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  • Using the fsc mount option with nfsroot kernel parameter to allow FS-cache

    - by meanderix
    I'm PXE-booting a Ubuntu 10.10 system, where I specify the kernel parameters as follows: append root=/dev/nfs initrd=ubuntu-boot/initrd.img-2.6.35-24-generic nfsroot=11.22.33.44:/data/nfsroot,fsc ip=dhcp rw I need to use the mount option 'fsc' in order to use FS-cache functionality (the cachefilesd package.) However, when I try this I get the following error upon boot: nfsmount: bad option 'fsc' Why doesn't nfsmount permit this option? (It works fine when you mount manually with "mount -o fsc" after booting up.)

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  • Unable to boot Ubuntu 13.10 (nVidia GTX 770m and Intel HD 4600)

    - by Raziel Gonzalez
    Ever since I bought this laptop I've been trying to install Ubuntu on it. It came with W8 preinstalled. Up to this point, I've been able to boot in UEFI mode with a black screen. I can tell it's trying to use the nVidia card (there's a led on the computer, depending on the color you can tell which GPU is using) and if I press crtl+alt+F1 I can go to console mode. Taking this advantage I tried to install bumblebee and after a successful install the led that indicates which GPU is being used change, indicating that it switched to the Intel HD 4600 graphics. After the installation I tried to initiate the graphic interface (startx) with no success. Xorg.0.log shows the error: [ 3706.779] X.Org X Server 1.14.3 Release Date: 2013-09-12 [ 3706.782] X Protocol Version 11, Revision 0 [ 3706.783] Build Operating System: Linux 3.2.0-37-generic x86_64 Ubuntu [ 3706.783] Current Operating System: Linux ubuntu 3.11.0-12-generic #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013 x86_64 [ 3706.783] Kernel command line: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper nomodeset -- [ 3706.785] Build Date: 15 October 2013 09:23:37AM [ 3706.786] xorg-server 2:1.14.3-3ubuntu2 (For technical support please see http://www.ubuntu.com/support) [ 3706.786] Current version of pixman: 0.30.2 [ 3706.788] Before reporting problems, check http://wiki.x.org to make sure that you have the latest version. [ 3706.788] Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown. [ 3706.791] (==) Log file: "/var/log/Xorg.0.log", Time: Sat Nov 2 12:28:52 2013 [ 3706.792] (==) Using system config directory "/usr/share/X11/xorg.conf.d" [ 3706.792] (==) No Layout section. Using the first Screen section. [ 3706.792] (==) No screen section available. Using defaults. [ 3706.792] (**) |-->Screen "Default Screen Section" (0) [ 3706.792] (**) | |-->Monitor "<default monitor>" [ 3706.792] (==) No monitor specified for screen "Default Screen Section". Using a default monitor configuration. [ 3706.792] (==) Automatically adding devices [ 3706.792] (==) Automatically enabling devices [ 3706.792] (==) Automatically adding GPU devices [ 3706.792] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist. [ 3706.792] Entry deleted from font path. [ 3706.792] (WW) The directory "/usr/share/fonts/X11/100dpi/" does not exist. [ 3706.792] Entry deleted from font path. [ 3706.792] (WW) The directory "/usr/share/fonts/X11/75dpi/" does not exist. [ 3706.792] Entry deleted from font path. [ 3706.792] (WW) The directory "/usr/share/fonts/X11/100dpi" does not exist. [ 3706.792] Entry deleted from font path. [ 3706.792] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist. [ 3706.792] Entry deleted from font path. [ 3706.792] (==) FontPath set to: /usr/share/fonts/X11/misc, /usr/share/fonts/X11/Type1, built-ins [ 3706.792] (==) ModulePath set to "/usr/lib/x86_64-linux-gnu/xorg/extra-modules,/usr/lib/xorg/extra-modules,/usr/lib/xorg/modules" [ 3706.792] (II) The server relies on udev to provide the list of input devices. If no devices become available, reconfigure udev or disable AutoAddDevices. [ 3706.792] (II) Loader magic: 0x7ff680918d20 [ 3706.792] (II) Module ABI versions: [ 3706.792] X.Org ANSI C Emulation: 0.4 [ 3706.792] X.Org Video Driver: 14.1 [ 3706.792] X.Org XInput driver : 19.1 [ 3706.792] X.Org Server Extension : 7.0 [ 3706.793] (--) PCI:*(0:0:2:0) 8086:0416:1462:10e8 rev 6, Mem @ 0xf7400000/4194304, 0xb0000000/268435456, I/O @ 0x0000f000/64 [ 3706.793] (II) Open ACPI successful (/var/run/acpid.socket) [ 3706.794] Initializing built-in extension Generic Event Extension [ 3706.795] Initializing built-in extension SHAPE [ 3706.796] Initializing built-in extension MIT-SHM [ 3706.797] Initializing built-in extension XInputExtension [ 3706.797] Initializing built-in extension XTEST [ 3706.798] Initializing built-in extension BIG-REQUESTS [ 3706.799] Initializing built-in extension SYNC [ 3706.799] Initializing built-in extension XKEYBOARD [ 3706.800] Initializing built-in extension XC-MISC [ 3706.801] Initializing built-in extension SECURITY [ 3706.802] Initializing built-in extension XINERAMA [ 3706.802] Initializing built-in extension XFIXES [ 3706.803] Initializing built-in extension RENDER [ 3706.804] Initializing built-in extension RANDR [ 3706.804] Initializing built-in extension COMPOSITE [ 3706.805] Initializing built-in extension DAMAGE [ 3706.806] Initializing built-in extension MIT-SCREEN-SAVER [ 3706.806] Initializing built-in extension DOUBLE-BUFFER [ 3706.807] Initializing built-in extension RECORD [ 3706.807] Initializing built-in extension DPMS [ 3706.808] Initializing built-in extension X-Resource [ 3706.809] Initializing built-in extension XVideo [ 3706.809] Initializing built-in extension XVideo-MotionCompensation [ 3706.810] Initializing built-in