** Basics Q: Is Mono the same as Microsoft's .NET initiative? A: It is not. .NET is a company-wide initiative at Microsoft that encompasses many different areas. The .NET development framework, Passport, Biztalk, new server products, and anything that is remotely connected to .NET gets the ".NET-stamping" treatment. Some components of Microsoft's .NET initiative have been announced and some others are in the works. Mono is a project to implement several technologies developed by Microsoft that have now been submitted to the ECMA Standards Body. Q: What technologies are included in Mono? A: Mono contains a number of components useful for building new software: The CLR and the Common Type System (CTS) enables applications and libraries to be written in a number of languages. Classes and methods created in one language can be used from a different language. This means for example that if you define a class to do algebraic manipulation in C#, that class can be reused from any other language that supports the CLI. You could create a class in C#, subclass it in C++ and instantiate it in an Eiffel program. A single object system, threading system, class libraries, and garbage collection system can be shared across all these languages. Q: Where can I find the specification for these technologies? A: You can find the work-in-progress documentation from the T3G ECMA group here: http://www.dotnetexperts.com Q: Will you implement the .NET Framework SDK class libraries? A: Yes, we will be implementing the APIs of the .NET Framework SDK class libraries. Q: What does Mono stand for? A: Mono is the word for `Monkey' in Spanish. We like monkeys. Q: When will you ship it? A: We do not know when the code will be shipped. The more contributions we get to the project, the sooner it will ship. A rough estimate is that we might be able to run our C# compiler on Linux by the end of the year. That means running the Windows Executable generated by a Microsoft .NET compiler on the Linux platform. We expect that doing GUI applications will require more work on the class libraries. That could take another six months. Q: How can I contribute? A: Check the contributing section. Q: You guys should innovate instead of copying. A: In this particular case, we see a clear advantage in the platform and we are interested in using the features of the CLI on open source systems. We have decided that we should spend our limited resources towards implementing an existing specification instead of designing and implementing our own. Designing and implementing our own would be possible, but it doesn't make sense to do that just because the specification comes from a proprietary vendor. ** Ximian Q: Why is Ximian working on .NET? A: We are interested in providing the best tools for programmers to develop applications for Free Operating Systems. For more information, read the project rationale page. Q: Will Ximian be able to take on a project of this size? A: Ximian will not be able to taken on the whole project on its own. Mono will be a free software/open source community project, that is the only way we can hope to implement something of this size. You can contribute to this effort. Q: What pieces will Ximian be working on? A: We will focus on building a development and execution environment. The idea is to get Mono to a state of that would allow third parties to actually be able to use it real-world development. Q: Why does Ximian even care? A: We like the features that the CLI and its related technologies bring to the table. An exciting addition to the developer toolkit. The goal of Mono is to bring this technology to non-Windows platforms (although we hope Mono will also run on Windows, for debugging and comparative purposes). ** Licensing Q: Will I be able to write proprietary applications that run with Mono? A: Yes. We will make sure that the licensing will allow developers to create proprietary applications. Q: What license is Mono on? A: The C# Compiler is released under the terms of the GPL. The class libraries will be under the LGPL or the GPL with a special exception. The runtime libraries are under the LGPL. Here is the exception for the class libraries: The library is distributed under the terms of the GNU General Public License with the following exception: If you link this library against your own program, then you do not need to release the source code for that program. However, any changes that you make to the library itself, or to any native methods upon which the library relies, must be re-distributed in accordance with the terms of the GPL. This is similar in spirit to GNU Classpath. Q: Will you accept code under the XXX License? A: If the XXX License is compatible with the license we use in that specific piece of code, then yes. If you want to use the BSD license, make sure you use the BSD license without the advertisement clause (The `Ousterhout License'). ** Mono and .NET Q: If applications use Mono, does that mean that I have to pay a service fee? A: No. Mono is not related to Microsoft's initiative of software-as-a-service. Q: If you implement .NET, will I depend on Microsoft Passport to run my software? A: No. The .NET Framework is a runtime infrastructure and collection of class libraries. Passport may be required to access certain web services written for that framework, but only if the programmer chooses Passport as the authentication mechanism. Q: Is .NET just a bunch of marketing slogans? A: Although the `.NET initiative' is still quite nebulous, The .NET Framework has been available for some time. Mono is not an implementation of the .NET initiative, just the development framework. Q: What is a 100% .NET application? A: A `100% .NET application' is one that only uses the APIs defined under the System namespace and does not use PInvoke. These applications would in theory run unmodified on Windows, Linux, HP-UX, Solaris, MacOS X and others. Q: But Microsoft will release a port of the real thing under the `Shared Source' license, why bother with anything else? A: The Shared Source implementation will not be usable for commercial purposes. We are working towards an implementation that will grant a number of rights to recipients: use for any purpose, redistribution, modification, and redistribution of modifications. This is what we call Free Software ** Passport Q: Is this a free implementation of Passport? A: No. Passport is part of Microsoft's Hailstorm initiative. Mono is just a runtime, a compiler and a set of class libraries. Q: Will the System.Web.Security.PassportIdentity class, mean that my software will depend on Passport? A: No. That just means that applications might use that API to contact a Passport site. As long as your application does not use Passport, you will not need Passport. It might even be possible to implement that class with a set of dummy functions, or use an alternate Passport implementation. We do not know at this time whether the Passport protocol is documented and whether we will be able to talk to passport.com Q: What is your opinion? A: You can read my personal opinion on passport. ** Mono and Windows Q: Will Mono allow me to run Microsoft Office on Linux? A: No, it will not. Microsoft Office is a Windows application. To run Windows applications on Intel Unix systems refer to the Wine Project ** GNOME Q: How is this related to GNOME? A: In a number of ways: * Mono will use existing components that have been developed for GNOME when it makes sense. For example on X systems, we will use Gtk+ and Libart to implement Winforms and the Drawing2D API. For database access, we will use LibGDA (not really depending on GNOME, but related to). * This project was born out of the need of providing improved tools for the GNOME community. * We would like to add support to our CLR implementation to deal with GObjects (in GNOME 1.x, they are called GtkObjects), and allow Mono developers to provide GObjects or use and extend existing GObjects. Q: Has the GNOME Foundation or the GNOME team adopted Mono? A: Mono is too new to be adopted by those groups. We hope that the tools that we will provide will be adopted by free software programmers including the GNOME Foundation members and the GNOME project generally. Q: Should GNOME programmers switch over to Mono? A: Mono will not be ready even within the next six months, and a complete implementation is probably one year away. We encourage GNOME developers to continue using the existing tools, libraries and components. Improvements made to GNOME will have an impact on Mono, as they will provide the "backend" for various classes. Q: Will Mono include compatibility with Bonobo components? A: Yes, we will provide a set of classes for implementing and using Bonobo components from within Mono. ** Mono and the Web Q: Is Mono a way of running Java applets? A: No. ** Web Services Q: Is Mono just a new way of writing Web Services? A: No. Q: If this implements the SDK classes, will I be able to write and execute .NET Web Services with this? A: Yes, you will. When the project is finished, you will be able to use the same technologies that are available through the .NET Framework SDK on Windows to write Web Services. Q: What about Soup? A: Soup is a library for GNOME applications to create SOAP server and SOAP clients. You can browse the source code for soup using GNOME's Bonsai Q: Can I use CORBA? A: Yes. The CLI contains enough information about a class that exposing it to other RPC systems (like CORBA) is really simple, and does not even require support from an object. We will be implementing CORBA interoperation as an extension to the Mono classes so that we can integrate with Bonobo, just like Microsoft provides COM interoperation classes and support mechanisms. Q: Can I serialize my objects to other things other than XML? A: Yes, although the serializing tools have not yet been planned, and you would probably have to implement them yourself. ** Development Tools Q: Will it be possible to use the CLI features without using bytecodes or the JIT? A: Yes. The CLI engine will be made available as a shared library. The garbage collection engine, the threading abstraction, the object system, the dynamic type code system and the JIT will be available for C developers to integreate with their applications if they wish to do so. Q: Will you have new development tools? A: Hopefully Free Software enthusiasts will contribute tools to improve the developer environment. These tools could be developed initially using Microsoft implementation of the CLI and then executed later with Mono. ** Mono and Java Q: What about using Java? After all there are many languages that target the Java VM. A: You can get very good tools for doing Java development on free systems right now. Red Hat has contributed a GCC frontend for Java that can take Java sources or Java byte codes and generate native executables; Transvirtual has implemented Kaffe a JIT engine for Java; Intel also has a Java VM called ORP. The JVM is not designed to be a general purpose virtual machine. The Common Intermediate Language (CIL), on the other hand, is designed to be a target for a wide variety of programming languages, and has a set of rules designed to be optimal for JITers. Q: What kind of rules make the Common Intermediate Language useful for JITers? A: The main rule is that the stack in the CLI is not a general purpose stack. You are not allowed to use it for other purposes than computing values and passing arguments to functions or return values. At any given call or return instruction, the types on the stack have to be the same independently of the flow of execution of your code. Q: I heard that the CIL is ideal for JITing and not efficient for interpreters, is this the case? A: The CIL is better suited to be JITed than JVM byte codes, but you can interpret them as trivially as you can interpret JVM byte codes. ** Extending Mono Q: Would you allow other classes other than those in the specification? A: Yes. The Microsoft class collection is very big, but it is by no means complete. It would be nice to have a port of `Camel' (the Mail API used by Evolution inspired by Java Mail) for Mono applications. You might also want to look into implementing CORBA for Mono. Not only because it would be useful, but because it sounds like a fun thing to do, given the fact that the CLI is such a type rich system. For more information on extending Mono, see our ideas page. ** Mono and portability Q: Will Mono only work on Linux? A: Currently, we are doing our work on Linux-based systems and Windows. We do not expect many Linux-isms in the code, so it should be easy to port Mono to other UNIX