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• Conceptual data modeling: Is RDF the right tool? Other solutions?

  - by paprika

  I'm planning a system that combines various data sources and lets users do simple queries on these. A part of the system needs to act as an abstraction layer that knows all connected data sources: the user shouldn't [need to] know about the underlying data "providers". A data provider could be anything: a relational DBMS, a bug tracking system, ..., a weather station. They are hooked up to the query system through a common API that defines how to "offer" data. The type of queries a certain data provider understands is given by its "offer" (e.g. I know these entities, I can give you aggregates of type X for relationship Y, ...). My concern right now is the unification of the data: the various data providers need to agree on a common vocabulary (e.g. the name of the entity "customer" could vary across different systems). Thus, defining a high level representation of the entities and their relationships is required. So far I have the following requirements: I need to be able to define objects and their properties/attributes. Further, arbitrary relations between these objects need to be represented: a verb that defines the nature of the relation (e.g. "knows"), the multiplicity (e.g. 1:n) and the direction/navigability of the relation. It occurs to me that RDF is a viable option, but is it "the right tool" for this job? What other solutions/frameworks do exist for semantic data modeling that have a machine readable representation and why are they better suited for this task? I'm grateful for every opinion and pointer to helpful resources.

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• Can a method return an NSRange?

  - by Dan Donaldson

  I have a method that returns an NSRange. When I call this method from outside the class I get a compile error. NSRange tmpRange; tmpRange = [phrase rangeInString:searchString forString:theLetter goingForward:YES]; return tmpRange.location == -1; in the .h file: #import <Foundation/Foundation.h> @interface Phrase : NSObject { } - (NSRange) rangeInString:(NSString *) tgt forString:(NSString *) find goingForward:(BOOL) fwd; @end This method is called within the Phrase object by other methods without problems. The compiler says 'incompatible types in assignment'. Can anyone explain this to me? I assume it has to do with returning an NSRange/struct type value generated outside the object, but I don't know why it works in one place and not the other.

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• Selecting dictionary items by key efficiently in Python

  - by user248237

  suppose I have a dictionary whose keys are strings. How can I efficiently make a new dictionary from that which contains only the keys present in some list? for example: # a dictionary mapping strings to stuff mydict = {'quux': ..., 'bar': ..., 'foo': ...} # list of keys to be selected from mydict keys_to_select = ['foo', 'bar', ...] The way I came up with is: filtered_mydict = [mydict[k] for k in mydict.keys() \ if k in keys_to_select] but I think this is highly inefficient because: (1) it requires enumerating the keys with keys(), (2) it requires looking up k in keys_to_select each time. at least one of these can be avoided, I would think. any ideas? I can use scipy/numpy too if needed.

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• JPA Bidirectional OneToMany and ManyToOne?

  - by PhoenixJon

  I'm using Oracle JDeveloper 11g Release 2. I created two tables A and B using SQL developer. Table A has a FK to table B. Using the Entities from Tables function, I created two JPA files from it. A has @ManyToOne annotation on FK. And also B has @OneToMany annotation to A. I don't want this. Can I remove this @OneToMany annotation automatically? public class A implements Serializable { ... @ManyToOne @JoinColumn(name = "FIELD_B") private B b; ... } public class B implements Serializable { ... @OneToMany(mappedBy = "B") private List<A> assetList; ... } I don't need @OneToMany mapping.

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• How do you combine a Move and Rotate effect in Flex 3?

  - by Impirator

  I realize you can make one of each effect, set the same target, and hit .play();, but this produces weird results (acknowledged by Adobe, fixed in Flex 4). I'm trying to have an object move from the top of the screen to the bottom while it rotates around it's own center. When called independently, both of these effects work perfectly. When called together, the object always rotates around the top left corner. I even tried putting them both inside a <Parallel> tag with no success. Has anyone come up with a workaround?

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• Splitting a double in two, C#

  - by Stacey

  I'm attempting to use a double to represent a bit of a dual-value type in a database that must sometimes accept two values, and sometimes accept only one (int). So the field is a float in the database, and in my C# code, it is a double (since mapping it via EF makes it a double for some reason... ) So basically what I want to do .. let's say 2.5 is the value. I want to separate that out into 2, and 5. Is there any implicit way to go about this?

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• Why doesn't list.get(0).equals(null) work?

  - by Jessy

  The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ if(choice.get(0).equals(null)) System.out.println("I am empty"); //it doesn't print this output } }

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• Why does obj.getBounds().height give a larger height than obj.height?

