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• What Design Pattern is seperating transform converters

  - by RevMoon

  For converting a Java object model into XML I am using the following design: For different types of objects (e.g. primitive types, collections, null, etc.) I define each its own converter, which acts appropriate with respect to the given type. This way it can easily extended without adding code to a huge if-else-then construct. The converters are chosen by a method which tests whether the object is convertable at all and by using a priority ordering. The priority ordering is important so let's say a List is not converted by the POJO converter, even though it is convertable as such it would be more appropriate to use the collection converter. What design pattern is that? I can only think of a similarity to the command pattern.

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• The Design of the Namecheap Site [on hold]

  - by Guest

  I was just wondering what design Namecheap.com is using for their site. I asked their support personnel and I suppose the employees aren't generally aware. It really looks like a customized wordpress site, but I was wondering if anyone here knew any more details about their setup. Been googling for it but the problem is, since namecheap DEALS with CMS's/web design for their business, you'll get google hits regarding their business rather than describing their site itself. Just interested. If anyone's got any info on it let me know.

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• What Design Pattern is separating transform converters

  - by RevMoon

  For converting a Java object model into XML I am using the following design: For different types of objects (e.g. primitive types, collections, null, etc.) I define each its own converter, which acts appropriate with respect to the given type. This way it can easily extended without adding code to a huge if-else-then construct. The converters are chosen by a method which tests whether the object is convertable at all and by using a priority ordering. The priority ordering is important so let's say a List is not converted by the POJO converter, even though it is convertable as such it would be more appropriate to use the collection converter. What design pattern is that? I can only think of a similarity to the command pattern.

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• Design Pattern for Data Validation

  - by melodui

  What would be the best design pattern for this problem: I have an Object A. Object A can either be registered or deleted from the database depending on the user request. Data validation is performed before registration or deletion of the object. There are a set of rules to be checked before the object can be registered and another set of rules for deletion. Some of these rules are common for both operations. So far, I think the Chain of Responsibility design pattern fits the most but I'm having trouble implementing it.

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• What should you do when presented with a horrible design?

  - by plua

  Our firm makes websites. We also design websites. But sometimes our client brings his/her own design. This is often made by an in-house designer, or it is the same design they used for something else. However, sometimes these designs look awful. And I am talking really unprofessional, unbalanced, uncool. But the client really wants this design. I really do not like working with a design that is so awful. It takes away all pleasure in coding. You code. You check the demo. Works great. Looks awful. It's just not fun. And ultimately the client might be happy, but 1) I do not feel proud of the final product and 2) the community sees you 'develop' ugly websites, which is bad for your image. Anybody experiencing this kind of stuff? What do you recommend? I've been thinking: Blocking these clients. If somebody has an 'own' design, ask to see it first. Then somehow politely decline. Drawback: you lose a client. Create a new design. Have our in-house designers work one something really cool. Drawbacks: client would need to pay for this (without asking for it), or it will be declined and the company loses time = money. And it might come as an insult if you propose a new design out of the blue. THEIR designer won't like it for sure. Put a clear disclaimer at the bottom of the site: Website design by XXXXX, Website development by US. Helps for the community-impact (if people pay attention), but not for the uneasy feeling.

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• Book Recommendation: Web Design

  - by injekt

  I'm looking to get back into advanced Web Design. I'd say I was already fairly advanced but I haven't designed much in a good few years and haven't got any books any more. I was just interested to know if anyone had any good recommendations for Web Design books and resources, I've spent the last couple of days looking around but can't make my mind up. Any contributions are greatly appreciated. PS. I have looked around at other questions on StackOverflow that could be related, but couldn't find any that fitted.

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• User Interface design books/resources for programmers

  - by mmacaulay

  Hi, I'm going to make my monthly trip to the bookstore soon and I'm kind of interested in learning some user interface and/or design stuff - mostly web related, what are some good books I should look at? One that I've seen come up frequently in the past is Don't Make Me Think, which looks promising. I'm aware of the fact that programmers often don't make great designers, and as such this is more of a potential hobby thing than a move to be a professional designer. I'm also looking for any good web resources on this topic. I subscribed to Jakob Nielsen's Alertbox newsletter, for instance, although it seems to come only once a month or so. Thanks! Somewhat related questions: http://stackoverflow.com/questions/75863/what-are-the-best-resources-for-designing-user-interfaces http://stackoverflow.com/questions/7973/user-interface-design

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• Design Solution For Storing-Fetching Images

  - by Chaitanya

  This is a design doubt am facing, I have a collection of 1500 images which are to be displayed on an asp.net page, the images to be displayed differ from one page to another, the count of these images will increase in the time to come, a.) is it a good idea to have the images on the database, but the round trip time to fetch the images from the database might be high. b.) is it good to have all the images on a directory, and have a virtual file system over it, and the application will access the images from the directory Do we have in particular any design strategy in a traditional database for fetching images with the least round trip time, does any solution other than usage of a traditional database exists? ps: I use SQL Server to store these images.

