The refrigerator has multiple compartments（eg：fridge room \freezer room）,but we can only control temperature for one chamber when used the "TemperatureControl Trait", So how do we choose the Trait to control the temperature of different compartments separately?
Base on the current Smarthome framework I don't think it is possible to achieve exactly what you need. A workaround which coming up in my head is to add Mode trait for freezer room which allows you to name your mode and setting freely (of course you will lose the functionality to control the exact temperature).
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Is there a way in JGraphT that I can assign multiple weights to a single edge? For example, suppose I have a graph representing travel-time between cities. I want to assign edge-weights for "time by plane", "time by car", "time by bus", etc., and then find least-cost route by some specified mode of travel.
One approach I can think of is to have distinct graph for each travel mode and then add every city vertex to every graph but that seems like a messy and memory intensive solution.
My next thought was that I might be able to extend the class implementing the graph ( probably DirectedWeightedPseudograph) and customize the getEdgeWeight() method to take an additional argument specifying which weight value to use. That, however, would require extending all the algorithm classes as well (e.g., DijkstraShortestPath) which I am trying to avoid.
To get around that problem I considered the following:
Extend my Graph class by adding a method setWeightMode(enum mode)
customize the getEdgeWeight() method to use the currently assigned mode to determine which weight value to return to the caller.
On the plus side it would be 100% transparent to any existing analysis classes. On the negative side, it would not be thread-safe.
At this point I'm out of ideas. Can anyone suggest an approach that is scalable for large graphs, supports multi-threading, and minimizes the need to re-implement code already provided by JGraphT?
There exists a much easier solution: you want to use the AsWeightedGraph class. This is a wrapper class that allows you to create different weighted views of an underlying graph. From the class description:
Provides a weighted view of a graph. The class stores edge weights internally. All getEdgeWeight calls are handled by this view; all other graph operations are propagated to the graph backing this view.
This class can be used to make an unweighted graph weighted, to override the weights of a weighted graph, or to provide different weighted views of the same underlying graph. For instance, the edges of a graph representing a road network might have two weights associated with them: a travel time and a travel distance. Instead of creating two weighted graphs of the same network, one would simply create two weighted views of the same underlying graph.
I should model a system that clients can apply some configuration on separated entities.
Let me explain with an example:
We have users that have a config tab in their dashboards.
We have a feature to send notifications on their browsers and we have a feature which we can send an email to them.
We also have a feature as a pop-up.
The user should be able to modify our default notification message, modify our default email template, modify our default text on email or elements.
For the pop-up, The user should be able to modify the width and height of the pop-up, change the default texts, modify background color, change the button location on the pop-up.
And when I want to send an email to the user I should apply these settings on the template then send the email. Also when the front-end wants to show those pop-ups, wants to get these configs from my API and apply them.
These settings will be more and more in the future. So I can not specify a settings table with some fields. I think it is not a good idea.
What can I do? How to design and model this scenario? What are the best practices?
Can I use a NoSQL like MongoDB instead of a relational database?
Thanks a lot.
PS:
I am using Django to develop this system.
I have built similar sub-systems before, by hand.
I don't know much about Django, but do some research to see if it has any "out of the box" or community developed / open source add-ons that do what you want.
If you have to do it yourself...
A key-value pair is not going to be enough, but it's close. You only need a simple data structure:
ID (how your code recognizes this property), e.g. UserPopupBackgroundColor.
Property name (what the user see's / how they recognize this property in the UI), e.g. "Popup Background Color".
Optional - Data type. This is essential if you want to do any sensible input validation. E.g. pop up height should probably expect an integer, and have a sensible min/max value on it, where as an email address is totally different.
Optional, some kind of flag to identify valid properties.
That last flag is bit of an edge case, but it's useful if you use the subsystem to hold more properties than you want users to have access to. E.g. imagine you want to get a list of all properties and display the list to the user - are there any 'special' ones you need to filter out that they should not see?
You then need somewhere to put the values, and link them to the user:
Row ID / GUID. You can use a unique constraint across the User and PropertyID if you wanted to instead, but personally I find a unique row ID is a reliable and flexible approach for most scenarios.
UserID.
PropertyID - refers to ID mentioned above.
PropertyValue
Depending on how serious you need to get, you can dump all the values into the one PropertyValue column (assuming you're persisting this in a database) - which means that column needs to be a string, or, you can add a column per data type.
If you want to add a column per data type, don't kill yourself. The most I have ever done is:
PropertyValue_text (text/varchar)
PropertyValue_int (or double)
PropertyValue_DateTime (date/time - surprise!!)
So when I say 'column per data type' I mean per data type your stack needs/wants to handle - not the 'optional' data types you define in the logic - since that data type is partially just about input validation.
Obviously if you use different logical data types, you can map those to data type columns in the database. The reasons for doing this (using the different data types in the database are:
To reduce the amount of casting you need to do (code to database, and vis-a-versa).
To leverage database level query features, which can be useful. E.g. find emails values and verify them; find expired date values; etc.
It takes a bit of work to build all this, but it's powerful once you get set-up because you can add any number of properties. If you are using the 'full' solution with explicit data types then adding new logical data types isn't too painful if you already have a few set-up.
Before you design and build this, think about future reuse, and anyway you can package it up for later - or community use. Remember it impact all layers (UI, logic and data).
Final tip - when coming up with the property ID's (that the code uses) make them human readable, and use some sort of naming convention so that adding new ones later is easy and follows a predictable path.
