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  • SMTP POP3 & PST. Acronyms from Hades.

    - by mikef
    A busy SysAdmin will occasionally have reason to curse SMTP. It is, certainly, one of the strangest events in the history of IT that such a deeply flawed system, designed originally purely for campus use, should have reached its current dominant position. The explanation was that it was the first open-standard email system, so SMTP/POP3 became the internet standard. We are, in consequence, dogged with a system with security weaknesses so extreme that messages are sent in plain text and you have no real assurance as to who the message came from anyway (SMTP-AUTH hasn't really caught on). Even without the security issues, the use of SMTP in an office environment provides a management nightmare to all commercial users responsible for complying with all regulations that control the conduct of business: such as tracking, retaining, and recording company documents. SMTP mail developed from various Unix-based systems designed for campus use that took the mail analogy so literally that mail messages were actually delivered to the users, using a 'store and forward' mechanism. This meant that, from the start, the end user had to store, manage and delete messages. This is a problem that has passed through all the releases of MS Outlook: It has to be able to manage mail locally in the dreaded PST file. As a stand-alone system, Outlook is flawed by its neglect of any means of automatic backup. Previous Outlook PST files actually blew up without warning when they reached the 2 Gig limit and became corrupted and inaccessible, leading to a thriving industry of 3rd party tools to clear up the mess. Microsoft Exchange is, of course, a server-based system. Emails are less likely to be lost in such a system if it is properly run. However, there is nothing to stop users from using local PSTs as well. There is the additional temptation to load emails into mobile devices, or USB keys for off-line working. The result is that the System Administrator is faced by a complex hybrid system where backups have to be taken from Servers, and PCs scattered around the network, where duplication of emails causes storage issues, and document retention policies become impossible to manage. If one adds to that the complexity of mobile phone email readers and mail synchronization, the problem is daunting. It is hardly surprising that the mood darkens when SysAdmins meet and discuss PST Hell. If you were promoted to the task of tormenting the souls of the damned in Hades, what aspects of the management of Outlook would you find most useful for your task? I'd love to hear from you. Cheers, Michael

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  • MSSQL 2000 installation error: Setup failed to configure the server. Refer to the server error logs.

    - by kaneuniversal
    I'm trying to install MSSQL 2000 on a virtual Windows 2003 instance. However, every time I run the install program, it fails to start the service. This is the error log: 21:46:50 C:\Program Files\Microsoft SQL Server\80\Tools\Binn\cnfgsvr.exe -F "C:\WINDOWS\sqlstp.log" -I MSSQLSERVER -V 1 -M 0 -Q "SQL_Latin1_General_CP1_CI_AS" -H 131408 -U sa -P ############################################################################### Starting Service ... SQL_Latin1_General_CP1_CI_AS -m -Q -T4022 -T3659 Connecting to Server ... driver={sql server};server=xxxxxxxxxx;UID=sa;PWD=;database=master [Microsoft][ODBC SQL Server Driver]Timeout expired driver={sql server};server=xxxxxxxxxx;UID=sa;PWD=;database=master [Microsoft][ODBC SQL Server Driver]Timeout expired driver={sql server};server=xxxxxxxxxx;UID=sa;PWD=;database=master [Microsoft][ODBC SQL Server Driver]Timeout expired SQL Server configuration failed. ############################################################################### 21:49:34 Process Exit Code: (-1) 22:19:04 Setup failed to configure the server. Refer to the server error logs and C:\WINDOWS\sqlstp.log for more information. 22:19:04 Action CleanUpInstall: 22:19:04 C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\1\SqlSetup\Bin\scm.exe -Silent 1 -Action 4 -Service SQLSERVERAGENT 22:19:05 Process Exit Code: (1060) The specified service does not exist as an installed service. 22:19:05 C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\1\SqlSetup\Bin\scm.exe -Silent 1 -Action 4 -Service MSSQLSERVER 22:19:05 Process Exit Code: (0) 22:19:05 StatsGenerate returned: 2 22:19:05 StatsGenerate (0x0,0x1,0xf00000,0x200,1033,303,0x0,0x1,0,0,0 22:19:05 StatsGenerate -1,Administrator) 22:19:05 Installation Failed. Has anyone had this problem? Any ideas about how to fix it? Thanks very much, Michael

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  • Mustek 1200 CP driver SFC4.SYS bluescreens with BAD_POOL_HEADER

    - by Slink84
    I have Windows XP SP2. Recently it started bluescreening right after starting up with 'BAD_POOL_HEADER', 0x00000019 error caused by SFC4.SYS driver. After googling for a while I've found out that this is my Mustek's 1200 CP scanner driver. Booting in safe mode and uninstalling it solved the problem... And created another one: now I can't use my scanner. The weird thing is, that it has been working for a while on this PC without any problems. It all started suddenly, and I can't remember installing anything that might have affected it. Reverting to several earlier system restore points didn't help. I've tried re-installing it from the Mustek website, just in case if my copy got corrupted or infected by a virus, but it did not help - it still bluescreens. Also, I've installed Avast and scanned my PC - there were no viruses found. If anyone had such a problem before or has an idea what might have caused it, please help. ED: @Michael Todd: ...try installing on another PC... I've installed it on my friends PC. He has the same OS version, with the latest updates just like mine (he wasn't too happy, even after I've assured him that it is easy to fix by uninstalling that driver :] ). It worked fine - no bluescreens or whatsoever. So I think I've narrowed it down to either BIOS settings, or some wicked driver conflict. Next thing I'm going to try is to re-install XP, or install windows 7. I'm not too happy with a prospect of mucking about with BIOS settings...

