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• Hostapd - WLAN as AP

  - by BBK

  I'm trying to start hostapd but without success. I'm using Headless Ubuntu 11.10 oneiric 3.0.0-16-server x86_64. WLAN driver is rt2800usb and my wireless nic card TP-Link TL-WN727N supports AP mode as shows below: us0# ifconfig wlan0 wlan0 Link encap:Ethernet HWaddr 00:27:19:be:cd:b6 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) us0# lsusb Bus 003 Device 003: ID 148f:3070 Ralink Technology, Corp. RT2870/RT3070 Wireless Adapter us0# lshw -C network *-network:3 description: Wireless interface physical id: 4 bus info: usb@3:2 logical name: wlan0 serial: 00:27:19:be:cd:b6 capabilities: ethernet physical wireless configuration: broadcast=yes driver=rt2800usb driverversion=3.0.0-16-server firmware=0.29 link=no multicast=yes wireless=IEEE 802.11bgn us0# hostapd /etc/hostapd/hostapd.conf Configuration file: /etc/hostapd/hostapd.conf Could not read interface wlan0 # The int flags: No such device nl80211 driver initialization failed. ELOOP: remaining socket: sock=4 eloop_data=0xd3e4a0 user_data=0xd3ecc0 handler=0x433880 ELOOP: remaining socket: sock=6 eloop_data=0xd411f0 user_data=(nil) handler=0x43cc10 us0# cat /etc/hostapd/hostapd.conf ssid=Home interface=wlan0 # The interface name of the card #driver=rt2800usb driver=nl80211 macaddr_acl=0 ieee80211n=1 channel=1 hw_mode=g auth_algs=1 ignore_broadcast_ssid=0 wpa=2 wpa_passphrase=88888888 wpa_key_mgmt=WPA-PSK wpa_pairwise=TKIP rsn_pairwise=CCMP us0# iw list Wiphy phy0 Band 1: Capabilities: 0x172 HT20/HT40 Static SM Power Save RX Greenfield RX HT20 SGI RX HT40 SGI RX STBC 1-stream Max AMSDU length: 7935 bytes No DSSS/CCK HT40 Maximum RX AMPDU length 65535 bytes (exponent: 0x003) Minimum RX AMPDU time spacing: 2 usec (0x04) HT RX MCS rate indexes supported: 0-7, 32 TX unequal modulation not supported HT TX Max spatial streams: 1 HT TX MCS rate indexes supported may differ Frequencies: * 2412 MHz [1] (20.0 dBm) * 2417 MHz [2] (20.0 dBm) * 2422 MHz [3] (20.0 dBm) * 2427 MHz [4] (20.0 dBm) * 2432 MHz [5] (20.0 dBm) * 2437 MHz [6] (20.0 dBm) * 2442 MHz [7] (20.0 dBm) * 2447 MHz [8] (20.0 dBm) * 2452 MHz [9] (20.0 dBm) * 2457 MHz [10] (20.0 dBm) * 2462 MHz [11] (20.0 dBm) * 2467 MHz [12] (20.0 dBm) (passive scanning, no IBSS) * 2472 MHz [13] (20.0 dBm) (passive scanning, no IBSS) * 2484 MHz [14] (20.0 dBm) (passive scanning, no IBSS) Bitrates (non-HT): * 1.0 Mbps * 2.0 Mbps (short preamble supported) * 5.5 Mbps (short preamble supported) * 11.0 Mbps (short preamble supported) * 6.0 Mbps * 9.0 Mbps * 12.0 Mbps * 18.0 Mbps * 24.0 Mbps * 36.0 Mbps * 48.0 Mbps * 54.0 Mbps max # scan SSIDs: 4 Supported interface modes: * IBSS * managed * AP * AP/VLAN * WDS * monitor * mesh point Supported commands: * new_interface * set_interface * new_key * new_beacon * new_station * new_mpath * set_mesh_params * set_bss * authenticate * associate * deauthenticate * disassociate * join_ibss * Unknown command (68) * Unknown command (55) * Unknown command (57) * Unknown command (59) * Unknown command (67) * set_wiphy_netns * Unknown command (65) * Unknown command (66) * connect * disconnect The question is: Why the hostapd not starting?

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• Multiple render targets and gamma correctness in Direct3D9

  - by Mario

  Let's say in a deferred renderer when building your G-Buffer you're going to render texture color, normals, depth and whatever else to your multiple render targets at once. Now if you want to have a gamma-correct rendering pipeline and you use regular sRGB textures as well as rendertargets, you'll need to apply some conversions along the way, because your filtering, sampling and calculations should happen in linear space, not sRGB space. Of course, you could store linear color in your textures and rendertargets, but this might very well introduce bad precision and banding issues. Reading from sRGB textures is easy: just set SRGBTexture = true; in your texture sampler in your HLSL effect code and the hardware does the conversion sRGB-linear for you. Writing to an sRGB rendertarget is theoretically easy, too: just set SRGBWriteEnable = true; in your effect pass in HLSL and your linear colors will be converted to sRGB space automatically. But how does this work with multiple rendertargets? I only want to do these corrections to the color textures and rendertarget, not to the normals, depth, specularity or whatever else I'll be rendering to my G-Buffer. Ok, so I just don't apply SRGBTexture = true; to my non-color textures, but when using SRGBWriteEnable = true; I'll do a gamma correction to all the values I write out to my rendertargets, no matter what I actually store there. I found some info on gamma over at Microsoft: http://msdn.microsoft.com/en-us/library/windows/desktop/bb173460%28v=vs.85%29.aspx For hardware that supports Multiple Render Targets (Direct3D 9) or Multiple-element Textures (Direct3D 9), only the first render target or element is written. If I understand correctly, SRGBWriteEnable should only be applied to the first rendertarget, but according to my tests it doesn't and is used for all rendertargets instead. Now the only alternative seems to be to handle these corrections manually in my shader and only correct the actual color output, but I'm not totally sure, that this'll not have any negative impact on color correctness. E.g. if the GPU does any blending or filtering or multisampling after the Linear-sRGB conversion... Do I even need gamma correction in this case, if I'm just writing texture color without lighting to my rendertarget? As far as I know, I DO need it because of the texture filtering and mip sampling happening in sRGB space instead, if I don't correct for it. Anyway, it'd be interesting to hear other people's solutions or thoughts about this.