Update - Defining Property and PropertyValue in database tables is an obvious way to go. Depending on the situation you can also define Property in code - especially if you don't add new ones or change existing ones very frequently. Another bonus is that if you're in an MVP situation you can use the code effectively as a stub, and build out the database/persistence part for that later.
I was looking for a already defined Media Type on the IANA to represent time series charts but I didn't find one.
Does anyone know of a media type, and if not, do you just use generic collection media types like Collection+JSON or even HAL?
I do think your best bet for now would be to go with HAL or Collection+JSON. If you are new to Hypermedia then I would start with HAL. It is the has the simpler implementation details but is still very flexible.
However, you are free to create your own media type and then get it registered. I looked through the types and could not find any for time series. I think there will be a need for a timeline based type. Perhaps something like Collection+JSON but every collection has a date time.
I'm supporting a server for an online card game and while thinking about refactoring it into a better state I have found myself unable to decide what is a proper object model for my needs.
I have a Player class which has a lot of attributes. The first problem is just that - the class is too big. The second problem is that I don't know how to refactor it. I will list some of the attributes and issues with these.
Some attributes are very tightly bound to a player: nick, email, last login &c. These, I suppose, are to be kept directly in the player class and in the same table in the DB.
Now, some attributes are a little more difficult, like money and gold amount. The problem with these is that they are historically stored in a different table, there might be some more currencies later on and that they MUST be synched into the database at their own pace.
Third category of attributes are loosely coupled to the player, like status string, experience, achievements, statistics &c. These are stored in different tables in the DB and MUST be stored, retrieved, cached and synchronized at their own pace.
Note that one of the big problems here is that we have to implement relatively complex database synchronization schemes because we have a lot of online players and our game is soft-realtime and we have to make load on the DB as low as possible.
My questions are:
How to determine which attributes to store within a player class and which not to? Say, experience, nickname, money amount?
When one has some attributes that may be grouped together like (strength, agility, endurance, &c.) and (handItem, headItem, feetItem, weapon) when they should be grouped and when not?
What to do with complex database synchronization schemes? Make a separate model for each attribute that needs to be synched independently or make some DataManager classes to take them apart and work with them?
What to do with the need for a class to have several different "data representations" for external consumers? Like XML, Json, another XML for some external service, human-readable string, &c.
I'm sorry if my questions are bogus, I'm not really good at OOP design, I'm more an FP guy. And my English is not very good =).
There is no "limit" to what you can store in a player class. As long as it is concerning him and him only, it should be in his class. But one thing you should consider is to make several player classes. The idea is : if you don't need is, don't query it. You may have PlayerView_Small, PlayerBuying, PlayerFighting, PlayerSettings (depending on your game, they may not be fulfilling the exact same purpose)... This way for each "need" of info on a player, you only load the player data you need, and can handle it properly. Also, you may use inheritance if some class is only a more detailed version of the other.
If you are talking about the class, it may be in a sub-class PlayerAttributes of which an instance is contained into PlayerFighting and PlayerView_Detailed. In the database, it might be interesting to store it as a string (conveniently outputted by our class, and accepted in constructor), to avoid having too much fields, but you will lose the sorting ability. That's probably not a problem in our case, but might be in some others.
Blank for now, I don't understand where there is synchronization, will edit when informed.
In your PlayerViewDetailInfo(or in your PlayerAllData depending what you need), you place some methods such as ToXmlClient1(), ToJson(), ToHumanReadableString() (although that might be a bit confusing to the eye, you should consider HTML^^). The class having the method should be the class with the least (but sufficient to provide the answer) data. When requested, you load the Player... which has the method giving the correct output, and you write it directly in the response.
I would like to make a program (I would prefer in C language) , but even in cocoa , that can take data from an external program (such as iTunes or adium) and will use them. For example i would like to take the data of a listbox or the text of the chat so as to manipulate it. I need a place to start. In windows I think it is possible with some apis that find the hWnd of a window and then find a pointer to the listbox or textbox. Please give me some info on how to start. Thanks you in advance.
It's not clear exactly what you want to do. It's either impossible or severely restricted.
For one thing, different applications use different ways of constructing a “listbox”—Cocoa applications use NSTableView, Carbon applications use DataBrowser, and GTK, Qt, and Java applications use even more different APIs. These do not all go through some common kind of list box thingy; each is an independent implementation.
(You could hope that either NSTableView or DataBrowser would be based on the other, but don't count on it.)
For another, it is impossible to obtain a pointer to that control. You cannot access another application's NSTableView or DataBrowser view or GTK/Qt/Java equivalent unless (and this only works for NSTableView) that application deliberately serves it up to you. It doesn't sound like that's your situation.
The closest you can get to that is Accessibility, which may be pretty close, but is unlikely to work with most applications not based on Cocoa.
Even then, the view may not be showing you all the data. A table view may be lazily populated, and a table view designed in imitation of the iOS UITableView may even never have all the data (because it only has what it can show).
(All of the above applies to every kind of view, not just table views. Collection views, text fields, buttons—same deal for all of them.)
The only way to get at the true, complete copy of the data is to ask the controller that owns it. And, again, that's impossible if the application is not specifically offering it to you. Not to mention, the application might not even have a controller (not object-oriented, not MVC, or just sloppily made).
… so as to manipulate it.
Getting the data in the first place is the easy part. It is nigh-impossible to mess with data in another application—for good reason.
The closest you're going to get to either of these goals is the Accessibility interfaces.