be permanently lost? I've gotten different answers from everybody at GoDaddy so I kind of don't trust them anymore... Any help would be greatly appreciated Thanks, Tyson

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• Is 2 lines of push/pop code for each pre-draw-state too many?

  - by Griffin

  I'm trying to simplify vector graphics management in XNA; currently by incorporating state preservation. 2X lines of push/pop code for X states feels like too many, and it just feels wrong to have 2 lines of code that look identical except for one being push() and the other being pop(). The goal is to eradicate this repetitiveness,and I hoped to do so by creating an interface in which a client can give class/struct refs in which he wants restored after the rendering calls. Also note that many beginner-programmers will be using this, so forcing lambda expressions or other advanced C# features to be used in client code is not a good idea. I attempted to accomplish my goal by using Daniel Earwicker's Ptr class: public class Ptr<T> { Func<T> getter; Action<T> setter; public Ptr(Func<T> g, Action<T> s) { getter = g; setter = s; } public T Deref { get { return getter(); } set { setter(value); } } } an extension method: //doesn't work for structs since this is just syntatic sugar public static Ptr<T> GetPtr <T> (this T obj) { return new Ptr<T>( ()=> obj, v=> obj=v ); } and a Push Function: //returns a Pop Action for later calling public static Action Push <T> (ref T structure) where T: struct { T pushedValue = structure; //copies the struct data Ptr<T> p = structure.GetPtr(); return new Action( ()=> {p.Deref = pushedValue;} ); } However this doesn't work as stated in the code. How might I accomplish my goal? Example of code to be refactored: protected override void RenderLocally (GraphicsDevice device) { if (!(bool)isCompiled) {Compile();} //TODO: make sure state settings don't implicitly delete any buffers/resources RasterizerState oldRasterState = device.RasterizerState; DepthFormat oldFormat = device.PresentationParameters.DepthStencilFormat; DepthStencilState oldBufferState = device.DepthStencilState; { //Rendering code } device.RasterizerState = oldRasterState; device.DepthStencilState = oldBufferState; device.PresentationParameters.DepthStencilFormat = oldFormat; }

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• Ubuntu is booting on acer e1-510 laptop, but screen displays nothing

  - by user287602

  Tried loading ubuntu 12.04 (32-bit as well 64 bit) through bootable usb , on a brand new 64-bit acer E1-510 laptop. It shows the 'Try ubuntu without installing screen' and I selected that option. But instead of showing ubuntu's logo(which implies it is loading). I get a blank screen. The screen is on, but it shows nothing. I tried the same on an old model laptop acer aspire 5738 and it worked like a charm. However, I realized that Ubuntu is actually booting on E1-510 and only the display is not working. How did I arrive at this conclusion? When I select on 'Try ubuntu without installing screen', after about 8-10 seconds I see that the WiFi indicator light on the laptop panel switches on(just like when we boot up a Windows OS or even Ubuntu ). I got an idea that the system booted Ubuntu. To confirm this, I tried to adjust volume using keyboard shortcuts. Voila, I can hear the sound of adjusting volume! That means it has already booted Ubuntu. I confirmed this with another step. I pressed the power button once and after two seconds I pressed ENTER. It began the process of switching off and within 5 seconds the laptop was powered off. You may ask, Why is this a confirmation that Ubuntu has booted? This is because in Ubuntu when you press on power button, a dialog box opens with shut down, restart, suspend option- and the shut down option is already selected by default; so all I have to do is press ENTER to shut down. This again proved that Ubuntu was indeed up and running. Unlike previous 'AskUbunutu' posts about Acer e1-510, I must mention that my laptop came WITH the Legacy BIOS mode, so its not really a problem to boot ubuntu from a bootable pendrive. Only the screen is not working. In case you need to know, I am running Windows 7-Ultimate 64 bit on acer e1-510.

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• Oracle GoldenGate: Knowledge Document Series Post #2

  - by Doug Reid

  0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} 0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} For our second post in this series the team would like to highlight the knowledge document “How-To: Oracle GoldenGate – Heartbeat Process to Monitor Lag and Performance”. This knowledge document outlines a procedure to reliably measure lag between source and target systems through the use of 'heartbeat' tables. The basic idea is to have a table on the source system that gets updated at a predetermined interval. In your capture processes you would capture the update from the heartbeat table. Using tokens you would add some additional information to the heartbeat record to be able to tell which extract process was capturing the update. This additional information would be used downstream to calculate the real lag time between the source and target systems for a given extract and by checking the last update time on the heartbeat at the target you could also determine if data has stopped flowing between the source and target.  Click here to view the document

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• Wesquare (NL) helps major CG customer integrating Oracle Service Cloud (RightNow) with JDEdwards