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• OpenWorld Day 1

  - by Antony Reynolds

  A Day in the Life of an OpenWorld Attendee Part I Lots of people are blogging insightfully about OpenWorld so I thought I would provide some non-insightful remarks to buck the trend! With 50,000 attendees I didn’t expect to bump into too many people I knew, boy was I wrong!  I walked into the registration area and immediately was hailed by a couple of customers I had worked with a few months ago.  Moving to the employee registration area in a different hall I bumped into a colleague from the UK who was also registering.  As soon as I got my badge I bumped into a friend from Ireland!  So maybe OpenWorld isn’t so big after all! First port of call was Larrys Keynote.  As always Larry was provocative and thought provoking.  His key points were announcing the Oracle cloud offering in IaaS, PaaS and SaaS, pointing out that Fusion Apps are cloud enabled and finally announcing the 12c Database, making a big play of its new multi-tenancy features.  His contention was that multi-tenancy will simplify cloud development and provide better security by providing DB level isolation for applications and customers. Next day, Monday, was my first full day at OpenWorld.  The first session I attended was on monitoring of OSB, very interesting presentation on the benefits achieved by an Illinois area telco – US Cellular.  Great discussion of why they bought the SOA Management Packs and the benefits they are already seeing from their investment in terms of improved provisioning and time to market, as well as better performance insight and assistance with capacity planning. Craig Blitz provided a nice walkthrough of where Coherence has been and where it is going. Last night I attended the BOF on Managed File Transfer where Dave Berry replayed Oracles thoughts on providing dedicated Managed File Transfer as part of the 12c SOA release.  Dave laid out the perceived requirements and solicited feedback from the audience on what if anything was missing.  He also demoed an early version of the functionality that would simplify setting up MFT in SOA Suite and make tracking activity much easier. So much for Day 1.  I also ran into scores of old friends and colleagues and had a pleasant dinner with my friend from Ireland where I caught up on the latest news from Oracle UK.  Not bad for Day 1!

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• Attunity Oracle CDC Solution for SSIS - Beta

  We in no way work for Attunity but we were asked to test drive a beta version of their Oracle CDC solution for SSIS.  Everybody should know that moving more data than you need to takes too much time and uses resources that may better be employed doing something else.  Change data Capture is a technology that is designed to help you identify only the data that has had something done to it and you can therefore move only what is needed.  Microsoft have implemented this exact functionality into SQL server 2008 and I really like it there.  Attunity though are doing it on Oracle. DISCLAIMER: This is a BETA release and some of the parts are a bit ugly/difficult to work with.  The idea though is definitely right and the product once working does exactly what it says on the tin.  They have always been helpful to me when I have had a problem with the product and if that continues then beta testing pain should be eased somewhat. In due course I am going to be doing some videos around me using the product.  If you use Oracle and SSIS then give it a go. Here is their product description.   Attunity is a Microsoft SQL Server technology partner and the creator of the Microsoft Connectors for Oracle and Teradata, currently available in SQL Server 2008 Enterprise Edition. Attunity released a beta version of the Attunity Oracle-CDC for SSIS, a product that integrates continually changing Oracle data into SSIS, efficiently and in real-time. Attunity designed the product and integrated it into SSIS to create the simple creation of change data capture (CDC) solutions, accelerate implementation time, and reduce resources and costs. They also utilize log-based CDC so the solution has minimal impact on the Oracle source system. You can use the product to implement enterprise-class data replication, synchronization, and real-time business intelligence (BI) and data warehousing projects, quickly and efficiently, leveraging their existing SQL Server investments and resource skills. Attunity architected the product specifically for the Microsoft SSIS developer community and the product is available for both SQL Server 2005 and SQL Server 2008. It offers the following key capabilities: · Log-based, non-intrusive Oracle CDC · Full integration into SSIS and the Business Intelligence Developer Studio · Automatic generation of SSIS packages for CDC as well as full-loads of Oracle data · Filtering of Oracle tables and columns at the source · Monitoring and control of CDC processing Click to learn more and download the beta.

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• How to sort a ListView control by a column in Visual C#

  - by bconlon

  Microsoft provide an article of the same name (previously published as Q319401) and it shows a nice class 'ListViewColumnSorter ' for sorting a standard ListView when the user clicks the column header. This is very useful for String values, however for Numeric or DateTime data it gives odd results. E.g. 100 would come before 99 in an ascending sort as the string compare sees 1 < 9. So my challenge was to allow other types to be sorted. This turned out to be fairly simple as I just needed to create an inner class in ListViewColumnSorter which extends the .Net CaseInsensitiveComparer class, and then use this as the ObjectCompare member's type. Note: Ideally we would be able to use IComparer as the member's type, but the Compare method is not virtual in CaseInsensitiveComparer , so we have to create an exact type: public class ListViewColumnSorter : IComparer {     private CaseInsensitiveComparer ObjectCompare;     private MyComparer ObjectCompare;     ... rest of Microsofts class implementation... } Here is my private inner comparer class, note the 'new int Compare' as Compare is not virtual, and also note we pass the values to the base compare as the correct type (e.g. Decimal, DateTime) so they compare correctly: private class MyComparer : CaseInsensitiveComparer {     public new int Compare(object x, object y)     {         try         {             string s1 = x.ToString();             string s2 = y.ToString();               // check for a numeric column             decimal n1, n2 = 0;             if (Decimal.TryParse(s1, out n1) && Decimal.TryParse(s2, out n2))                 return base.Compare(n1, n2);             else             {                 // check for a date column                 DateTime d1, d2;                 if (DateTime.TryParse(s1, out d1) && DateTime.TryParse(s2, out d2))                     return base.Compare(d1, d2);             }         }         catch (ArgumentException) { }           // just use base string compare         return base.Compare(x, y);     } } You could extend this for other types, even custom classes as long as they support ICompare. Microsoft also have another article How to: Sort a GridView Column When a Header Is Clicked that shows this for WPF, which looks conceptually very similar. I need to test it out to see if it handles non-string types. #

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• Configurable Objects - Introduction