  - by TC

  I'm new to Flash and ActionScript, but managing quite nicely. One thing that is continuously getting in my way are the width and height properties of DisplayObject(Container)s. I'm finally starting to get my head around them and learned that the width and height of a Sprite are determined solely by their contents for example. I do not understand the following though: I've got a Sprite that I add a bunch of Buttons to. The buttons all have a height of 30 and an y of 0. As such, I'd expect the height of the containing Sprite to be 30. Surprisingly, the height is 100. The Adobe documentation of the height property of a DisplayObject states: Indicates the height of the display object, in pixels. The height is calculated based on the bounds of the content of the display object. Apparently, the 'bounds' of the object are important. So I went ahead and wrote this little test in the Sprite that contains the Buttons: for (var i:int = 0; i < numChildren; ++i) { trace("Y: " + getChildAt(i).y + " H: " + getChildAt(i).height); trace("BOUNDS H: " + getChildAt(i).getBounds(this).height); } trace("SCALEY: " + scaleY + " TOTAL HEIGHT: " + height); This code iterates through all the objects that are added to its display list and shows their y, height and getBounds().height values. Surprisingly, the output is: Y: 0 H: 30 BOUNDS H: 100 ... (5x) SCALEY: 1 TOTAL HEIGHT: 100 This shows that the bounds of the buttons are actually larger than their height (and the height that they appear to be, visually). I have no clue why this is the case however. So my questions are: Why are the bounds of my buttons larger than their height? How can I set the bounds of my buttons so that my Sprite isn't larger than I'd expect it to be based on the position and size of the objects it contains? By the way, the buttons are created as follows: var control:Button = new Button(); control.setSize(90, 30); addChild(control);

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• Noob question: Draw a quad parallel to the view.

  - by Jack

  Hi all, ok what I want to do is to draw a quad in the scene that lays on a plane parallel to the view. So it should appear flat. More in particular, I think I didn't get very well how the mechanism of gluLookAt works in comparison with the functions glTranslate and glRotate: If I position the view "manually" using the functions glTranslate and glRotate whenever I draw an object its position is relative to the current view. And I understand that this is due to the transformation matrix in the stack. However when I use the gluLookAt that should automatically set the view, the coordinates of the object I want to draw must be "absolute" to show it properly. Thanks in advance.

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• Convert sets to frozensets as values of a dictionary

  - by Space_C0wb0y

  I have dictionary that is built as part of the initialization of my object. I know that it will not change during the lifetime of the object. The dictionary maps keys to sets. I want to convert all the values from sets to frozensets, to make sure they do not get changed. Currently I do that like this: for key in self.my_dict.iterkeys(): self.my_dict[key] = frozenset(self.my_dict[key]) Is there a simpler way to achieve this? I cannot build frozenset right away, because I do not how much items will be in each set until i have built the complete dictionary.

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• AS3: How to get all XML-Nodes with a special attribute? (With sourch)

  - by insnet

  Hi there The Challenge: i d like to collect all nodes with the attribute "id". The Problem: The code doenst work with nested nodes. <?xml version="1.0" encoding="utf-8"?><contentmap><fonts id="fonts"> fonts/Arial.swf swf/library_main.swf private function onXMLLoader(event : Event) : void { _xml = _loader.getXML(event.target.url.url); var searchTerms : XMLList = _xml.*.(hasOwnProperty('@id')); if (searchTerms.length() 0 ) { _NodeArray = new Array(); _parseNode(searchTerms); } private function _parseNode(xml : XMLList) : void { for each (var node: XML in xml) { if(!node.hasSimpleContent()) { _parseNode(node.children()); } else { var nodeObject : Object = new Object(); nodeObject['value'] = node.text(); for each(var a:XML in node.@*) { var name : String = String(a.name()); nodeObject[name] = a.toXMLString(); } _NodeArray.push(nodeObject); } } }

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• C# determining generic type

  - by Chris Klepeis

  I have several templated objects that all implement the same interface: I.E. MyObject<datatype1> obj1; MyObject<datatype2> obj2; MyObject<datatype3> obj3; I want to store these objects in a List... I think I would do that like this: private List<MyObject<object>> _myList; I then want to create a function that takes 1 parameter, being a datatype, to see if an object using that datatype exists in my list.... sorta clueless how to go about this. In Pseudo code it would be: public bool Exist(DataType T) { return (does _myList contain a MyObject<T>?); }

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• Setting the size of a silverlight window at runtime automatically?