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  • K8NDRE motherboard in server fails to complete BIOS load with error 0078

    - by John
    K8NDRE motherboard with 4 sata drives, was running fine. Drives had raid-0 and raid-1 partitions, using mdadm. The onboard raid is disabled. Upon reformatting the drives, setting a new partition structure and new raid partitions, the bios fails to finish loading, with 0078 in the bottom right corner. Tried using completely new set of drives, and bios worked fine. Able to boot from a usb, format the drives, partition them, start raid, and then installed os. Reboot and received the same error from the bios, 0078. Works fine if I unplug the sata drives. Any thoughts? Physical inspection reveals no damage cables, connectors, or capacitors. Server was running happily for over a year, and this is the first problem it has had. Per Michael Hampton's answer: The drives, unjumpered and supporting sata III worked fine originally, and worked fine for formatting and having new partitions and raid installed on them. I did try jumpering one, with no change. If I put a brand new unformatted drive in, the motherboard recognizes it and I can proceed with formatting and installing. When I reboot, I get the 0078. I have 4 sata cables-the board supports 4 drives, so I tried each and no change. I am close to calling the motherboard done.

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  • GPG - why am I encrypting with subkey instead of primary key?

    - by khedron
    When encrypting a file to send to a collaborator, I see this message: gpg: using subkey XXXX instead of primary key YYYY Why would that be? I've noticed that when they send me an encrypted file, it also appears to be encrypted towards my subkey instead of my primary key. For me, this doesn't appear to be a problem; gpg (1.4.x, macosx) just handles it & moves on. But for them, with their automated tool setup, this seems to be an issue, and they've requested that I be sure to use their primary key. I've tried to do some reading, and I have the Michael Lucas's "GPG & PGP" book on order, but I'm not seeing why there's this distinction. I have read that the key used for signing and the key used for encryption would be different, but I assumed that was about public vs private keys at first. In case it was a trust/validation issue, I went through the process of comparing fingerprints and verifying, yes, I trust this key. While I was doing that, I noticed the primary & subkeys had different "usage" notes: primary: usage: SCA subkey: usage: E "E" seems likely to mean "Encryption". But, I haven't been able to find any documentation on this. Moreover, my collaborator has been using these tools & techniques for some years now, so why would this only be a problem for me?

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  • solution for an offline server

    - by dashmug
    I'm trying to setup a development server at work that will ideally be able to test drive a couple of projects in PHP, Rails, or Django (not always running at the same time). I develop the apps locally on a Mac and then I'll put the projects up on this server for testing with my actual users (non-techies) before deploying to a production server. My problem is that we have a very poor internet connection (almost negligible) at work and doing the usual apt-get/yum/ports (make, clean, install) processes for setting up servers always get their packages from online repositories somewhere. I know I could probably download the source and then compile them myself but that's going to be too much of a hassle for me. I'm thinking about two solutions: Plan A: Run a server VM on my Mac and then use this VM as the source repository for the offline server. I've read about Ubuntu's apt-proxy and it seems to be good enough though I haven't tried it yet. I'm not sure if this is possible but can I simply do apt-get install nginx --downloadonly so that the package and its dependencies will be downloaded into my VM and my server can use the VM as the source repo for apt-get? Plan B: Run a server VM on my Mac (which I can setup/update easily when I'm home) and then clone the VM to the offline development server. Maybe I should simply make the server a VM host so I can simply copy the VM over. I think this is okay for the first-time setup but subsequent updates will take too long (cloning the VM image). If I was working on Windows, I imagine it'd be easier because most services have an installer file that I can download and then run at the server. If you could suggest another way, it would be much appreciated. Update: From Michael Hampton's answer, I found a possible solution which is apt-cacher. I also found this page on Ubuntu's website. I wonder if there is a better tool than this one.

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  • Speed up SQL Server queries with PREFETCH