extension SELinux [ 3706.811] Initializing built-in extension XFree86-VidModeExtension [ 3706.811] Initializing built-in extension XFree86-DGA [ 3706.812] Initializing built-in extension XFree86-DRI [ 3706.812] Initializing built-in extension DRI2 [ 3706.812] (II) "glx" will be loaded by default. [ 3706.812] (WW) "xmir" is not to be loaded by default. Skipping. [ 3706.812] (II) LoadModule: "dri2" [ 3706.812] (II) Module "dri2" already built-in [ 3706.812] (II) LoadModule: "glamoregl" [ 3706.813] (II) Loading /usr/lib/xorg/modules/libglamoregl.so [ 3706.813] (II) Module glamoregl: vendor="X.Org Foundation" [ 3706.813] compiled for 1.14.2.901, module version = 0.5.1 [ 3706.813] ABI class: X.Org ANSI C Emulation, version 0.4 [ 3706.813] (II) LoadModule: "glx" [ 3706.813] (II) Loading /usr/lib/xorg/modules/extensions/libglx.so [ 3706.813] (II) Module glx: vendor="X.Org Foundation" [ 3706.813] compiled for 1.14.3, module version = 1.0.0 [ 3706.813] ABI class: X.Org Server Extension, version 7.0 [ 3706.813] (==) AIGLX enabled [ 3706.814] Loading extension GLX [ 3706.814] (==) Matched intel as autoconfigured driver 0 [ 3706.814] (==) Matched vesa as autoconfigured driver 1 [ 3706.814] (==) Matched modesetting as autoconfigured driver 2 [ 3706.814] (==) Matched fbdev as autoconfigured driver 3 [ 3706.814] (==) Assigned the driver to the xf86ConfigLayout [ 3706.814] (II) LoadModule: "intel" [ 3706.814] (II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so [ 3706.814] (II) Module intel: vendor="X.Org Foundation" [ 3706.814] compiled for 1.14.3, module version = 2.99.904 [ 3706.814] Module class: X.Org Video Driver [ 3706.814] ABI class: X.Org Video Driver, version 14.1 [ 3706.814] (II) LoadModule: "vesa" [ 3706.814] (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so [ 3706.814] (II) Module vesa: vendor="X.Org Foundation" [ 3706.814] compiled for 1.14.1, module version = 2.3.2 [ 3706.814] Module class: X.Org Video Driver [ 3706.814] ABI class: X.Org Video Driver, version 14.1 [ 3706.814] (II) LoadModule: "modesetting" [ 3706.814] (II) Loading /usr/lib/xorg/modules/drivers/modesetting_drv.so [ 3706.814] (II) Module modesetting: vendor="X.Org Foundation" [ 3706.814] compiled for 1.14.1, module version = 0.8.0 [ 3706.814] Module class: X.Org Video Driver [ 3706.814] ABI class: X.Org Video Driver, version 14.1 [ 3706.814] (II) LoadModule: "fbdev" [ 3706.814] (II) Loading /usr/lib/xorg/modules/drivers/fbdev_drv.so [ 3706.815] (II) Module fbdev: vendor="X.Org Foundation" [ 3706.815] compiled for 1.14.1, module version = 0.4.3 [ 3706.815] Module class: X.Org Video Driver [ 3706.815] ABI class: X.Org Video Driver, version 14.1 [ 3706.815] (II) intel: Driver for Intel(R) Integrated Graphics Chipsets: i810, i810-dc100, i810e, i815, i830M, 845G, 854, 852GM/855GM, 865G, 915G, E7221 (i915), 915GM, 945G, 945GM, 945GME, Pineview GM, Pineview G, 965G, G35, 965Q, 946GZ, 965GM, 965GME/GLE, G33, Q35, Q33, GM45, 4 Series, G45/G43, Q45/Q43, G41, B43, HD Graphics, HD Graphics 2000, HD Graphics 3000, HD Graphics 2500, HD Graphics 4000, HD Graphics P4000, HD Graphics 4600, HD Graphics 5000, HD Graphics P4600/P4700, Iris(TM) Graphics 5100, HD Graphics 4400, HD Graphics 4200, Iris(TM) Pro Graphics 5200 [ 3706.815] (II) VESA: driver for VESA chipsets: vesa [ 3706.815] (II) modesetting: Driver for Modesetting Kernel Drivers: kms [ 3706.815] (II) FBDEV: driver for framebuffer: fbdev [ 3706.815] (--) using VT number 7 [ 3706.819] (WW) Falling back to old probe method for modesetting [ 3706.819] (EE) open /dev/dri/card0: No such file or directory [ 3706.819] (WW) Falling back to old probe method for fbdev [ 3706.819] (II) Loading sub module "fbdevhw" [ 3706.819] (II) LoadModule: "fbdevhw" [ 3706.819] (II) Loading /usr/lib/xorg/modules/libfbdevhw.so [ 3706.819] (II) Module fbdevhw: vendor="X.Org Foundation" [ 3706.819] compiled for 1.14.3, module version = 0.0.2 [ 3706.819] ABI class: X.Org Video Driver, version 14.1 [ 3706.819] (II) Loading sub module "vbe" [ 3706.819] (II) LoadModule: "vbe" [ 3706.819] (II) Loading /usr/lib/xorg/modules/libvbe.so [ 3706.819] (II) Module vbe: vendor="X.Org Foundation" [ 3706.819] compiled for 1.14.3, module version = 1.1.0 [ 3706.819] ABI class: X.Org Video Driver, version 14.1 [ 3706.819] (II) Loading sub module "int10" [ 3706.819] (II) LoadModule: "int10" [ 3706.819] (II) Loading /usr/lib/xorg/modules/libint10.so [ 3706.819] (II) Module int10: vendor="X.Org Foundation" [ 3706.819] compiled for 1.14.3, module version = 1.0.0 [ 3706.819] ABI class: X.Org Video Driver, version 14.1 [ 3706.819] (II) VESA(0): initializing int10 [ 3706.820] (EE) VESA(0): V_BIOS address 0x0 out of range [ 3706.820] (II) UnloadModule: "vesa" [ 3706.820] (II) UnloadSubModule: "int10" [ 3706.820] (II) Unloading int10 [ 3706.820] (II) UnloadSubModule: "vbe" [ 3706.820] (II) Unloading vbe [ 3706.820] (EE) Screen(s) found, but none have a usable configuration. [ 3706.820] (EE) Fatal server error: [ 3706.820] (EE) no screens found(EE) [ 3706.820] (EE) Please consult the The X.Org Foundation support at http://wiki.x.org for help. [ 3706.820] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information. [ 3706.820] (EE) [ 3706.827] (EE) Server terminated with error (1). Closing log file. I also saved the dsmeg output to see if it can be of any help. In order to be able to get to this stage I had to boot with nomodeset option and removed quiet and splash. Anyone got this same error? Any guidance? I've tried other linux distros and so far the only one that is able to boot is Opensuse 12.3 without any issues (but only when I switch to legacy mode instead of UEFI).

