3 Q: Is Mono the same as Microsoft's .NET initiative?
7 .NET is a company-wide initiative at Microsoft that
8 encompasses many different areas. The .NET development framework,
9 Passport, Biztalk, new server products, and anything that is
10 remotely connected to .NET gets the ".NET-stamping" treatment.
11 Some components of Microsoft's .NET initiative have been announced
12 and some others are in the works.
14 Mono is a project to implement several technologies developed by
15 Microsoft that have now been submitted to the ECMA Standards Body.
17 Q: What technologies are included in Mono?
19 A: Mono contains a number of components useful for building new
23 * A Common Language Infrastructure (CLI) virtual
24 machine that contains a class loader, Just-in-time
25 compiler, and a garbage collecting runtime.
27 * A class library that can work with any language
28 which works on the CLR.
30 * A compiler for the C# language. In the future we
31 might work on other compilers that target the Common
34 Windows has compilers that target the
36 <a href="http://msdn.microsoft.com/net/thirdparty/default.asp#lang">a
37 number of languages:</a> Managed C++, Java Script,
38 Eiffel, Component Pascal, APL, Cobol, Oberon, Perl,
39 Python, Scheme, Smalltalk, Standard ML, Haskell,
43 The CLR and the Common Type System (CTS) enables applications and
44 libraries to be written in a number of languages. Classes and
45 methods created in one language can be used from a different
48 This means for example that if you define a class to do algebraic
49 manipulation in C#, that class can be reused from any other
50 language that supports the CLI. You could create a class in C#,
51 subclass it in C++ and instantiate it in an Eiffel program.
53 A single object system, threading system, class libraries, and
54 garbage collection system can be shared across all these languages.
56 Q: Where can I find the specification for these technologies?
58 A: You can find the work-in-progress documentation from the T3G ECMA
61 <a href="http://www.dotnetexperts.com">http://www.dotnetexperts.com</a>
63 Q: Will you implement the .NET Framework SDK class libraries?
65 A: Yes, we will be implementing the APIs of the .NET Framework SDK
68 Q: What does Mono stand for?
70 A: Mono is the word for `Monkey' in Spanish. We like monkeys.
72 Q: When will you ship it?
74 A: We do not know when the code will be shipped. The more
75 contributions we get to the project, the sooner it will ship.
77 A rough estimate is that we might be able to run our C# compiler on
78 Linux by the end of the year. That means running the Windows
79 Executable generated by a Microsoft .NET compiler on the Linux
82 We expect that doing GUI applications will require more work on the
83 class libraries. That could take another six months.
85 Q: How can I contribute?
87 A: Check the <a href="contributing.html">contributing</a> section.
89 Q: You guys should innovate instead of copying.
91 A: In this particular case, we see a clear advantage in the platform
92 and we are interested in using the features of the CLI on open source systems.
94 We have decided that we should spend our limited resources towards
95 implementing an existing specification instead of designing and
98 Designing and implementing our own would be possible, but it doesn't make
99 sense to do that just because the specification comes from a
104 Q: Why is Ximian working on .NET?
106 A: We are interested in providing the best tools for programmers to
107 develop applications for Free Operating Systems.
109 For more information, read the project <a
110 href="rationale.html">rationale</a> page.
112 Q: Will Ximian be able to take on a project of this size?
114 A: Ximian will not be able to taken on the whole project on its own.
115 Mono will be a free software/open source community project, that is
116 the only way we can hope to implement something of this size. You
117 can <a href="contributing.html">contribute</a> to this effort.
119 Q: What pieces will Ximian be working on?
121 A: We will focus on building a development and execution
124 The idea is to get Mono to a state of that would allow
125 third parties to actually be able to use it real-world development.
127 Q: Why does Ximian even care?
129 A: We like the features that the CLI and its related technologies
130 bring to the table. An exciting addition to the developer toolkit.
131 The goal of Mono is to bring this technology to non-Windows
132 platforms (although we hope Mono will also run on Windows, for
133 debugging and comparative purposes).