    - by Akshay Deep Lamba
    Problem The SAN data volume has a throughput capacity of 400MB/sec; however my query is still running slow and it is waiting on I/O (PAGEIOLATCH_SH). Windows Performance Monitor shows data volume speed of 4MB/sec. Where is the problem and how can I find the problem? Solution This is another summary of a great article published by R. Meyyappan at www.sqlworkshops.com.  In my opinion, this is the first article that highlights and explains with working examples how PREFETCH determines the performance of a Nested Loop join.  First of all, I just want to recall that Prefetch is a mechanism with which SQL Server can fire up many I/O requests in parallel for a Nested Loop join. When SQL Server executes a Nested Loop join, it may or may not enable Prefetch accordingly to the number of rows in the outer table. If the number of rows in the outer table is greater than 25 then SQL will enable and use Prefetch to speed up query performance, but it will not if it is less than 25 rows. In this section we are going to see different scenarios where prefetch is automatically enabled or disabled. These examples only use two tables RegionalOrder and Orders.  If you want to create the sample tables and sample data, please visit this site www.sqlworkshops.com. The breakdown of the data in the RegionalOrders table is shown below and the Orders table contains about 6 million rows. In this first example, I am creating a stored procedure against two tables and then execute the stored procedure.  Before running the stored proceudre, I am going to include the actual execution plan. --Example provided by www.sqlworkshops.com --Create procedure that pulls orders based on City --Do not forget to include the actual execution plan CREATE PROC RegionalOrdersProc @City CHAR(20) AS BEGIN DECLARE @OrderID INT, @OrderDetails CHAR(200) SELECT @OrderID = o.OrderID, @OrderDetails = o.OrderDetails       FROM RegionalOrders ao INNER JOIN Orders o ON (o.OrderID = ao.OrderID)       WHERE City = @City END GO SET STATISTICS time ON GO --Example provided by www.sqlworkshops.com --Execute the procedure with parameter SmallCity1 EXEC RegionalOrdersProc 'SmallCity1' GO After running the stored procedure, if we right click on the Clustered Index Scan and click Properties we can see the Estimated Numbers of Rows is 24.    If we right click on Nested Loops and click Properties we do not see Prefetch, because it is disabled. This behavior was expected, because the number of rows containing the value ‘SmallCity1’ in the outer table is less than 25.   Now, if I run the same procedure with parameter ‘BigCity’ will Prefetch be enabled? --Example provided by www.sqlworkshops.com --Execute the procedure with parameter BigCity --We are using cached plan EXEC RegionalOrdersProc 'BigCity' GO As we can see from the below screenshot, prefetch is not enabled and the query takes around 7 seconds to execute. This is because the query used the cached plan from ‘SmallCity1’ that had prefetch disabled. Please note that even if we have 999 rows for ‘BigCity’ the Estimated Numbers of Rows is still 24.   Finally, let’s clear the procedure cache to trigger a new optimization and execute the procedure again. DBCC freeproccache GO EXEC RegionalOrdersProc 'BigCity' GO This time, our procedure runs under a second, Prefetch is enabled and the Estimated Number of Rows is 999.   The RegionalOrdersProc can be optimized by using the below example where we are using an optimizer hint. I have also shown some other hints that could be used as well. --Example provided by www.sqlworkshops.com --You can fix the issue by using any of the following --hints --Create procedure that pulls orders based on City DROP PROC RegionalOrdersProc GO CREATE PROC RegionalOrdersProc @City CHAR(20) AS BEGIN DECLARE @OrderID INT, @OrderDetails CHAR(200) SELECT @OrderID = o.OrderID, @OrderDetails = o.OrderDetails       FROM RegionalOrders ao INNER JOIN Orders o ON (o.OrderID = ao.OrderID)       WHERE City = @City       --Hinting optimizer to use SmallCity2 for estimation       OPTION (optimize FOR (@City = 'SmallCity2'))       --Hinting optimizer to estimate for the currnet parameters       --option (recompile)       --Hinting optimize not to use histogram rather       --density for estimation (average of all 3 cities)       --option (optimize for (@City UNKNOWN))       --option (optimize for UNKNOWN) END GO Conclusion, this tip was mainly aimed at illustrating how Prefetch can speed up query execution and how the different number of rows can trigger this.

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  • OOW 2013 Summary for Fusion Middleware Architects & Administrators by Simon Haslam

    - by JuergenKress
    OOW 2013 Summary for Fusion Middleware Architects & Administrators by Simon Haslam This September during Oracle OpenWorld 2013 the weather in San Francisco, as you see can from the photo, was exceptionally sunny. The dramatic final few days of the Americas Cup sailing competition, being held every day in the bay, coincided with the conference and meant that there was almost a holiday feel to the whole event. Here's my annual round-up of what I think was most interesting at OpenWorld 2013 for Fusion Middleware architects and administrators; I hope you find it useful and if you think I've missed something please add a comment! WebLogic and Cloud Application Foundation (CAF) The big WebLogic release of the year has already happened a few months ago with 12.1.2 so I won't duplicate that here. Will Lyons discussed the WebLogic and Coherence roadmap which essentially is that 12.1.3 will probably be released to coincide with SOA 12c next year and that 12.1.4, the next feature-rich WebLogic release, is more likely to be in 2015. This latter release will probably include full Java EE 7 support, have enhancements for multi-tenancy and further auto-scaling features to support increased density (i.e. more WebLogic usage for the same amount of hardware). There's a new Oracle Virtual Assembly Builder (OVAB) out already and an Oracle Traffic Director (OTD) 12c release round the corner too. Also of relevance to administrators is that Oracle has increased the support lifetime for Fusion Middleware 11g (e.g. WebLogic 10.3.6) so that Premier Support will now run to the end of 2018 and Extended Support until 2021 - this should remove any Oracle-driven pressure to upgrade at least. Java Mission Control Java Mission Control (JMC) is the HotSpot Java 7 version of JRockit 6 Mission Control, a very nice performance monitoring tool from Oracle's BEA acquisition. Flight Recorder is a feature built into the JVM which records diagnostic events into, typically, a circular buffer which can then be used for historical analysis, particularly in the case of a JVM crash or hang. It's been available separately for WebLogic only for perhaps a year now but, more significantly, it now includes JVM events and was bundled in with JDK7 Update 40 a few weeks ago. I attended a couple of interesting Java One sessions on JMC/Flight Recorder and have to say it's looking really good - it has all the previous JRMC features except for memory leak detector, plus some enhancements around operative sets and ECID filtering I think. Marcus also showed how you could add your own events into flight recorder by building your own event class - they are then available for graphing alongside all the other events in JMC. This uses a currently an unsupported/undocumented API, but it's also the same one that WebLogic uses for WLDF events so I imagine it is stable. I'm not sure quite whether this would be useful to custom applications, as opposed to infrastructure services or ISV packaged applications, but it was a very nice demonstration. I've been testing JMC / FR enabling on several environments recently and my confidence is growing - it feels robust and I think could very soon be part of my standard builds. Read the full article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: OOW,Simon Haslam,Oracle OpenWorld,WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

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  • Xsigo and Oracle's Storage

