1 <a href="#basics">Basics</a><br>
2 <a href="#ximian">The Ximian Role in the Mono project</a><br>
3 <a href="#gnome">Mono and GNOME</a><br>
4 <a href="#gui">Building GUI applications with Mono</a><br>
5 <a href="#msft">Mono and Microsoft</a><br>
6 <a href="#pnpproject">Mono and the Portable.NET Project</a><br>
7 <a href="#webservices">Web Services</a><br>
8 <a href="#devel">Development Tools and Issues</a><br>
9 <a href="#java">Mono and Java</a><br>
10 <a href="#extending">Extending Mono</a><br>
11 <a href="#portability">Portability</a><br>
12 <a href="#reuse">Reusing Existing Code</a><br>
13 <a href="#gcc">Mono and GCC</a><br>
14 <a href="#performance">Performance</a><br>
15 <a href="#licensing">Licensing</a><br>
16 <a href="#etc">Miscellaneous Questions</a><br>
22 Q: What is Mono exactly?
24 A: The Mono Project is an open development initiative sponsored by
25 Ximian that is working to develop an open source, Linux-based
26 version of the Microsoft .NET development platform. Its objective
27 is to enable Linux developers to build and
28 deploy cross-platform .NET Applications. The project will
29 implement various technologies developed by Microsoft that have now
30 been submitted to the ECMA for standardization.
32 Q: What is the difference between Mono and the .NET Initiative?
34 A: The ".NET Initiative" is a somewhat nebulous company-wide effort by
35 Microsoft, one part of which is a cross-platform development
36 framework. Mono is an implementation of the development framework,
37 but not an implementation of anything else related to the .NET
38 Initiative, such as Passport, software-as-a-service, or
41 Q: What technologies are included in Mono?
43 A: Mono contains a number of components useful for building new
47 * A Common Language Infrastructure (CLI) virtual
48 machine that contains a class loader, Just-in-time
49 compiler, and a garbage collecting runtime.
51 * A class library that can work with any language
52 which works on the CLR.
54 * A compiler for the C# language. In the future we
55 might work on other compilers that target the Common
60 Windows has compilers that target the virtual machine from <a
61 href="http://msdn.microsoft.com/net/thirdparty/default.asp#lang">a
62 number of languages:</a> Managed C++, Java Script, Eiffel,
63 Component Pascal, APL, Cobol, Oberon, Perl, Python, Scheme,
64 Smalltalk, Standard ML, Haskell, Mercury and Oberon.
66 The CLR and the Common Type System (CTS) enables applications and
67 libraries to be written in a collection of different languages that
70 This means for example that if you define a class to do algebraic
71 manipulation in C#, that class can be reused from any other
72 language that supports the CLI. You could create a class in C#,
73 subclass it in C++ and instantiate it in an Eiffel program.
75 A single object system, threading system, class libraries, and
76 garbage collection system can be shared across all these languages.
78 Q: Where can I find the specification for these technologies?
80 A: You can find the work-in-progress documentation from the T3G ECMA
83 <a href="http://www.dotnetexperts.com">http://www.dotnetexperts.com</a>
85 Q: Will you implement the .NET Framework SDK class libraries?
87 A: Yes, we will be implementing the APIs of the .NET Framework SDK
90 Q: Will you offer an ECMA-compliant set of class libraries?
92 A: Eventually we will. Our current focus is on interoperating
93 with the Microsoft SDK, but we will also offer an ECMA compliant
96 Q: What does the name "Mono" mean?
98 A: Mono is the word for `monkey' in Spanish. We like monkeys.
102 A: The JIT engine is usable on Intel x86 machines. An interpreter
103 can be used on other non-Intel x86 machines.
105 The class libraries are not yet mature enough to run real applications,
106 but if you are interested in trying out Mono, you can definetly start
107 testing things out as many programs run.
109 The C# compiler has made significant progress, it can even compile
110 itself now, but it can not yet be ran with our class libraries as
111 they are missing some features.
113 Q: When will you ship it?
115 A: It is premature to target a shipdate for the code, but we
116 anticipate that it will be available some time in the middle of
119 Q: How can I contribute?
121 A: Check the <a href="contributing.html">contributing</a> section.
123 Q: Aren't you just copying someone else's work?
125 A: We are interested in providing the best tools for programmers to
126 develop applications for Free Operating Systems. We also want to help
127 provide the interoperability that will allow those systems to fit in
128 with other standards.