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• Security in Software

  The term security has many meanings based on the context and perspective in which it is used. Security from the perspective of software/system development is the continuous process of maintaining confidentiality, integrity, and availability of a system, sub-system, and system data. This definition at a very high level can be restated as the following: Computer security is a continuous process dealing with confidentiality, integrity, and availability on multiple layers of a system. Key Aspects of Software Security Integrity Confidentiality Availability Integrity within a system is the concept of ensuring only authorized users can only manipulate information through authorized methods and procedures. An example of this can be seen in a simple lead management application.  If the business decided to allow each sales member to only update their own leads in the system and sales managers can update all leads in the system then an integrity violation would occur if a sales member attempted to update someone else’s leads. An integrity violation occurs when a team member attempts to update someone else’s lead because it was not entered by the sales member.  This violates the business rule that leads can only be update by the originating sales member. Confidentiality within a system is the concept of preventing unauthorized access to specific information or tools.  In a perfect world the knowledge of the existence of confidential information/tools would be unknown to all those who do not have access. When this this concept is applied within the context of an application only the authorized information/tools will be available. If we look at the sales lead management system again, leads can only be updated by originating sales members. If we look at this rule then we can say that all sales leads are confidential between the system and the sales person who entered the lead in to the system. The other sales team members would not need to know about the leads let alone need to access it. Availability within a system is the concept of authorized users being able to access the system. A real world example can be seen again from the lead management system. If that system was hosted on a web server then IP restriction can be put in place to limit access to the system based on the requesting IP address. If in this example all of the sales members where accessing the system from the 192.168.1.23 IP address then removing access from all other IPs would be need to ensure that improper access to the system is prevented while approved users can access the system from an authorized location. In essence if the requesting user is not coming from an authorized IP address then the system will appear unavailable to them. This is one way of controlling where a system is accessed. Through the years several design principles have been identified as being beneficial when integrating security aspects into a system. These principles in various combinations allow for a system to achieve the previously defined aspects of security based on generic architectural models. Security Design Principles Least Privilege Fail-Safe Defaults Economy of Mechanism Complete Mediation Open Design Separation Privilege Least Common Mechanism Psychological Acceptability Defense in Depth Least Privilege Design PrincipleThe Least Privilege design principle requires a minimalistic approach to granting user access rights to specific information and tools. Additionally, access rights should be time based as to limit resources access bound to the time needed to complete necessary tasks. The implications of granting access beyond this scope will allow for unnecessary access and the potential for data to be updated out of the approved context. The assigning of access rights will limit system damaging attacks from users whether they are intentional or not. This principle attempts to limit data changes and prevents potential damage from occurring by accident or error by reducing the amount of potential interactions with a resource. Fail-Safe Defaults Design PrincipleThe Fail-Safe Defaults design principle pertains to allowing access to resources based on granted access over access exclusion. This principle is a methodology for allowing resources to be accessed only if explicit access is granted to a user. By default users do not have access to any resources until access has been granted. This approach prevents unauthorized users from gaining access to resource until access is given. Economy of Mechanism Design PrincipleThe Economy of mechanism design principle requires that systems should be designed as simple and small as possible. Design and implementation errors result in unauthorized access to resources that would not be noticed during normal use. Complete Mediation Design PrincipleThe Complete Mediation design principle states that every access to every resource must be validated for authorization. Open Design Design PrincipleThe Open Design Design Principle is a concept that the security of a system and its algorithms should not be dependent on secrecy of its design or implementation Separation Privilege Design PrincipleThe separation privilege design principle requires that all resource approved resource access attempts be granted based on more than a single condition. For example a user should be validated for active status and has access to the specific resource. Least Common Mechanism Design PrincipleThe Least Common Mechanism design principle declares that mechanisms used to access resources should not be shared. Psychological Acceptability Design PrincipleThe Psychological Acceptability design principle refers to security mechanisms not make resources more difficult to access than if the security mechanisms were not present Defense in Depth Design PrincipleThe Defense in Depth design principle is a concept of layering resource access authorization verification in a system reduces the chance of a successful attack. This layered approach to resource authorization requires unauthorized users to circumvent each authorization attempt to gain access to a resource. When designing a system that requires meeting a security quality attribute architects need consider the scope of security needs and the minimum required security qualities. Not every system will need to use all of the basic security design principles but will use one or more in combination based on a company’s and architect’s threshold for system security because the existence of security in an application adds an additional layer to the overall system and can affect performance. That is why the definition of minimum security acceptably is need when a system is design because this quality attributes needs to be factored in with the other system quality attributes so that the system in question adheres to all qualities based on the priorities of the qualities. Resources: Barnum, Sean. Gegick, Michael. (2005). Least Privilege. Retrieved on August 28, 2011 from https://buildsecurityin.us-cert.gov/bsi/articles/knowledge/principles/351-BSI.html Saltzer, Jerry. (2011). BASIC PRINCIPLES OF INFORMATION PROTECTION. Retrieved on August 28, 2011 from  http://web.mit.edu/Saltzer/www/publications/protection/Basic.html Barnum, Sean. Gegick, Michael. (2005). Defense in Depth. Retrieved on August 28, 2011 from  https://buildsecurityin.us-cert.gov/bsi/articles/knowledge/principles/347-BSI.html Bertino, Elisa. (2005). Design Principles for Security. Retrieved on August 28, 2011 from  http://homes.cerias.purdue.edu/~bhargav/cs526/security-9.pdf