    - by Philippe Deverchère
    Xsigo, a virtual network infrastructure provider, has recently been acquired by Oracle. Following this acquisition, one might ask ourselves why it is important to Oracle and how Oracle's storage is going to benefit on the long term from this virtualized infrastructure layer. Well, the first thing to understand is that Virtual Networking addresses both network and storage connectivity. Oracle Virtual Networking, as the Xsigo technology is now called, connects any server to any network and storage, so this is not just about connecting servers to the Internet or Intranet. It is also for a large part connecting servers to NAS and SAN storage. Connecting servers to storage has become increasingly complex in the past few years because of the strong emergence of virtualization at the Operating System level. 50% of enterprise workloads are now virtualized, up from 18% in 2009, resulting in a strong consolidation of various applications in a high density server footprint. At the same time, server I/O capability increased 8x in the last 8 years. All this has pushed IT administrators to multiply the number of I/O connections in the back-end of their physical servers, resulting in a messy and very hard to manage networking infrastructure. Here is a typical view of a rack back-end when no virtual networking is used. We consider that today: - 75% of users have ten or more Ethernet ports per server - 85% of users have two or more SAN ports per server - 58% have had to add connectivity to a server specifically for VMs - 65% consider cable reduction a priority The average is 12 or more ports per server, resulting in an extremely complex infrastructure to manage. What Oracle wants to achieve with its Oracle Virtual Networking offering is pretty simple. The objective is to eliminate the complexity through a dramatic reduction of cabling between servers and storage/networks. It is also to provide a software based management system so that any server can be connected to any network or any storage, on demand, and without physical intervention on the infrastructure. At the end of the day, the picture on the left shows what one wants to get for the back-end of customer's racks: just a couple of connections on each physical server to provide a simple, agile and fast network infrastructure for both storage and networking access. This is exactly what the Oracle Virtual Networking solution does. It transforms a complex, error-prone, difficult to manage and expensive networking infrastructure into a simple, high performance and agile solution for the data center. Practically speaking, and for the sake of simplicity, imagine that each server just hosts a minimal number of physical InfiniBand HCAs (Host Channel Adapter) with two links (for redundancy) onto the Oracle Fabric Interconnect director. Using the Oracle Fabric Manager software, you'll then be able to create virtual NICs and HBAs (called vNIC and vHBA) that will be seen by the servers as standard NICs and HBAs and associate them to networks and storage systems which are physically connected to the back-end of the director through standard Fibre Channel and Ethernet GbE/10GbE ports. In addition to this incredibly simple "at-a-click" connectivity capability, the Oracle Virtual Networking solution offers powerful features such as network isolation, Quality of Service, advanced performance monitoring and non-disruptive reconfiguration, migration and scalability of networking infrastructure. So let's go back now to our initial question: why is Oracle Virtual Networking especially important to Oracle's storage solutions? After all, one could connect any storage in the back-end of the Oracle Fabric Interconnect directors, right? The answer is pretty simple: since Oracle owns both the virtualized networking infrastructure and the storage (ZFS-SA, Pillar Axiom and tape), it is possible to imagine several ways in the future to add value when it comes to connect storage to a virtualized storage network: enhanced storage capabilities, converged management between storage and network, improved diagnostic capabilities and optimized integration resulting in higher performance and unique features/functions. Of course, all this is not going to be done overnight, and future will tell us is which evolutions come first. But there is little doubt that the integration of Xsigo within Oracle is going to create opportunities for Oracle's storage!

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  • Cocos2d Box2d how to shoot an object inside the screen

    - by Ahoura Ghotbi
    I have the code below : - (id) initWithGame:(mainGame*)game { if ((self = [super init])) { isTouchEnabled_ = YES; self.game = game; CGSize size = [[CCDirector sharedDirector] winSize]; screenH = size.height; screenW = size.width; character = [CCSprite spriteWithFile:@"o.png"]; character.position = ccp( size.width /2 , size.height/2 ); character.contentSize = CGSizeMake(72, 79); [self addChild:character z:10 tag:1]; _body = NULL; _radius = 14.0f; // Create ball body and shape b2BodyDef ballBodyDef; ballBodyDef.type = b2_dynamicBody; ballBodyDef.position.Set(100/PTM_RATIO, 100/PTM_RATIO); ballBodyDef.userData = character; _body = _game.world->CreateBody(&ballBodyDef); b2CircleShape circle; circle.m_radius = 26.0/PTM_RATIO; b2FixtureDef ballShapeDef; ballShapeDef.shape = &circle; ballShapeDef.density = 1.0f; ballShapeDef.friction = 0.2f; ballShapeDef.restitution = 0.8f; _body->CreateFixture(&ballShapeDef); [self schedule:@selector(gameChecker:)]; [self schedule:@selector(tick:)]; } return self; } - (void)gameChecker:(ccTime) dt{ if(character.position.y > 200){ [self unschedule:@selector(tick:)]; [self schedule:@selector(dropObject:)]; } } - (void)tick:(ccTime) dt { b2Vec2 force; force.Set(_body->GetLinearVelocity().x, _body->GetLinearVelocity().y+1.0f); for (b2Body* b = _game.world->GetBodyList(); b; b = b->GetNext()) { if (b->GetUserData() == character) { b->SetLinearVelocity(force); } } _game.world->Step(dt, 10, 10); for(b2Body *b = _game.world->GetBodyList(); b; b=b->GetNext()) { if (b->GetUserData() != NULL) { CCSprite *ballData = (CCSprite *)b->GetUserData(); ballData.position = ccp(b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO); ballData.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle()); } } } -(void)dropObject:(ccTime) dt{ b2Vec2 force; force.Set(_body->GetLinearVelocity().x, _body->GetLinearVelocity().y-1.0f); for (b2Body* b = _game.world->GetBodyList(); b; b = b->GetNext()) { if (b->GetUserData() == character) { b->SetLinearVelocity(force); } } _game.world->Step(dt, 10, 10); for(b2Body *b = _game.world->GetBodyList(); b; b=b->GetNext()) { if (b->GetUserData() != NULL) { CCSprite *ballData = (CCSprite *)b->GetUserData(); ballData.position = ccp(b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO); ballData.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle()); } } } I have been trying to get the effect that fruit ninja has when shooting the fruits. but it seems like its hard to get such animation so I was wondering if anyone can point me to the right direction and/or give me a sample code for a single object that gets thrown into the screen with a direction.