  - by Anthony Shorten

  One of the interesting facilities in the framework is Configurable Object functionality (it is also known as Task Optimization and also known as Cool Tools). The idea is that any implementation can create their own views of the base product objects and services and implement functionality against those new views. For example, in Oracle Utilities Customer Care and Billing, there is a Person object. That object is used to store and manage information about individuals as well as companies. In the base product you would use the Person Maintenance screen and fill in some of the screen when you wanted to register or maintain and individual as well and fill out other parts of the screen when you wanted to register or maintain a company. This can be somewhat confusing to some customers. Using Configurable Objects this can be simplified. A business object can be created that is a view of the any object. For example, you could create a Human business object which would cover the aspects of the Person object pertaining to an individual and a Company business object to cover the aspects unique to a company. Even the tag names (i.e. Field Names) in the object can be changed to be more what the implementation is familiar with. The object can also restructure the object. For example, a common identifier for an individual in the USA is the Social Security number, this value is a Person Identifier (as this varies in each country). In the new Human object you can remap the Person Identifier as a Social Security number. To define a Business Object you use a schema editor built into the browser user interface and use a mapping language to setup the business objects. An example of the language is shown below in an extract of the schema for the Human business object. As you can see there are mapping as well as formatting and other tags. This information can be built manually or using a wizard which generates the base structure for you to alter. This is all stored as meta data when saved. Once a Business object is built it can be used as basis for code, other business objects (we support inheritance), called by a screen (called a UI Map) or even as a Web Service. This is just a start with Configurable Objects as you can also create views of base services called Business Services, Service Scripts used for non-object or complex object processing (as well as other things), UI Maps used for screens and Data Areas to reuse definitions across multiple objects. Configurable Objects are powerful and I only really touched on them here. Over the next few months I hope to add lots more entries about them.

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• Keybindings for individual letter keys (not modifier-combinations) on a GtkTextView widget (Gtk3 and PyGI)

  - by monotasker

  I've been able to set several keybord shortcuts for a GtkTextView and a GtkTextEntry using the new css provider system. I'm finding, though, that I only seem to be able to establish keybindings for combinations including a modifier key. The widget doesn't respond to any bindings I set up that use: the delete key the escape key individual letter or punctuation keys alone Here's the code where I set up the css provider for the keybindings: #set up style context keys = Gtk.CssProvider() keys.load_from_path(os.path.join(data_path, 'keybindings.css')) #set up style contexts and css providers widgets = {'window': self.window, 'vbox': self.vbox, 'toolbar': self.toolbar, 'search_entry': self.search_entry, 'paned': self.paned, 'notelist_treeview': self.notelist_treeview, 'notelist_window': self.notelist_window, 'notetext_window': self.notetext_window, 'editor': self.editor, 'statusbar': self.statusbar } for l, w in widgets.iteritems(): w.get_style_context().add_provider(keys, Gtk.STYLE_PROVIDER_PRIORITY_USER) Then in keybindings.css this is an example of what works: @binding-set gtk-vi-text-view { bind "<ctrl>b" { "move-cursor" (display-lines, -5, 0) }; /* 5 lines up */ bind "<ctrl>k" { "move-cursor" (display-lines, -1, 0) }; /* down */ bind "<ctrl>j" { "move-cursor" (display-lines, 1, 0) }; /* up */ } Part of what I'm trying to do is just add proper delete-key function to the text widgets (right now the delete key does nothing at all). So if I add a binding like one of these, nothing happens: bind "Delete" { "delete-selection" () }; bind "Delete" { "delete-from-cursor" (chars, 1) }; The other part of what I want to do is more elaborate. I want to set up something like Vim's command and visual modes. So at the moment I'm just playing around with (a) setting the widget to editable=false by hitting the esc key; and (b) using homerow letters to move the cursor (as a proof-of-concept exercise). So far there's no response from the escape key or from the letter keys, even though the bindings work when I apply them to modifier-key combinations. For example, I do this in the css for the text-widget: bind "j" { "move-cursor" (display-lines, 1, 0) }; /* down */ bind "k" { "move-cursor" (display-lines, -1, 0) }; /* up */ bind "l" { "move-cursor" (logical-positions, 1, 0) }; /* right */ bind "h" { "move-cursor" (logical-positions, -1, 0) }; /* left */ but none of these bindings does anything, even if other bindings in the same set are respected. What's especially odd is that the vim-like movement bindings above are respected when I attach them to a GtkTreeView widget for navigating the tree-view options: @binding-set gtk-vi-tree-view { bind "j" { "move-cursor" (display-lines, 1) }; /* selection down */ bind "k" { "move-cursor" (display-lines, -1) }; /* selection up */ } So it seems like there are limitations or overrides of some kind on keybindings for the TextView widget (and for the del key?), but I can't find documentation of anything like that. Are these just things that can't be done with the css providers? If so, what are my alternatives for non-modified keybindings? Thanks.

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• Compute directional light frustum from view furstum points and light direction

  - by Fabian

  I'm working on a friends engine project and my task is to construct a new frustum from the light direction that overlaps the view frustum and possible shadow casters. The project already has a function that creates a frustum for this but its way to big and includes way to many casters (shadows) which can't be seen in the view frustum. Now the only parameter of this function are the normalized light direction vector and a view class which lets me extract the 8 view frustum points in world space. I don't have any additional infos about the scene. I have read some of the related Questions here but non seem to fit very well to my problem as they often just point to cascaded shadow maps. Sadly i can't use DX or openGl functions directly because this engine has a dedicated math library. From what i've read so far the steps are: Transform view frustum points into light space and find min/max x and y values (or sometimes minima and maxima of all three axis) and create a AABB using the min/max vectors. But what comes after this step? How do i transform this new AABB back to world space? What i've done so far: CVector3 Points[8], MinLight = CVector3(FLT_MAX), MaxLight = CVector3(FLT_MAX); for(int i = 0; i<8;++i){ Points[i] = Points[i] * WorldToShadowMapMatrix; MinLight = Math::Min(Points[i],MinLight); MaxLight = Math::Max(Points[i],MaxLight); } AABox box(MinLight,MaxLight); I don't think this is the right way to do it. The near plain probably has to extend into the direction of the light source to include potentional shadow casters. I've read the Microsoft article about cascaded shadow maps http://msdn.microsoft.com/en-us/library/windows/desktop/ee416307%28v=vs.85%29.aspx which also includes some sample code. But they seem to use the scenes AABB to determine the near and far plane which I can't since i cant access this information from the funtion I'm working in. Could you guys please link some example code which shows the calculation of such frustum? Thanks in advance! Additional questio: is there a way to construct a WorldToFrustum matrix that represents the above transformation?

