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• Is MongoDB a good choice or not for my application?

  - by shubham

  I have a Reporting application which stores the reports in xml format as recieved from source (XML schema is not defined, it can be any format) and those reports contain some keys and values. Like jobid, setid be keys for 1 type of report and userid, groupId for another type of report etc. The type of keys that can be referred from the document is determined by the namespaces used in the xml doc. These keys are stored on the basis of namespace used in the xml document. For e.g. If a tag in xml fragment uses namespace= "myspace1", then I have keys A and B for myspace1 stored in another table. It will fetch those keys from that table for this namespace, look for their values in xml doc and store it in another table along with the pointer to this xml document (Id of a record storing complete xml document in a cell). Use cases: When the user comes and queries for that key and value, I return the document or a set of documents that are having those key/value pairs. When the user comes and queries for a certain key and provide a name for xslt (pre stored), I fetch the set of documents fulfilling that criteria and convert that xml to html with the specified xslt. When the user comes and asks for a particular fragment of a doc then it can fetch a subset from a particular document also. When the user comes and queries for top x values of a certain key, I return the set of documents that are having top 10 values of that key. I am using DB2 database for its support of xml along with relational capabilities. That makes easier for me to run xpath expressions and fetch values of keys and also aggregate a set of documents fullfilling a criteria, all on the database side. Problems: DB2 stores XML doc of upto 2GB in size. Retrieval is very slow. If some thing involves many documents, then it takes significant time for things to show up in browser, and the user has to wait. Can MongoDb help in this case, as it is document oriented? can I do xml related xpath queries and document transformations on db side? Or is it ok to use both in such a case?

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• As a tooling/automation developer, can I be making better use of OOP?

  - by Tom Pickles

  My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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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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• What algorithms can I use to detect if articles or posts are duplicates?

  - by michael

  I'm trying to detect if an article or forum post is a duplicate entry within the database. I've given this some thought, coming to the conclusion that someone who duplicate content will do so using one of the three (in descending difficult to detect): simple copy paste the whole text copy and paste parts of text merging it with their own copy an article from an external site and masquerade as their own Prepping Text For Analysis Basically any anomalies; the goal is to make the text as "pure" as possible. For more accurate results, the text is "standardized" by: Stripping duplicate white spaces and trimming leading and trailing. Newlines are standardized to \n. HTML tags are removed. Using a RegEx called Daring Fireball URLs are stripped. I use BB code in my application so that goes to. (ä)ccented and foreign (besides Enlgish) are converted to their non foreign form. I store information about each article in (1) statistics table and in (2) keywords table. (1) Statistics Table The following statistics are stored about the textual content (much like this post) text length letter count word count sentence count average words per sentence automated readability index gunning fog score For European languages Coleman-Liau and Automated Readability Index should be used as they do not use syllable counting, so should produce a reasonably accurate score. (2) Keywords Table The keywords are generated by excluding a huge list of stop words (common words), e.g., 'the', 'a', 'of', 'to', etc, etc. Sample Data text_length, 3963 letter_count, 3052 word_count, 684 sentence_count, 33 word_per_sentence, 21 gunning_fog, 11.5 auto_read_index, 9.9 keyword 1, killed keyword 2, officers keyword 3, police It should be noted that once an article gets updated all of the above statistics are regenerated and could be completely different values. How could I use the above information to detect if an article that's being published for the first time, is already existing within the database? I'm aware anything I'll design will not be perfect, the biggest risk being (1) Content that is not a duplicate will be flagged as duplicate (2) The system allows the duplicate content through. So the algorithm should generate a risk assessment number from 0 being no duplicate risk 5 being possible duplicate and 10 being duplicate. Anything above 5 then there's a good possibility that the content is duplicate. In this case the content could be flagged and linked to the article's that are possible duplicates and a human could decide whether to delete or allow. As I said before I'm storing keywords for the whole article, however I wonder if I could do the same on paragraph basis; this would also mean further separating my data in the DB but it would also make it easier for detecting (2) in my initial post. I'm thinking weighted average between the statistics, but in what order and what would be the consequences...

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• Cloning a dual boot system from HDD to SSD

