this is a totally unfamiliar area for me. can anyone point me in the right direction on how to create a social graph and the best way to represent it? i'm building a website in C#/asp net and need to create a "friends" feature... is this type of thing usually stored entirely in the DB? if so, how?
Is your primary concern painting a picture of the social network or storing the data?
For storage you might consider a graph database. However, the most mature product in this space is neo4j, which has the name suggests is written in Java. This SO discussion list some alternative approaches for .Net.
edit
You are still not being clear whether you need design advice or code samples. Andrew Siemer wrote a two-part article which outlines the issues and then presents some ASP.net code. I don't think it's by any means a complete solution but it could give you a steer in the right direction.
Your question is rather open-ended. For drawing complex graphs, one of my favorite tools is Graphviz. Graphviz can work with directed or non-directed graphs. It can take the input as a simple text file, and then output the graph in a variety of formats.
So your problem is primarily a data storage issue, and how to store and retrieve edges in your graph. Applying some simple graph terms to your problem:
Node/Vertex: In your case each person will represent a node.
Edge/Link: The relationship between nodes, in this case 'friends', will create an undirected edge between two nodes.
So you will need to maintain a data structure in your DB that allows you to resolve the edge relationships between friends.
Some useful information can probably be found in this question:
challenge-how-to-implement-an-algorithm-for-six-degree-of-separation
Also, something you should consider when deciding how to store your edge list is how many edges you think your site will generate. This will probably effect the storage mechanism you decide on.
Hope those pointers help.
Related
I am attempting to map out social networks
For example, i have person A and he has 5 followers, these followers and the person would be represented by a vertex, and then have an edge connecting them. And most likely, at least half of them are following each other, creating a big sort of "web".
I tried doing this in QuickGraph, however i ran into a few issues:
The graph ends up looking like more like a flow chart then a web, example from earlier in QuickGraph:
When i test with real data, the graph just becomes a huge, laggy, spaghetti mess of ink
What would be the best way to create this sort of graph?
For reference i am looking to make a graph that looks like this:
So the data structure you are working with is a Directed Graph - that is, the edges of your node have a direction, from follower to followed.
It looks like you are using dot to render your graph, which is a great way to lay things out if your data has some kind of start and end - if there is an overall sense of earlier to later, sources to sinks, simpler to more complex.
You don't really have that, and your example picture is more typical of an undirected graph. The same people that do dot also do neato, which gives you diagrams much closer to your desired picture.
I don't know QuickGraph's API at all, but I'd look to either;
change the graph data structure you're creating -- try switching to something like UndirectedGraph and see if that ends up switching the render
see if there are options in your render method to render an undirected graph rather than a directed graph.
Despite Googling around a fair amount, the only things that surfaced were on neural networks and using existing APIs to find tags about an image, and on webcam tracking.
What I would like to do is create my own data set for some objects (a database containing the images of a product (or a fingerprint of each image), and manufacturer information about the product), and then use some combination of machine learning and object detection to find if a given image contains any product from the data I've collected.
For example, I would like to take a picture of a chair and compare that to some data to find which chair is most likely in the picture from the chairs in my database.
What would be an approach to tackling this problem? I have already considered using OpenCV, and feel that this is a starting point and probably how I'll detect the object, but I've not found how to use this to solve my problem.
I think in the end it doesn't matter what tool you use to tackle your problem. You will probably need some kind of machine learning. It's hard to say which method would result in the best detection, for this I'd recommend to use a tool like weka. It's a collection of multiple machine learning algorithms and lets you easily try out what works best for you.
Before you can start trying out the machine learning you will first need to extract some features out of your dataset. Since you can hardly compare the images pixel by pixel which would result in huge computational effort and does not even necessarily provide the needed results. Try to extract features which make your images unique, like average colour or brightness, maybe try to extract some shapes or sizes out of the image. So in the end you will feed your algorithm just with the features you extracted out of your images and not the images itself.