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• WinMo&rsquo;s Demise: Notifying Next of &ldquo;Kin&rdquo;

  - by andrewbrust

  This past Monday, April 12th, Visual Studio 2010 was launched.  And on that same day, Microsoft also launched a new line of  mobile phone handsets, called Kin.  The two product launches are actually connected, but only by what they do not have in common, and what they commonly lack. On the former point: VS 2010 had released to manufacturing a couple weeks prior to its launch.  The Kin phones, meanwhile are not yet available.  We don’t even know what they will cost.  (And I think cost will be a major factor in Kin’s success…I told ChannelWeb’s Yara Souza so in this article). What do the two products both lack? Simple: Windows Mobile 6.x. For example, Kin seems to be based on the same platform as Windows Phone 7 (albeit a subset).  And VS 2010 does not support .NET Compact Framework development, which means no .NET development support for WinMo 6.x and earlier. So I guess April 12th marks Windows Phone “clean slate day.”  If you want to develop for the old phone platform, you will need to use the old version of Visual Studio (i.e. 2008).  Luckily VS 2010 and 2008 can be installed side-by-side.  But I doubt that’s much consolation to developers who still target WinMo 6.5 and earlier. Remember, WinMo isn’t just about the phone.  There are all sorts of non-telephony mobile devices, including ruggedized Pocket PC-style instruments, bar code readers and shop-floor-deployed units that don’t run Windows Phone 7 and couldn’t, even if they wanted to. Where will developers in these markets go?  I would guess some will stick with WinMo 6.x and earlier, until Windows Phone 7 can handle their workloads, assuming that does indeed happen.  Others will likely go to Google’s Android platform. For OEMs and developers who need a customizable mobile software stack, Android is turning out to be out-WinMo-ing WinMo.  As I wrote in this post, Google took Microsoft’s model (minus the licensing fees) and combined it with a modern SmartPhone feature set (rather than a late 90s/early oughts PDA paradigm), to great success.  You might say Google embraced and extended. You might also say Microsoft shunned and withdrew.

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• Thank you Geeks With Blogs for letting me join your community!

  - by GreeNTUG

  First, a link to the blog I can no longer edit because Office Live blew away my digital identity and so I can no longer log into it (the source of a loooong blog about protecting your digital identity sometime when I have more time and after it has played out to the end) http://greentug.spaces.live.com/ The following are the communities I participate in: Green & Sustainability.  I run a virtual user group on Green and Sustainability as it relates to developers and software architects.  It was located at greentug.groups.live.com, and we will need to find a new digital location for it, because I am locked out of that site as well. BizSpark Tampa Bay:  I run a BizSpark group for Microsoft technologists (meetup.com, search for BizSpark Tampa Bay) and speak at Code Camps about "No Better Time to Start Your Own Tech Business".  The meetup group facilitates a balanced presentation that is respectful to anyone wanting to start their own business, whether part-time or full-time, whether micro (just you), sustainable (grow to 2-25-ish, self-funded), high growth (get venture capital or other funding, grow it, sell it within 5 years, do it again), or hybrid (the new model going forward).  It is an "action" group, with assignments and homework if you want to get the most out of it.   At the end of a year you will either have your business on the path to where you want it to be, or you will know the steps you need to do to get it there. Women in Technology Have been participating in the Women in Technology community since 2008, my main interests in this area are mentoring women in the workplace to have them believe they can become geeks and double their income, and to mentor them with respect to starting and running their own business. Access 2010/SharePoint 2010.  This is a game-changer with respect to the Access community (the ap both devs and IT Pros love to hate, the other a-word that's not a fruit).  I conducted Lunch n Learns and Brunch n Learns around this topic before the Office 2010/SharePoint 2010 launch, and spoke on the topic at SharePoint Saturday Tampa in Nov 2009. Interested in learning more about: Using Silverlight HD Streaming out in the non-technical world (horses and equestrian sport).  Migrating to Access Web Services and VB .Net from VBA (see the Access 2010/SharePoint 2010 interest above) Windows Phone 7!  Exciting opportunities both for Green and Sustainability and for my "day job" of Environmental, Health & Safety (EHS). My day job is Environmental, Health & Safetey (EHS) consulting and software solutions, where that interfaces with the developer world is with respect to opportunities around Green and Sustainability, The SmartGrid and Juval Lowy's EnergyNet, both of which will require a lot of technology and software to make them work, The new Microsoft Partner competency for "Digital Home", and The Y2K kind of deadline around how managing chemicals in ERP systems is changing because of Global Harmonization, which hits the EU with a hard deadline on 11/30/10 (yes, this year), and hits the USA about 15 months later. Hope you enjoy my contributions to the digital geek community, and feel free to email me, [email protected] (the email leftover after my digital identity was blown away), and [email protected] (this one could go away at some future point) Best, Kathy Malone

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• Dynamic character animation - Using the physics engine or not

  - by Lex Webb

  I'm planning on building a dynamic reactant animation engine for the characters in my 2D Game. I have already built templates for a skeleton based animation system using key frames and interpolation to specify a limbs position at any given moment in time. I am using Farseer physics (an extension of Box2D) in Monogame/XNA in C# My real question lies in how i go about tying this character animation into the physics engine. I have two options: Moving limbs using physics engine - applying a interpolated force to each limb (dynamic body) in order to attempt to get it to its position as donated by the skeleton animation. Moving limbs by simply changing the position of a fixed body - Updating the new position of each limb manually, attempting to take into account physics collisions. Then stepping the physics after the animation to allow for environment interaction. Each of these methods have their distinct advantages and disadvantages. Physics based movement Advantages: Possibly more natural/realistic movement Better interaction with game objects as force applying to objects colliding with characters would be calculated for me. No need to convert to dynamic bodies when reacting to projectiles/death/fighting. Disadvantages: Possible difficulty in calculating correct amount of force to move a limb a certain distance at a constant rate. Underlying character balance system would need to be created that would need to be robust enough to prevent characters falling over at the touch of a feather. Added code complexity and processing time for the above. Static Object movement Advantages: Easy to interpolate movement of limbs between game steps Moving limbs is as simple as applying a rotation to the skeleton bone. Greater control over limbs, wont need to worry about characters falling over as all animation would be pre-defined. Disadvantages: Possible unnatural movement (Depends entirely on my animation skills!) Bad physics collision reactions with physics engine (Dynamic bodies simply slide out of the way of static objects) Need to calculate collisions with physics objects and my limbs myself and apply directional forces to them. Hard to account for slopes/stairs/non standard planes when animating walking/running animations. Need to convert objects to dynamic when reacting to projectile/fighting/death physics objects. The Question! As you can see, i have thought about this extensively, i have also had Google into physics based animation and have found mostly dissertation papers! Which is filling me with sense that it may a lot more advanced than my mathematics skills. My question is mostly subjective based on my findings above/any experience you may have: Which of the above methods should i use when creating my game? I am willing to spend the time to get a physics solution working if you think it would be possible. In the end i want to provide the most satisfying experience for the gamer, as well as a robust and dynamic system i can use to animate pretty much anything i need.