variants. Q: What about Mono on non X-based systems? A: Our main intention at Ximian is to be able to develop GNOME applications with Mono, but if you are interested in providing a port of the Winform classes to other platforms (frame buffer or MacOS X for example), we would gladly integrate them, as long they are under a Free Software License. ** Reusing existing Code Q: What projects will you reuse or build upon? A: We want to get Mono in the hands of programmers soon. We are interested in reusing existing open source software. Q: What about Intel's research JIT framework, ORP? A: At this time, we are investigating whether we can use elements of ORP for Mono. ORP is a research JIT engine that has a clear defined API that splits the JIT from the GC system and the actual byte code implementation. It is a research product. Q: What about using GNU Lightning? A: We are also researching GNU Lightning. ** Ximian and Microsoft Q: Didn't Miguel de Icaza say that `Unix Sucks'? A: Yes, he did, as a catch phrase in his opening remark on the Ottawa Linux Symposium. His talk focused on various ways to improve Unix. There is a paper describing some ways to improve Unix at: http://primates.ximian.com/~miguel/bongo-bong.html Q: Didn't Ximian's Miguel work for Microsoft? A: Actually, Nat Friedman (Ximian's co-founder) did work as an intern for Microsoft for one summer but Miguel did not. Q: Did Nat and Miguel meet at Microsoft? A: They met online on the Linux IRC network; They met in person for the first time in 1997. ** Mono and Microsoft Q: How can you expect Mono to compete with Microsoft, wont this require an effort too large? A: You are right. Mono will never become a reality without the help of other contributors. Ximian is a small company that can not finish Mono alone. We will be working with members of the community to deliver the product. Q: Is Microsoft and Corel involved in the Mono implementation? A: No, they are not. Q: Are you writing Mono from the ECMA specs? A: yes, we are writing them from the ECMA specs and the published materials in print about .NET ** Acronyms Q: What is the difference between CLR (Common Language Runtime) and CLI (Common Language Infrastructure)? A: CLI is the specification of an execution system. The Microsoft implementation of this specification is named CLR. Unless we come up with our own acronym, we could just call ours also CLR, just because it would do exactly the same thing the Microsoft implementation does. ** Mono and GCC Q: Should someone work on a GCC front-end to C#? A: I would love if someone does, and we would love to help anyone that takes on that task, but we do not have the time or expertise to build a C# compiler with the GCC engine. I find it a lot more fun personally to work on C# on a C# compiler, which has an intrinsic beauty. Q: Should someone make a GCC backend that will generate CIL images? A: I would love to see a backend to GCC that generates CIL images. It would provide a ton of free compilers that would generate CIL code. This is something that people would want to look into anyways for Windows interoperation in the future. Q: What about making a front-end to GCC that takes CIL images and generates native code? A: I would love to see this, specially since GCC supports this same feature for Java Byte Codes. You could use the metadata library from Mono to read the byte codes (ie, this would be your "front-end") and generate the trees that get passed to the optimizer. Ideally our implementation of the CLI will be available as a shared library that could be linked with your application as its runtime support. Q: But would this work around the GPL in the GCC compiler and allow people to work on non-free front-ends? A: People can already do this by targeting the JVM byte codes (there are about 130 compilers for various languages that target the JVM). Q: Why are you writing a JIT engine instead of a front-end to GCC? A: The JIT engine and runtime engine will be able to execute CIL executables generated on Windows. ** Mono and GNU Q: Is Mono part of the GNU project? A: Mono is a Ximian project, that is also part of the GNU project. ** Mono and Portability Q: Will Mono work on other variants of Unix? A: Yes. We do not expect to add any gratuitous incompatibilities. Q: Will Mono run on Windows? A: Hopefully yes. Currently some parts of Mono only run on Windows (the C# compiler is a .NET executable) and other parts have only been compiled on Linux, but work on Windows with Cygwin. Q: Will Mono depend on GNOME? A: It will depend only if you are using a particular assembly (for example, for doing GUI applications). If you are just interested in Mono for implementing a `Hello World Enterprise P2P Web Service', you will not need any GNOME component. ** Performance Q: How fast will be Mono? A: We can not predict the future, but a conservative estimate is that it would be at least `as fast as other JIT engines'. Now, wishfully thinking I hope that we will ship various JITs with Mono just like Microsoft has done. A fast JITer when maximum performance is not needed, but fast load times are important; And an optimizing JITer that would be slower at generating code but produce more optimal output. The CIL has some advantages over the Java byte code: it is really an intermediate representation and there are a number of restrictions on how you can emit CIL code that simplify creating better JIT engines. For example, on the CIL the stack is not really an abstraction available for the code generator to use at will: it is just a way of creating a postfix representation of the parsed tree. At any given call point or return point, the contents of the stack are expected to contain the same object types independently of how the instructions was reached. ** Assorted questions Q: You say that the CLI allows multiple languages to execute on the same environment. Isn't this the purpose of CORBA? A: CORBA can be used for this purpose, but think of CORBA mostly as a inter-process (local machine or remote machine) communication system. Think of the CLI to be targeted to interoperation of languages in the same process, and CORBA as being a nifty addition for out-of-process. Sure, we have used CORBA for in-proc components, but the lack of an ABI for in-proc components does not translate into a good framework for in-proc systems