Before starting a project, it's essential that a team studies its costumers and user needs, so it can have a clear goal and understanding of a solution's required properties.
Software ystem requirements describe what a system should do, the services it provides and its operation constraints. Some of the problems that arise during the requirements engineering process are due to not separating these different levels of description properly.
They are divided into two categories: user requirements and system requirements.
Requirement engineering processes may include four important high-level activities. assessment of utility to a specified business (feasibility study), discovering requirements (elicitation and analysis), standardization of the latter (specification), and verifying that these do indeed meet the customer's needs (validation).
For requirements elicitation, we interviewed the main Citra team developers, as well as obtaining information from their website, https://citra-emu.org/.
As said by one of the main developers, the requeriments are mostly fixing bugs and implementing new features.
Since Citra is not supported by any company, they do not have a deadline to implement features. So how does the team decide on whether or not to implement a new feature?
With an emulator, they already have a "spec" to follow - the original console that they're trying to emulate, so new "features" generally mean emulating part of that console that had not already been implemented (or at times, implemented partialy). User requests often do not relate to emulation, but rather usability features. For example, a user won't request to implement the 3DS's fragment lighting (they already know how to do that, it's part of the hardware!), but they might request to implement cheat code support or changes to the user interface. These types of usability features tend to be in a lower priority (as they still don't have the most important thing, the fully working emulation, completed), so they aren't a big driving factor in the work that they do currently. As said by the main developer,this may change as the project becomes more mature.
Lastly, they say optimization is another big area - lots of effort is spent identifying bottlenecks and rewriting things to improve speed. Emulation of modern video game systems requires both fast/efficient code and a fast computer.
They implement features when they want or when the contributors have a feature that have the quality they require in order to avoid bugs or setbacks but their main focus right now is having a fully working emulation completed,to fix bugs that stop games from booting and bugs that crashes the program when running.Issues about specific games not booting are valid bugs but they are currently not interested in them unless there are several games which fail with the same or similar messages. There are too many non-working games right now to file individual issues for every one of them.
In future they intend to implement features like cheat code support, improve speed of cut scenes and support for mobile platforms.
Given the circumstances of this project (hobby, volunteers, low amount of time that developers have to work and inconsistent frequency of commits, specific knowledge about console hardware, emulation, among other areas) the reality of the new features is, contributors of Citra contribute what they like and not always what is ideal.
Citra works on all three major desktop operating systems and is actively tested and supported on various 64-bit version of Windows (7 and up), Linux and Mac OS X. Other platforms may work, but aren't tested by developers. In far future, mobile platforms may be targeted as well. They have no plans to support 32-bit operating system officially.
At this point, Citra is simply not fast enough to run most commercial games at full speed, even if your computer can run the most demanding of PC games just fine.
The only hard requirements for the official version of Citra is a graphics chip that supports at least OpenGL 3.3 and a 64-bit OS, but you definitely want a processor with the highest possible performance per core.
A system's functional requirements describe what the system should do. With Citra, they include having the emulator running smoothly, with no crashes, while performing as accurately as possible to the physical console. Another one is Hardware Specifics emulation - as the purpose of the emulator is to emulate the hardware's functionality.
Non-functional requirements, as the name suggests, do not concern the actual workings of the system. In Citra's case, they manifest as code standards and matching a specific design process.
The use cases describes what Citra does from a user’s perspective. Since we are not dealing with a game, but an actual emulator, the nuances of certain game features are not the concern of this model. Although very simple, these are the uses cases for Citra Emulator.
| Indie Developer & Gamer | Emulate Game | This is the core feature of an emulator, no explanation required. |
| Indie Developer | Debug | A developer should be able to debug his game on Citra. |
| Gamer | Save Game & Load Game | Although some (if not all) games already come with a save/load game feature, some emulators allow users to save the state of the emulation. |
Domain model is a conceptual model of the domain that incorporates both behavior and data. Its purpose is to connect Use Case Model with Software Design Model. Since this emulator is such a simple concept, and the problem domain is rather small, there really isn't the need for real world classes. With this in mind we decided, that this would be the domain model for the project:
