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  • Analysis and Design for Functional Programming

    - by edalorzo
    How do you deal with analysis and design phases when you plan to develop a system using a functional programming language like Haskell? My background is in imperative/object-oriented programming languages, and therefore, I am used to use case analysis and the use of UML to document the design of program. But the thing is that UML is inherently related to the object-oriented way of doing software. And I am intrigued about what would be the best way to develop documentation and define software designs for a system that is going to be developed using functional programming. Would you still use use case analysis or perhaps structured analysis and design instead? How do software architects define the high-level design of the system so that developers follow it? What do you show to you clients or to new developers when you are supposed to present a design of the solution? How do you document a picture of the whole thing without having first to write it all? Is there anything comparable to UML in the functional world?

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  • Problems with i18n using django translation on App-Engine with Korean and Hindi

    - by Greg
    I've got a setup based on the post here, and it works perfectly. Adding more languages to the mix, it recognises them fine, except for Korean (ko) and Hindi (hi). Chinese/Japanese/Hebrew are all fine, so nothing to do with encodings/charsets I don't think. Taking a look into the django code inside the app-engine SDK, I notice that all the languages that I'm using except for ko and hi are ones that ship with django - in the default settings.py and inside the locale folder they are missing. If I copy one of the locale folders inside the /usr/local/google_appengine/lib/django[...]/conf/locale and rename it to be 'ko', then it starts working in my app, but I won't be able to replicate this modification when I deploy to app-engine, so need a bit of help understanding what I might be doing wrong. my settings.py is definitely being taken into account, as if I remove languages from there then they stop working (as they should). If I copied the django modules into my app, under 'lib' there say, could I use those instead of the ones app-engine tries to use, maybe? I'm brand new to python/django/app-engine, and developing on a Mac with Leopard, if that makes any difference. I have the latest app-engine SDK as of tuesday.

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  • Text to a PNG on App Engine (Python)

    - by Bemmu
    Note: I am cross-posting this from App Engine group because I got no answers there. As part of my site about Japan, I have a feature where the user can get a large PNG for use as desktop background that shows the user's name in Japanese. After switching my site hosting entirely to App Engine, I removed this particular feature because I could not find any way to render text to a PNG using the image API. In other words, how would you go about outputting an unicode string on top of an image of known dimensions (1024x768 for example), so that the text will be as large as possible horizontally, and centered vertically? Is there a way to do this is App Engine, or is there some external service besides App Engine that could make this easier for me, that you could recommend (besides running ImageMagick on your own server)?

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  • Best Design for creating Historic Reports on GAE

    - by charming30
    My App requires Daily reports based on various user activities. My current design does not sum the daily totals in database, which means I must compute them everytime. For example A report that shows Top 100 users based on the number of submissions they have made on a given day. For such a report If I have 50,000 users, what is the best way to create daily report? How to create monthly and yearly report with such data? If this is not a good design, then how to deal with such design decision when the metrics of the report are not clear during db design and by the time it is clear we already have huge data with limited parameters (fields). Please advice.

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  • Using an observer within an Engine

    - by Tim
    I've created an Engine which is basically used for all of our projects. Now what I want to do is add a before_create callback to all of the models in this Engine. After some searching I found out that an observer is the way to go. So, I've created this observer: class AuthObserver < ActiveRecord::Observer def before_create( record ) p record end end And now I need to add it to the application, but of course in my Engine there is no such file as application.rb. What I tried is adding it to an initializer located in /config/initializers/observers.rb Like so: Rails.application.config.active_record.observers = :auth_observer But this doesn't work, and it throws no errors. Anybody out here has experience using an observer inside an engine? Thanks a lot!

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  • Open Source PHP search engine

    - by Ravi Gupta
    I am looking for an open source search engine plugin written in php for my website(eCommerce). Before anybody answer that I have a doubt regarding the search engine. Usually search engine crawl web pages, create indexes and then use them while looking for contents. But will the same model work for eCommerce websites? Yeah, it can crawl products pages, index them but don't you think it would be better if it crawls the database directly and index the products stored in the database? And when a user search for any product, it will simply give us the rows of the table which matches the user query? May be what I am asking is a stupid question but I am new to web development, so kindly help me to understand the concept. I have looked at a search engine called Sphider but didn't get what all I have to do to make it work with an eCommerce website.

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  • Flow-Design Cheat Sheet &ndash; Part I, Notation

    - by Ralf Westphal
    You want to avoid the pitfalls of object oriented design? Then this is the right place to start. Use Flow-Oriented Analysis (FOA) and –Design (FOD or just FD for Flow-Design) to understand a problem domain and design a software solution. Flow-Orientation as described here is related to Flow-Based Programming, Event-Based Programming, Business Process Modelling, and even Event-Driven Architectures. But even though “thinking in flows” is not new, I found it helpful to deviate from those precursors for several reasons. Some aim at too big systems for the average programmer, some are concerned with only asynchronous processing, some are even not very much concerned with programming at all. What I was looking for was a design method to help in software projects of any size, be they large or tiny, involing synchronous or asynchronous processing, being local or distributed, running on the web or on the desktop or on a smartphone. That´s why I took ideas from all of the above sources and some additional and came up with Event-Based Components which later got repositioned and renamed to Flow-Design. In the meantime this has generated some discussion (in the German developer community) and several teams have started to work with Flow-Design. Also I´ve conducted quite some trainings using Flow-Orientation for design. The results are very promising. Developers find it much easier to design software using Flow-Orientation than OOAD-based object orientation. Since Flow-Orientation is moving fast and is not covered completely by a single source like a book, demand has increased for at least an overview of the current state of its notation. This page is trying to answer this demand by briefly introducing/describing every notational element as well as their translation into C# source code. Take this as a cheat sheet to put next to your whiteboard when designing software. However, please do not expect any explanation as to the reasons behind Flow-Design elements. Details on why Flow-Design at all and why in this specific way you´ll find in the literature covering the topic. Here´s a resource page on Flow-Design/Event-Based Components, if you´re able to read German. Notation Connected Functional Units The basic element of any FOD are functional units (FU): Think of FUs as some kind of software code block processing data. For the moment forget about classes, methods, “components”, assemblies or whatever. See a FU as an abstract piece of code. Software then consists of just collaborating FUs. I´m using circles/ellipses to draw FUs. But if you like, use rectangles. Whatever suites your whiteboard needs best.   The purpose of FUs is to process input and produce output. FUs are transformational. However, FUs are not called and do not call other FUs. There is no dependency between FUs. Data just flows into a FU (input) and out of it (output). From where and where to is of no concern to a FU.   This way FUs can be concatenated in arbitrary ways:   Each FU can accept input from many sources and produce output for many sinks:   Flows Connected FUs form a flow with a start and an end. Data is entering a flow at a source, and it´s leaving it through a sink. Think of sources and sinks as special FUs which conntect wires to the environment of a network of FUs.   Wiring Details Data is flowing into/out of FUs through wires. This is to allude to electrical engineering which since long has been working with composable parts. Wires are attached to FUs usings pins. They are the entry/exit points for the data flowing along the wires. Input-/output pins currently need not be drawn explicitly. This is to keep designing on a whiteboard simple and quick.   Data flowing is of some type, so wires have a type attached to them. And pins have names. If there is only one input pin and output pin on a FU, though, you don´t need to mention them. The default is Process for a single input pin, and Result for a single output pin. But you´re free to give even single pins different names.   There is a shortcut in use to address a certain pin on a destination FU:   The type of the wire is put in parantheses for two reasons. 1. This way a “no-type” wire can be easily denoted, 2. this is a natural way to describe tuples of data.   To describe how much data is flowing, a star can be put next to the wire type:   Nesting – Boards and Parts If more than 5 to 10 FUs need to be put in a flow a FD starts to become hard to understand. To keep diagrams clutter free they can be nested. You can turn any FU into a flow: This leads to Flow-Designs with different levels of abstraction. A in the above illustration is a high level functional unit, A.1 and A.2 are lower level functional units. One of the purposes of Flow-Design is to be able to describe systems on different levels of abstraction and thus make it easier to understand them. Humans use abstraction/decomposition to get a grip on complexity. Flow-Design strives to support this and make levels of abstraction first class citizens for programming. You can read the above illustration like this: Functional units A.1 and A.2 detail what A is supposed to do. The whole of A´s responsibility is decomposed into smaller responsibilities A.1 and A.2. FU A thus does not do anything itself anymore! All A is responsible for is actually accomplished by the collaboration between A.1 and A.2. Since A now is not doing anything anymore except containing A.1 and A.2 functional units are devided into two categories: boards and parts. Boards are just containing other functional units; their sole responsibility is to wire them up. A is a board. Boards thus depend on the functional units nested within them. This dependency is not of a functional nature, though. Boards are not dependent on services provided by nested functional units. They are just concerned with their interface to be able to plug them together. Parts are the workhorses of flows. They contain the real domain logic. They actually transform input into output. However, they do not depend on other functional units. Please note the usage of source and sink in boards. They correspond to input-pins and output-pins of the board.   Implicit Dependencies Nesting functional units leads to a dependency tree. Boards depend on nested functional units, they are the inner nodes of the tree. Parts are independent, they are the leafs: Even though dependencies are the bane of software development, Flow-Design does not usually draw these dependencies. They are implicitly created by visually nesting functional units. And they are harmless. Boards are so simple in their functionality, they are little affected by changes in functional units they are depending on. But functional units are implicitly dependent on more than nested functional units. They are also dependent on the data types of the wires attached to them: This is also natural and thus does not need to be made explicit. And it pertains mainly to parts being dependent. Since boards don´t do anything with regard to a problem domain, they don´t care much about data types. Their infrastructural purpose just needs types of input/output-pins to match.   Explicit Dependencies You could say, Flow-Orientation is about tackling complexity at its root cause: that´s dependencies. “Natural” dependencies are depicted naturally, i.e. implicitly. And whereever possible dependencies are not even created. Functional units don´t know their collaborators within a flow. This is core to Flow-Orientation. That makes for high composability of functional units. A part is as independent of other functional units as a motor is from the rest of the car. And a board is as dependend on nested functional units as a motor is on a spark plug or a crank shaft. With Flow-Design software development moves closer to how hardware is constructed. Implicit dependencies are not enough, though. Sometimes explicit dependencies make designs easier – as counterintuitive this might sound. So FD notation needs a ways to denote explicit dependencies: Data flows along wires. But data does not flow along dependency relations. Instead dependency relations represent service calls. Functional unit C is depending on/calling services on functional unit S. If you want to be more specific, name the services next to the dependency relation: Although you should try to stay clear of explicit dependencies, they are fundamentally ok. See them as a way to add another dimension to a flow. Usually the functionality of the independent FU (“Customer repository” above) is orthogonal to the domain of the flow it is referenced by. If you like emphasize this by using different shapes for dependent and independent FUs like above. Such dependencies can be used to link in resources like databases or shared in-memory state. FUs can not only produce output but also can have side effects. A common pattern for using such explizit dependencies is to hook a GUI into a flow as the source and/or the sink of data: Which can be shortened to: Treat FUs others depend on as boards (with a special non-FD API the dependent part is connected to), but do not embed them in a flow in the diagram they are depended upon.   Attributes of Functional Units Creation and usage of functional units can be modified with attributes. So far the following have shown to be helpful: Singleton: FUs are by default multitons. FUs in the same of different flows with the same name refer to the same functionality, but to different instances. Think of functional units as objects that get instanciated anew whereever they appear in a design. Sometimes though it´s helpful to reuse the same instance of a functional unit; this is always due to valuable state it holds. Signify this by annotating the FU with a “(S)”. Multiton: FUs on which others depend are singletons by default. This is, because they usually are introduced where shared state comes into play. If you want to change them to be a singletons mark them with a “(M)”. Configurable: Some parts need to be configured before the can do they work in a flow. Annotate them with a “(C)” to have them initialized before any data items to be processed by them arrive. Do not assume any order in which FUs are configured. How such configuration is happening is an implementation detail. Entry point: In each design there needs to be a single part where “it all starts”. That´s the entry point for all processing. It´s like Program.Main() in C# programs. Mark the entry point part with an “(E)”. Quite often this will be the GUI part. How the entry point is started is an implementation detail. Just consider it the first FU to start do its job.   Patterns / Standard Parts If more than a single wire is attached to an output-pin that´s called a split (or fork). The same data is flowing on all of the wires. Remember: Flow-Designs are synchronous by default. So a split does not mean data is processed in parallel afterwards. Processing still happens synchronously and thus one branch after another. Do not assume any specific order of the processing on the different branches after the split.   It is common to do a split and let only parts of the original data flow on through the branches. This effectively means a map is needed after a split. This map can be implicit or explicit.   Although FUs can have multiple input-pins it is preferrable in most cases to combine input data from different branches using an explicit join: The default output of a join is a tuple of its input values. The default behavior of a join is to output a value whenever a new input is received. However, to produce its first output a join needs an input for all its input-pins. Other join behaviors can be: reset all inputs after an output only produce output if data arrives on certain input-pins

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  • OOP, Interface Design and Encapsulation

    - by Mau
    C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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  • Oracle Launches Mobile Applications User Experience Design Patterns

    - by ultan o'broin
    OK, you heard Joe Huang (@JoeHuang_Oracle) Product Manager for Oracle Application Development Framework (ADF) Mobile. If you're an ADF developer, or a Java (yeah, Java in iOS) developer, well now you're a mobile developer as well. And, using the newly launched Applications User Experience (UX) team's Mobile UX Design Patterns, you're a UX developer rockstar too, offering users so much more than just cool functionality. Mobile Design Pattern for Inline Actions Mobile design requires a different way of thinking. Use Oracle’s mobile design patterns to design iPhone, Android, or browser-based smartphone apps. Oracle's sharing these cutting edge mobile design patterns and their baked-in, scientifically proven usability to enable Oracle customers and partners to build mobile apps quickly. The design patterns are common solutions that developers can easily apply across all application suites. Crafted by the UX team's insight into Oracle Fusion Middleware, the patterns are designed to work with the mobile technology provided by the Oracle Application Development Framework. Other great UX-related information on using ADF Mobile to design task flows and the development experience on offer are on the ADF EMG podcast series. Check out FXAer Brian 'Bex' Huff (@bex of Bezzotech talking about ADF Mobile in podcast number 6 and also number 8 which has great tips about getting going with Android and iOS mobile app development too.