130 For more background, read the <a href="http://www.go-mono.com/rationale.html">Mono
131 Project white paper</a>.
135 <a name="ximian"></a>
137 ** The Ximian Role in the Mono Project
139 Q: Why is Ximian working on .NET?
141 A: Ximian is interested in providing the best tools for programmers to
142 develop applications for Free Operating Systems.
144 For more information, read the project <a
145 href="rationale.html">rationale</a> page.
147 Q: Will Ximian be able to take on a project of this size?
149 A: Of course not. Ximian a supporter of the Mono project, but the only way
150 to implement something of this size is for the entire free software
151 community to get involved. Visit the <a href="contributing.html">contributing</a>
152 page if you'd like to help out.
154 Q: What pieces will Ximian be working on?
156 A: We will devote most of our resources to work on the pieces which are
157 on the critical path to release a development and execution
158 environment. Once the project is at a stage where it is useful in
159 the real world, it will achieve a critical mass of developers to
162 Q: Will Ximian offer Mono commercially?
164 A: When Mono is ready to be shipped Ximian will offer a commercial
165 support and services for Mono.
167 Q: Will you wait until Mono is finished?
169 A: Mono will ship on various stages as they mature. Some people
170 require only a subset of the technologies, those will ship first.
172 More advanced features will take more time to develop. A support
173 timeline will be available in June 2002.
178 Q: How is Mono related to GNOME?
180 A: In a number of ways. This project was born out of the need of
181 providing improved tools for the GNOME community, and will use
182 existing components that have been developed for GNOME when they
183 are available. For example, we plan to use Gtk+ and Libart to
184 implement Winforms and the Drawing2D API and are considering
187 Q: Has the GNOME Foundation or the GNOME team adopted Mono?
189 A: Mono is too new to be adopted by those groups. We hope that the
190 tools that we will provide will be adopted by free software
191 programmers including the GNOME Foundation members and the GNOME
194 Q: Should GNOME programmers switch over to Mono now?
196 A: It is still far to early for discussions of "switching over." No
197 pieces of Mono will be ready within the next six months, and a
198 complete implementation is roughly one year away.
200 We encourage GNOME developers to continue using the existing tools,
201 libraries and components. Improvements made to GNOME will have an
202 impact on Mono, as they would be the "backend" for various classes.
204 Q: Will Mono include compatibility with Bonobo components? What is the
205 relationship between Mono and Bonobo?
207 A: Yes, we will provide a set of classes for implementing and using
208 Bonobo components from within Mono. Mono should allow you to write
209 Bonobo components more easily, just like .NET on Windows allows you
210 to export .NET components to COM.
212 Q: Does Mono depend on GNOME?
214 A: No, Mono does not depend on GNOME. We use a few packages produced by
215 the GNOME team like the `glib' library.
217 Q: But will I be able to build GNOME applications?
219 A: Yes, we will enable people to write GNOME applications using Mono.
224 Q: Will Mono enable GUI applications to be authored?
226 A: Yes, you will be able to build GUI applications. Indeed, that is our
227 main focus. We will provide both the Windows.Forms API and the Gtk# AP(I.
229 Q: What is the difference between Gtk# and System.Windows.Forms?
231 A: Gtk# is a set of bindings for the Gtk+ toolkit for C# (and other
232 CIL-enabled languages). System.Windows.Forms is an API defined
233 by Microsoft to build GUI applications.
235 Q: Will I be able to run my smart clients on systems powered by Mono?
237 A: As long as your applications are 100% .NET and do not make use
238 of P/Invoke to call Win32 functions, your smart client applications
239 will run on Mono platforms.
242 ** Mono and Microsoft
244 Q: Is Microsoft helping Ximian with this project?
246 A: No. Ximian CTO Miguel de Icaza had a friendly conversation with
247 Microsoft software architect David Stutz, but that's about the
248 extent of the contact. Microsoft is interested in other
249 implementations of .NET and are willing to help make the ECMA spec
250 more accurate for this purpose.
252 Ximian representatives have also spoken with Sam Ruby at the ECMA
253 TG3 committee to discuss the same issues.
255 Q: Is Microsoft or Corel paying Ximian to do this?
259 Q: Do you fear that Microsoft will change the spec and render Mono
262 A: No. Microsoft proved with the CLI and the C# language that it was
263 possible to create a powerful foundation for many languages to
264 interoperate. We will always have that.