  - by Alex

  I'm planning on replacing my laptop's HDD with a 256GB SSD, but I have a dual-boot (12.04 and Windows 7) setup and I'd like to be able to directly migrate Ubuntu over without having to reinstall and lose all of my settings. GParted reports the following partition setup on my HDD. I am, of course, able to modify it if necessary. /dev/sda1 (NTFS) 66.92 out of 200.00 MB used I'm honestly not sure what this partition is for. Maybe for Windows 7 system files? I'm hesitant to mess with it. (edit; it turns out it is a partition for Windows recovery files in the event of OS corruption, so I don't want to remove it. Plus it also appears to be a major pain to remove anyways) /dev/sda2 (NTFS) 116.35 out of 339.06 GB used (boot) This partition is the C:/ drive on my Windows installation. I don't use it on my Ubuntu installation, except it is the boot partition and thus has grub on it. /dev/sda4 (extended) > /dev/sda5 (ext4) 14.49 out of 91.34 GB used > /dev/sda6 (linux-swap) 5.92 GB These are my Ubuntu partitions. /sda5 contains my documents and all of the files I use on Ubuntu, and (as far as I know) the system files for Ubuntu itself (it's the partition I created when prompted by the Live-DVD installer). /sda6 is, of course, the swap partition which I only need for hibernation (6GB of RAM). /dev/sda3 (NTFS) 9.89 out of 14.75 GB used This is an annoying partition that Lenovo created to store some drivers and files that I might need later on. For example, it allows me to use OneKeyRecovery for a quick factory recovery if absolutely necessary, not sure if that'll work on an SSD. It also contains not-so-important files for bloatware installation. In total, my HDD only has about 150GB of files on it so it should fit comfortably on the SSD. The problem is, I want to exactly migrate my files, partitions, OSes, MBR, etc. from my HDD to my SSD and I'm not quite sure how to do this. I've seen CloneZilla referenced before, but I'm not all too experienced and the documentation for it quite frankly seems a bit like a foreign language to me. So, put simply, is there any way I can exactly clone this HDD to an SSD without a massive headache? Also, if it matters, I'll probably be using an external hard drive case (as recommended in online tutorials) to externally attach the SSD to my laptop during the cloning process due to the lack of two hard drive slots in the machine.

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• Windows 8 and the future of Silverlight

  - by Laila

  After Steve Ballmer's indiscrete 'MisSpeak' about Windows 8, there has been a lot of speculation about the new operating system. We've now had a few glimpses, such as the demonstration of 'Mosh' at the D9 2011 conference, and the Youtube video, which showed a touch-centric new interface for apps built using HTML5 and JavaScript. This has caused acute anxiety to the programmers who have followed the recommended route of WPF, Silverlight and .NET, but it need not have caused quite so much panic since it was, in fact, just a thin layer to make Windows into an apparently mobile-friendly OS. More worryingly, the press-release from Microsoft was at pains to say that 'Windows 8 apps use the power of HTML5, tapping into the native capabilities of Windows using standard JavaScript and HTML', as if all thought of Silverlight, dominant in WP7, had been jettisoned. Ironically, this brave new 'happening' platform can all be done now in Windows 7 and an iPad, using Adobe Air, so it is hardly cutting-edge; in fact the tile interface had a sort of Retro-Zune Metro UI feel first seen in Media Centre, followed by Windows Phone 7, with any originality leached out of it by the corporate decision-making process. It was kinda weird seeing old Excel running alongside stodgily away amongst all the extreme paragliding videos. The ability to snap and resize concurrent apps might be a novelty on a tablet, but it is hardly so on a PC. It was at that moment that it struck me that here was a spreadsheet application that hadn't even made the leap to the .NET platform. Windows was once again trying to be all things to all men, whereas Apple had carefully separated Mac OS X development from iOS. The acrobatic feat of straddling all mobile and desktop devices with one OS is looking increasingly implausible. There is a world of difference between an operating system that facilitates business procedures and a one that drives a device for playing pop videos and your holiday photos. So where does this leave Silverlight? Pretty much where it was. Windows 8 will support it, and it will continue to be developed, but if these press-releases reflect the thinking within Microsoft, it is no longer seen as the strategic direction. However, Silverlight is still there and there will be a whole new set of developer APIs for building touch-centric apps. Jupiter, for example, is rumoured to involve an App store that provides new, Silverlight based "immersive" applications that are deployed as AppX packages. When the smoke clears, one suspects that the Javascript/HTML5 is merely an alternative development environment for Windows 8 to attract the legions of independent developers outside the .NET culture who are unlikely to ever take a shine to a more serious development environment such as WPF or Silverlight. Cheers, Laila

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• Making A Photo-Sharing App For Android In Eclipse [on hold]

  - by user3694394

  I've only just started developing mobile apps, which is something that I've been wanting to learn for a while now. I'm from an indie games studio, making PC games for around the last 3 years, and I finally decided to move into android app development. The only problem I'm having is that I don't know where to start. The project which I'm aiming to create will be something similar to Instagram, basically a photo-sharing app which allows users to take new photos, or pull them from their device, and add filters to them, before posting them. I have a rough idea of how I could go about doing this, but I need pointing towards any tutorials available for each specific step. So, here's my idea: Create a UI in eclipse (this wont be a problem for me, I should be able to do this fine through xml files) Setup a server-side database to store all user info and uploaded images (the images will need to be converted into byte arrays, and I have no idea how to do this through a database). My best idea would be to use a MySQL database to do this. Add user interactions (likes, favourites, reposts, etc.). This would, again, have to be stored in the database (or, at least, i think it would). Add the ability to take new photos using the phone's camera (I can probably do this anyway, using the Camera API). Add the ability to pull existing photos from the device (again, pretty simple to do). Add the ability to add filters to any photos (I had a look around, and there are some repos and resources which allow you to do this, but they're mainly for iOS development). Add facebook/twitter integration (possibly) to allow phots to be shared to other social networks. Create a news feed which shows users all of the latest photos from their friends, and allows them to post their own images to it. Give all registered users their own wall/page which has their latest posts/images displayed on it. Add the ability to allow users to follow other users, and display their followed users posts on their news feed. Yep. It's not going to be easy, and I don't even know if it's possible for me to do alone in Eclipse. However, this is the plan, and I'm going to do my best to learn everything I need to know to do this successfully. My actual question would be how should I start doing this- where do I begin learning how to do all of this? I've had a look at snapify, which can be edited via Parse, but I won't be spending hundreds of dollars (since I'm 15 and just don't have the available funds) on software. I have extensive knowledge of Java (again, I've been making games for around 3 years, mainly in Java), and various scripting languages. So, hopefully, this will be of some use here. Thanks in advance, Josh.