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• Tuxedo Load Balancing

  - by Todd Little

  A question I often receive is how does Tuxedo perform load balancing.  This is often asked by customers that see an imbalance in the number of requests handled by servers offering a specific service. First of all let me say that Tuxedo really does load or request optimization instead of load balancing.  What I mean by that is that Tuxedo doesn't attempt to ensure that all servers offering a specific service get the same number of requests, but instead attempts to ensure that requests are processed in the least amount of time.   Simple round robin "load balancing" can be employed to ensure that all servers for a particular service are given the same number of requests.  But the question I ask is, "to what benefit"?  Instead Tuxedo scans the queues (which may or may not correspond to servers based upon SSSQ - Single Server Single Queue or MSSQ - Multiple Server Single Queue) to determine on which queue a request should be placed.  The scan is always performed in the same order and during the scan if a queue is empty the request is immediately placed on that queue and request routing is done.  However, should all the queues be busy, meaning that requests are currently being processed, Tuxedo chooses the queue with the least amount of "work" queued to it where work is the sum of all the requests queued weighted by their "load" value as defined in the UBBCONFIG file.  What this means is that under light loads, only the first few queues (servers) process all the requests as an empty queue is often found before reaching the end of the scan.  Thus the first few servers in the queue handle most of the requests.  While this sounds non-optimal, in fact it capitalizes on the underlying operating systems and hardware behavior to produce the best possible performance.  Round Robin scheduling would spread the requests across all the available servers and thus require all of them to be in memory, and likely not share much in the way of hardware or memory caches.  Tuxedo's system maximizes the various caches and thus optimizes overall performance.  Hopefully this makes sense and now explains why you may see a few servers handling most of the requests.  Under heavy load, meaning enough load to keep all servers that can handle a request busy, you should see a relatively equal number of requests processed.  Next post I'll try and cover how this applies to servers in a clustered (MP) environment because the load balancing there is a little more complicated. Regards,Todd LittleOracle Tuxedo Chief Architect

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• Tellago releases a RESTful API for BizTalk Server business rules

  - by Charles Young

  Jesus Rodriguez has blogged recently on Tellago Devlabs' release of an open source RESTful API for BizTalk Server Business Rules.   This is an excellent addition to the BizTalk ecosystem and I congratulate Tellago on their work.   See http://weblogs.asp.net/gsusx/archive/2011/02/08/tellago-devlabs-a-restful-api-for-biztalk-server-business-rules.aspx   The Microsoft BRE was originally designed to be used as an embedded library in .NET applications. This is reflected in the implementation of the Rules Engine Update (REU) Service which is a TCP/IP service that is hosted by a Windows service running locally on each BizTalk box. The job of the REU is to distribute rules, managed and held in a central database repository, across the various servers in a BizTalk group.   The engine is therefore distributed on each box, rather than exploited behind a central rules service.   This model is all very well, but proves quite restrictive in enterprise environments. The problem is that the BRE can only run legally on licensed BizTalk boxes. Increasingly we need to deliver rules capabilities across a more widely distributed environment. For example, in the project I am working on currently, we need to surface decisioning capabilities for use within WF workflow services running under AppFabric on non-BTS boxes. The BRE does not, currently, offer any centralised rule service facilities out of the box, and hence you have to roll your own (and then run your rules services on BTS boxes which has raised a few eyebrows on my current project, as all other WCF services run on a dedicated server farm ).   Tellago's API addresses this by providing a RESTful API for querying the rules repository and executing rule sets against XML passed in the request payload. As Jesus points out in his post, using a RESTful approach hugely increases the reach of BRE-based decisioning, allowing simple invocation from code written in dynamic languages, mobile devices, etc.   We developed our own SOAP-based general-purpose rules service to handle scenarios such as the one we face on my current project. SOAP is arguably better suited to enterprise service bus environments (please don't 'flame' me - I refuse to engage in the RESTFul vs. SOAP war). For example, on my current project we use claims based authorisation across the entire service bus and use WIF and WS-Federation for this purpose.   We have extended this to the rules service. I can't release the code for commercial reasons :-( but this approach allows us to legally extend the reach of BRE far beyond the confines of the BizTalk boxes on which it runs and to provide general purpose decisioning capabilities on the bus.   So, well done Tellago.   I haven't had a chance to play with the API yet, but am looking forward to doing so.

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• Looking for tips on managing complexity with SCM repositories

  - by Philip Regan

  I am a solo developer in my department and I have a lot of individual projects, all created and managed by me. I started using SVN at ProjectLocker via Versions on the Mac a couple years ago when the variety of projects started getting unwieldy. Scenario 1: Now I have a process that is of reasonable complexity it can be broken up into multiple smaller applications and they all share files. In one phase, there is a single shared file—a constants file—that is shared between a Cocoa app and an iPhone app framework. In the second phase, the iPhone app framework will be used to create individual apps of the same ilk—controller classes and what not will all be the same—but with different content in each. The problem that I am running across is that the file in the first phase is in one repository with the application that started it, and the app framework is in a second, separate repository. Scenario 2: I have another application framework that partially relies on code from an open source project. This is all internal, non-commerical work, but again, the application framework is going to be used to create a variety of unique products and processes. So, now I have an internally managed repository and an externally managed one out of my control. I make little changes to the open source code to meet the needs of my framework when there is an update I download, but I never commit back into the external repository (though, now that I think about it, I don't think I'm committing it to mine either. Oops). The Problem I have all of this set up on my production Mac quite nicely, but duplicating and subsequently maintaining that environment on my laptop has been challenging. For Scenario 1, I've thought of merging these two projects together into the same repository because they are, for all intents and purposes inextricably linked. But, Scenario 2, I think I'm stuck just managing files as best I can. The Question I'm wondering if anyone has any tips on how to manage either of these situations, as well as other complex SCM scenarios when it comes to linking various files from various repositories together. My familiarity with SVN only comes from my work with Versions. It's been great, but I'm a little out of my depth here.