Which are good features is hard to define, it depends on your special case. Generally it helps to have not just one but multiple features covering completely different aspects of the image. To extract the features you could use openCV, or any other image processing tool you like. Get the features of all images in your dataset and get started with the machine learning.
From what I understood, you want to build a Content Based Image Retrieval system.
There are plenty of methods to do this. What defines the best method to solve your problem has to do with:
the type of objects you want to recognize,
the type of images that will be introduced to search the objects,
the priorities of your system (efficiency, robustness, etc.).
You gave the example of recognizing chairs. In your system which would be the determining factor for selecting the most similar chair? The color of the chair? The shape of the chair? These are typical question that you have to answer before choosing the method.
Either way one of the most used methods to solve such problems is the Bag-of-Words model (also Referred the Bag of Features). I wish I could help more but for that I need that you explain it better which are the final goals of your work / project.
I have researched for some time the Orchard CMS and I'm pleased with some of his futures but also I have some issues that I don't know how to deal with them:
All the items (content type) are linear and they don't support a tree like data structure
(Ex: books > titles > web-links)
One of the big problem (depending how you see things) is that the model and the view for the items are coupled (content part > driver with display / editor views)
So for a new page the model, view and position are locked and you can have only one view of the model.
Use of advance language futures the are not suited for beginner developers and are not very clear (dynamic functions, clay objects - nice future, ...)
// Creating table VPlayerRecord
SchemaBuilder.CreateTable("VPlayerRecord", table => table
.ContentPartRecord()
.Column("Title", DbType.String)
.Column("VideoUrl", DbType.String)
.Column("WidthPx", DbType.Double)
.Column("HeightPx", DbType.Double)
);
This syntax is not very clear for beginner developers and is a bit over engineered. Also because the model is a dynamic object in the view we don't have any intellisense support.
To build a new page we have something like three degree of separation (3 projects)
Build a content part module
Build a content type
Build a theme module
How do you overcome these issues in your projects with Orchard CMS? and what other issues have you found and fixes :)
read this: http://orchardproject.net/docs/Creating-1-n-and-n-n-relations.ashx and this: http://orchardproject.net/docs/Creating-lists.ashx
How is this a problem and why do you see this as coupling? What alternative do you see?
Where do you see this as a problem and how has it blocked you?
edit on 2: it is not true that you can have only one view of the model. You can have any number of display types. For example, the summary view of items is handled this way. You also have display types for admin views, and you can add your own.
Not sure what you mean by "position is locked". If we mean the same thing by position, I'm puzzled by how you could have gotten such an idea. Relative positioning of parts and fields can be changed through placement.info.
edit on 3: even with this example, I'm not sure what would be difficult here. This is fairly expressive imo. Were you confused yourself or are you just assuming people would be?
You are claiming that this is over-engineered. How would you simplify it then? What feature do you think is not needed?
You don't get IntelliSense in views on model objects but the flexibility you gain by doing so justifies it by a very large margin. Ask anyone who's been making real use of it.
new 4th point: I can't see a reason why you would separate that into three modules or why you think you should. I've certainly never seen an example of that. I would also point out that creating a part and a type are often done by two different people (a type creator is often just a consumer of existing parts). But again you don't have to separate them into different modules.
A theme is clearly a different concern from the two others and makes sense to be a separate project but a theme can come with code and can actually in principle do everything a module is doing. So if you want to package a part, type and theme into a single package, you could do that. It wouldn't make a lot of sense but you could.
Finally, I don't see how any of those four points are related to page creation.
Orchard has to be taken as a challenge. As a beginner I have quickly built a few sites with ease. After that the learning curve became steeper. I've read many articles on the subject, numerous times.
I have used some CMS's before and had some knowledge what is the nature of managing content. Learning Orchard opened a whole new definition of content management. Now I can think of solving some everyday tasks and various business processes by implementing Orchard.
The whole thing is built in a very abstract layer, forcing you to think abstract too. If you follow this way, there are many blog posts, as well as official documentation to help you.