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• Why enumerator structs are a really bad idea (redux)

  - by Simon Cooper

  My previous blog post went into some detail as to why calling MoveNext on a BCL generic collection enumerator didn't quite do what you thought it would. This post covers the Reset method. To recap, here's the simple wrapper around a linked list enumerator struct from my previous post (minus the readonly on the enumerator variable): sealed class EnumeratorWrapper : IEnumerator<int> { private LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } If you have a look at the Reset method, you'll notice I'm having to cast to IEnumerator to be able to call Reset on m_Enumerator. This is because the implementation of LinkedList<int>.Enumerator.Reset, and indeed of all the other Reset methods on the BCL generic collection enumerators, is an explicit interface implementation. However, IEnumerator is a reference type. LinkedList<int>.Enumerator is a value type. That means, in order to call the reset method at all, the enumerator has to be boxed. And the IL confirms this: .method public hidebysig newslot virtual final instance void Reset() cil managed { .maxstack 8 L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> EnumeratorWrapper::m_Enumerator L_0007: box [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> L_000c: callvirt instance void [mscorlib]System.Collections.IEnumerator::Reset() L_0011: nop L_0012: ret } On line 0007, we're doing a box operation, which copies the enumerator to a reference object on the heap, then on line 000c calling Reset on this boxed object. So m_Enumerator in the wrapper class is not modified by the call the Reset. And this is the only way to call the Reset method on this variable (without using reflection). Therefore, the only way that the collection enumerator struct can be used safely is to store them as a boxed IEnumerator<T>, and not use them as value types at all.

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• Creating smooth lighting transitions using tiles in HTML5/JavaScript game

  - by user12098

  I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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• The State of the Internet -- Retail Edition

  - by David Dorf

  Over at Business Insider, there's a great presentation on the State of the Internet done in the Mary Meeker style.  Its 138 slides so I took the liberty of condensing it down to the 15 slides that directly apply to the retail industry.  However, I strongly recommend looking at the entire deck when you have time.  And while you're at it, Business Insider just launched a retail portal that's dedicated to retail industry content.  Please check it out as well.  My take-aways are below after the slide show. &amp;amp;amp;amp;lt;span id=&amp;amp;amp;amp;quot;XinhaEditingPostion&amp;amp;amp;amp;quot;&amp;amp;amp;amp;gt;&amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;gt; [Source: Business Insider] Here are a few things I took away from the statistics: Facebook and Twitter are in their infancy.  While all retailers should have social programs, search is still the driver and therefore should receive the lions share of investment.  Facebook referrals are up 92% year-over-year, but Google still does 80% of the referrals. E-commerce continues to grow at breakneck speed, but in-store commerce is still king. Stores are not showrooms yet.  And social commerce pure-plays like Gilt and Groupon are tiny but worthy of some attention. There are more smartphones than PCs on the internet, and the disparity will continue to grow. PC growth will be flat and Tablet use will continue to grow. Mobile accounts for 12% of all internet traffic. A quarter of smartphone sales come from China, so anyone with a presence there better have a strong mobile strategy. 38% of people have used their smartphone to make a purchase, and many use their smartphones inside stores.  Smartphones are a critical consumer tool for shopping. Mobile is starting to drive significant traffic to e-commerce sites, especially tablets.  Tablet strategies are crucial for retailers. Mobile payments from the likes of Paypal and Square are growing quickly.  It will be interesting to see how NFC plays in this area. Mobile operating systems are losing market share to iOS and Android.  I wonder in Microsoft can finally make a dent? The internet is being dominated by mobile devices, and retailers had better have a strong mobile strategy to meet consumer demand.

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• What is a good strategy for binding view objects to model objects in C++?

  - by B.J.

  Imagine I have a rich data model that is represented by a hierarchy of objects. I also have a view hierarchy with views that can extract required data from model objects and display the data (and allow the user to manipulate the data). Actually, there could be multiple view hierarchies that can represent and manipulate the model (e.g. an overview-detail view and a direct manipulation view). My current approach for this is for the controller layer to store a reference to the underlying model object in the View object. The view object can then get the current data from the model for display, and can send the model object messages to update the data. View objects are effectively observers of the model objects and the model objects broadcast notifications when properties change. This approach allows all the views to update simultaneously when any view changes the model. Implemented carefully, this all works. However, it does require a lot of work to ensure that no view or model objects hold any stale references to model objects. The user can delete model objects or sub-hierarchies of the model at any time. Ensuring that all the view objects that hold references to the model objects that have been deleted is time-consuming and difficult. It feels like the approach I have been taking is not especially clean; while I don't want to have to have explicit code in the controller layer for mediating the communication between the views and the model, it seems like there must be a better (implicit) approach for establishing bindings between the view and the model and between related model objects. In particular, I am looking for an approach (in C++) that understands two key points: There is a many to one relationship between view and model objects If the underlying model object is destroyed, all the dependent view objects must be cleaned up so that no stale references exist While shared_ptr and weak_ptr can be used to manage the lifetimes of the underlying model objects and allows for weak references from the view to the model, they don't provide for notification of the destruction of the underlying object (they do in the sense that the use of a stale weak_ptr allows for notification), but I need an approach that notifies the dependent objects that their weak reference is going away. Can anyone suggest a good strategy to manage this?