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  • database modeling for google app engine for multiple revison of entity.

    - by iamgopal
    hi, in my application ( kind of wiki clone ) - an article is frequently changing. and i need to track all changes that are done on that article. { text only. } one crude way i have done it, is to add a datetime property and create a new entity everytime something change. which is too much database wasting. { and also un-necessary index waste too. } and also need to re-create parent-child and entity relationships. i also have log which can show changes -- but i want some thing easier , so that jumping from one version to another version could be easier. ideas ? thanks.

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  • What modern design pattern / software engineering books for Java SE 6 do you recommend ?

    - by Scott Davies
    Hi, I am very familiar with Java 6 SE language features and am now looking for modern books that cover design patterns in Java for beginners as well as software engineering books that discuss architectures, algorithms and best practices in Java coding (sort of like the Effective C# books). I am aware of the classic GoF design patterns book, however, I'd like a more modern reference that takes advantage of the features of Java 6 SE. What books would you recommend ? Thanks, Scott

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  • Easiest, most fun way to program 2D games? Flash? XNA? Some other engine?

    - by Maxi
    Hi, this is a post detailing my search for the most enjoyable way for a hobbyist game programmer to sweeten his free time with making a game. My requirements: I looked at Flash first, I made a couple of small games but I'm doubtful of the performance. I would like to make a fairly large strategy game, with several hundred units fighting simultaneously, explosions and animations included. Also zoomable maps. I saw that Adobe has a new 3D API for Flash, but I don't know if that improves 2D performance aswell, I couldn't find anything related to that question on their MAX10 sessions. Would you say that Flash is a good technology for making large 2D games easily? I really like Actionscript, and I love how easy everything is in Flash. There are several engines available which make it even easier. I just do this for fun, and it would be even better if there were proper animation/particle editors available and if the engine I were to use, would be available for multiple platforms. (so more people can play my game once finished). I'd like to have it available on many mobile platforms aswell. (because I love touch input for some reason) I do know the XNA framework pretty well, but there are no good engines available for it, and it will only run on Windows, which is a huge turn off. Even bigger is, that you need to install the XNA redistributable each time you want to give the game to someone. If I use XNA, I would have to make all the tools myself, and I'd probably have to make them with WPF. (I'd love to make tools with Adobe AIR, but unfortunately the API's for image manipulation etc. are far worse in Flash, than they are in XNA/WPF.) Now, I'm aware that I could make my own engine that supports each of those platforms, but quite frankly, that would be too much work plowing through APIs. After all, I want to make a game, not an engine. So the question becomes: Is there maybe a cross platform (free or free to develop?) engine available that I could use for 2D development? I prefer: C#, Actionscript. I don't mind using c++ if the toolset is above average, but I highly doubt that there is something out there like that. Please prove me wrong :) So summary: I'd like to use Flash, but I don't know if it scales well enough. I'm not a scripter, I want some real APIs that I can work with inside a proper IDE. Just for information, I looked at several alternatives, I'm actually looking for a long time already. You'd help me a lot to make a decision finally. Feature-wise the Flatredball engine would be ideal. But I tried their tools, and quite frankly, they are horrible. Absolutely unusable, I'd need to make my own for sure. I didn't look at their API, but if their tools are so bad, I'm not inclined to look further. Unity3D. This one is quite nice, but I really don't need 3D, and it is quite ...a lot of work to learn. I also don't like that it is so expensive to use for different platforms and that I can only code for it through scripting. You have to buy each platform separately. The editor usability is average, the product overall is good enough for most purposes, but learning it myself would be overkill. Shiva 3D. It looks good enough, but again: I don't really need 3D. The editor usability is a little worse than Unity3D in my opinion and it wasn't clear to me how to start programming. I think it requires C++ for coding, so that's a negative too. I want to have fun, and c# is fun ;) SDL. Quite frankly, I'd still need to port to all those different SDL implementations. And I don't like OpenGL style programming, it's just plain ugly. And it needs c++, I know that there might be some wrappers available, but I don't like to use wrappers, because... Irrlicht. A lot of features, but support seems to be low and it is aimed at enthusiasts. C# bindings get dropped repeatedly. I'm not an engine enthusiast, I just want to make a game. I don't see this happening with Irrlicht. Ogre3D. Way too much work, it's just a graphics engine. Also no multiple platform support and c++. Torque2D. Costs something to use, and I didn't hear a lot of good things about support and documentation. Also costs extra for each platform.