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• Design pattern for an ASP.NET project using Entity Framework

  - by MPelletier

  I'm building a website in ASP.NET (Web Forms) on top of an engine with business rules (which basically resides in a separate DLL), connected to a database mapped with Entity Framework (in a 3rd, separate project). I designed the Engine first, which has an Entity Framework context, and then went on to work on the website, which presents various reports. I believe I made a terrible design mistake in that the website has its own context (which sounded normal at first). I present this mockup of the engine and a report page's code behind: Engine (in separate DLL): public Engine { DatabaseEntities _engineContext; public Engine() { // Connection string and procedure managed in DB layer _engineContext = DatabaseEntities.Connect(); } public ChangeSomeEntity(SomeEntity someEntity, int newValue) { //Suppose there's some validation too, non trivial stuff SomeEntity.Value = newValue; _engineContext.SaveChanges(); } } And report: public partial class MyReport : Page { Engine _engine; DatabaseEntities _webpageContext; public MyReport() { _engine = new Engine(); _databaseContext = DatabaseEntities.Connect(); } public void ChangeSomeEntityButton_Clicked(object sender, EventArgs e) { SomeEntity someEntity; //Wrong way: //Get the entity from the webpage context someEntity = _webpageContext.SomeEntities.Single(s => s.Id == SomeEntityId); //Send the entity from _webpageContext to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context //Right(?) way: //Get the entity from the engine context someEntity = _engine.GetSomeEntity(SomeEntityId); //undefined above //Send the entity from the engine's context to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context } } Because the webpage has its own context, giving the Engine an entity from a different context will cause an error. I happen to know not to do that, to only give the Engine entities from its own context. But this is a very error-prone design. I see the error of my ways now. I just don't know the right path. I'm considering: Creating the connection in the Engine and passing it off to the webpage. Always instantiate an Engine, make its context accessible from a property, sharing it. Possible problems: other conflicts? Slow? Concurrency issues if I want to expand to AJAX? Creating the connection from the webpage and passing it off to the Engine (I believe that's dependency injection?) Only talking through ID's. Creates redundancy, not always practical, sounds archaic. But at the same time, I already recuperate stuff from the page as ID's that I need to fetch anyways. What would be best compromise here for safety, ease-of-use and understanding, stability, and speed?

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• TechEd 2010 Day Three: The Database Designer (Isn't)

  - by BuckWoody

  Yesterday at TechEd 2010 here in New Orleans I worked the front-booth, answering general SQL Server questions for the masses. I was actually a little surprised to find most of the questions I got were from folks that wanted to know more about Stream Insight and Master Data Services. In past conferences I've been asked a lot of "free consulting" questions, about problems folks have had from older products. I don't mind that a bit - in fact, I'm always happy to help in any way I can. But this time people are really interested in the new features in the product, and I like that they are thinking ahead, not just having to solve problems in production. My presentation was on "Database Design in an Hour". We had the usual fun, and SideShow Bob made an appearance - I kid you not. The guy in the back of the room looked just like Sideshow Bob, so I quickly held a "bes thair" contest, and he won. Duing the presentation, I explain the tools you can use to design databases. I also explain that the "Database Designer" tool in SQL Server Management Studio (SSMS) isn't truly a desinger - it uses non-standard notation, doesn't have a meta-data dictionary, and worst of all, it works at the physical level. In other words, whatever you do in SSMS will automatically change the field/table/relationship structures in the database. We fixed this in SSMS 2008 and higher by adding an option to block that, but the tool is not a good design function nonetheless. To be fair, no one I know of at Microsoft recommends that it is - but I was shocked to hear so many developers in the room defending it as a good tool. I think the main issue for someone who doesn't have to work with Relational Systems a great deal is that it can be difficult to figure out Foreign Keys. The syntax makes them look "backwards", so it's just easier to grab a field and place it on the table you want to point to. There are options. You can download a couple of free tools (CA has a community edition of ER-WIN, Quest has one, and Embarcadero also has one) and if you design more than one or two databases a year, it may be worth buying a true design tool. For years I used Visio, but we changed it so that it doesn't forward-engineer (create the DDL) any more, so it isn't a true design tool either. So investigate those free and not-so-free tools. You'll find they help you in your job - but stay away from the Database Designer in SSMS. Or I'll send Sideshow Bob over there to straighten you out. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• SSAS Tabular Workshop online and other upcoming dates (and updates!) #ssas #tabular

  - by Marco Russo (SQLBI)

  After many conferences and travels, this summer I had some time to write and prepare new sessions for the next wave of conferences. In reality I am just doing that, even if I already restarted traveling for consulting and training. So expect new content about DAX and Tabular coming in the next months! Starting to see real customer adopting Tabular is showing many new challenges and there is still a lot to learn and to create. If you still didn’t started working on Tabular, well, you should. As I always say, as a BI developer you should be able to choose between Tabular and Multidimensional, and in order to do that you should know both of them! One thing that I don’t like very much about marketing is that “Tabular is simpler”, because it’s often translated in “Tabular is for simple projects” when this last statement is not true. Actually, I see a lot of good reasons to adopt Tabular in complex data models, especially in non-traditional scenarios. I know, this is because I love to understand what are the actual limits of a technology, and I’m learning that there is simple a lot of space of improvement also for Tabular. It’s already fast, but it could be faster! How can you start? Well, first of all, by reading our book. Then, by attending to our SSAS Tabular workshop. There is an online edition of the workshop on September 3-4, 2012 (hurry up if you want to register), and there are already several dates planned for the next months (and others will be added soon!). And, of course, by installing SQL Server 2012 and trying to create models over your databases. If you are too lazy, just start with PowerPivot. As soon as you start working with Tabular or PowerPivot, you will see that there is one important skill you need: learning DAX. In the next few days I should publish an article that I’m finishing these days about best practices using SUMMARIZE and ADDCOLUMNS. If only someone published this article one year ago, I would have saved many hours of my life. But, you know, flight manuals are written in blood… and someone has to write! Stay tuned.