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• Hadoop, NOSQL, and the Relational Model

  - by Phil Factor

  (Guest Editorial for the IT Pro/SysAdmin Newsletter)Whereas Relational Databases fit the world of commerce like a glove, it is useless to pretend that they are a perfect fit for all human endeavours. Although, with SQL Server, we’ve made great strides with indexing text, in processing spatial data and processing markup, there is still a problem in dealing efficiently with large volumes of ephemeral semi-structured data. Key-value stores such as Cassandra, Project Voldemort, and Riak are of great value for ephemeral data, and seem of equal value as a data-feed that provides aggregations to an RDBMS. However, the Document databases such as MongoDB and CouchDB are ideal for semi-structured data for which no fixed schema exists; analytics and logging are obvious examples. NoSQL products, such as MongoDB, tackle the semi-structured data problem with panache. MongoDB is designed with a simple document-oriented data model that scales horizontally across multiple servers. It doesn’t impose a schema, and relies on the application to enforce the data structure. This is another take on the old ‘EAV’ problem (where you don’t know in advance all the attributes of a particular entity) It uses a clever replica set design that allows automatic failover, and uses journaling for data durability. It allows indexing and ad-hoc querying. However, for SQL Server users, the obvious choice for handling semi-structured data is Apache Hadoop. There will soon be an ODBC Driver for Apache Hive .and an Add-in for Excel. Additionally, there are now two Hadoop-based connectors for SQL Server; the Apache Hadoop connector for SQL Server 2008 R2, and the SQL Server Parallel Data Warehouse (PDW) connector. We can connect to Hadoop process the semi-structured data and then store it in SQL Server. For one steeped in the culture of Relational SQL Databases, I might be expected to throw up my hands in the air in a gesture of contempt for a technology that was, judging by the overblown journalism on the subject, about to make my own profession as archaic as the Saggar makers bottom knocker (a potter’s assistant who helped the saggar maker to make the bottom of the saggar by placing clay in a metal hoop and bashing it). However, on the contrary, I find that I'm delighted with the advances made by the NoSQL databases in the past few years. Having the flow of ideas from the NoSQL providers will knock any trace of complacency out of the providers of Relational Databases and inspire them into back-fitting some features, such as horizontal scaling, with sharding and automatic failover into SQL-based RDBMSs. It will do the breed a power of good to benefit from all this lateral thinking.

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• cloud programming for OpenStack in C / C++

  - by Basile Starynkevitch

  (Sorry for such a fuzzy question, I am very newbie to cloud programming) I am interested in designing (and developing) a (free software) program in C or C++ (probably, most of it being meta-programmed, i.e. part of the C code code being generated). I am still in the thinking / designing phase. And I might perhaps give up. For reference, I am the main architect and implementor of GCC MELT, a domain specific language to extend the GCC compiler (the MELT language is translated to C/C++ and is bootstrapped: the MELT to C/C++ translator being written in MELT). And I am dreaming of extending it with some cloud computing abilities. But I am a newbie in cloud computing. (I am only interested in free-software, GPLv3 friendly, based cloud computing, which probably means openstack). I believe that "compiling on the cloud with some enhanced GCC" could make sense (for super-optimizations or static analysis of e.g. an entire Linux distribution, or at least a massive GCC compiled free software like Qt, GCC itself, or the Linux kernel). I'm dreaming of a MELT specific monitoring program which would store, communicate, and and enhance GCC compilation (extended by MELT). So the picture would be that each GCC process (actually the cc1 or cc1plus started by the gcc driver, suitably extended by some MELT extension) would communicate with some monitor. That "monitoring/persisting" program would run "on the cloud" (and probably manage some information produced by GCC e.g. on NoSQL bases). So, how should some (yet to be written) C program (some Linux daemon) be designed to be cloud-friendly? So far, I understood that it should provide some Web service, probably thru a RESTful service, so should use an HTTP server library like onion. And that OpenStack is able to start (e.g. a dozen of) such services. But I don't have a clear picture of what OpenStack brings. So far, I noticed the ability to manage (and distribute) virtual machines (with some Python API). It is less clear how can it distribute some ELF executable, how can it start it, etc. Do you have any references or examples of C / C++ programming on the cloud? How should a "cloud-friendly" (actually, OpenStack friendly) C/C++ server application be designed?