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• Suggestions on switching from lamp based web design-development to game design-development

  - by Sandeepan Nath

  I have around 2.5 years of experience as a web developer cum designer working mainly on the LAMP platform. Now, I want to try out game development (of the likes of First Person Shooter games like Call of Duty (COD)). It is one of my dreams to some day succeed in making a profitable, popular, commercial game of this type. However, I have never done any kind of business nor even freelancing yet even in the web domain. Okay, first things first, I am just starting and I don't yet have any idea about the technologies, languages, engines (game engines) etc involved in that. I would like this question to be a complete guide for people with similar interests. Best resources for getting hold really fast What would be the best approach to get the basic hold of the domain really fast? Any resource(s) for programmers coming from other domains/experienced in other domains would be the ideal ones for me. E.g., if anybody would ask me some good resource for quickly learning PHP/Mysql, I would suggest books like "How to do everything with PHP & MySql" - because - it introduces all the basics of the domain (not the advanced things which can be later learnt by practice and also a lot by searching in stackoverflow questions) it contains some very nice working projects in the end, which help in applying the skills learnt in the chapters of the book. This is the best way for self learners, I feel. I would appreciate some similar resource which connects all concepts together to get the bigger picture. I have read about C, C++, C#, JAVA being used in game programming but not sure which language to go for (I have previously learnt a little of C and JAVA). I have also read about game engines but there would be various other concepts. Commonly accepted ways of learning Should 3D games like these be tried after 2D games? Are there some commonly accepted ways of learning such kind of games? Like in web development, we should go for frameworks after practising well with basic language, AJAX after getting properly done with simple page-reload processing etc. Apart from these, any useful tips (like language choices etc.) would be much appreciated. Like it is highly recommended to contribute to open source web projects for getting recognition, are there similar open source game projects? Thanks, Sandeepan

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• Oracle Database Machine and Exadata Storage Server

  - by jean-marc.gaudron(at)oracle.com

  Master Note for Oracle Database Machine and Exadata Storage Server (Doc ID 1187674.1)This Master Note is intended to provide an index and references to the most frequently used My Oracle Support Notes with respect to Oracle Exadata and Oracle Database Machine environments. This Master Note is subdivided into categories to allow for easy access and reference to notes that are applicable to your area of interest. This includes the following categories: • Database Machine and Exadata Storage Server Concepts and Overview• Database Machine and Exadata Storage Server Configuration and Administration• Database Machine and Exadata Storage Server Troubleshooting and Debugging• Database Machine and Exadata Storage Server Best Practices• Database Machine and Exadata Storage Server Patching• Database Machine and Exadata Storage Server Documentation and References• Database Machine and Exadata Storage Server Known Problems• ASM and RAC Documentation• Using My Oracle Support Effectively