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  • Consolidation in a Database Cloud

    - by B R Clouse
    Consolidation of multiple databases onto a shared infrastructure is the next step after Standardization.  The potential consolidation density is a function of the extent to which the infrastructure is shared.  The three models provide increasing degrees of sharing: Server: each database is deployed in a dedicated VM. Hardware is shared, but most of the software infrastructure is not. Standardization is often applied incompletely since operating environments can be moved as-is onto the shared platform. The potential for VM sprawl is an additional downside. Database: multiple database instances are deployed on a shared software / hardware infrastructure. This model is very efficient and easily implemented with the features in the Oracle Database and supporting products. Many customers have moved to this model and achieved significant, measurable benefits. Schema: multiple schemas are deployed within a single database instance. The most efficient model, it places constraints on the environment. Usually this model will be implemented only by customers deploying their own applications.  (Note that a single deployment can combine Database and Schema consolidations.) Customer value: lower costs, better system utilization In this phase of the maturity model, under-utilized hardware can be used to host more workloads, or retired and those workloads migrated to consolidation platforms. Customers benefit from higher utilization of the hardware resources, resulting in reduced data center floor space, and lower power and cooling costs. And, the OpEx savings from Standardization are multiplied, since there are fewer physical components (both hardware and software) to manage. Customer value: higher productivity The OpEx benefits from Standardization are compounded since not only are there fewer types of things to manage, now there are fewer entities to manage. In this phase, customers discover that their IT staff has time to move away from "day-to-day" tasks and start investing in higher value activities. Database users benefit from consolidating onto shared infrastructures by relieving themselves of the requirement to maintain their own dedicated servers. Also, if the shared infrastructure offers capabilities such as High Availability / Disaster Recovery, which are often beyond the budget and skillset of a standalone database environment, then moving to the consolidation platform can provide access to those capabilities, resulting in less downtime. Capabilities / Characteristics In this phase, customers will typically deploy fixed-size clusters and consolidate on a cluster until that cluster is deemed "full," at which point a new cluster is built. Customers will define one or a few cluster architectures that are used wherever possible; occasionally there may be deployments which must be handled as exceptions. The "full" policy may be based on number of databases deployed on the cluster, or observed peak workload, etc. IT will own the provisioning of new databases on a cluster, making the decision of when and where to place new workloads. Resources may be managed dynamically, e.g., as a priority workload increases, it may be given more CPU and memory to handle the spike. Users will be charged at a fixed, relatively coarse level; or in some cases, no charging will be applied. Activities / Tasks Oracle offers several tools to plan a successful consolidation. Real Application Testing (RAT) has a feature to help plan and validate database consolidations. Enterprise Manager 12c's Cloud Management Pack for Database includes a planning module. Looking ahead, customers should start planning for the Services phase by defining the Service Catalog that will be made available for database services.

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  • Code Golf: Code 39 Bar Code

    - by gwell
    The challenge The shortest code by character count to draw an ASCII representation of a Code 39 bar code. Wikipedia article about Code 39: http://en.wikipedia.org/wiki/Code_39 Input The input will be a string of legal characters for Code 39 bar codes. This means 43 characters are valid: 0-9 A-Z (space) and -.$/+%. The * character will not appear in the input as it is used as the start and stop characters. Output Each character encoded in Code 39 bar codes have nine elements, five bars and four spaces. Bars will be represented with # characters, and spaces will be represented with the space character. Three of the nine elements will be wide. The narrow elements will be one character wide, and the wide elements will be three characters wide. A inter-character space of a single space should be added between each character pattern. The pattern should be repeated so that the height of the bar code is eight characters high. The start/stop character * (bWbwBwBwb) would be represented like this: # # ### ### # # # ### ### # # # ### ### # # # ### ### # # # ### ### # # # ### ### # # # ### ### # # # ### ### # ^ ^ ^^ ^ ^ ^ ^^^ | | || | | | ||| narrow bar -+ | || | | | ||| wide space ---+ || | | | ||| narrow bar -----+| | | | ||| narrow space ------+ | | | ||| wide bar --------+ | | ||| narrow space ----------+ | ||| wide bar ------------+ ||| narrow space --------------+|| narrow bar ---------------+| inter-character space ----------------+ The start and stop character * will need to be output at the start and end of the bar code. No quiet space will need to be included before or after the bar code. No check digit will need to be calculated. Full ASCII Code39 encoding is not required, just the standard 43 characters. No text needs to be printed below the ASCII bar code representation to identify the output contents. The character # can be replaced with another character of higher density if wanted. Using the full block character U+2588, would allow the bar code to actually scan when printed. Test cases Input: ABC Output: # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # # # ### ### # ### # # # ### # ### # # ### ### ### # # # # # ### ### # Input: 1/3 Output: # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # # # ### ### # ### # # # ### # # # # # ### ### # # # # # ### ### # Input: - $ (minus space dollar) Output: # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # # # ### ### # # # # ### ### # ### # ### # # # # # # # # ### ### # Code count includes input/output (full program).