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• Data Transformation Pipeline

  - by davenewza

  I have create some kind of data pipeline to transform coordinate data into more useful information. Here is the shell of pipeline: public class PositionPipeline { protected List<IPipelineComponent> components; public PositionPipeline() { components = new List<IPipelineComponent>(); } public PositionPipelineEntity Process(Position position) { foreach (var component in components) { position = component.Execute(position); } return position; } public PositionPipeline RegisterComponent(IPipelineComponent component) { components.Add(component); return this; } } Every IPipelineComponent accepts and returns the same type - a PositionPipelineEntity. Code: public interface IPipelineComponent { PositionPipelineEntity Execute(PositionPipelineEntity position); } The PositionPipelineEntity needs to have many properties, many which are unused in certain components and required in others. Some properties will also have become redundant at the end of the pipeline. For example, these components could be executed: TransformCoordinatesComponent: Parse the raw coordinate data into a Coordinate type. DetermineCountryComponent: Determine and stores country code. DetermineOnRoadComponent: Determine and store whether coordinate is on a road. Code: pipeline .RegisterComponent(new TransformCoordinatesComponent()) .RegisterComponent(new DetermineCountryComponent()) .RegisterComponent(new DetermineOnRoadComponent()); pipeline.Process(positionPipelineEntity); The PositionPipelineEntity type: public class PositionPipelineEntity { // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLatitude { get; set; } // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLongitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLatitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLongitude { get; set; } // Set in DetermineCountryComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public string CountryCode { get; set; } // Set in DetermineOnRoadComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public bool OnRoad { get; set; } } Problems: I'm very concerned about the dependency that a component has on properties. The way to solve this would be to create specific types for each component. The problem then is that I cannot chain them together like this. The other problem is the order of components in the pipeline matters. There is some dependency. The current structure does not provide any static or runtime checking for such a thing. Any feedback would be appreciated.

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• Enabling EUS support in OUD 11gR2 using command line interface

  - by Sylvain Duloutre

  Enterprise User Security (EUS) allows Oracle Database to use users & roles stored in LDAP for authentication and authorization.Since the 11gR2 release, OUD natively supports EUS. EUS can be easily configured during OUD setup. ODSM (the graphical admin console) can also be used to enable EUS for a new suffix. However, enabling EUS for a new suffix using command line interface is currently not documented, so here is the procedure: Let's assume that EUS support was enabled during initial setup.Let's o=example be the new suffix I want to use to store Enterprise users. The following sequence of command must be applied for each new suffix: // Create a local database holding EUS context infodsconfig create-workflow-element --set base-dn:cn=OracleContext,o=example --set enabled:true --type db-local-backend --element-name exampleContext -n // Add a workflow element in the call path to generate on the fly attributes required by EUSdsconfig create-workflow-element --set enabled:true --type eus-context --element-name eusContext --set next-workflow-element:exampleContext -n // Add the context to a workflow for routingdsconfig create-workflow --set base-dn:cn=OracleContext,o=example --set enabled:true --set workflow-element:eusContext --workflow-name exampleContext_workflow -n //Add the new workflow to the appropriate network groupdsconfig set-network-group-prop --group-name network-group --add workflow:exampleContext_workflow -n // Create the local database for o=exampledsconfig create-workflow-element --set base-dn:o=example --set enabled:true --type db-local-backend --element-name example -n // Create a workflow element in the call path to the user data to generate on the fly attributes expected by EUS dsconfig create-workflow-element --set enabled:true --set eus-realm:o=example --set next-workflow-element:example --type eus --element-name eusWfe// Add the db to a workflow for routingdsconfig create-workflow --set base-dn:o=example --set enabled:true --set workflow-element:eusWfe --workflow-name example_workflow -n //Add the new workflow to the appropriate network groupdsconfig set-network-group-prop --group-name network-group --add workflow:example_workflow -n  // Add the appropriate acis for EUSdsconfig set-access-control-handler-prop \           --add global-aci:'(target="ldap:///o=example")(targetattr="authpassword")(version 3.0; acl "EUS reads authpassword"; allow (read,search,compare) userdn="ldap:///??sub?(&(objectclass=orclservice)(objectclass=orcldbserver))";)' dsconfig set-access-control-handler-prop \       --add global-aci:'(target="ldap:///o=example")(targetattr="orclaccountstatusevent")(version 3.0; acl "EUS writes orclaccountstatusenabled"; allow (write) userdn="ldap:///??sub?(&(objectclass=orclservice)(objectclass=orcldbserver))";)' Last but not least you must adapt the content of the ${OUD}/config/EUS/eusData.ldif  file with your suffix value then inport it into OUD.

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• Reading a ZFS USB drive with Mac OS X Mountain Lion