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  • Software Architecture verses Software Design

    Recently, I was asked what the differences between software architecture and software design are. At a very superficial level both architecture and design seem to mean relatively the same thing. However, if we examine both of these terms further we will find that they are in fact very different due to the level of details they encompass. Software Architecture can be defined as the essence of an application because it deals with high level concepts that do not include any details as to how they will be implemented. To me this gives stakeholders a view of a system or application as if someone was viewing the earth from outer space. At this distance only very basic elements of the earth can be detected like land, weather and water. As the viewer comes closer to earth the details in this view start to become more defined. Details about the earth’s surface will start to actually take form as well as mane made structures will be detected. The process of transitioning a view from outer space to inside our earth’s atmosphere is similar to how an architectural concept is transformed to an architectural design. From this vantage point stakeholders can start to see buildings and other structures as if they were looking out of a small plane window. This distance is still high enough to see a large area of the earth’s surface while still being able to see some details about the surface. This viewing point is very similar to the actual design process of an application in that it takes the very high level architectural concept or concepts and applies concrete design details to form a software design that encompasses the actual implementation details in the form of responsibilities and functions. Examples of these details include: interfaces, components, data, and connections. In review, software architecture deals with high level concepts without regard to any implementation details. Software design on the other hand takes high level concepts and applies concrete details so that software can be implemented. As part of the transition between software architecture to the creation of software design an evaluation on the architecture is recommended. There are several benefits to including this step as part of the transition process. It allows for projects to ensure that they are on the correct path as to meeting the stakeholder’s requirement goals, identifies possible cost savings and can be used to find missing or nonspecific requirements that cause ambiguity in a design. In the book “Evaluating Software Architectures: Methods and Case Studies”, they define key benefits to adding an architectural review process to ensure that an architecture is ready to move on to the design phase. Benefits to evaluating software architecture: Gathers all stakeholders to communicate about the project Goals are clearly defined in regards to the creation or validation of specific requirements Goals are prioritized so that when conflicts occur decisions will be made based on goal priority Defines a clear expectation of the architecture so that all stakeholders have a keen understanding of the project Ensures high quality documentation of the architecture Enables discoveries of architectural reuse  Increases the quality of architecture practices. I can remember a few projects that I worked on that could have really used an architectural review prior to being passed on to developers. This project was to create some new advertising space on the company’s website in order to sell space based on the location and some other criteria. I was one of the developer selected to lead this project and I was given a high level design concept and a long list of ever changing requirements due to the fact that sales department had no clear direction as to what exactly the project was going to do or how they were going to bill the clients once they actually agreed to purchase the Ad space. In my personal opinion IT should have pushed back to have the requirements further articulated instead of forcing programmers to code blindly attempting to build such an ambiguous project.  Unfortunately, we had to suffer with this project for about 4 months when it should have only taken 1.5 to complete due to the constantly changing and unclear requirements. References  Clements, P., Kazman, R., & Klein, M. (2002). Evaluating Software Architectures. Westford, Massachusetts: Courier Westford. 

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  • What design pattern shall I use in this question?

    - by iyad al aqel
    To be frank, this is a homework question, so I'll tell you my opinion. Can you let me know my mistakes rather than giving me the solution? This is the question : Assume a restaurant that only offers the following two types of meals: (a) a full meal and (b)an economic meal. The full meal consists of the following food items and is served in the following order: 1. Appetizer 2. Drink 3. Main dish 4. Dessert Meanwhile the economic meal consists of the following food items and is served in the following order: 1. Drink 2. Main dish Identify the most appropriate design pattern that can be used to allow a customer to only order using one of the two types of meals provided and that the meal components must be served in the given order. I'm confused between the Factory and the Iterator and using them both together. Using the factory Pattern we can create the two meals full and economic and provide the user with with a base object class that will decide upon. But how can we enforce the ordering of the elements, I thought of using the iterator along that will iterate through the the composite of the two created factories sort of speak. What do you think?

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  • Quick and Good: ( Requirement -> Validation -> Design ) for self use?