138 Q: Will I be able to write proprietary applications that run with
141 A: Yes. We will make sure that the licensing will allow developers to
142 create proprietary applications.
144 Q: What license is Mono on?
146 A: The C# Compiler is released under the terms of the GPL. The
147 class libraries are under the LGPL. The runtime libraries are
150 We are considering using the GPL with a special permission, to even
151 allow Mono to be used for embedded system work (I want to see mono
152 in my Tivo or the next generation toy for example). This will be a
153 license that is even laxer than the LGPL.
155 Q: Will you accept code under the XXX License?
157 A: If the XXX License is compatible with the license we use in that
158 specific piece of code, then yes. If you want to use the BSD license, make
159 sure you use the BSD license without the advertisement clause (The
160 `Ousterhout License').
164 Q: If applications use Mono, does that mean that I have to pay a service fee?
166 A: No. Mono is not related to Microsoft's initiative of
167 software-as-a-service.
169 Q: If you implement .NET, will I depend on Microsoft Passport to run my software?
171 A: No. The .NET Framework is a runtime infrastructure and collection
172 of class libraries. Passport may be required to access certain web
173 services written for that framework, but only if the programmer
174 chooses Passport as the authentication mechanism.
176 Q: Is .NET just a bunch of marketing slogans?
178 A: Although the `.NET initiative' is still quite nebulous, The .NET Framework
179 has been available for some time. Mono is not an implementation of the .NET
180 initiative, just the development framework.
182 Q: What is a 100% .NET application?
184 A: A `100% .NET application' is one that only uses the APIs defined
185 under the System namespace and does not use PInvoke. These
186 applications would in theory run unmodified on Windows, Linux,
187 HP-UX, Solaris, MacOS X and others.
189 Q: But Microsoft will release a port of the real thing under the
190 `Shared Source' license, why bother with anything else?
192 A: The Shared Source implementation will not be usable for commercial
193 purposes. We are working towards an implementation that will grant
194 a number of rights to recipients: use for any purpose,
195 redistribution, modification, and redistribution of modifications.
197 This is what we call <a
198 href="http://www.gnu.org/philosophy/free-sw.html">Free Software</a>
202 Q: Is this a free implementation of Passport?
204 A: No. Passport is part of Microsoft's Hailstorm initiative. Mono
205 is just a runtime, a compiler and a set of class libraries.
207 Q: Will the System.Web.Security.PassportIdentity class, mean
208 that my software will depend on Passport?
210 A: No. That just means that applications might use that API to
211 contact a Passport site.
213 As long as your application does not use Passport, you will not
216 It might even be possible to implement that class with
217 a set of dummy functions, or use an alternate Passport implementation.
219 We do not know at this time whether the Passport protocol is
220 documented and whether we will be able to talk to
223 Q: What is your opinion?
225 A: You can read my personal <a href="passport.html">opinion on
230 Q: Will Mono allow me to run Microsoft Office on Linux?
232 A: No, it will not. Microsoft Office is a Windows application. To
233 run Windows applications on Intel Unix systems refer to <a
234 href="http://www.winehq.com">the Wine Project</a>
238 Q: How is this related to GNOME?
240 A: In a number of ways:
242 * Mono will use existing
243 components that have been developed for GNOME when it makes
244 sense. For example on X systems, we will use Gtk+ and
245 Libart to implement Winforms and the Drawing2D API.
247 For database access, we will use LibGDA (not really
248 depending on GNOME, but related to).
250 * This project was born out of the need of providing improved
251 tools for the GNOME community.
253 * We would like to add support to our CLR implementation to
254 deal with GObjects (in GNOME 1.x, they are called
255 GtkObjects), and allow Mono developers to provide GObjects
256 or use and extend existing GObjects.
258 Q: Has the GNOME Foundation or the GNOME team adopted Mono?
260 A: Mono is too new to be adopted by those groups. We hope that the
261 tools that we will provide will be adopted by free software
262 programmers including the GNOME Foundation members and the GNOME
265 Q: Should GNOME programmers switch over to Mono?
267 A: Mono will not be ready even within the next six months, and a
268 complete implementation is probably one year away.