266 Even if changes happened in the platform which were undocumented,
267 the existing platform would a value on its own.
269 Q: Are you writing Mono from the ECMA specs?
271 A: Yes, we are writing them from the ECMA specs and the published
272 materials in print about .NET.
274 Q: If my applications use Mono, will I have to pay a service fee?
276 A: No. Mono is not related to Microsoft's initiative of
277 software-as-a-service.
279 Q: Is the Mono Project is related to the Microsoft Hailstorm effort? Is
280 Ximian endorsing Hailstorm?
282 A: No. The Mono Project is focused on providing a compatible set of
283 tools for the Microsoft .NET development platform. It does not
284 address, require, or otherwise endorse the MS Passport-based
285 Hailstorm single sign-on system that is part of Windows XP and
288 Q: Will Mono or .NET applications depend on Microsoft Passport?
290 A: No. MS Passport is unrelated to running .NET compatible applications
291 produced with the Mono tools. The only thing you will need is a
292 just-in-time compiler (JIT).
294 Q: What is a 100% .NET application?
296 A: A `100% .NET application' is one that only uses the APIs defined
297 under the System namespace and does not use PInvoke. These
298 applications would in theory run unmodified on Windows, Linux,
299 HP-UX, Solaris, MacOS X and others.
301 Q: If Microsoft will release a port of their .NET platform under the
302 `Shared Source' license, why should I bother with anything else?
304 A: The Shared Source implementation will be expensive and its uses
305 will be tightly restricted, especially for commercial use. We are
306 working towards an implementation that will grant a number of
307 important rights to recipients: use for any purpose,
308 redistribution, modification, and redistribution of modifications.
310 This is what we call <a
311 href="http://www.gnu.org/philosophy/free-sw.html">Free Software</a>
313 Q: Is Mono a free implementation of Passport?
315 A: No. Mono is just a runtime, a compiler and a set of class
318 Q: Will the System.Web.Security.PassportIdentity class mean
319 that my software will depend on Passport?
321 A: No. Applications may use that API to contact a Passport site, but
322 are not required to do so.
324 As long as your application does not use Passport, you will not
327 Q: Will Mono running on Linux make Passport available for Linux?
329 A: No. However, the Passport toolkit for Linux-based web servers is
330 available from Microsoft.
332 Q: Will Mono allow me to run Microsoft Office on Linux?
334 A: No, it will not. Microsoft Office is a Windows application. To
335 learn more about running Windows applications on Intel Unix systems
336 refer to <a href="http://www.winehq.com">the Wine Project</a>.
338 <a name="pnpproject"></a>
339 ** Mono and Portable.NET
341 Q: What are the differences between Mono and Portable.NET?
343 A: Most of Mono is being written using C#, with only
344 a few parts written in C (The JIT engine, the runtime, the
345 interfaces to the garbage collection system). The Portable.NET
346 Project is using C for development.
348 <a name="webservices"></a>
351 Q: How is Mono related to Web Services?
353 A: Mono is only related to Web Services in that it will implement the
354 same set of classes that have been authored in the .NET Framework
355 to simplify and streamline the process of building Web Services.
357 But most importantly, Mono is an Open Source implementation of the
360 Q: Can I author Web Services with Mono?
362 A: You will be able to write Web Services on .NET that run on Mono and
365 Q: If Mono implements the SDK classes, will I be able to write and
366 execute .NET Web Services with it?
368 A: Yes. When the project is finished, you will be able to use the
369 same technologies that are available through the .NET Framework SDK
370 on Windows to write Web Services.
372 Q: What about Soup? Can I use Soup without Mono?
374 A: Soup is a library for GNOME applications to create SOAP servers and
375 SOAP clients, and can be used without Mono. You can browse the
376 source code for soup using <a
377 href="http://cvs.gnome.org/bonsai">GNOME's Bonsai</a>.
381 A: Yes. The CLI contains enough information about a class that
382 exposing it to other RPC systems (like CORBA) is really simple, and
383 does not even require support from an object.
385 We will be implementing CORBA interoperation as an extension to the
386 Mono classes so that we can integrate with Bonobo, just like
387 Microsoft provides COM interoperation classes and support
390 Q: Can I serialize my objects to other things other than XML?
392 A: Yes, although the serializing tools have not yet been planned, and
393 you would probably have to implement them yourself.