  - by Karim Berrah

  The problem: I'm using a MacBook, mainly with Solaris 11, but something with Mac OS X (ML). The only missing thing is that Mac OS X can't read my external ZFS based USB drive, where I store all my data. So, I decided to look for a solution. Possible solution: I decided to use VirtualBox with a Solaris 11 VM as a passthrough to my data. Here are the required steps: Installing a Solaris 11 VM Install VirtualBox on your Mac OS X, add the extension pack (needed for USB) Plug your ZFS based USB drive on your Mac, ignore it when asked to initialize it. Create a VM for Solaris (bridged network), and before installing it, create a USB filter (in the settings of your Vbox VM, go to Ports, then USB, then add a new USB filter from the attached device "grey usb-connector logo with green plus sign")  Install a Solaris 11 VM, boot it, and install the Guest addition check with "ifconfg -a" the IP address of your Solaris VM Creating a path to your ZFS USB drive In MacOS X, use the "Disk Utility" to unmount the USB attached drive, and unplug the USB device. Switch back to VirtualBox, select the top of the window where your Solaris 11 is running plug your ZFS USB drive, select "ignore" if Mac OS invite you to initialize the disk In the VirtualBox VM menu, go to "Devices" then "USB Devices" and select from the dropping menu your "USB device" Connection your Solaris VM to the USB drive Inside Solaris, you might now check that your device is accessible by using the "format" cli command If not, repeat previous steps Now, with root privilege, force a zpool import -f myusbdevicepoolname because this pool was created on another system check that you see your new pool with "zpool status" share your pool with NFS: share -F NFS /myusbdevicepoolname Accessing the USB ZFS drive from Mac OS X This is the easiest step: access an NFS share from mac OS Create a "ZFSdrive" folder on your MacOS desktop from a terminal under mac OS: mount -t nfs IPadressofMySoalrisVM:/myusbdevicepoolname  /Users/yourusername/Desktop/ZFSdrive et voila ! you might access your data, on a ZFS USB drive, directly from your Mountain Lion Desktop. You might play with the share rights in order to alter any read/write rights as needed. You might activate compression, encryption inside the Solaris 11 VM ...

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• Managing Joomla via Android

  Surprisingly, it was only today that I actually looked for possible solutions to write more content for my blog. Since quite some time I'm using my Samsung Galaxy Tab 10.1 for all kind of social media activities like Google+, FB, etc. but also for my casual mail during the evening hours. And yes, I feel a little bit guilty about missing the chance to use my tablet to write some content here... OK, only a little bit. ;-) These are not the droids you are looking for But those lazy times are over! While searching the Play Store with the expression 'joomla' I got three interesting hits: - Joomla Admin Mobile! - Joooid - Joomla! Security Checklist After reading the reviews I installed the two later apps. Joomla! Security Checklist The author clearly outlines here that the app is primarily for his personal purpose to have safety checklist at hand at anytime. I guess that any reader of this article has an Android based smartphone or tablet, so that simple app should be part of your toolbox when using Joomla! for your websites. Joooid plugin & app Although I was looking for an app that could work with the default XML RPC interface of Joomla I have to admit that this combination of an enhanced Web service suits me better, mainly due to performance reason. The official website has not only the downloads for Joomla versions 1.5 - 2.5 but also very good and easy to follow step-by-step instructions to prepare your server for the Android app. It will take you less than 5 minutes to get it up and running. For safety reasons, I recommend that you should configure your Web server to have an additional authentication layer on the plugins folder. The smartphone app has the ability to run against HTTP authentication. Personally, I like the look and feel of the app. It is a little bit different compared to the web UI but still easy to use. In fact, this article is the first one written in the Joooid app. At the moment, I only miss the ability to have list tags. Quick and easy Writing full-fledged articles with images, a couple of hyperlinks and some styling here and there should be left to the desktop. At least for the moment. Let's see whether I'm going to change my mind on this during the upcoming months... I'll give it a try, and hope to publish at least once per month to write some content using Joooid. Actually, it would be great to have some feedback about other Joomla! clients in the wild.

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• Should I go back to college and graduate with a poor GPA or try to jump into an entry-level development position? [closed]

  - by jshin47

  I once attended a top-10 American university but I am currently not in school for several different reasons. Chief among them is that I did very poorly two semesters and even failed one of them (got two F's) which put me in automatic suspension. My major is not CS but math. I am in a pickle at the moment. After I was suspended I got a job at a niche IT company in the area. I am employed as something of an IT generalist; my primary responsibilities are Windows systems administration/networking but I also do some Android, iOS, and .NET development. I have released a few apps to the app store under my name and my company's name, and we have done work for a few big clients. I started working at my job about 1.5 years ago and I am somewhat happily employed but I do not see it as a long-term fit because it is a small company with little opportunity to advance. I would like to move out to California and particularly to the Bay Area to get a job at a more reputable or exciting company, even at a lower rate of pay, but I am not sure if I should do that or try to go back to school. If I went back to school, it would take 1-1.5 years to graduate and some $. Best case scenario I would graduate with a 2.9 or 3.0 GPA. It is a top-10 school, but that's a crappy GPA. If I do not go back to school, I will be a field where most people have degrees, without a degree. If anything goes wrong I could be really screwed as I feel I will get no respect without a degree. On the other hand I really would like to get started in the field and get more serious about developing good development practices, learning new languages/frameworks, and working with people who know a lot more than I so I can learn and grow as a developer and eventually do my own thing. Basically, I am wondering: Should I just go back to school? How much does the bad GPA / good school reputation weigh in? What about the fact that I am a Math major and not a CS major (have never taken a CS course)? Does my skill set as something of a generalist bode well for me finding work at a start up in the Bay Area? If not (2), should I hunker down and focus on producing a really good (or a few medicore) iOS apps? Android apps? etc... How would you look at someone who did great in HS, kind of goofed off in college and eventually quit, and got into development? Thanks for any thoughts or input.