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  • Changing the Android emulator locale automatically

    - by Christopher
    For automated testing (using Hudson) I have a script that generates a bunch of emulators for many combinations of Android OS version, screen resolution, screen density and language. This works fine, except for the language part. I need to find a way to change the Android system locale automatically. Here's some approaches I can think of, in order of preference: Extracting/editing/repacking a QEMU image directly before starting the emulator Running some sort of system-locale-changing APK on the emulator after startup Changing the locale settings on the emulator filesystem after startup Changing the locale settings in some SQLite DB on the emulator after startup Running a key sequence (via the emulator's telnet interface) that would open the settings app and change the locale Manually starting the emulator for each platform version, changing the locale by hand in the settings, saving it and archiving the images for later deployment Any ideas whether this can be done, either via the above methods or otherwise? Do you know where locale settings are persisted to/read from by the system? Solution: Thanks to dtmilano's info about the relevant properties, and some further investigation on my part, I came up with a solution even better and simpler simpler than all the ideas above! I have updated the answer below with the details.

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  • What do you mean by the expressiveness in a programming language?

    - by prosseek
    I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming language? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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  • Android Camera without Preview

    - by eyurdakul
    I am writing an android 1.5 application which starts just after boot-up. This is a service and should take a picture without preview. This app will log the light density in some areas whatever. I was able to take a picture but the picture was black. After googling like crazy, i came across a bug thread about it. If you don't generate a preview, the image will be black since android camera needs preview to setup exposure and focus. I've created a surfaceview and listener but the onSurfaceCreated event never gets fired. I guess the reason is, the surface is not being created visually. I've also seen some examples of calling the camera statically with MediaStore.CAPTURE_OR_SOMETHING which takes a picture and saves in the desired folder with two lines of code but it doesn't take a picture too. Do i need to use ipc and bindservice to call this function or do you have any suggestion to achieve my goal (taking a picture without preview) and if so, would you give me a small piece of code as example?

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  • Implementing Naïve Bayes algorithm in Java - Need some guidance

    - by techventure
    hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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  • Assistance with building an inverted-index

    - by tipu
    It's part of an information retrieval thing I'm doing for school. The plan is to create a hashmap of words using the the first two letters of the word as a key and any words with the two letters saved as a string value. So, hashmap["ba"] = "bad barley base" Once I'm done tokenizing a line I take that hashmap, serialize it, and append it to the text file named after the key. The idea is that if I take my data and spread it over hundreds of files I'll lessen the time it takes to fulfill a search by lessening the density of each file. The problem I am running into is when I'm making 100+ files in each run it happens to choke on creating a few files for whatever reason and so those entries are empty. Is there any way to make this more efficient? Is it worth continuing this, or should I abandon it? I'd like to mention I'm using PHP. The two languages I know relatively intimately are PHP and Java. I chose PHP because the front end will be very simple to do and I will be able to add features like autocompletion/suggested search without a problem. I also see no benefit in using Java. Any help is appreciated, thanks.

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  • how to define fill colours in ggplot histogram?

    - by Andreas
    I have the following simple data data <- structure(list(status = c(9, 5, 9, 10, 11, 10, 8, 6, 6, 7, 10, 10, 7, 11, 11, 7, NA, 9, 11, 9, 10, 8, 9, 10, 7, 11, 9, 10, 9, 9, 8, 9, 11, 9, 11, 7, 8, 6, 11, 10, 9, 11, 11, 10, 11, 10, 9, 11, 7, 8, 8, 9, 4, 11, 11, 8, 7, 7, 11, 11, 11, 6, 7, 11, 6, 10, 10, 9, 10, 10, 8, 8, 10, 4, 8, 5, 8, 7), statusgruppe = c(0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, NA, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0)), .Names = c("status", "statusgruppe"), class = "data.frame", row.names = c(NA, -78L )) from that I'd like to make a histogram: ggplot(data, aes(status))+ geom_histogram(aes(y=..density..), binwidth=1, colour = "black", fill="white")+ theme_bw()+ scale_x_continuous("Staus", breaks=c(min(data$status,na.rm=T), median(data$status, na.rm=T), max(data$status, na.rm=T)),labels=c("Low", "Middle", "High"))+ scale_y_continuous("Percent", formatter="percent") Now - i'd like for the bins to take colou according to value - e.g. bins with value 9 gets dark grey - everything else should be light grey. I have tried with "fill=statusgruppe", scale_fill_grey(breaks=9) etc. - but I can't get it to work. Any ideas?

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  • Calculate posterior distribution of unknown mis-classification with PRTools in MATLAB

    - by Samuel Lampa
    I'm using the PRTools MATLAB library to train some classifiers, generating test data and testing the classifiers. I have the following details: N: Total # of test examples k: # of mis-classification for each classifier and class I want to do: Calculate and plot Bayesian posterior distributions of the unknown probabilities of mis-classification (denoted q), that is, as probability density functions over q itself (so, P(q) will be plotted over q, from 0 to 1). I have that (math formulae, not matlab code!): P(q|k,N) = Posterior * Prior / Normalization constant = P(k|q,N) * P(q|N) / P(k|N) The prior is set to 1, so I only need to calculate the posterior and normalization constant. I know that the posterior can be expressed as (where B(N,k) is the binomial coefficient): P(k|q,N) = B(N,k) * q^k * (1-q)^(N-k) ... so the Normalization constant is simply an integral of the posterior above, from 0 to 1: P(k|N) = B(N,k) * integralFromZeroToOne( q^k * (1-q)^(N-k) ) (The Binomial coefficient ( B(N,k) ) can be omitted thoughappears in both the posterior and normalization constant, so it can be omitted.) Now, I've heard that the integral for the normalization constant should be able to be calculated as a series ... something like: k!(N-k)! / (N+1)! Is that correct? (I have some lecture notes from with this series, but can't figure out if it is for the normalization constant integral, or for the posterior distribution of mis-classification (q)) Also, hints are welcome as how to practically calculate this? (factorials are easily creating truncation errors right?) ... AND, how to practically calculate the final plot (the posterior distribution over q, from 0 to 1).