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• Azure Storage Explorer

  - by kaleidoscope

  Azure Storage Explorer –  an another way to Deploy the services on Cloud Azure Storage Explorer is a useful GUI tool for inspecting and altering the data in your Azure cloud storage projects including the logs of your cloud-hosted applications. All three types of cloud storage can be viewed: blobs, queues, and tables. You can also create or delete blob/queue/table containers and items. Text blobs can be edited and all data types can be imported/exported between the cloud and local files. Table records can be imported/exported between the cloud and spreadsheet CSV files. Why Azure Storage Explorer Azure Storage Explorer is a licensed CodePlex project provided by Neudesic – a Microsoft partner.  It is a simple UI that requires you to input your blob storage name, access key and endpoints in the Storage Settings dialog. For more details please refer to the link: http://azurestorageexplorer.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=35189   Anish, S

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• Why is business-class storage so expensive?

  - by Mark Henderson

  This is a Canonical Question about the Cost of Enterprise Storage. See also the following question: What's the best way to explain storage issues to developers and other users Regarding general questions like: Why do I have to pay 50 bucks a month per extra gigabyte of storage? Our file server is always running out of space, why doesn't our sysadmin just throw an extra 1TB drive in there? Why is SAN equipment so expensive? The Answers here will attempt to provide a better understanding of how enterprise-level storage works and what influences the price. If you can expand on the Question or provide insight as to the Answer, please post.

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• TP-Link storage server accessing from Mac OS

  - by coure2011

  I have a storage/print server by TP-Link http://www.tp-link.com/en/products/details/?categoryid=232&model=TL-PS310U I just connect usb-storage to the print server and on windows I can access that usb-device from my windows computers. But how can I access that device from Mac? I found an article that I can add usb printer to mac using that device but not able to find how to access the storage device. please help me out!

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• Windows API BackupRead failing with error 50 on Windows Storage Server 2008 R2

  - by Jason F

  We have a backup application that uses the Windows API BackupRead. It works correctly on Windows Server 2003, 2008, 2008 R2. It does not work on Storage Server 2008 R2. It always fails with error 50 - The request is not supported. The documentation for BackupRead gives no indication that it will not work with Storage Server 2008 R2. Anyone else have any experience using this API on Storage Server 2008 R2?

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• When is the default storage rule not really the default storage rule?

  - by Kevin Smith

  In 11g WebCenter Content (WCC) introduced dispersion rules in the vault and weblayout directory paths to better distribute content across the directories. The dispersion rule was based on dRevClassID. The only problem with this is that dRevClassID did not remain the same when you copied content from one WCC instance to another using Archiver like in a contribution-consumption scenario. This could cause problems because the web-viewable path would not be the same between the contribution and consumption instances. In the PS5 (11.1.1.6.0) release of WCC they addressed this by configuring the File Store Provider (FSP) so that all new content would use a storage rule with a dispersion rule based on dDocName, which would stay the same when content was copied to another WCC instance. To support migration from older versions of WCC they left the default storage rule unchanged and created a new storage rule called DispByContentId and made that the default storage rule for all new content. I only stumbled upon this a while back when I was trying to change the FSP configuration so that all content used a webless storage rule. I changed the default storage rule, restarted WCC, and checked in a new content item. To my surprise the new content was not created as webless. I struggled with this for a while until I noticed there were multiple storage rules defined in the FSP configuration. When I looked at the default value for the xStorageRule field in Configuration Manager, sure enough it was no longer default, but was now DispByContentId. Once I updated the DispByContentId storage rule to webless and restarted WCC all my new content was now created using the webless storage rule, just like I wanted. I noticed when I was creating this blog post that the default storage rule is also listed on the File Store Provider Information page, but I guess I didn't see that when I originally did this.