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• Inline template efficiency

  - by Darryl Gove

  I like inline templates, and use them quite extensively. Whenever I write code with them I'm always careful to check the disassembly to see that the resulting output is efficient. Here's a potential cause of inefficiency. Suppose we want to use the mis-named Leading Zero Detect (LZD) instruction on T4 (this instruction does a count of the number of leading zero bits in an integer register - so it should really be called leading zero count). So we put together an inline template called lzd.il looking like: .inline lzd lzd %o0,%o0 .end And we throw together some code that uses it: int lzd(int); int a; int c=0; int main() { for(a=0; a<1000; a++) { c=lzd(c); } return 0; } We compile the code with some amount of optimisation, and look at the resulting code: $ cc -O -xtarget=T4 -S lzd.c lzd.il $ more lzd.s .L77000018: /* 0x001c 11 */ lzd %o0,%o0 /* 0x0020 9 */ ld [%i1],%i3 /* 0x0024 11 */ st %o0,[%i2] /* 0x0028 9 */ add %i3,1,%i0 /* 0x002c */ cmp %i0,999 /* 0x0030 */ ble,pt %icc,.L77000018 /* 0x0034 */ st %i0,[%i1] What is surprising is that we're seeing a number of loads and stores in the code. Everything could be held in registers, so why is this happening? The problem is that the code is only inlined at the code generation stage - when the actual instructions are generated. Earlier compiler phases see a function call. The called functions can do all kinds of nastiness to global variables (like 'a' in this code) so we need to load them from memory after the function call, and store them to memory before the function call. Fortunately we can use a #pragma directive to tell the compiler that the routine lzd() has no side effects - meaning that it does not read or write to memory. The directive to do that is #pragma no_side_effect(<routine name), and it needs to be placed after the declaration of the function. The new code looks like: int lzd(int); #pragma no_side_effect(lzd) int a; int c=0; int main() { for(a=0; a<1000; a++) { c=lzd(c); } return 0; } Now the loop looks much neater: /* 0x0014 10 */ add %i1,1,%i1 ! 11 ! { ! 12 ! c=lzd(c); /* 0x0018 12 */ lzd %o0,%o0 /* 0x001c 10 */ cmp %i1,999 /* 0x0020 */ ble,pt %icc,.L77000018 /* 0x0024 */ nop

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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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• DTLoggedExec 1.1.2008.4 Released!

  - by Davide Mauri

  Today I've relased the latest version of my DTExec replacement tool, DTLoggedExec. The main changes are the following: Used a new strategy for version numbers. Now it will follow the following pattern Major.Minor.TargetSQLServerVersion.Revision Added support for Auto Configurations Fixed a bug that reported incorrect number of errors and warnings to Log Providers Fixed a buf that prevented correct casting of values when using /Set and /Param options Errors and Warnings are now counted more precisely. Updated database and log import scripts to categorize logs by projects and sections. E.g.: Project: MyBIProject; Sections: Staging, Datawarehouse Removed unused report stored procedures from database Updated Samples: 12 samples are now available to show ALL DTLoggedExec features From this version only SSIS 2008 will be supported http://dtloggedexec.codeplex.com/releases/view/62218  It useful to say something more on a couple of specific points: From this version only SSIS 2008 will be supportedYes, Integration Services 2005 are not supported anymore. The latest version capable of running SSIS 2005 Packages is the 1.0.0.2. Updated database and log import scripts to categorize logs by projects and sectionsWhen you import a log file, you can now assign it to a Project and to a Section of that project. In this way it's easier to gather statistical information for an entire project or a subsection of it. This also allows to store logged data of package belonging to different projects in the same database. For example:  Updated SamplesA complete set of samples that shows how to use all DTLoggedExec features are now shipped with the product. Enjoy! Added support for Auto ConfigurationsThis point will have a post on its own, since it's quite important and is by far the biggest new feature introduced in this release. To explain it in a few words, I can just say that you don't need to waste time with complex DTS configuration files or options, since a package will configure itself automatically. You just need to write a single statement as a parameter for DTLoggedExec. This feature can simplify deployment *a lot* :)   I the next days I'll write the mentioned post on Auto-Configurations and i'll update the documentation available on theDTLoggedExec website:   http://dtloggedexec.davidemauri.it/MainPage.ashx

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• Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

  - by Rowan Freeman

  Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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• Behaviour Trees with irregular updates

  - by Robominister

  I'm interested in behaviour trees that aren't iterated every game tick, but every so often. (Edit: the tree could specify how many frames within the main game loop to wait before running its tick function again). Every theoretical implementation I have seen of behaviour trees talks of the tree search being carried out every game update - which seems necessary, because a leaf node (eg a behaviour, like 'return to base') needs to be constantly checked to see if is still running, failed or completed. Can anyone suggest how I might start implementing a tree that isnt run every tick, or point me in the direction of good material specific to this case (I am struggling to find anything)? My thoughts so far: action leaf nodes (when they start) must only push some kind of action object onto a list for an entity, rather than directly calling any code that makes the entity do something. The list of actions for the entity would be run every frame (update any that need to run, pop any that have completed from the list). the return state from a given action must be fed back into the tree, so that when we run the tree iteration again (and reach the same action leaf node - so the tree has so far determined that we ought to still be trying this action) - that the action has completed, or is still running etc. If my actual action code is running from an action list on an entity, then I possibly need to cancel previously running actions in the list - i am thinking that I can just delete the entire stack of queued up actions. I've seen the idea of ActionLists which block lower priority actions when a higher priority one is added, but this seems like very close logic to behaviour trees, and I dont want to be duplicating behaviour. This leaves me with some questions 1) How would I feed the action return state back into the tree? Its obvious I need to store some information relating to 'currently executing actions' on the entity, and check that in the tree tick, but I can't imagine how. 2) Does having a seperate behaviour tree (for deciding behaviour) and action list (for carrying out actual queued up actions) sound like a reasonable approach? 3) Is the approach of updating a behaviour tree irregularly actually used by anyone? It seems like a nice idea for budgeting ai search time when you have a lot of ai entities to process. (Edit) - I am also thinking about storing a single instance of a given behaviour tree in memory, and providing it by reference to any entity that uses it. So any information about what action was last selected for execution on an entity must be stored in a data context relative to the entity (which the tree can check). (I am probably answering my own questions as i go!) I hope I have expressed my questions adequately! Thanks in advance for any help :)