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  • Android application listed as compatible with Sony Xperia S but still filtered from google play

    - by mlidal
    I have published an Android application and some users are complaining that it is listed as not compatible with Sony Xperia S. According to the developer console Xperia S (LT26i) is listed as compatible. Do anyone know of any reason why the app is still filtered from google play? I have seen people reporting problems with big apk files. This app is about 20Mb in size, with the largest file being 14Mb. Quite a bit but not enough to cause problems I think... Here is the output from aapt dump badging: package: name='no.bouvet.nrkut' versionCode='4' versionName='1.0' sdkVersion:'4' targetSdkVersion:'13' uses-permission:'android.permission.ACCESS_FINE_LOCATION' uses-permission:'android.permission.ACCESS_COARSE_LOCATION' uses-permission:'android.permission.ACCESS_WIFI_STATE' uses-permission:'android.permission.ACCESS_NETWORK_STATE' uses-permission:'android.permission.INTERNET' uses-permission:'android.permission.WRITE_EXTERNAL_STORAGE' application-label:'UT.no' application-icon-120:'res/drawable-ldpi/utno_launcher.png' application-icon-160:'res/drawable-mdpi/utno_launcher.png' application-icon-240:'res/drawable-hdpi/utno_launcher.png' application-icon-320:'res/drawable-xhdpi/utno_launcher.png' application: label='UT.no' icon='res/drawable-mdpi/utno_launcher.png' launchable-activity: name='no.bouvet.nrkut.MainActivity' label='UT.no' icon='' uses-feature:'android.hardware.location' uses-feature:'android.hardware.location.gps' uses-feature:'android.hardware.location.network' uses-feature:'android.hardware.wifi' uses-feature:'android.hardware.touchscreen' uses-feature:'android.hardware.screen.portrait' main other-activities search supports-screens: 'small' 'normal' 'large' 'xlarge' supports-any-density: 'true' locales: '--_--' densities: '120' '160' '240' '320'

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  • SQL Server 2008 spatial index and CPU utilization with MapGuide Open Source 2.1

    - by Antonio de la Peña
    I have a SQL Server table with hundreds of thousands of geometry type parcels. I have made indexes on them trying different combinations of density and objects per cell settings. So far I'm settiling for LOW, LOW, MEDIUM, MEDIUM and 16 objects per cell and I made a SP that sets the bounding box according to the extents of the entities in the table. There is an incredible performance boost from queries taking almost minutes without index to less than seconds, it gets faster when the zoom is closer thus less objects are displayed. Yet the CPU utilization gets to 100% when querying for features, even when the queries themselves are fast. I'm worrying this will not fly in a production environment. I am using MapGuide Open Source 2.1 for this project, but I am positive the CPU load is caused by SQL Server. I wonder if my indexes are set properly. I haven't found any clear documentation on how to properly set them up. Every article I've read basically says "it depends..." but nothing specific. Do you have any recommendations for me, including books, articles? Thank you.

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  • What do you mean by the expressiveness in programming lanuguage?

    - by prosseek
    I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming lanuage? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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  • Handling inheritance with overriding efficiently