396 ** Development Tools and Issues
398 Q: Will it be possible to use the CLI features without using bytecodes
401 A: Yes. The CLI engine will be made available as a shared library.
402 The garbage collection engine, the threading abstraction, the
403 object system, the dynamic type code system and the JIT will be
404 available for C developers to integreate with their applications if
407 Q: Will you have new development tools?
409 A: With any luck, Free Software enthusiasts will contribute tools to
410 improve the developer environment. These tools could be developed
411 initially using the Microsoft implementation of the CLI and then
412 executed later with Mono.
414 Q: What kind of rules make the Common Intermediate Language useful for
417 A: The main rule is that the stack in the CLI is not a general purpose
418 stack. You are not allowed to use it for other purposes than
419 computing values and passing arguments to functions or return
422 At any given call or return instruction, the types on the stack
423 have to be the same independently of the flow of execution of your
426 Q: Is it true that the CIL is ideal for JITing and not efficient for
429 A: The CIL is better suited to be JITed than JVM byte codes, but you
430 can interpret them as trivially as you can interpret JVM byte
436 Q: Why don't you use Java? After all, there are many languages that
439 A: You can get very good tools for doing Java development on free
440 systems right now. <a href="http://www.redhat.com">Red Hat</a> has
441 contributed a <a href="http://gcc.gnu.org">GCC</a> <a
442 href="http://gcc.gnu.org/java">frontend for Java</a> that can take
443 Java sources or Java byte codes and generate native executables; <a
444 href="http://www.transvirtual.com">Transvirtual</a> has implemented
445 <a href="http://www.kaffe.org">Kaffe</a> a JIT engine for Java;
446 Intel also has a Java VM called <a
447 href="http://www.intel.com/research/mrl/orp">ORP</a>.
449 The JVM is not designed to be a general purpose virtual machine.
450 The Common Intermediate Language (CIL), on the other hand, is
451 designed to be a target for a
452 wide variety of programming languages, and has a set of rules
453 designed to be optimal for JITers.
455 Q: Could Java target the CLI?
457 A: Yes, Java could target the CLI. We have details on a <a
458 href="ideas.html#guavac">project</a> that someone could take on to
461 Microsoft has an implemenation of the Java language called J# that
462 can target the CIL execution engine.
464 <a name="extending"></a>
467 Q: Would you allow other classes other than those in the
470 A: Yes. The Microsoft class collection is very big, but it is by no
471 means complete. It would be nice to have a port of `Camel' (the
472 Mail API used by Evolution inspired by Java Mail) for Mono
475 You might also want to look into implementing CORBA for Mono. Not
476 only because it would be useful, but because it sounds like a fun
477 thing to do, given the fact that the CLI is such a type rich
480 For more information on extending Mono, see our <a
481 href="ideas.html">ideas</a> page.
483 Q: Do you plan to Embrace and Extend .NET?
485 A: Embracing a good technology is good. Extending technologies in
486 incompatible ways is bad for the users, so we do not plan on
487 extending the technologies.
489 If you have innovative ideas, and want to create new classes, we
490 encourage you to make those classes operate correctly well in both
493 <a name="portability"></a>
496 Q: Will Mono only work on Linux?
498 A: Currently, we are doing our work on Linux-based systems and
499 Windows. We do not expect many Linux-isms in the code, so it
500 should be easy to port Mono to other UNIX variants.
502 Q: What about Mono on non X-based systems?
504 A: Our main intention at Ximian is to be able to develop GNOME
505 applications with Mono, but if you are interested in providing a
506 port of the Winform classes to other platforms (frame buffer or
507 MacOS X for example), we would gladly integrate them, as long
508 they are under an open source license.
510 Q: Will Mono run on Windows?
512 A: We hope so. Currently some parts of Mono only run on Windows
513 (the C# compiler is a .NET executable) and other parts have only
514 been compiled on Linux, but work on Windows with Cygwin.
516 Q: Will Mono depend on GNOME?
518 A: It will depend only if you are using a particular assembly (for
519 example, for doing GUI applications). If you are just interested
520 in Mono for implementing a `Hello World Enterprise P2P Web
521 Service', you will not need any GNOME components.
524 ** Reusing Existing Code
526 Q: What projects will you reuse or build upon?
528 A: We want to get Mono in the hands of programmers soon. We are
529 interested in reusing existing open source software.