  - by Richard Lefebvre

  Normal 0 false false false EN-US X-NONE X-NONE When this well known, Italy based, CG player claimed that they needed a new CRM tool, Oracle partner WeSquare had a precise idea of what would be required, knowing that the customer was using JDEdwards as an ERP: they immediately thoughts about a solution that would help synchronizing the customer’s back-end system with the new CRM interface. The customer asked for presentations from three companies, including Oracle, and eventually selected Oracle Service Cloud (RightNow) with Alfa Sistemi (Oracle Platinum Partner) as a System Integrator supported by Wesquare (Oracle Gold partner specialized in RightNow). Synchronizing an On Premises ERP with a new SaaS based CRM platform could be seen as an uphill task, but WeSquare was determined, during the presales cycle, to prove that they had the skills and the attitude to make the difference. So, they rolled up their sleeves and got to it: five days of relentless work, missed lunches, and hours of brainstorming showed its result in the form of a new interface that works fabulously well with the JDEdwards ERP back-end and was successfully pitched by Oracle to the end-customer to win the deal! WeSquare took the occasion to learn that they can integrate Oracle Service Cloud (RightNow) with practically every other solution that a customer may run. As part of the project, WeSquare was also involved in different add-on’s development with the aim of enriching Oracle Service Cloud’s functionality. WeSquare is based in The Netherlands with an in-shore practice supported by off-shore teams in India. WeSquare can integrate and synchronize any application with RightNow. For more information, visit www.wesquare.nl or contact Wiebe Blankenberg (Managing Director) at +31 (0) 6 3632 1104 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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• The Birth of SSAS Compare

  - by Red Gate Software BI Tools Team

  Noemi Moreno, Red Gate Business Intelligence Specialist Software vendors – even Microsoft – tend to forget about the needs of business intelligence developers. We are a rare and rather invisible species. For example, BIDS remained in VS 2008 until SQL Server 2012. It took until this release before we got something as simple as an “undo” function. Before I joined Red Gate as a BI specialist, I worked on SQL Development. I’ll never forget the time I discovered Red Gate’s SQL Compare tool and how it reduced the task of preparing a database release from a couple of days to ten minutes. When I moved to SSAS, MDX and cubes, I became frustrated with the deployment process because I couldn’t find a tool that made Cube releases as easy as they are with SQL Compare. This became my quest. I pitched the idea to a few people in Red Gate’s regular Down Tools Week, when everyone puts down their day-to-day tasks and works on their own projects. My task was to reason with a roomful of cynical developers, hardened to the blandishments of project managers, for help to develop a tool that would compare two different SSAS databases and create the script to process only the objects that needed processing, thereby reducing release time to only a few minutes. I walked to the podium and gave them the full story of the distressed BI specialists, doomed to spend tedious hours preparing deployment scripts. A few developers recovered from their torpor to cast a languid eye at my presentation. It wasn’t enough. In a sudden impulse, I blurted out a promise to perform a flamenco dance for just the team if the tool was able to successfully compare two SSAS databases and generate a script by the end of the week. I was lucky enough that some of them believed me and jumped in: David Pond (Dev), Matt Burton (Dev), Tilman Bregler (Dev), Shobana Sekar (Test), Ruchija Raj (Test), Nick Sutherland (Product Manager) and Irma Tanovic (BI). They didn’t know that Irma and I would be away on a conference in Amsterdam and would leave them without our support. But to my surprise, they had a working tool by the time we came back – basic, and with a few bugs, but a working tool nonetheless! Seeing it compare a very basic SSAS database, detect the changes and generate the scripts was amazing! Something that normally takes half a day was done in under a minute. Since then, a few months have passed and a BI Tools team has been created at Red Gate to work full time on BI tools for BI developers, starting with SSAS Compare. How cool is that? So download the free beta and give us your feedback. And the flamenco? I still need to deliver that. Tilman reminds me every day! I need to get the full flamenco costume.

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• Can't install alternate CD from USB?