    - by Fyodor Soikin
    I have the following two data structures. First, a list of properties applied to object triples: Object1 Object2 Object3 Property Value O1 O2 O3 P1 "abc" O1 O2 O3 P2 "xyz" O1 O3 O4 P1 "123" O2 O4 O5 P1 "098" Second, an inheritance tree: O1 O2 O4 O3 O5 Or viewed as a relation: Object Parent O2 O1 O4 O2 O3 O1 O5 O3 O1 null The semantics of this being that O2 inherits properties from O1; O4 - from O2 and O1; O3 - from O1; and O5 - from O3 and O1, in that order of precedence. NOTE 1: I have an efficient way to select all children or all parents of a given object. This is currently implemented with left and right indexes, but hierarchyid could also work. This does not seem important right now. NOTE 2: I have tiggers in place that make sure that the "Object" column always contains all possible objects, even when they do not really have to be there (i.e. have no parent or children defined). This makes it possible to use inner joins rather than severely less effiecient outer joins. The objective is: Given a pair of (Property, Value), return all object triples that have that property with that value either defined explicitly or inherited from a parent. NOTE 1: An object triple (X,Y,Z) is considered a "parent" of triple (A,B,C) when it is true that either X = A or X is a parent of A, and the same is true for (Y,B) and (Z,C). NOTE 2: A property defined on a closer parent "overrides" the same property defined on a more distant parent. NOTE 3: When (A,B,C) has two parents - (X1,Y1,Z1) and (X2,Y2,Z2), then (X1,Y1,Z1) is considered a "closer" parent when: (a) X2 is a parent of X1, or (b) X2 = X1 and Y2 is a parent of Y1, or (c) X2 = X1 and Y2 = Y1 and Z2 is a parent of Z1 In other words, the "closeness" in ancestry for triples is defined based on the first components of the triples first, then on the second components, then on the third components. This rule establishes an unambigous partial order for triples in terms of ancestry. For example, given the pair of (P1, "abc"), the result set of triples will be: O1, O2, O3 -- Defined explicitly O1, O2, O5 -- Because O5 inherits from O3 O1, O4, O3 -- Because O4 inherits from O2 O1, O4, O5 -- Because O4 inherits from O2 and O5 inherits from O3 O2, O2, O3 -- Because O2 inherits from O1 O2, O2, O5 -- Because O2 inherits from O1 and O5 inherits from O3 O2, O4, O3 -- Because O2 inherits from O1 and O4 inherits from O2 O3, O2, O3 -- Because O3 inherits from O1 O3, O2, O5 -- Because O3 inherits from O1 and O5 inherits from O3 O3, O4, O3 -- Because O3 inherits from O1 and O4 inherits from O2 O3, O4, O5 -- Because O3 inherits from O1 and O4 inherits from O2 and O5 inherits from O3 O4, O2, O3 -- Because O4 inherits from O1 O4, O2, O5 -- Because O4 inherits from O1 and O5 inherits from O3 O4, O4, O3 -- Because O4 inherits from O1 and O4 inherits from O2 O5, O2, O3 -- Because O5 inherits from O1 O5, O2, O5 -- Because O5 inherits from O1 and O5 inherits from O3 O5, O4, O3 -- Because O5 inherits from O1 and O4 inherits from O2 O5, O4, O5 -- Because O5 inherits from O1 and O4 inherits from O2 and O5 inherits from O3 Note that the triple (O2, O4, O5) is absent from this list. This is because property P1 is defined explicitly for the triple (O2, O4, O5) and this prevents that triple from inheriting that property from (O1, O2, O3). Also note that the triple (O4, O4, O5) is also absent. This is because that triple inherits its value of P1="098" from (O2, O4, O5), because it is a closer parent than (O1, O2, O3). The straightforward way to do it is the following. First, for every triple that a property is defined on, select all possible child triples: select Children1.Id as O1, Children2.Id as O2, Children3.Id as O3, tp.Property, tp.Value from TriplesAndProperties tp -- Select corresponding objects of the triple inner join Objects as Objects1 on Objects1.Id = tp.O1 inner join Objects as Objects2 on Objects2.Id = tp.O2 inner join Objects as Objects3 on Objects3.Id = tp.O3 -- Then add all possible children of all those objects inner join Objects as Children1 on Objects1.Id [isparentof] Children1.Id inner join Objects as Children2 on Objects2.Id [isparentof] Children2.Id inner join Objects as Children3 on Objects3.Id [isparentof] Children3.Id But this is not the whole story: if some triple inherits the same property from several parents, this query will yield conflicting results. Therefore, second step is to select just one of those conflicting results: select * from ( select Children1.Id as O1, Children2.Id as O2, Children3.Id as O3, tp.Property, tp.Value, row_number() over( partition by Children1.Id, Children2.Id, Children3.Id, tp.Property order by Objects1.[depthInTheTree] descending, Objects2.[depthInTheTree] descending, Objects3.[depthInTheTree] descending ) as InheritancePriority from ... (see above) ) where InheritancePriority = 1 The window function row_number() over( ... ) does the following: for every unique combination of objects triple and property, it sorts all values by the ancestral distance from the triple to the parents that the value is inherited from, and then I only select the very first of the resulting list of values. A similar effect can be achieved with a GROUP BY and ORDER BY statements, but I just find the window function semantically cleaner (the execution plans they yield are identical). The point is, I need to select the closest of contributing ancestors, and for that I need to group and then sort within the group. And finally, now I can simply filter the result set by Property and Value. This scheme works. Very reliably and predictably. It has proven to be very powerful for the business task it implements. The only trouble is, it is awfuly slow. One might point out the join of seven tables might be slowing things down, but that is actually not the bottleneck. According to the actual execution plan I'm getting from the SQL Management Studio (as well as SQL Profiler), the bottleneck is the sorting. The problem is, in order to satisfy my window function, the server has to sort by Children1.Id, Children2.Id, Children3.Id, tp.Property, Parents1.[depthInTheTree] descending, Parents2.[depthInTheTree] descending, Parents3.[depthInTheTree] descending, and there can be no indexes it can use, because the values come from a cross join of several tables. EDIT: Per Michael Buen's suggestion (thank you, Michael), I have posted the whole puzzle to sqlfiddle here. One can see in the execution plan that the Sort operation accounts for 32% of the whole query, and that is going to grow with the number of total rows, because all the other operations use indexes. Usually in such cases I would use an indexed view, but not in this case, because indexed views cannot contain self-joins, of which there are six. The only way that I can think of so far is to create six copies of the Objects table and then use them for the joins, thus enabling an indexed view. Did the time come that I shall be reduced to that kind of hacks? The despair sets in.

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  • What is a recommended Android utility class collection?

    - by Sebastian Roth
    I often find myself writing very similar code across projects. And more often than not, I copy stuff over from old projects. Things like: Create images with round corners read density into a static variable & re-use. 4 lines.. disable / hide multiple views / remote views at once. Example: } public static void disableViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.GONE); } } public static void showViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.VISIBLE); } } I'd love to package these kind of functions into 1 letter / 2 letter class names, i.e. V.showViews(RemoteViews views, int... ids) would be easy to write & remember I hope. I'm searching for Github recommendations, links and if nothing is found, I perhaps will start a small project on github to collect.

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  • Design by Contract with Microsoft .Net Code Contract

    - by Fredrik N
    I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract   Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null.   Pre- and Postconditions   When working with DbC we are specifying pre- and postconditions.  Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT.   There are two kinds of Queries, the Basic Queries  (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration.   Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count].   1. Separate Commands and Queries   When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack.   2. Separate basic queries from derived queries There are two different kinds of queries,  the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query.   3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries.   When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   4. For each command, write a postcondition that specifies the value of every basic query.   For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called)  plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle.   5. For every query and command, decide on a suitable precondition.   We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   6. Write invariants to define unchanging properties of objects.   The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract:   public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

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