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  • What are the design decisions involved in choosing how to expose a Java web application?

    - by Gary Rowe
    There are many ways to expose a Java web application to the consumer: application container (JBoss etc), servlet container (Tomcat etc), OSGi (Knopflerfish etc), self-executable WAR (Winstone etc) and so on. Are there any clear considerations where one approach should be favoured over another? As an example, could a collection of self-executable WARs running as raw Unix processes outperform the same applications deployed within Tomcat taking into account administration and scalability concerns?

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  • RealTek RTL8188CE WiFi adapter doesn't connect reliably

    - by ken.ganong
    I recently bought a new system76 laptop which came pre-installed with Ubuntu 11.10. I've been having trouble with my wireless connectivity. It seems that my connection with my wireless network keeps going in and out. It is not my network--I have seen the same problem on multiple WiFi networks and at different distances and reported link qualities. OS version: Ubuntu 11.10 oneiric kernel version: 3.0.0-14-generic lspci: lspci -nnk | grep -iA2 net 04:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter [10ec:8176] (rev 01) Subsystem: Realtek Semiconductor Co., Ltd. Device [10ec:9196] Kernel driver in use: rtl8192ce -- 05:00.0 Ethernet controller [0200]: JMicron Technology Corp. JMC250 PCI Express Gigabit Ethernet Controller [197b:0250] (rev 05) Subsystem: CLEVO/KAPOK Computer Device [1558:2500] Kernel driver in use: jme iwconfig: iwconfig lo no wireless extensions. eth0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"peppermintpatty" Mode:Managed Frequency:2.462 GHz Access Point: 98:FC:11:6C:E0:22 Bit Rate=72.2 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr=2347 B Fragment thr:off Power Management:off Link Quality=49/70 Signal level=-61 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:1103 Missed beacon:0 lshw: sudo lshw -class network *-network description: Wireless interface product: RTL8188CE 802.11b/g/n WiFi Adapter vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:04:00.0 logical name: wlan0 version: 01 serial: 00:1c:7b:a1:95:04 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=rtl8192ce driverversion=3.0.0-14-generic firmware=N/A ip=192.168.1.106 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn resources: irq:18 ioport:e000(size=256) memory:f7d00000-f7d03fff *-network description: Ethernet interface product: JMC250 PCI Express Gigabit Ethernet Controller vendor: JMicron Technology Corp. physical id: 0 bus info: pci@0000:05:00.0 logical name: eth0 version: 05 serial: 00:90:f5:c0:42:b3 size: 10Mbit/s capacity: 1Gbit/s width: 32 bits clock: 33MHz capabilities: pm pciexpress msix msi bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=jme driverversion=1.0.8 duplex=half latency=0 link=no multicast=yes port=MII speed=10Mbit/s resources: irq:56 memory:f7c20000-f7c23fff ioport:d100(size=128) ioport:d000(size=256) memory:f7c10000-f7c1ffff memory:f7c00000-f7c0ffff Any help would be appreciated. The last time I've dealt with wireless issues, the most given solution was NDIS wrapper and I seem sorely out-of-date.