    - by Yugal Jindle
    How to casually do the required Software Engineering and designing? I am an inexperienced developer and face the following problem: My company is a start up and has no fix Software engineering systems. I am assigned tasks with not very clear and conflicting requirements. I don't have to follow any designs or verify requirements officially. Problem: I code all day and finally get stuck where requirement conflicts and I have to start over again. I can-not spend a lot of time doing proper SRS or SDD. How should I: List out Requirements for myself. (Not an official document) How to verify and validate the requirements? How to visualize them? How to design them with minimum effort? (As its going to be with me only) I don't want to waste my time coding something that's gonna collapse according to requirement conflict or something! I don't want to compromise with quality but don't want to re-write everything on some change that I didn't expected. I imagine making a diagram for my thought process that will show me conflict in the diagram itself, then finally correcting the diagram - I decide my design and structure my code in terms of interfaces or something. And then finally start implementing my design. I am able to sense the lack of systematic approach, but don't know how to proceed! Update: Please suggest me some tools that can ask me the questions and help me aggregate important details. How can I have diagram that I talked about for requirement verification?

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  • Parsing unicode XML with Python SAX on App Engine

    - by Derek Dahmer
    I'm using xml.sax with unicode strings of XML as input, originally entered in from a web form. On my local machine (python 2.5, using the default xmlreader expat, running through app engine), it works fine. However, the exact same code and input strings on production app engine servers fail with "not well-formed". For example, it happens with the code below: from xml import sax class MyHandler(sax.ContentHandler): pass handler = MyHandler() # Both of these unicode strings return 'not well-formed' # on app engine, but work locally xml.parseString(u"<a>b</a>",handler) xml.parseString(u"<!DOCTYPE a[<!ELEMENT a (#PCDATA)> ]><a>b</a>",handler) # Both of these work, but output unicode xml.parseString("<a>b</a>",handler) xml.parseString("<!DOCTYPE a[<!ELEMENT a (#PCDATA)> ]><a>b</a>",handler) resulting in the error: File "<string>", line 1, in <module> File "/base/python_dist/lib/python2.5/xml/sax/__init__.py", line 49, in parseString parser.parse(inpsrc) File "/base/python_dist/lib/python2.5/xml/sax/expatreader.py", line 107, in parse xmlreader.IncrementalParser.parse(self, source) File "/base/python_dist/lib/python2.5/xml/sax/xmlreader.py", line 123, in parse self.feed(buffer) File "/base/python_dist/lib/python2.5/xml/sax/expatreader.py", line 211, in feed self._err_handler.fatalError(exc) File "/base/python_dist/lib/python2.5/xml/sax/handler.py", line 38, in fatalError raise exception SAXParseException: <unknown>:1:1: not well-formed (invalid token) Any reason why app engine's parser, which also uses python2.5 and expat, would fail when inputting unicode?

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  • Optimising RSS parsing on App Engine to avoid high CPU warnings

    - by Danny Tuppeny
    I'm pulling some RSS feeds into a datastore in App Engine to serve up to an iPhone app. I use cron to schedule updating the RSS every x minutes. Each task only parses one RSS feed (which has 15-20 items). I frequently get warnings about high CPU usage in the App Engine dashboard, so I'm looking for ways to optimise my code. Currently, I use minidom (since it's already there on App Engine), but I suspect it's not very efficient! Here's the code: dom = minidom.parseString(urlfetch.fetch(url).content) if dom: items = [] for node in dom.getElementsByTagName('item'): item = RssItem( key_name = self.getText(node.getElementsByTagName('guid')[0].childNodes), title = self.getText(node.getElementsByTagName('title')[0].childNodes), description = self.getText(node.getElementsByTagName('description')[0].childNodes), modified = datetime.now(), link = self.getText(node.getElementsByTagName('link')[0].childNodes), categories = [self.getText(category.childNodes) for category in node.getElementsByTagName('category')] ); items.append(item); db.put(items); def getText(self, nodelist): rc = '' for node in nodelist: if node.nodeType == node.TEXT_NODE: rc = rc + node.data return rc There isn't much going on, but the scripts often take 2-6 seconds CPU time, which seems a bit excessive for looping through 20ish items and reading a few attributes. What can I do to make this faster? Is there anything particularly bad in the above code, or should I change to another way of parsing? Are there are any libraries (that work on App Engine) that would be better, or would I be better parsing the RSS myself?