270 We encourage GNOME developers to continue using the existing tools,
271 libraries and components. Improvements made to GNOME will have an
272 impact on Mono, as they will provide the "backend" for various
275 Q: Will Mono include compatibility with Bonobo components?
277 A: Yes, we will provide a set of classes for implementing and using
278 Bonobo components from within Mono.
282 Q: Is Mono a way of running Java applets?
288 Q: Is Mono just a new way of writing Web Services?
292 Q: If this implements the SDK classes, will I be able to write and
293 execute .NET Web Services with this?
297 When the project is finished, you will be able to use the same
298 technologies that are available through the .NET Framework SDK on
299 Windows to write Web Services.
303 A: Soup is a library for GNOME applications to create SOAP server and
304 SOAP clients. You can browse the source code for soup using <a
305 href="http://cvs.gnome.org/bonsai">GNOME's Bonsai</a>
309 A: Yes. The CLI contains enough information about a class that
310 exposing it to other RPC systems (like CORBA) is really simple, and
311 does not even require support from an object.
313 We will be implementing CORBA interoperation as an extension to the
314 Mono classes so that we can integrate with Bonobo, just like
315 Microsoft provides COM interoperation classes and support
318 Q: Can I serialize my objects to other things other than XML?
320 A: Yes, although the serializing tools have not yet been planned, and
321 you would probably have to implement them yourself.
325 Q: Will it be possible to use the CLI features without using bytecodes
328 A: Yes. The CLI engine will be made available as a shared library.
329 The garbage collection engine, the threading abstraction, the
330 object system, the dynamic type code system and the JIT will be
331 available for C developers to integreate with their applications if
334 Q: Will you have new development tools?
336 A: Hopefully Free Software enthusiasts will contribute tools to
337 improve the developer environment. These tools could be developed
338 initially using Microsoft implementation of the CLI and then
339 executed later with Mono.
343 Q: What about using Java? After all there are many languages that
346 A: You can get very good tools for doing Java development on free
347 systems right now. <a href="http://www.redhat.com">Red Hat</a> has
348 contributed a <a href="http://gcc.gnu.org">GCC</a> <a
349 href="http://gcc.gnu.org/java">frontend for Java</a> that can take
350 Java sources or Java byte codes and generate native executables; <a
351 href="http://www.transvirtual.com">Transvirtual</a> has implemented
352 <a href="http://www.kaffe.org">Kaffe</a> a JIT engine for Java;
353 Intel also has a Java VM called <a
354 href="http://www.intel.com/research/mrl/orp">ORP</a>.
356 The JVM is not designed to be a general purpose virtual machine.
357 The Common Intermediate Language (CIL), on the other hand, is
358 designed to be a target for a
359 wide variety of programming languages, and has a set of rules
360 designed to be optimal for JITers.
362 Alex Graveley pointed out to this article: <a
363 href="http://www.objectwatch.com/issue_33.htm">http://www.objectwatch.com/issue_33.htm</a>.
365 Alex said: <i>``Just found this article about the reality of Java's
366 language neutrality. It does not point to any technical reason why
367 language neutrality is not possible in java, but rather attempts to
368 analyse real-world non-java-the-language java bytecode compiler
369 implementations.''</i> and finally added: <i>``Keep in mind of course
370 that Roger Sessions is strongly tied to Microsoft, COM, and now
371 .NET on a career-enabling basis. Still interesting nonetheless.''</i>
374 Q: What kind of rules make the Common Intermediate Language useful for
377 A: The main rule is that the stack in the CLI is not a general purpose
378 stack. You are not allowed to use it for other purposes than
379 computing values and passing arguments to functions or return
382 At any given call or return instruction, the types on the stack
383 have to be the same independently of the flow of execution of your
386 Q: I heard that the CIL is ideal for JITing and not efficient for
387 interpreters, is this the case?