  - by dilbert789

  I need to be able to change the size of my Silverlight object at run time because I have content that changes in size dramatically between pages, and I'd rather not show a Silverlight scroll bar inside the browser scroll bar. I was able to do the following to get it to work: In the aspx page hosting the silverlight control: - Set your Div to the starting size you need it to be - Set the Silverlight Obejct to width=”100%” height=”100%” In your Main page add this: public static void ChangeSize(string height) { var myDiv = HtmlPage.Plugin.Parent; while (myDiv.TagName != "div") myDiv = myDiv.Parent; myDiv.SetStyleAttribute("height", height); } Anywhere you want to now change the size of the page do this: string newHeight = (App.Current.Host.Content.ActualHeight + 75).ToString(); MainPage.ChangeSize(newHeight + "px"); //App.Current.Host.Content.ActualHeight will get the current actual height of the object Is there a way that I can set this to re-size automatically so that I do not have to specify the amount to change? Currently using SL 2, interested in if there is another way in a different version though.

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• Designing operation (a,b) -> (c,d)

  - by golergka

  I have an operation that I need to design. That operation takes two objects of a certain class X, and returns two new objects of the same class (I may need the originals later). The logic that dictates the selection of this object is contained in class Y. On one hand, I don't want class Y to know details about class X implementation; on the other, I don't want class X to know details about selecting the different objects to perform this operation on. If that was all the problem, I'd just create a static method on class A. However, the methods in language I'm working on return only one object. Also, the operation needs to be robust, and calling operation two times to get C and D respectively isn't possible, as both C & D both rely on a single random number. How should I design such operation? Update: I'm using Obejctive C.

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• Java synchronizing static list ?

  - by JavaUser

  Hi, In a Java class , i am having a static list so this list is shared across all the objects of this class.The business logic in this class will run periodically which is invoked by some method with out passing instance parameters.Now I want to invoke this run method based on the list(I will add some vales into this list based on JMS) ,this list may empty sometimes and after finishing the run , i am emptying this list.Now my question is , whether I need to synchronize this list or not? Also let me know is there any other way to pass value in one object instance(Thread1) to other object instance (Thread2) other than having Static variable(static list)? Thx

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• fields_for to stop pluralizing.

  - by Dmitriy Likhten

  I have a fields_for tag, where I specify the prefix (lets say for some good reasons), and this is supposed to represent a one-to-one relationship. I am trying to represent a relationship widget has_many thingamagigs thingamagig has_one whatchamacallit The field_for code is: fields_for "widgt[thingamagigs_attributes][][whatchamacallit_attributes]", thingamagig.whatchamacallit do |x| which generates names (wrongly): widget[thingamagigs_attributes][][whatchamacallit_attributes][][value] The better solution would be t.fields_for :whatchamacallit do |x| where t = fields_for the thingamagig... However if I do that, the following names are generated widgt[thingamagigs_attributes][whatchamacallit_attributes][] which is completely wrong as all other fields for a thingamagig is... widgt[thingamagigs_attributes][][name] So in all cases I am screwed. The original field_for using a string cannot be used with accepts_nested_attributes_for :whatchamacallit since whatchamacallit is a singular relationship and an object is expected not an array. The second fields_for will simply not work because rails cannot parse the params object correctly. Is there a way to tell the first forms_for to not add the [] after [whatchamacallit_attributes] in all field names?

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• Switching from php to python

  - by ts

  Hello I am trying to make a list of things which can be difficult/surprising to someone who is changing language from PHP to Python. so far i have rather short list: forget require / include, learn import (this was most difficult to me - to understand package - module - class - object hierarchy and its mapping to filesystem) you can't just upload file on server to have webpage (-mod_python, wsgi etc) learn the python way for use variable class names (new $class() vs import + getattr) / operator in python 2.x and all float-related horrors those were difficult to me, it takes few days before mind adapts a new paradigm after i found that there is few other areas which could be challenging for someone with (too) many years of php: everything is an object you have to live with exceptions array vs list, set, dictionary, tuple ... learn (effective) list comprehensions learn generators any other ideas / personal experiences ?

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• How to map one class against multiple tables with SQLAlchemy?

  - by tote

  Lets say that I have a database structure with three tables that look like this: items - item_id - item_handle attributes - attribute_id - attribute_name item_attributes - item_attribute_id - item_id - attribute_id - attribute_value I would like to be able to do this in SQLAlchemy: item = Item('item1') item.foo = 'bar' session.add(item) session.commit() item1 = session.query(Item).filter_by(handle='item1').one() print item1.foo # => 'bar' I'm new to SQLAlchemy and I found this in the documentation (http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables): j = join(items, item_attributes, items.c.item_id == item_attributes.c.item_id). \ join(attributes, item_attributes.c.attribute_id == attributes.c.attribute_id) mapper(Item, j, properties={ 'item_id': [items.c.item_id, item_attributes.c.item_id], 'attribute_id': [item_attributes.c.attribute_id, attributes.c.attribute_id], }) It only adds item_id and attribute_id to Item and its not possible to add attributes to Item object. Is what I'm trying to achieve possible with SQLAlchemy? Is there a better way to structure the database to get the same behaviour of "dynamic columns"?

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• WPF/Silverlight DataBinding to interface property (with hidden implementation)

  - by Dave

  I have the following (C#) code namespace A { interface IX { bool Prop { get; set; } } class X : IX { public bool Prop { ... } } // hidden implementation of IX } namespace B { .. A.IX x = ...; object.DataContext = x; object.SetBinding(SomeDependencyProperty, new Binding("Prop")); .. } So I have a hidden implementation of an interface with a property "Prop" and I need to bind to this property in code. My problem is that the binding isn't working unless I make class X public. Is there any way around this problem?

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• DAQ Triggers in Matlab

  - by RidePlanet

  I'm writing a program that detects the speed of a object by hall effect sensors that are run into MATLAB through a DAQ (MCC USB-1408FS) The problem that has arisen is that I'm using a non-stop scan technique to detect the state of one of 3 sensors. Unfortunately this means that unless the object is rotating past each sensor at the exact rate the program runs, I will see an instantaneous speed (done by comparing the time between two sensors) of zero. I need the sensors to signal the program to count when they are hit, instead of constantly scanning for the signal. How can this be done?

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• Removing exception

  - by Nikhil K

  I have used this code for extracting urls from web page.But in the line of 'foreach' it is showing Object reference not set to an instance of an object exception. What is the problem? how can i correct that? WebClient client = new WebClient(); string url = "http://www.google.co.in/search?hl=en&q=java&start=10&sa=N"; string source = client.DownloadString(url); HtmlDocument doc = new HtmlDocument(); doc.LoadHtml(source); foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href and @rel='nofollow']")) { Console.WriteLine(link.Attributes["href"].Value); }

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• what is the purpose of numeric/boolean/string objects as opposed to primitive values?

  - by zespri

  In javascript you can call a function as a function or as a constructor. For example you can do : myObject = new Number(13); myPrimitiveValue = Number(13); or simply myPrimitiveValue = 13; I understand the difference between the results. Can you explain me under which reasonable circumstances creating a number, a boolean or a string as an object is desirable? For example, ability to set new properties (this is something you can do on objects but can't really do on primitive values) is almost always a bad idea for objects containing number/boolean/string. Why would I want a numeric/boolean/string object?

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• Media player hide control

  - by Geetha

  Hi All, I am using the following code to play video in asp.net application. I want to hide the mediaplayer default controls. Code: <object id="mediaPlayer" classid="clsid:22D6F312-B0F6-11D0-94AB-0080C74C7E95" codebase="http://activex.microsoft.com/activex/controls/mplayer/en/nsmp2inf.cab#Version=5,1,52,701" width="480" height="270" standby="Loading Microsoft Windows Media Player components..." type="application/x-oleobject"> <param name="fileName" value="" /> <param name="animationatStart" value="true" /> <param name="transparentatStart" value="true" /> <param name="autoStart" value="true" /> <param name="showControls" value="true" /> <param name="volume" value="150" /> <param name="loop" value="false" /> <param name="windowlessVideo" value="true" /> </object>

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• Find number of serialized objects

  - by tmosier

  Hello all. My issue is trying to determine a number of objects created, the objects being serialized from an XML document. The XML document should be set up for simplicity, so any developer can add an additional object and need no further modification to the code. However each of these objects need to be handled/updated seperately, and specifically, some of the objects are of different sub-classes, which need to be handled differently. Here is some pseudocode for what I am going for class A { public B myClassB; public void Update() { // for every object of whatever type in myClassB // update logic } } XML: <\data <\object1 etc... So what would be my simplest course of action, allowing other to add objects via the XML, but still ensuring the proper logic happenes for each?

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• Java: set-size List issue UnsupportedOperationException thrown

  - by tuckster

  I am having a problem changing a List that has a set-size in Java. I understand that I can't add or remove from this list but why can't I use set? When I use set the UnsupportedOperationException is thrown as well as when I use add and remove which is expected. set public Object set(int index, Object element) Replaces the element at the specified position in this list with the specified element (optional operation). I understand its an optional operation its just that want to replace that one element of the list with another element. Is there any way I can do this?

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