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• How to implement a simple bullet trajectory

  - by AirieFenix

  I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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• What are the default mount settings for mount / fstab?

  - by John Craick

  What are the default mounting options for a non root partition ? The man entry for mount says ... defaults - use default options: rw, suid, dev, exec, auto, nouser, and async. ... so that might be what we expect to see. But, unless I'm missing something, that's not what happens. I have an ext3 partition labelled "NewHome20G" which is seen as /dev/sdc6 by the system. This we can see from ... root@john-pc1204:~# blkid | grep NewHome20G /dev/sdc6: LABEL="NewHome20G" UUID="d024bad5-906c-46c0-b7d4-812daf2c9628" TYPE="ext3" I have an entry in fstab as follows ... root@john-pc1204:~# cat /etc/fstab | grep NewHome LABEL=NewHome20G /media/NewHome20G ext3 rw,nosuid,nodev,exec,users 0 2 Note the option settings that are specified in that fstab line. Now I look at how the partition is actually mounted after boot up ... root@john-pc1204:~# mount -l | grep sdc6 /dev/sdc6 on /media/NewHome20G type ext3 (rw,noexec,nosuid,nodev) [NewHome20G] ... so, when the filesystem gets mounted the exec & users options I specified seem to have been ignored. Just to be sure, I unmount sdc6, remount it and look at the mount options again ... root@john-pc1204:~# umount /dev/sdc6 root@john-pc1204:~# mount /dev/sdc6 root@john-pc1204:~# mount -l | grep sdc6 /dev/sdc6 on /media/NewHome20G type ext3 (rw,noexec,nosuid,nodev) [NewHome20G] .... same result Now I unmount the partition again, remount it specifying the exec option and look at the result ... root@john-pc1204:~# umount /dev/sdc6 root@john-pc1204:~# mount /dev/sdc6 -o exec root@john-pc1204:~# mount -l | grep sdc6 /dev/sdc6 on /media/NewHome20G type ext3 (rw,nosuid,nodev) [NewHome20G] ... and here the exec option has finally taken effect and the noexec setting has vanished. Just for interest, I re-mount the partition with the defaults option root@john-pc1204:~# umount /dev/sdc6 root@john-pc1204:~# mount /dev/sdc6 -o defaults root@john-pc1204:~# mount -l | grep sdc6 /dev/sdc6 on /media/NewHome20G type ext3 (rw,noexec,nosuid,nodev) [NewHome20G] The noexec is back, so it looks very like rw,noexec,nosuid,nodev are the default options which is NOT what man says. Why does this matter ? I have a folder full of useful scripts stored on a data disk. Because that disk is mounted noexec those scripts won't run, even though they have all been set with chmod 777. I can work round this in several ways but it's disappointing that the man entry seems to be wrong. Have I missed something obvious here or have the default options in Ubuntu changed from what they were a few versions ago ?

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• What source code organization approach helps improve modularity and API/Implementation separation?

  - by Berin Loritsch

  Few languages are as restrictive as Java with file naming standards and project structure. In that language, the file name must match the public class declared in the file, and the file must live in a directory structure matching the class package. I have mixed feelings about that approach. While I never have to guess where a file lives, there's still a lot of empty directories and artificial constraints. There's several languages that define everything about a class in one file, at least by convention. C#, Python (I think), Ruby, Erlang, etc. The commonality in most these languages is that they are object oriented, although that statement can probably be rebuffed (there is one non-OO language in the list already). Finally, there's quite a few languages mostly in the C family that have a separate header and implementation file. For C I think this makes sense, because it is one of the few ways to separate the API interface from implementations. With C it seems that feature is used to promote modularity. Yet, with C++ the way header and implementation files are split seems rather forced. You don't get the same clean API separation that you do with C, and you are forced to include some private details in the header you would rather keep only in the implementation. There's quite a few languages that have a concept that overlaps with interfaces like Java, C#, Go, etc. Some languages use what feels like a hack to provide the same concept like C# using pure virtual abstract classes. Still others don't really have an interface concept and rely on "duck" typing--for example Ruby. Ruby has modules, but those are more along the lines of mixing in behaviors to a class than they are for defining how to interact with a class. In OO terms, interfaces are a powerful way to provide separation between an API client and an API implementation. So to hurry up and ask the question, from a personal experience point of view: Does separation of header and implementation help you write more modular code, or does it get in the way? (it helps to specify the language you are referring to) Does the strict file name to class name scheme of Java help maintainability, or is it unnecessary structure for structure's sake? What would you propose to promote good API/Implementation separation and project maintenance, how would you prefer to do it?

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• SQL SERVER – A Brief Note on SET TEXTSIZE

  - by pinaldave

  Here is a small conversation I received. I thought though an old topic, indeed a thought provoking for the moment. Question: Is there any difference between LEFT function and SET TEXTSIZE? I really like this small but interesting question. The question does not specify the difference between usage or performance. Anyway we will quickly take a look at how TEXTSIZE works. You can run the following script to see how LEFT and SET TEXTSIZE works. USE TempDB GO -- Create TestTable CREATE TABLE MyTable (ID INT, MyText VARCHAR(MAX)) GO INSERT MyTable (ID, MyText) VALUES(1, REPLICATE('1234567890', 100)) GO -- Select Data SELECT ID, MyText FROM MyTable GO -- Using Left SELECT ID, LEFT(MyText, 10) MyText FROM MyTable GO -- Set TextSize SET TEXTSIZE 10; SELECT ID, MyText FROM MyTable; SET TEXTSIZE 2147483647 GO -- Clean up DROP TABLE MyTable GO Now let us see the usage result which we receive from both of the example. If you are going to ask what you should do – I really do not know. I can tell you where I will use either of the same. LEFT seems to be easy to use but again if you like to do extra work related to SET TEXTSIZE go for it. Here is how I will use SET TEXTSIZE. If I am selecting data from in my SSMS for testing or any other non production related work from a large table which has lots of columns with varchar data, I will consider using this statement to reduce the amount of the data which is retrieved in the result set. In simple word, for testing purpose I will use it. On the production server, there should be a specific reason to use the same. Here is my candid opinion – I do not think they can be directly comparable even though both of them give the exact same result. LEFT is applicable only on the column of a single SELECT statement. where it is used but it SET TEXTSIZE applies to all the columns in the SELECT and follow up SELECT statements till the SET TEXTSIZE is not modified again in the session. Uncomparable! I hope this sample example gives you idea how to use SET TEXTSIZE in your daily use. I would like to know your opinion about how and when do you use this feature. Please leave a comment. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• What are the tradeoffs for using 'partial view models'?