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  • Desktop Fun: Vacation and Travel Icon Packs

    - by Asian Angel
    Do you have an upcoming vacation, place that you would like to travel to, or a favorite destination that you have visited in the past? With an appropriate wallpaper you can help set the mood for your desktop with our Vacation and Travel Icon Packs collection. Note: To customize the icon setup on your Windows 7 & Vista systems see our article here. Using Windows XP? We have you covered here. Sneak Preview After seeing “Tiki Time! 1.0” set shown below we just could not resist putting together a nice sunset beach desktop as an example to share with you. That is definitely so relaxing to look at… Note: Wallpaper can be found here. Looking very nice close up… At the Beach *.ico format only Download Sea Shells *.ico format only Download Beach Icon Collection *.ico and .png format Download Tiki Time! 1.0 *.ico format only Download Underwater Icons *.ico format only Download Shutter Shades Icon Pack *.ico and .png format Download Life Saver *.ico format only Download Les 12 Maisons *.ico format only Download Back In Time *.ico format only Download Tourism *.ico and .png format Download The Lovely Bones *.ico format only Download Japanicons Pack *.ico and .png format, also has bonus wallpaper included! Here is what the included 1280*1024 wallpaper looks like. Download Ukrainian Motifs *.ico format only Download Las Vegas Icons *.ico format only Download Las Vegas 2 *.ico format only Download Be sure to visit our new Desktop Fun section for more customization goodness! Similar Articles Productive Geek Tips Desktop Fun: Video Game Icon PacksDesktop Fun: Sci-Fi Icons Packs Series 2Restore Missing Desktop Icons in Windows 7 or VistaAdd Home Directory Icon to the Desktop in Windows 7 or VistaQuick Help: Downloadable Show Desktop Icon for XP TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips VMware Workstation 7 Acronis Online Backup DVDFab 6 Revo Uninstaller Pro Hyperwords addon (Firefox) Backup Outlook 2010 Daily Motivator (Firefox) FetchMp3 Can Download Videos & Convert Them to Mp3 Use Flixtime To Create Video Slideshows Creating a Password Reset Disk in Windows

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  • Windows Azure Recipe: Big Data

    - by Clint Edmonson
    As the name implies, what we’re talking about here is the explosion of electronic data that comes from huge volumes of transactions, devices, and sensors being captured by businesses today. This data often comes in unstructured formats and/or too fast for us to effectively process in real time. Collectively, we call these the 4 big data V’s: Volume, Velocity, Variety, and Variability. These qualities make this type of data best managed by NoSQL systems like Hadoop, rather than by conventional Relational Database Management System (RDBMS). We know that there are patterns hidden inside this data that might provide competitive insight into market trends.  The key is knowing when and how to leverage these “No SQL” tools combined with traditional business such as SQL-based relational databases and warehouses and other business intelligence tools. Drivers Petabyte scale data collection and storage Business intelligence and insight Solution The sketch below shows one of many big data solutions using Hadoop’s unique highly scalable storage and parallel processing capabilities combined with Microsoft Office’s Business Intelligence Components to access the data in the cluster. Ingredients Hadoop – this big data industry heavyweight provides both large scale data storage infrastructure and a highly parallelized map-reduce processing engine to crunch through the data efficiently. Here are the key pieces of the environment: Pig - a platform for analyzing large data sets that consists of a high-level language for expressing data analysis programs, coupled with infrastructure for evaluating these programs. Mahout - a machine learning library with algorithms for clustering, classification and batch based collaborative filtering that are implemented on top of Apache Hadoop using the map/reduce paradigm. Hive - data warehouse software built on top of Apache Hadoop that facilitates querying and managing large datasets residing in distributed storage. Directly accessible to Microsoft Office and other consumers via add-ins and the Hive ODBC data driver. Pegasus - a Peta-scale graph mining system that runs in parallel, distributed manner on top of Hadoop and that provides algorithms for important graph mining tasks such as Degree, PageRank, Random Walk with Restart (RWR), Radius, and Connected Components. Sqoop - a tool designed for efficiently transferring bulk data between Apache Hadoop and structured data stores such as relational databases. Flume - a distributed, reliable, and available service for efficiently collecting, aggregating, and moving large log data amounts to HDFS. Database – directly accessible to Hadoop via the Sqoop based Microsoft SQL Server Connector for Apache Hadoop, data can be efficiently transferred to traditional relational data stores for replication, reporting, or other needs. Reporting – provides easily consumable reporting when combined with a database being fed from the Hadoop environment. Training These links point to online Windows Azure training labs where you can learn more about the individual ingredients described above. Hadoop Learning Resources (20+ tutorials and labs) Huge collection of resources for learning about all aspects of Apache Hadoop-based development on Windows Azure and the Hadoop and Windows Azure Ecosystems SQL Azure (7 labs) Microsoft SQL Azure delivers on the Microsoft Data Platform vision of extending the SQL Server capabilities to the cloud as web-based services, enabling you to store structured, semi-structured, and unstructured data. See my Windows Azure Resource Guide for more guidance on how to get started, including links web portals, training kits, samples, and blogs related to Windows Azure.

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  • Game Development Blog Aggregators [duplicate]

    - by Eric Richards
    This question already has an answer here: Game development Blogs [closed] 57 answers I'm a big fan of link collection blogs like Alvin Ashcraft's Morning Dew, Jason Haley's Interesting Finds, and Chris Alcock's The Morning Brew for aggregating interesting blogs on .Net related development stuff. I'd like to find something similar for game development blogs. I follow GameDev.net's articles and developer journals, and #AltDevBlogADay, but would love to see some more, if anyone knows of any interesting links.

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  • Where should I redirect (removed) phishing pages

    - by tinjaw
    I was unfortunately the victim of a PHP exploit. Looking through my webserver logs, people are still attempting to reach the URL used in the phish. I want to redirect them to a site that will educate these people on what phishing is. My question: Is there a (generic / vendor-neutral) phishing education website that you suggest I send them to with a 301 redirect? (I assume a 301 is the best option.)

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  • Where do I file bugs for the Ubuntu One music client for Android?