There are few basic building blocks and concepts that can be used like a bricks. Sounds like a phrase, I've heard it hunderts of times. I have also seen thousands of houses built from red square bricks, and they were all different, while the bricks were all equal. Such things can be accomplished with Orchard.
Read and understand the programming patterns. They are essential part of knowledge that will help you in solving Orchard based tasks. They will also help you change the way you are accomplishing your non Orchard related tasks.
I would say, there are two basic areas one need to understand. Storing and retreiving the piece of content is one, while presenting it to the crowd is the other. It might look difficult, it is difficult, but the goodies behind are delightfull. Not to mention great guys, some from evil empire, some not, that will certainly help you along the way. Not to forget, git's are your best friend. There are many wheels already invented. Caution, neither comes with free lunch.
P.S. I haven't write such a long post since usenet times. It might not be suitable for a site like this. It's kind a way to give a thanks to this French guy, and to all other Orchard evangelists from Poland, over Cyprus to the States. They saved my ass in many occasions.
I've been reading about using the winged-edge data structure for storing a boundary representation. However, the linked site says that this is one of the oldest data structres for storing b-reps, are there newer better ones?
Secondly, is there an implementation of this in C#?
The datastructure used for a B-rep is very similar to those used for polygonal modeling - you just replace the edges with curves and the faces with surfaces.
The wikipedia page on polygonal meshes has several types listed, including winged edge. Personally I like half-edge meshes. The only thing they can't do well is non-manifold topology, which you may or may not need. If you do, look for radial edge topology.
There's also a freely available B-rep datastructure from OpenNurbs (McNeel, the makers of Rhino). That also gets you file IO, which is nice.
Boundary Representation Modelling Techniques by Ian Stroud will give you a survey of ways people have approached B-reps, along with a plethora of diagrams with all the Euler operators, and concrete data structures and algorithms for implementing B-reps imperatively.
Whether you want to move a few characters forward into F# or not, you may glean quite a bit of info from the source code for Wings3d (written in Erlang). Just don't get lost making spaceships and forget you were supposed to be coding!
Also the GML will allow you to investigate interactively what you can do with your B-reps, and the data structure is the code.
Not sure if this will help or not but there are Geometry objects in the XNA library for dealing with 3D Structures and what not. There may be something in there. However my guess is that it will either be Point based or Triangle based vs edge based.
But it might be a place to look.
This may be a silly question (with MSDN and all), but maybe some of you will be able to help me sift through amazing amounts of information.
I need to know the specifics of the implementations of common data structures and algorithms in C#. That is, for example, I need to know, say, how Linked Lists are handled and represented, how they and their methods are defined.
Is there a good centralized source of documentation for this (with code), or should I just reconstruct it? Have you ever had to know the specifics of these things to decide what to use?
Regards, and thanks.
Scott Mitchell has a great 6-part article that covers many .NET data structures:
An Extensive Examination of Data Structures
For an algorithmic overview of data structures, I suggest reading the algorithm textbook: "Introduction to Algorithms" by Cormen, et al..
For details on each .NET data structure the MSDN page on that specific class is good.
When all of them fail to address issues, Reflector is always there. You can use it to dig through the actual source and see things for yourself.
If you really want to learn it, try making your own.
Googling for linked lists will give you a lot of hits and sample code to go off of. Wikipedia will also be a good resource.
Depends on the language. Most languages have the very basics now pre-built with them, but that doesn't mean their implementations are the same. The same named object--LinkedList in C# is completely different than the LinkedList in Java or C++. Even the String library is different. C# for instance is known to create a new String object every time you assign a string a new value...this becomes something you learn quickly when it brings your program to a crashing halt when you're working with substrings in C# for the first time.
So the answer to your question is massively complicated because I don't know quite what you're after. If you're just going to be teaching a class what a generic version of these algorithms and data structures are, you can present them without getting into the problems I mentioned above. You'll just need to select, lookup, read about a particular type of implementation of them. Like for LinkedList you need to be able to instantiate the list, destroy the list, copy the list, add to the list somewhere (usually front/back), remove from the list, etc. You could get fancy and add as many methods as you want.