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  • Media recommendation engine - Single user system - How to start

    - by Microkernel
    Hi guys, I want to implement a media recommendation engine. I saw a similar posts on this, but I think my requirements are bit different from those, so posting here. Here is the deal. I want to implement a recommendation engine for media players like VLC, which would be an engine that has to care for only single user. Like, it would be embedded in a media player on a PC which is typically used by single user. And it will start learning the likes and dislikes of the user and gradually learns what a user likes. Here it will not be able to find similar users for using their data for recommendation as its a single user system. So how to go about this? Or you can consider it as a recommendation engine that has to be put in say iPods, which has to learn about a single user and recommend music/Movies from the collections it has. I thought of start collecting the genre of music/movies (maybe even artist name) that user watches and recommend movies from the most watched Genre, but it look very crude, isn't it? So is there any algorithms I can use or any resources I can refer up to? Regards, MicroKernel :)

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  • Deploy GWT Application to Google App Engine using NetBeans

    - by Yan Cheng CHEOK
    Hello, I try to deploy a GWT application, to Google App Engine using NetBeans. I had successful run GWT sample http://code.google.com/webtoolkit/doc/latest/tutorial/create.html using Personal GlassFish v3 Prelude Domain, by 1) Copy generated source code from StockWatcher to C:\Projects\StockWatcherNetbeans\src\java\com\google\ 2) Modify C:\Projects\StockWatcherNetbeans\nbproject\gwt.properties gwt.module=com.google.gwt.stockwatcher.StockWatcher 3) Select Personal GlassFish v3 Prelude Domain, and run. All works fine! Now, I try to select Google App Engine server, and run. However, I get the error "There is no appengine web project opened!" I check... There is file called C:\Projects\StockWatcherNetbeans\war\WEB-INF\appengine-web.xml with content <?xml version="1.0" encoding="UTF-8"?> <appengine-web-app xmlns="http://appengine.google.com/ns/1.0" xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://kenai.com/projects/nbappengine/downloads/download/schema/appengine-web.xsd appengine-web.xsd'> <application>StockWatcherNetbeans</application> <version>1</version> </appengine-web-app> I am using NetBeans 6.7.1 GWT4NB (GWT Plugin for NetBeans) 2.6.12 Google App Engine plugin for NetBeans from http://kenai.com/downloads/nbappengine/1.0_NetBeans671/updates.xml Anything I had missed out? Even when I right click to the project, the Deploy to Google App Engine options is disabled. And yes, please do not ask me why not use Eclipse.

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  • Windows Phone 7 Design using Expression Blend - Resources

    - by Nikita Polyakov
    I’ve been doing a series of talks across Florida regarding Windows Phone 7 Design using Microsoft Expression Blend 4. I discuss the WP7 phone and application experience; show how to use Expression Blend toolset to effectively design such apps. Next presentation is on 5/4/2010 at 6:30PM EST will be a webcast format over LiveMeeting at Ft. Lauderdale Online group. Registration and the LiveMeeting link are both here: http://www.fladotnet.com/Reg.aspx?EventID=459 [I will post a link if it’s recorded]   Here are the resources from my presentations: The Biggest source is the Windows Phone UI and Design Language video from MIX10 Windows Phone 7 Design Guide as it’s found on the WP7 Dev Home Page Study The Silverlight Mobile Tutorials on official Silverlight website I will be blogging a separate entry for a new demo app that will showcase the elements I presented. I suggest you actually watch all of the MIX videos about SL and Design as great primer to get you thinking the WP7 way.   A lot happening with WP7Dev and it’s just the beginning! So watch these Twitter accounts and blogs: @Ckindel - Charlie Kindel - WP7 Dev Head http://blogs.msdn.com/ckindel @WP7Dev - Official Dev Twitter @WP7 - Official WP7 Twitter Peter Torr - http://blogs.msdn.com/ptorr Mike Harsh - http://blogs.msdn.com/mharsh Shawn Oster - http://www.shawnoster.com   Other worthwhile mention my local friends speaking and blogging about Windows Phone 7: Bill Reiss is doing great presentations on Building games with XNA for Windows Phone 7. Be on the lookout for those around Florida. Bill is a Silverlight MVP and has a legacy of XNA and Silverlight games, see his site. Kevin Wolf aka ByteMaster he is a Device Application Developer MVP with tremendous experience building mobile applications. He has developed WinMo-GF a multi-platform gaming framework. Get these tools and get creating! You will need the following components installed in this order: Expression Blend 4 Beta Windows Phone Developer Tools Microsoft Expression Blend Add-in Preview for Windows Phone Microsoft Expression Blend SDK Preview for Windows Phone Want more training? Don’t forget that Channel 9 has complete walkthroughs of their WP7 Training Kit posted online. PS: To continue with all this design talk check out Microsoft .toolbox “Learn to create Silverlight applications using Expression Studio and to apply fundamental design principles.” A great website with a lot of design tutorials set up as a wonderful full course on design all for free, including a great forum community and neat little avatars you can build yourself.