531 Q: What about Intel's research JIT framework, ORP?
533 A: At this time, we are investigating whether we can use elements of
534 ORP for Mono. ORP is a research JIT engine that has a clearly
535 defined API that splits the JIT from the GC system and the actual
536 byte code implementation.
538 Q: What about using GNU Lightning?
540 A: We are also researching <a
541 href="http://www.gnu.org/software/lightning/lightning.html">GNU
547 Q: Are you working on a GCC front-end to C#? A GCC backend that will
548 generate CIL images? What about making a front-end to GCC that
549 takes CIL images and generates native code?
551 A: We are currently seeking volunteers for those projects.
552 Visit the <a href="contributing.html">contributing</a> section if
555 Q: But would this work around the GPL in the GCC compiler and allow
556 people to work on non-free front-ends?
558 A: People can already do this by targeting the JVM byte codes (there
559 are about 130 compilers for various languages that target the JVM).
561 Q: Why are you writing a JIT engine instead of a front-end to GCC?
563 A: We want the JIT engine and runtime engine because they will be able
564 to execute CIL executables generated on Windows, and so no recompilation
567 <a name="performance"></a>
570 Q: How fast will Mono be?
572 A: We can not predict the future, but a conservative estimate is that
573 it would be at least `as fast as other JIT engines'.
575 We would like to ship various JIT engines with Mono, just like
576 Microsoft has done with their .NET development platform. We could
577 provide a faster, JIT for fast load times but lower performance,
578 and an and an optimizing JIT that would be slower at generating
579 code but produce more optimal output.
581 The CIL has some advantages over the Java byte code: it is really
582 an intermediate representation and there are a number of
583 restrictions on how you can emit CIL code that simplify creating
586 For example, on the CIL, the stack is not really an abstraction
587 available for the code generator to use at will. Rather, it is a
588 way of creating a postfix representation of the parsed tree. At
589 any given call point or return point, the contents of the stack are
590 expected to contain the same object types independently of how the
591 instruction was reached.
593 <a name="licensing"></a>
596 Q: Will I be able to write proprietary applications that run with
599 A: Yes. The licensing scheme is planned to allow proprietary
600 developers to write applications with Mono.
602 Q: What license or licenses are you using for the Mono Project?
604 A: The C# Compiler is released under the terms of the GPL. The class
605 libraries will be under the LGPL or the GPL with a special
606 exception. The runtime libraries are under the LGPL.
608 Since the LGPL is not suitable for embedded systems development, we
609 are also licensing the libraries under the GPL with the following exception:
611 If you link this library against your own program, then you do not
612 need to release the source code for that program. However, any
613 changes that you make to the library itself, or to any native
614 methods upon which the library relies, must be re-distributed in
615 accordance with the terms of the GPL.
617 This is similar in spirit to <a
618 href="http://www.gnu.org/software/classpath/classpath.html">GNU
621 Q: Can I subclass objects within the LGPL licensed Mono code and still release
622 the resulting software under a closed license?
624 A: Yes. Subclassing does not "count" as a modification to GPL'ed code.
625 This means that you may use subclasses when developing proprietary
628 Q: I would like to contribute code to Mono under a particular
629 license. What licenses will you accept?
631 A: We will have to evaluate the licenses for compatibility first,
632 but as a general rule, we will accept all GPL and LGPL-compatible
633 licenses. If you want to use the BSD
634 license, make sure you use the BSD license without the
635 advertisement clause (The `Ousterhout License').
638 ** Miscellaneous Questions
640 Q: You say that the CLI allows multiple languages to execute on the
641 same environment. Isn't this the purpose of CORBA?
643 A: The key difference between CORBA (and COM) and the CLI is that the
644 CLI allows "data-level interoperability" because every
645 language/component uses the same data layout and memory management.
647 This means you can operate directly upon the datatypes that someone
648 else provides, without having to go via their interfaces. It also
649 means you don't have to "marshall" (convert) parameters (data
650 layouts are the same, so you can just pass components directly) and
651 you don't have to worry about memory managment, because all
652 languages/components share the same garbage collector and address
653 space. This means much less copying and no need for reference
656 Q: Will you support COM?
658 A: The runtime will support XPCOM on Unix systems and COM on Windows.
659 Most of the code for dynamic trampolines exists already.