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• Shared storage solution for our sql server backups

  - by Gokhan

  We have 3 clustered sql servers. We have 5+ multi terrabyte databases and their backup files (compressed using quest litespeed) are hitting over 600gb each, We are required to keep at least a week or two weeks (if we can) of weekly full backups and then 6 days differential backups, and a week or 2 weeks worth of log backups local. We are currently limited to 2TB volumes from our san team, we can have multiple volumes but they are expensive ($200 per raw TB per month) and having to deal with many backup volumes instead of a single big volume is difficult. I think if we could have a shared network storage of 20TB+ raid 10 or so for all our servers for keeping the backups and another department will copy them to tape from the network storage and delete files according to the retention period would be good, if this box would be a build in operating system (even unix a complete file storage system) that would be good. What do you guys think, does this make sense to you, is there any manufacturer that sells a storage product like that which that work in a clustered environment? Thank you

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• Whole map design vs. tiles array design

  - by Mikalichov

  I am working on a 2D RPG, which will feature the usual dungeon/town maps (pre-generated). I am using tiles, that I will then combine to make the maps. My original plan was to assemble the tiles using Photoshop, or some other graphic program, in order to have one bigger picture that I could then use as a map. However, I have read on several places people talking about how they used arrays to build their map in the engine (so you give an array of x tiles to your engine, and it assemble them as a map). I can understand how it's done, but it seems a lot more complicated to implement, and I can't see obvious avantages. What is the most common method, and what are advantages/disadvantages of each?

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• Server 2012 Storage Pools, Raid Controller... can the Storage Pool deal with it?

  - by TomTom

  Before trying it out - I don't find any documentation. Given that Storage Pools have serious performance problems with parity, and do not rebalance data at the moment when you add discs, my preferred way to use them would be as think provisioned space, ISCSI targets - with every "Pool" running against 1 RAID that comes from a Raid controller (who also introduces SSD read and write caching - another thing missing from Storage Pools). The main question is - how does a Storage Pool handle the change in the underlying disc that can happen? I mostly talk about OCE (Online Capacity Expansion), where a disc after an expansion suddenly reports a larger space. Standard Windows allows you to use this additional space (and expand the partitions). How does a storage pool handle it?

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• ADO and Two Way Storage Tiering

  - by Andy-Oracle

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 We get asked the following question about Automatic Data Optimization (ADO) storage tiering quite a bit. Can you tier back to the original location if the data gets hot again? The answer is yes but not with standard Automatic Data Optimization policies, at least not reliably. That's not how ADO is meant to operate. ADO is meant to mirror a traditional view of Information Lifecycle Management (ILM) where data will be very volatile when first created, will become less active or cool, and then will eventually cease to be accessed at all (i.e. cold). I think the reason this question gets asked is because customers realize that many of their business processes are cyclical and the thinking goes that those segments that only get used during month end or year-end cycles could sit on lower cost storage when not being used. Unfortunately this doesn't fit very well with the ADO storage tiering model. ADO storage tiering is based on the amount of free and used space in the source tablespace. There are two parameters that control this behavior, TBS_PERCENT_USED and TBS_PERCENT_FREE. When the space in the tablespace exceeds the TBS_PERCENT_USED value then segments specified in storage tiering clause(s) can be moved until the percent of free space reaches the TBS_PERCENT_FREE value. It is worth mentioning that no checks are made for available space in the target tablespace. Now, it is certainly possible to create custom functions to control storage tiering, but this can get complicated. The biggest problem is insuring that there is enough space to move the segment back to tier 1 storage, assuming that that's the goal. This isn't as much of a problem when moving from tier 1 to tier 2 storage because there is typically more tier 2 storage available. At least that's the premise since it is supposed to be less costly, lower performing and higher capacity storage. In either case though, if there isn't enough space then the operation fails. In the case of a customized function, the question becomes do you attempt to free the space so the move can be made or do you just stop and return false so that the move cannot take place? This is really the crux of the issue. Once you cross into this territory you're really going to have to implement two-way hierarchical storage and the whole point of ADO was to provide automatic storage tiering. You're probably better off using heat map and/or business access requirements and building your own hierarchical storage management infrastructure if you really want two way storage tiering. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size: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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• Why is hosted storage so expensive?

  - by Mark Henderson

  There are many questions on Server Fault asking why server storage is so expensive. e.g. Why do I have to pay 50 bucks a month per extra gigabyte of storage or Our file server is always running out of space, why doesn't our sysadmin just throw an extra 1TB drive in there? These questions usually come from people who lack an understanding of how enterprise-level storage works and what influences the price. This question is designed to be the "question to end all questions" regarding the price of enterprise storage.