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• Focusing on Mobile @ Oracle OpenWorld

  - by Carlos Chang

  Plenty of exciting trends in the industry today: Cloud, Big Data, Mobile, etc. The first two are amazing of course, but for me, it's mobile, mobile and... MOBILE.   Why? Think back to the mozilla browser (Marc Andreessen's mozilla, not today's mozilla.org), Netscape and the nascent beginnings of the World Wide Web. Amazing times. Companies were just starting to set up their home pages, basic HTML, hyperlinks, images, ooooh, aaaah.  Yahoo! was *the* search engine back then. :-\   Anywhoo, I would pose that mobile today, we are in a similar junction. Sure, there's millions of apps on Apple's App Store and Google Play, but within the enterprise, it's just getting started. I'm talking about going beyond the simple, tactical apps such as calendaring, contacts or directory service lookup. And while mobile first a common mantra, I'm referring to mobile plus which includes and looks upon the whole enterprise holistically and adds new parameters, such as your GPS location, perhaps even your vital signs. (Apple's health kit?)  Everything is going mobile. Everything connected. But with the enterprise - scalability, security, integration, app management, user management, etc. Amazing times ahead. Ok, got that off my mind. Oracle OpenWorld 2014 - Going Mobile!  If you're coming to the big dance, I've highlighted some key mobile sessions below. And if you see me around, and there's a bar within reach, high five me for a beer. I mean, if you read this far, and didn't already jump to the list below, I think you deserve one.   Cheers!  Monday, 9/29/14 at 10:15 AM - General Session: Time for You to Rethink Mobile? Oracle Mobile Strategy and Roadmap Tuesday, 9/30/14 @ 12:00 PM; MW3020 - Develop and Deploy Mobile Applications with Oracle’s Mobile Wednesday, 10/1/2014 @10:15 AM; MW 3022 Introduction to Oracle Mobile Application Framework Wednesday, 10/1/2014 @11:30 AM Accelerate Enterprise Mobility with Oracle Mobile Cloud Service Click here to view the complete Focus on Mobile sessions at this years Oracle OpenWorld 2014, and don't forget to follow @OracleMobile on Twitter. 

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• Fixing a NoClassDefFoundError

  - by Chris Okyen

  I have some code: package ftc; import java.util.Scanner; public class Fer_To_Cel { public static void main(String[] argv) { // Scanner object to get the temp in degrees Farenheit Scanner keyboard = new Scanner(System.in); boolean isInt = true; // temporarily put as true in case the user enters a valid int the first time int degreesF = 0; // initialy set to 0 do { try { // Input the temperature text. System.out.print("\nPlease enter a temperature (integer number, no fractional part) in degrees Farenheit: "); degreesF = Integer.parseInt(keyboard.next()); // Get user input and Assign the far. temperature variable, which is casted from String to int. } // Let the user know in a user friendly notice that the value entered wasnt an int ( give int value range ) , and then give error log catch(java.lang.Exception e) { System.out.println("Sorry but you entered a non-int value ( needs to be between ( including ) -2,147,483,648 and 2,147,483,647 ).. \n"); e.printStackTrace(); isInt = false; } } while(!isInt); System.out.println(""); // print a new line. final int degreesC = (5*(degreesF-32)/9); // convert the degrees from F to C and store the resulting expression in degreesC // Print out a newline, then print what X degrees F is in Celcius. System.out.println("\n" + degreesF + " degrees Farenheit is " + degreesC + " degrees Celcius"); } } And The following error: C:\Program Files\Java\jdk1.7.0_06\bin>java Fer_To_Cel Exception in thread "main" java.lang.NoClassDefFoundError: Fer_To_Cel (wrong name: ftc/Fer_To_Cel) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:791) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14 at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:423) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:356) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:480) The code compiled without compile errors, but presented errors during execution. Which leads me to two questions. I know Errors can be termed Compiler, Runtime and Logic Errors, but the NoClassDefFoundError inherits java.lang.LinkageError. Does that make it a Linker error, being niether of the three types of errors I listed, If I am right this is the answer. For someone else who obtains the singular .java file and compiles it, would this be the only way to solve this problem? Or can I (should I ) do/have done something to fix this problem? Basically, based on a basis of programming, is this a fault of me as the writer? Could this be done once on, my half and be distributed and not needed be done again?

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