    - by Jorge Castro
    I've recently started using the Ubuntu One Music streaming client for Android. From the web page it says that the android app is based on Subsonic. I want to file bugs on the app, mostly feature requests and things like that, and from looking at the screenshots, the application seems to be Subsonic preconfigured to use my U1 music collection. Is it appropriate for me to file feature requests with Subsonic, or is there a Launchpad project where we're supposed to file bugs which are then vetted and sent upstream?

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  • Can not connect to wireless on 12.04 with Intel WiFi Link 5100

    - by WiData
    I am having problem in connecting to wifi. I have dual boot (Windows 7 and Ubuntu 12.04) on my Dell Studio 15. I upgraded to 12.04 quite some time ago (at least one month) from 11.10. Everything was working fine till yesterday. Since yesterday I can see the list of available Wifi connection but does not connect to any or if connects (after hours of trying) then disconnects after few minutes. My wifi interface is Intel WiFi Link 5100 AGN. However the problem is on both Windows and Ubuntu. Here are outputs of some commands which may be useful for those interested in helping: ~$ ifconfig eth0 Link encap:Ethernet HWaddr 00:22:19:fa:65:bb 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) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:794 errors:0 dropped:0 overruns:0 frame:0 TX packets:794 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:56280 (56.2 KB) TX bytes:56280 (56.2 KB) wlan0 Link encap:Ethernet HWaddr 00:22:fb:d2:fc:ce UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:239 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:53603 (53.6 KB) Here is the output for the command sudo lshw -C network *-network description: Wireless interface product: WiFi Link 5100 vendor: Intel Corporation physical id: 0 bus info: pci@0000:04:00.0 logical name: wlan0 version: 00 serial: 00:22:fb:d2:fc:ce width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=iwlwifi driverversion=3.2.0-48-generic-pae firmware=8.83.5.1 build 33692 latency=0 link=no multicast=yes wireless=IEEE 802.11abgn resources: irq:47 memory:f8000000-f8001fff My kernel version is kernel version 3.2.0-48-generic-pae I also checked this post which was helpful. But I am not sure if what is the exact problem. Any suggestions will be helpful. Should I be changing the firmware/driver? Currently my /lib/firmware has following iwlwifi files /lib/firmware/iwlwifi-1000-5.ucode /lib/firmware/iwlwifi-5000-5.ucode /lib/firmware/iwlwifi-100-5.ucode /lib/firmware/iwlwifi-5150-2.ucode /lib/firmware/iwlwifi-105-6.ucode /lib/firmware/iwlwifi-6000-4.ucode /lib/firmware/iwlwifi-135-6.ucode /lib/firmware/iwlwifi-6000g2a-5.ucode /lib/firmware/iwlwifi-2000-6.ucode /lib/firmware/iwlwifi-6000g2a-6.ucode /lib/firmware/iwlwifi-2030-6.ucode /lib/firmware/iwlwifi-6000g2b-6.ucode /lib/firmware/iwlwifi-3945-2.ucode /lib/firmware/iwlwifi-6050-5.ucode /lib/firmware/iwlwifi-4965-2.ucode Thanks a lot for the help.

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  • Why do none-working websites look like search indexes?

    - by Asaf
    An example of this could be shown on every .tk domain that doesn't exist, just write www.givemeacookie.tk or something, you get into a fake search engine/index Now these things are all over, I use to always ignore it because it was obvious just a fake template, but it's everywhere. I was wondering, where is it originated (here it's searchmagnified, but in their website it's also something generic) ? Is there a proper name for these type of websites?

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  • What algorithm to use to fill a KenKen square board with cages?

    - by JimmyBoh
    I am working on recreating KenKen, a popular math puzzle involving a blank grid that is divided into "cages". Each cage is just a collection of adjacent squares and has a clue which is generally a number and an operand, shown below: What type of algorithm would be best to fill the square with cages? Assume the maximum number of cells per cage would be 3 and the board is 4x4 in size, like in the example above.

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  • Is there any way to test how will the site perform under load

    - by Pankaj Upadhyay
    I have made an Asp.net MVC website and hosted it on a shared hosting provider. Since my website surrounds a very generic idea, it might have number of concurrent users sometime in future. So, I was thinking of a way to test my website for on-load performance. Like how will the site perform when 100 or 1000 users are online at the same time and surfing the website. This will also make me understand whether my LINQ queries are well written or not.

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  • How to customize the ubuntu gnome 3 desktop?

    - by Francesco
    This is maybe a stupid question, but how can I choose my own background image on ubuntu gnome 3?? I click on Settings - Background - then I click on the current background preview to change it but I see only the defaults images! No + symbol to add or something. On the 'Pictures' tab there is nothing to select, I get an empty white page? I am running ubuntu gnome 13.04 3.9.6-030906-generic. Thanks!

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  • Why do non-working websites look like search indexes?

    - by Asaf
    An example of this could be shown on every .tk domain that doesn't exist, just write www.givemeacookie.tk or something, you get into a fake search engine/index Now these things are all over, I use to always ignore it because it was obvious just a fake template, but it's everywhere. I was wondering, where is it originated (here it's searchmagnified, but in their website it's also something generic) ? Is there a proper name for these type of websites?