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• Better Understand the 'Strategy' Design Pattern

  - by Imran Omar Bukhsh

  Greetings Hope you all are doing great. I have been interested in design patterns for a while and started reading 'Head First Design Patterns'. I started with the first pattern called the 'Strategy' pattern. I went through the problem outlined in the images below and first tried to propose a solution myself so I could really grasp the importance of the pattern. So my question is that why is my solution ( below ) to the problem outlined in the images below not good enough. What are the good / bad points of my solution vs the pattern? What makes the pattern clearly the only viable solution ? Thanks for you input, hope it will help me better understand the pattern. MY SOLUTION Parent Class: DUCK <?php class Duck { public $swimmable; public $quackable; public $flyable; function display() { echo "A Duck Looks Like This<BR/>"; } function quack() { if($this->quackable==1) { echo("Quack<BR/>"); } } function swim() { if($this->swimmable==1) { echo("Swim<BR/>"); } } function fly() { if($this->flyable==1) { echo("Fly<BR/>"); } } } ?> INHERITING CLASS: MallardDuck <?php class MallardDuck extends Duck { function MallardDuck() { $this->quackable = 1; $this->swimmable = 1; } function display() { echo "A Mallard Duck Looks Like This<BR/>"; } } ?> INHERITING CLASS: WoddenDecoyDuck <?php class WoddenDecoyDuck extends Duck { function woddendecoyduck() { $this->quackable = 0; $this->swimmable = 0; } function display() { echo "A Wooden Decoy Duck Looks Like This<BR/>"; } } Thanking you for your input. Imran

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• Game software design

  - by L. De Leo

  I have been working on a simple implementation of a card game in object oriented Python/HTML/Javascript and building on the top of Django. At this point the game is in its final stage of development but, while spotting a big issue about how I was keeping the application state (basically using a global variable), I reached the point that I'm stuck. The thing is that ignoring the design flaw, in a single-threaded environment such as under the Django development server, the game works perfectly. While I tried to design classes cleanly and keep methods short I now have in front of me an issue that has been keeping me busy for the last 2 days and that countless print statements and visual debugging hasn't helped me spot. The reason I think has to do with some side-effects of functions and to solve it I've been wondering if maybe refactoring the code entirely with static classes that keep no state and just passing the state around might be a good option to keep side-effects under control. Or maybe trying to program it in a functional programming style (although I'm not sure Python allows for a purely functional style). I feel that now there's already too many layers that the software (which I plan to make incredibly more complex by adding non trivial features) has already become unmanageable. How would you suggest I re-take control of my code-base that (despite being still only at < 1000 LOC) seems to have taken a life of its own?

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• How far to go with Domain Driven Design?

  - by synti

  I've read a little about domain driven design and the usage of a rich domain model, as described by Martin Fowler, and I've decided to put it in practice in a personal project, instead of using transaction scripts. Everything went fine until UI implementation started. The thing is some views will use rich components that are backed up by unusual models and, thus, I must transform the domain model into what is used by those components. And that transformation is specially "complex" in the view-to-domain portion, up to the point that some business logic is involved. Wich brings me to the questioning: where should I do these adaptations? So far I've got the following conclusions: Doing it in the presentation layer is good because, well, if that layer imposes restrictions in it's model, then it should be the one to handle them. But it's bad because there'll be some business leakage. If I do it on the services objects (controllers, actions, whatever), then it'd be good because there won't be any change to the domain API just because of presentation layer, but it's bad because then I'd have transaction scripts, wich is not the intended design. Finally, if I do it on the domain model, there'd be no leakage of business logic at all. But in the future I could expect an explosion of the API into a series of methods designed just to handle that view-model <- domain-model adaptation. I hope I could make myself clear on this.

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• DDD Model Design and Repository Persistence Performance Considerations

  - by agarhy

  So I have been reading about DDD for some time and trying to figure out the best approach on several issues. I tend to agree that I should design my model in a persistent agnostic manner. And that repositories should load and persist my models in valid states. But are these approaches realistic practically? I mean its normal for a model to hold a reference to a collection of another type. Persisting that model should mean persist the entire collection. Fine. But do I really need to load the entire collection every time I load the model? Probably not. So I can have specialized repositories. Some that load maybe a subset of the object graph via DTOs and others that load the entire object graph. But when do I use which? If I have DTOs, what's stopping client code from directly calling them and completely bypassing the model? I can have mappers and factories to create my models from DTOs maybe? But depending on the design of my models that might not always work. Or it might not allow my models to be created in a valid state. What's the correct approach here?

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