  - by mattias

  Hi im trying to install ubuntu 12.04 with full hard disk encryption. After downloading and installing the Ubuntu live CD, I learned that truecrypt doesnt support full disk encryption on linux. I also learned that the best way to get "nearly full disk encryption" on ubuntu is by installing it from the alternate install CD. I tried that, but something is wrong with my CD reader/burner so it doesnt boot up when i insert the cd. My thought here was to take the .iso that I downloaded on my unencrypted Ubuntu system, use Unetbootin to make the usb drive. The usb drive used for this is exactly the same brand as one that I know has worked with a previous ubuntu live system on the same computer. I also used unetbootin for that usb, but I created it from windows that time. The usb stick boots up fine and i get through the first couple of steps in the installation process. However, After a while I get a "box" with the following error message "Load Installer components from CD" There was a problem reading data from the CD-ROM. Please make sure it is in the drive. If retrying does not work, you should check the integrity of your CD-ROM. "Failed to copy file from CD-ROM. Retry? " Then I cant get any further. I googled a lot and found this page which seems to tackle this very problem: http://www.dotkam.com/2010/11/29/ins...mage-from-usb/ I tried to do what it said. After pressing TAB, I wrote : cdrom-detect/try-usb=true without quotes because that's what i think is right. When I press TAB, there already is a text saying : /ubnkern initrd=/ubninit vga=788 -- quiet which can be removed. I have tried to both delete the text before the "--" and just inserting cdrom-detect/try-usb=true before it. Any idea of what can be wrong? I would like to do a full system encryption, or as full as it is possible. I dont want to just encrypt my /home folder. Maybe this isn't the easiest way. I use SanDisk usb sticks. I know there is a problem with U3 launcher on some SanDisks, but I never had to remove U3 before from similar disks, and the alternate install does boot up, so I dont think using U3 removal would help me. Any help or indication to an easier way to do this would be appreciated

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• design a model for a system of dependent variables

  - by dbaseman

  I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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• Accessing SQL Server data from iOS apps

  - by RobertChipperfield

  Almost all mobile apps need access to external data to be valuable. With a huge amount of existing business data residing in Microsoft SQL Server databases, and an ever-increasing drive to make more and more available to mobile users, how do you marry the rather separate worlds of Microsoft's SQL Server and Apple's iOS devices? The classic answer: write a web service layer Look at any of the questions on this topic asked in Internet discussion forums, and you'll inevitably see the answer, "just write a web service and use that!". But what does this process gain? For a well-designed database with a solid security model, and business logic in the database, writing a custom web service on top of this just to access some of the data from a different platform seems inefficient and unnecessary. Desktop applications interact with the SQL Server directly - why should mobile apps be any different? The better answer: the iSql SDK Working along the lines of "if you do something more than once, make it shared," we set about coming up with a better solution for the general case. And so the iSql SDK was born: sitting between SQL Server and your iOS apps, it provides the simple API you're used to if you've been developing desktop apps using the Microsoft SQL Native Client. It turns out a web service remained a sensible idea: HTTP is much more suited to the Big Bad Internet than SQL Server's native TDS protocol, removing the need for complex configuration, firewall configuration, and the like. However, rather than writing a web service for every app that needs data access, we made the web service generic, serving only as a proxy between the SQL Server and a client library integrated into the iPhone or iPad app. This client library handles all the network communication, and provides a clean API. OSQL in 25 lines of code As an example of how to use the API, I put together a very simple app that allowed the user to enter one or more SQL statements, and displayed the results in a rather primitively formatted text field. The total amount of Objective-C code responsible for doing the work? About 25 lines. You can see this in action in the demo video. Beta out now - your chance to give us your suggestions! We've released the iSql SDK as a beta on the MobileFoo website: you're welcome to download a copy, have a play in your own apps, and let us know what we've missed using the Feedback button on the site. Software development should be fun and rewarding: no-one wants to spend their time writing boiler-plate code over and over again, so stop writing the same web service code, and start doing exciting things in the new world of mobile data!

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• Alternatives to multiple inheritance for my architecture (NPCs in a Realtime Strategy game)?

  - by Brettetete

  Coding isn't that hard actually. The hard part is to write code that makes sense, is readable and understandable. So I want to get a better developer and create some solid architecture. So I want to do create an architecture for NPCs in a video-game. It is a Realtime Strategy game like Starcraft, Age of Empires, Command & Conquers, etc etc.. So I'll have different kinds of NPCs. A NPC can have one to many abilities (methods) of these: Build(), Farm() and Attack(). Examples: Worker can Build() and Farm() Warrior can Attack() Citizen can Build(), Farm() and Attack() Fisherman can Farm() and Attack() I hope everything is clear so far. So now I do have my NPC Types and their abilities. But lets come to the technical / programmatical aspect. What would be a good programmatic architecture for my different kinds of NPCs? Okay I could have a base class. Actually I think this is a good way to stick with the DRY principle. So I can have methods like WalkTo(x,y) in my base class since every NPC will be able to move. But now lets come to the real problem. Where do I implement my abilities? (remember: Build(), Farm() and Attack()) Since the abilities will consists of the same logic it would be annoying / break DRY principle to implement them for each NPC (Worker,Warrior, ..). Okay I could implement the abilities within the base class. This would require some kind of logic that verifies if a NPC can use ability X. IsBuilder, CanBuild, .. I think it is clear what I want to express. But I don't feel very well with this idea. This sounds like a bloated base class with too much functionality. I do use C# as programming language. So multiple inheritance isn't an opinion here. Means: Having extra base classes like Fisherman : Farmer, Attacker won't work.

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