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  • Securing WebSocket applications on Glassfish

    - by Pavel Bucek
    Today we are going to cover deploying secured WebSocket applications on Glassfish and access to these services using WebSocket Client API. WebSocket server application setup Our server endpoint might look as simple as this: @ServerEndpoint("/echo") public class EchoEndpoint { @OnMessage   public String echo(String message) {     return message + " (from your server)";   } } Everything else must be configured on container level. We can start with enabling SSL, which will require web.xml to be added to your project. For starters, it might look as following: <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee">   <security-constraint>     <web-resource-collection>       <web-resource-name>Protected resource</web-resource-name>       <url-pattern>/*</url-pattern>       <http-method>GET</http-method>     </web-resource-collection>     <!-- https -->     <user-data-constraint>       <transport-guarantee>CONFIDENTIAL</transport-guarantee>     </user-data-constraint>   </security-constraint> </web-app> This is minimal web.xml for this task - web-resource-collection just defines URL pattern and HTTP method(s) we want to put a constraint on and user-data-constraint defines that constraint, which is in our case transport-guarantee. More information about these properties and security settings for web application can be found in Oracle Java EE 7 Tutorial. I have some simple webpage attached as well, so I can test my endpoint right away. You can find it (along with complete project) in Tyrus workspace: [webpage] [whole project]. After deploying this application to Glassfish Application Server, you should be able to hit it using your favorite browser. URL where my application resides is https://localhost:8181/sample-echo-https/ (may be different, depends on other configuration). My browser warns me about untrusted certificate (I use what freshly built Glassfish provides - self signed certificates) and after adding an exception for this site, I can see my webpage and I am able to securely connect to wss://localhost:8181/sample-echo-https/echo. WebSocket client Already mentioned demo application also contains test client, but execution of this is skipped for normal build. Reason for this is that Glassfish uses these self-signed "random" untrusted certificates and you are (in most cases) not able to connect to these services without any additional settings. Creating test WebSocket client is actually quite similar to server side, only difference is that you have to somewhere create client container and invoke connect with some additional info. Java API for WebSocket allows you to use annotated and programmatic way to construct endpoints. Server side shows the annotated case, so let's see how the programmatic approach will look. final WebSocketContainer client = ContainerProvider.getWebSocketContainer(); client.connectToServer(new Endpoint() {   @Override   public void onOpen(Session session, EndpointConfig EndpointConfig) {     try {       // register message handler - will just print out the       // received message on standard output.       session.addMessageHandler(new MessageHandler.Whole<String>() {       @Override         public void onMessage(String message) {          System.out.println("### Received: " + message);         }       });       // send a message       session.getBasicRemote().sendText("Do or do not, there is no try.");     } catch (IOException e) {       // do nothing     }   } }, ClientEndpointConfig.Builder.create().build(),    URI.create("wss://localhost:8181/sample-echo-https/echo")); This client should work with some secured endpoint with valid certificated signed by some trusted certificate authority (you can try that with wss://echo.websocket.org). Accessing our Glassfish instance will require some additional settings. You can tell Java which certificated you trust by adding -Djavax.net.ssl.trustStore property (and few others in case you are using linked sample). Complete command line when you are testing your service might need to look somewhat like: mvn clean test -Djavax.net.ssl.trustStore=$AS_MAIN/domains/domain1/config/cacerts.jks\ -Djavax.net.ssl.trustStorePassword=changeit -Dtyrus.test.host=localhost\ -DskipTests=false Where AS_MAIN points to your Glassfish instance. Note: you might need to setup keyStore and trustStore per client instead of per JVM; there is a way how to do it, but it is Tyrus proprietary feature: http://tyrus.java.net/documentation/1.2.1/user-guide.html#d0e1128. And that's it! Now nobody is able to "hear" what you are sending to or receiving from your WebSocket endpoint. There is always room for improvement, so the next step you might want to take is introduce some authentication mechanism (like HTTP Basic or Digest). This topic is more about container configuration so I'm not going to go into details, but there is one thing worth mentioning: to access services which require authorization, you might need to put this additional information to HTTP headers of first (Upgrade) request (there is not (yet) any direct support even for these fundamental mechanisms, user need to register Configurator and add headers in beforeRequest method invocation). I filed related feature request as TYRUS-228; feel free to comment/vote if you need this functionality.

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  • Send raw data to USB parallel port after upgrading to 11.10

    - by zaphod
    I have a laser cutter connected via a generic USB to parallel adapter. The laser cutter speaks HPGL, as it happens, but since this is a laser cutter and not a plotter, I usually want to generate the HPGL myself, since I care about the ordering, speed, and direction of cuts and so on. In previous versions of Ubuntu, I was able to print to the cutter by copying an HPGL file directly to the corresponding USB "lp" device. For example: cp foo.plt /dev/usblp1 Well, I just upgraded to Ubuntu 11.10 oneiric, and I can't find any "lp" devices in /dev anymore. D'oh! What's the preferred way to send raw data to a parallel port in Ubuntu? I've tried System Settings Printing + Add, hoping that I might be able to associate my device with some kind of "raw printer" driver and print to it with a command like lp -d LaserCutter foo.plt But my USB to parallel adapter doesn't seem to show up in the list. What I do see are my HP Color LaserJet, two USB-to-serial adapters, "Enter URI", and "Network Printer". Meanwhile, over in /dev, I do see /dev/ttyUSB0 and /dev/ttyUSB1 devices for the 2 USB-to-serial adapters. I don't see anything obvious corresponding to the HP printer (which was /dev/usblp0 prior to the upgrade), except for generic USB stuff. For example, sudo find /dev | grep lp produces no output. I do seem to be able to print to the HP printer just fine, though. The printer setup GUI gives it a device URI starting with "hp:" which isn't much help for the parallel adapter. The CUPS administrator's guide makes it sound like I might need to feed it a device URI of the form parallel:/dev/SOMETHING, but of course if I had a /dev/SOMETHING I'd probably just go on writing to it directly. Here's what dmesg says after I disconnect and reconnect the device from the USB port: [ 924.722906] usb 1-1.1.4: USB disconnect, device number 7 [ 959.993002] usb 1-1.1.4: new full speed USB device number 8 using ehci_hcd And here's how it shows up in lsusb -v: Bus 001 Device 008: ID 1a86:7584 QinHeng Electronics CH340S Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x1a86 QinHeng Electronics idProduct 0x7584 CH340S bcdDevice 2.52 iManufacturer 0 iProduct 2 USB2.0-Print iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 32 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x80 (Bus Powered) MaxPower 96mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 2 bInterfaceClass 7 Printer bInterfaceSubClass 1 Printer bInterfaceProtocol 2 Bidirectional iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x02 EP 2 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0020 1x 32 bytes bInterval 0 Device Status: 0x0000 (Bus Powered)