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  • Design a T-shirt for .NET Reflector Pro

    - by Laila
    Win a .NET Reflector Pro license, a box of Red Gate goodies, and a t-shirt printed with your design! Red Gate likes t-shirts. Each of our teams has one. In fact, each individual person has one, numbered according to when they joined the company: Red Gate's 1st, 2nd, and so on right up to Red Gate's 170th, with the slogan "More than just a number". Those t-shirts are important, chiefly because they remind the people wearing them that they are important. But that isn't enough. What really makes us great are the people who choose to use our tools. So we'd like to extend our tradition of t-shirts to include you and put the design of our next shirt entirely in your hands. We'd like you to come up with a witty slogan or create an inventive or simply beautiful t-shirt design for .NET Reflector Pro, our add-in for Visual Studio, which allows you to step into decompiled assemblies whilst debugging in Visual Studio. When you're done, post your masterpiece to Twitter with the hash tag #reflectortees, and @redgate will take a look! We'll pick the best design, and the winner will get a licensed copy of .NET Reflector Pro and a box of Red Gate goodies - not to mention a copy of their t-shirt. The winning design will go into production and be worn and given out at tradeshows, conferences, and user group events across the world, proudly bearing the name of their designer. We'll also pick three runners-up who will receive licenses for .NET Reflector Pro. Red Gate goodie box Interested? If you're up for the challenge, then we've got some resources to get you started. Inside the .zip file you'll find high-quality versions of the following: T-shirt templates: don't forget to design the front and the back! Different versions of the .NET Reflector Pro logo and Red Gate logo. Colour sheets to give you an easy reference to the Red Gate colours, including hex and RGB values. You can create and send us as many designs as you like, and each of them will be considered for the prize. To submit your designs, simply tweet including the competition hash tag, #reflectortees, and a link to somewhere we can see your design: either an image hosting site such as Twitpic, Flickr or Picasa, or a personal blog. You will need to create a Twitter account (which is free), if you don't already have one. You only have three limits: The background colour of the t-shirt should be one of our brand colours (red, light/dark grey or black), though you're welcome to use other colours in the rest of the design. You need to make use of either the .NET Reflector Pro logo OR the Red Gate logo (please keep them as they are) If you include any text or slogan, stick with just one or two colors for it. Apart from that, go wild. Go and do whatever it is you do when you get creative: whether you walk barefoot on the grass with a pencil and paper, sit cross-legged on a pile of cushions with a laptop, or simply close your eyes and float through a mist of ideas, now is your chance. Make sure you enjoy it. We're looking forward to seeing your creations. Terms and conditions 1. The closing date for entries is June 11th, 2010 (4 p.m. UK time). Red Gate Software Ltd reserves the right to extend the competition deadline at its discretion. If there is a revision, the revised date will be published on this blog and the date for announcing the results will be postponed accordingly. 2. The winning designer will be notified on June 14th, 2010 through Twitter. The winner must claim his/her prize by sending us a high-resolution image of their design via email (i.e. Illustrator EPS files or appropriate format, ideally at 300dpi). If the winner does not come forward within 3 days of the announcement, they will forfeit their prize and another winner will be selected from the runners-up. The names of the winner and runners-up will be posted on this blog by June 18th.  3. Entry is completed on the designer posting a link to their entry in a tweet with the correct hash tag, #reflectortees. 4. Red Gate Software needs to hold the rights to using the winning design in order to put the t-shirt into production. We will make sure that this is fine with the winner before we do so, but if you do not want us holding the rights to your design, please do not submit your designs. We reserve the right to slightly alter or adjust any artwork we decide to use (mainly to make it easier to print), but we will make sure we contact the winner for approval first. The winner will also need to allow us the use of his/her name for purposes of promoting your design. 5. Entries must be entirely your own original work and must not breach any copyright or third party rights. Red Gate Software Ltd will not be made partially or fully liable for any non-original work submitted by you. 6. This competition is free: you do not need to buy anything or be an existing customer to enter. 7. This competition is not open to employees of Red Gate Software Ltd, their families, or any other company directly connected with the administration of this promotion.

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  • Google I/O 2010 - Testing techniques for Google App Engine

    Google I/O 2010 - Testing techniques for Google App Engine Google I/O 2010 - Testing techniques for Google App Engine App Engine 201 Max Ross We typically write tests assuming that our development stack closely resembles our production stack. What if our target environment only lives in the cloud? We will highlight the key differences between typical testing techniques and Google App Engine testing techniques. We will also present concrete strategies for testing against local and cloud-based implementations of App Engine services. Finally, we will explain how to use App Engine as a highly parallel test harness that runs existing test suites without modification. For all I/O 2010 sessions, please go to code.google.com/events/io/2010/sessions.html From: GoogleDevelopers Views: 6 1 ratings Time: 54:29 More in Science & Technology

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