  - by Kenny Evitt

  I've become aware of an itch due to some non-DRY code pertaining to view model classes in an (ASP.NET) MVC web application and I'm thinking of scratching my itch by organizing code in various 'partial view model' classes. By partial-view-model, I'm referring to a class like a view model class in an analogous way to how partial views are like views, i.e. a way to encapsulate common info and behavior. To strengthen the 'analogy', and to aid in visually organizing the code in my IDE, I was thinking of naming the partial-view-model classes with a _ prefix, e.g. _ParentItemViewModel. As a slightly more concrete example of why I'm thinking along these lines, imagine that I have a domain-model-entity class ParentItem and the user-friendly descriptive text that identifies these items to users is complex enough that I'd like to encapsulate that code in a method in a _ParentItemViewModel class, for which I can then include an object or a collection of objects of that class in all the view model classes for all the views that need to include a reference to a parent item, e.g. ChildItemViewModel can have a ParentItem property of the _ParentItemViewModel class type, so that in my ChildItemView view, I can use @Model.ParentItem.UserFriendlyDescription as desired, like breadcrumbs, links, etc. Edited 2014-02-06 09:56 -05 As a second example, imagine that I have entity classes SomeKindOfBatch, SomeKindOfBatchDetail, and SomeKindOfBatchDetailEvent, and a view model class and at least one view for each of those entities. Also, the example application covers a lot more than just some-kind-of-batches, so that it wouldn't really be useful or sensible to include info about a specific some-kind-of-batch in all of the project view model classes. But, like the above example, I have some code, say for generating a string for identifying a some-kind-of-batch in a user-friendly way, and I'd like to be able to use that in several views, say as breadcrumb text or text for a link. As a third example, I'll describe another pattern I'm currently using. I have a Contact entity class, but it's a fat class, with dozens of properties, and at least a dozen references to other fat classes. However, a lot of view model classes need properties for referencing a specific contact and most of those need other properties for collections of contacts, e.g. possible contacts to be referenced for some kind of relationship. Most of these view model classes only need a small fraction of all of the available contact info, basically just an ID and some kind of user-friendly description (i.e. a friendly name). It seems to be pretty useful to have a 'partial view model' class for contacts that all of these other view model classes can use. Maybe I'm just misunderstanding 'view model class' – I understand a view model class as always corresponding to a view. But maybe I'm assuming too much.

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• Development-led security vs administration-led security in a software product?

  - by haylem

  There are cases where you have the opportunity, as a developer, to enforce stricter security features and protections on a software, though they could very well be managed at an environmental level (ie, the operating system would take care of it). Where would you say you draw the line, and what elements do you factor in your decision? Concrete Examples User Management is the OS's responsibility Not exactly meant as a security feature, but in a similar case Google Chrome used to not allow separate profiles. The invoked reason (though it now supports multiple profiles for a same OS user) used to be that user management was the operating system's responsibility. Disabling Web-Form Fields A recurrent request I see addressed online is to have auto-completion be disabled on form fields. Auto-completion didn't exist in old browsers, and was a welcome feature at the time it was introduced for people who needed to fill in forms often. But it also brought in some security concerns, and so some browsers started to implement, on top of the (obviously needed) setting in their own preference/customization panel, an autocomplete attribute for form or input fields. And this has now been introduced into the upcoming HTML5 standard. For browsers that do not listen to this attribute, strange hacks* are offered, like generating unique IDs and names for fields to avoid them from being suggested in future forms (which comes with another herd of issues, like polluting your local auto-fill cache and not preventing a password from being stored in it, but instead probably duplicating its occurences). In this particular case, and others, I'd argue that this is a user setting and that it's the user's desire and the user's responsibility to enable or disable auto-fill (by disabling the feature altogether). And if it is based on an internal policy and security requirement in a corporate environment, then substitute the user for the administrator in the above. I assume it could be counter-argued that the user may want to access non-critical applications (or sites) with this handy feature enabled, and critical applications with this feature disabled. But then I'd think that's what security zones are for (in some browsers), or the sign that you need a more secure (and dedicated) environment / account to use these applications. * I obviously don't deny the ingeniosity of the people who were forced to find workarounds, just the necessity of said workarounds. Questions That was a tad long-winded, so I guess my questions are: Would you in general consider it to be the application's (hence, the developer's) responsiblity? Where do you draw the line, if not in the "general" case?

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• Win7 is not a tablet OS, no matter what the boys in Redmond think.

  - by John Conwell

  Despite what execs at Microsoft think, Windows 7 is NOT a tablet OS.  Just because you can install some software (or OS) on a device, doesn't mean that device is meant to run that software.  This seems to be the step that the non-engineer execs at Microsoft have seem to not understood.  In order to seamlessly work with a device, the software needs to be designed with that device in mind.  That has been the problem with the Windows PDA platform, the Windows Mobil platform, and now with trying to force fit Windows 7 on a tablet.  Its just not designed for that style of interaction.   Windows is designed to be interacted with via a mouse and keyboard.  In fact, it is brilliant at that.  But, It is NOT designed to be interacted with by your fingers.  And that is why the Windows tablet failed 10 years ago, and why it will fail today.  Its not the hardware's fault like Microsoft claimed 10 years ago.  Its the User Interaction design that failed. And this is why the iPhone and Android OS's work wonderfully on a tablet.  The user interaction was designed for small screens, navigated by big fat fingers.  I love these OS's and how I interact with them.  And when I play with a touch screen Windows 7 device, I am feel like I'm playing with a brittle wana-be.  And its not the hardware's fault.  The touchscreen is very responsive.  I actually like the hardware.  But the OS and the software are just not designed to be interacted with, with my big fat fingers.  In order to be successful, Microsoft needs to start from scratch, and build a platform AND SOFTWARE specifically for use by fingers.  Thats why everyone was so excited when they though Microsoft was going to release the Courier tablet.  Because it looked like a totally different platform.  Something that might actually work.  But Windows 7...I hate to burst your bubble, but you are not a touch platform.

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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