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  • Azure Service Bus - Authorization failure

    - by Michael Stephenson
    I fell into this trap earlier in the week with a mistake I made when configuring a service to send and listen on the azure service bus and I thought it would be worth a little note for future reference as I didnt find anything online about it.  After configuring everything when I ran my code sample I was getting the below error. WebHost failed to process a request.Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/28316044Exception: System.ServiceModel.ServiceActivationException: The service '/-------/BrokeredMessageService.svc' cannot be activated due to an exception during compilation.  The exception message is: Generic: There was an authorization failure. Make sure you have specified the correct SharedSecret, SimpleWebToken or Saml transport client credentials.. ---> Microsoft.ServiceBus.AuthorizationFailedException: Generic: There was an authorization failure. Make sure you have specified the correct SharedSecret, SimpleWebToken or Saml transport client credentials.   at Microsoft.ServiceBus.RelayedOnewayTcpClient.ConnectRequestReplyContext.Send(Message message, TimeSpan timeout, IDuplexChannel& channel)   at Microsoft.ServiceBus.RelayedOnewayTcpListener.RelayedOnewayTcpListenerClient.Connect(TimeSpan timeout)   at Microsoft.ServiceBus.RelayedOnewayTcpClient.EnsureConnected(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.RefcountedCommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.RelayedOnewayChannelListener.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.SocketConnectionTransportManager.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.TransportManager.Open(TimeSpan timeout, TransportChannelListener channelListener)   at Microsoft.ServiceBus.Channels.TransportManagerContainer.Open(TimeSpan timeout, SelectTransportManagersCallback selectTransportManagerCallback)   at Microsoft.ServiceBus.SocketConnectionChannelListener`2.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)   --- End of inner exception stack trace ---   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)   at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)Process Name: w3wpProcess ID: 8056As recommended by the error message I checked everything about the application configuration and also the keys and eventually I found the problem.When I set the permissions in the ACS rule group I had copied and pasted the claim name for net.windows.servicebus.action from the Azure portal and hadnt spotted the <space> character on the end of it like you sometimes pick up when copying text in the browser.  This meant that the listen and send permissions were not setup correctly which is why (as you would expect) my two applications could not connect to the service bus.So lesson learnt here, if you do copy and paste into the ACS rules just be careful you dont leave a space on the end of anything otherwise it will be difficult to spot that its configured incorrectly

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  • ANN: free DPack for VS.NET 2003/2005 v2.5.1 (3 replies)

    Hi all, I'm pleased to announce a new v2.5.1 availability of our free VS.NET 2003 and VS 2005 add ons collection called DPack. DPack includes various browser tools that allow the developer to quickly find solution's code members, types or files. Additional tools such as numbered bookmarks, solution backup and statistics, to name the few, are included as well. You can check the change log, see the ...

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  • The Sensemaking Spectrum for Business Analytics: Translating from Data to Business Through Analysis

    - by Joe Lamantia
    One of the most compelling outcomes of our strategic research efforts over the past several years is a growing vocabulary that articulates our cumulative understanding of the deep structure of the domains of discovery and business analytics. Modes are one example of the deep structure we’ve found.  After looking at discovery activities across a very wide range of industries, question types, business needs, and problem solving approaches, we've identified distinct and recurring kinds of sensemaking activity, independent of context.  We label these activities Modes: Explore, compare, and comprehend are three of the nine recognizable modes.  Modes describe *how* people go about realizing insights.  (Read more about the programmatic research and formal academic grounding and discussion of the modes here: https://www.researchgate.net/publication/235971352_A_Taxonomy_of_Enterprise_Search_and_Discovery) By analogy to languages, modes are the 'verbs' of discovery activity.  When applied to the practical questions of product strategy and development, the modes of discovery allow one to identify what kinds of analytical activity a product, platform, or solution needs to support across a spread of usage scenarios, and then make concrete and well-informed decisions about every aspect of the solution, from high-level capabilities, to which specific types of information visualizations better enable these scenarios for the types of data users will analyze. The modes are a powerful generative tool for product making, but if you've spent time with young children, or had a really bad hangover (or both at the same time...), you understand the difficult of communicating using only verbs.  So I'm happy to share that we've found traction on another facet of the deep structure of discovery and business analytics.  Continuing the language analogy, we've identified some of the ‘nouns’ in the language of discovery: specifically, the consistently recurring aspects of a business that people are looking for insight into.  We call these discovery Subjects, since they identify *what* people focus on during discovery efforts, rather than *how* they go about discovery as with the Modes. Defining the collection of Subjects people repeatedly focus on allows us to understand and articulate sense making needs and activity in more specific, consistent, and complete fashion.  In combination with the Modes, we can use Subjects to concretely identify and define scenarios that describe people’s analytical needs and goals.  For example, a scenario such as ‘Explore [a Mode] the attrition rates [a Measure, one type of Subject] of our largest customers [Entities, another type of Subject] clearly captures the nature of the activity — exploration of trends vs. deep analysis of underlying factors — and the central focus — attrition rates for customers above a certain set of size criteria — from which follow many of the specifics needed to address this scenario in terms of data, analytical tools, and methods. We can also use Subjects to translate effectively between the different perspectives that shape discovery efforts, reducing ambiguity and increasing impact on both sides the perspective divide.  For example, from the language of business, which often motivates analytical work by asking questions in business terms, to the perspective of analysis.  The question posed to a Data Scientist or analyst may be something like “Why are sales of our new kinds of potato chips to our largest customers fluctuating unexpectedly this year?” or “Where can innovate, by expanding our product portfolio to meet unmet needs?”.  Analysts translate questions and beliefs like these into one or more empirical discovery efforts that more formally and granularly indicate the plan, methods, tools, and desired outcomes of analysis.  From the perspective of analysis this second question might become, “Which customer needs of type ‘A', identified and measured in terms of ‘B’, that are not directly or indirectly addressed by any of our current products, offer 'X' potential for ‘Y' positive return on the investment ‘Z' required to launch a new offering, in time frame ‘W’?  And how do these compare to each other?”.  Translation also happens from the perspective of analysis to the perspective of data; in terms of availability, quality, completeness, format, volume, etc. By implication, we are proposing that most working organizations — small and large, for profit and non-profit, domestic and international, and in the majority of industries — can be described for analytical purposes using this collection of Subjects.  This is a bold claim, but simplified articulation of complexity is one of the primary goals of sensemaking frameworks such as this one.  (And, yes, this is in fact a framework for making sense of sensemaking as a category of activity - but we’re not considering the recursive aspects of this exercise at the moment.) Compellingly, we can place the collection of subjects on a single continuum — we call it the Sensemaking Spectrum — that simply and coherently illustrates some of the most important relationships between the different types of Subjects, and also illuminates several of the fundamental dynamics shaping business analytics as a domain.  As a corollary, the Sensemaking Spectrum also suggests innovation opportunities for products and services related to business analytics. The first illustration below shows Subjects arrayed along the Sensemaking Spectrum; the second illustration presents examples of each kind of Subject.  Subjects appear in colors ranging from blue to reddish-orange, reflecting their place along the Spectrum, which indicates whether a Subject addresses more the viewpoint of systems and data (Data centric and blue), or people (User centric and orange).  This axis is shown explicitly above the Spectrum.  Annotations suggest how Subjects align with the three significant perspectives of Data, Analysis, and Business that shape business analytics activity.  This rendering makes explicit the translation and bridging function of Analysts as a role, and analysis as an activity. Subjects are best understood as fuzzy categories [http://georgelakoff.files.wordpress.com/2011/01/hedges-a-study-in-meaning-criteria-and-the-logic-of-fuzzy-concepts-journal-of-philosophical-logic-2-lakoff-19731.pdf], rather than tightly defined buckets.  For each Subject, we suggest some of the most common examples: Entities may be physical things such as named products, or locations (a building, or a city); they could be Concepts, such as satisfaction; or they could be Relationships between entities, such as the variety of possible connections that define linkage in social networks.  Likewise, Events may indicate a time and place in the dictionary sense; or they may be Transactions involving named entities; or take the form of Signals, such as ‘some Measure had some value at some time’ - what many enterprises understand as alerts.   The central story of the Spectrum is that though consumers of analytical insights (represented here by the Business perspective) need to work in terms of Subjects that are directly meaningful to their perspective — such as Themes, Plans, and Goals — the working realities of data (condition, structure, availability, completeness, cost) and the changing nature of most discovery efforts make direct engagement with source data in this fashion impossible.  Accordingly, business analytics as a domain is structured around the fundamental assumption that sense making depends on analytical transformation of data.  Analytical activity incrementally synthesizes more complex and larger scope Subjects from data in its starting condition, accumulating insight (and value) by moving through a progression of stages in which increasingly meaningful Subjects are iteratively synthesized from the data, and recombined with other Subjects.  The end goal of  ‘laddering’ successive transformations is to enable sense making from the business perspective, rather than the analytical perspective.Synthesis through laddering is typically accomplished by specialized Analysts using dedicated tools and methods. Beginning with some motivating question such as seeking opportunities to increase the efficiency (a Theme) of fulfillment processes to reach some level of profitability by the end of the year (Plan), Analysts will iteratively wrangle and transform source data Records, Values and Attributes into recognizable Entities, such as Products, that can be combined with Measures or other data into the Events (shipment of orders) that indicate the workings of the business.  More complex Subjects (to the right of the Spectrum) are composed of or make reference to less complex Subjects: a business Process such as Fulfillment will include Activities such as confirming, packing, and then shipping orders.  These Activities occur within or are conducted by organizational units such as teams of staff or partner firms (Networks), composed of Entities which are structured via Relationships, such as supplier and buyer.  The fulfillment process will involve other types of Entities, such as the products or services the business provides.  The success of the fulfillment process overall may be judged according to a sophisticated operating efficiency Model, which includes tiered Measures of business activity and health for the transactions and activities included.  All of this may be interpreted through an understanding of the operational domain of the businesses supply chain (a Domain).   We'll discuss the Spectrum in more depth in succeeding posts.

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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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