389 A: The CIL is better suited to be JITed than JVM byte codes, but you
390 can interpret them as trivially as you can interpret JVM byte
395 Q: Would you allow other classes other than those in the
398 A: Yes. The Microsoft class collection is very big, but it is by no
399 means complete. It would be nice to have a port of `Camel' (the
400 Mail API used by Evolution inspired by Java Mail) for Mono
403 You might also want to look into implementing CORBA for Mono. Not
404 only because it would be useful, but because it sounds like a fun
405 thing to do, given the fact that the CLI is such a type rich
408 For more information on extending Mono, see our <a
409 href="ideas.html">ideas</a> page.
411 ** Mono and portability
413 Q: Will Mono only work on Linux?
415 A: Currently, we are doing our work on Linux-based systems and
416 Windows. We do not expect many Linux-isms in the code, so it
417 should be easy to port Mono to other UNIX variants.
419 Q: What about Mono on non X-based systems?
421 A: Our main intention at Ximian is to be able to develop GNOME
422 applications with Mono, but if you are interested in providing a
423 port of the Winform classes to other platforms (frame buffer or
424 MacOS X for example), we would gladly integrate them, as long
425 they are under a Free Software License.
427 ** Reusing existing Code
429 Q: What projects will you reuse or build upon?
431 A: We want to get Mono in the hands of programmers soon. We are
432 interested in reusing existing open source software.
434 Q: What about Intel's research JIT framework, ORP?
436 A: At this time, we are investigating whether we can use elements of
437 ORP for Mono. ORP is a research JIT engine that has a clear
438 defined API that splits the JIT from the GC system and the actual
439 byte code implementation. It is a research product.
441 Q: What about using GNU Lightning?
443 A: We are also researching <a
444 href="http://www.gnu.org/software/lightning/lightning.html">GNU
447 ** Ximian and Microsoft
449 Q: Didn't Miguel de Icaza say that `Unix Sucks'?
451 A: Yes, he did, as a catch phrase in his opening remark on the Ottawa
452 Linux Symposium. His talk focused on various ways to improve Unix.
454 There is a paper describing some ways to improve Unix at:
456 <a href="http://primates.ximian.com/~miguel/bongo-bong.html">
457 http://primates.ximian.com/~miguel/bongo-bong.html</a>
459 Q: Didn't Ximian's Miguel work for Microsoft?
461 A: Actually, Nat Friedman (Ximian's co-founder) did work as an
462 intern for Microsoft for one summer but Miguel did not.
464 Q: Did Nat and Miguel meet at Microsoft?
466 A: They met online on the Linux IRC network; They met in person for
467 the first time in 1997.
469 ** Mono and Microsoft
471 Q: How can you expect Mono to compete with Microsoft, wont this
472 require an effort too large?
474 A: You are right. Mono will never become a reality without the help
475 of other contributors. Ximian is a small company that can not
476 finish Mono alone. We will be working with members of the
477 community to deliver the product.
479 Q: Is Microsoft and Corel involved in the Mono implementation?
483 Q: Are you writing Mono from the ECMA specs?
485 A: yes, we are writing them from the ECMA specs and the published
486 materials in print about .NET
490 Q: What is the difference between CLR (Common Language Runtime) and
491 CLI (Common Language Infrastructure)?
493 A: CLI is the specification of an execution system. The Microsoft
494 implementation of this specification is named CLR.
496 Unless we come up with our own acronym, we could just call ours
497 also CLR, just because it would do exactly the same thing the
498 Microsoft implementation does.
503 Q: Should someone work on a GCC front-end to C#?
505 A: I would love if someone does, and we would love to help anyone that
506 takes on that task, but we do not have the time or expertise to
507 build a C# compiler with the GCC engine. I find it a lot more fun
508 personally to work on C# on a C# compiler, which has an intrinsic
511 Q: Should someone make a GCC backend that will generate CIL images?
513 A: I would love to see a backend to GCC that generates CIL images. It
514 would provide a ton of free compilers that would generate CIL
515 code. This is something that people would want to look into
516 anyways for Windows interoperation in the future.
518 Q: What about making a front-end to GCC that takes CIL images and
519 generates native code?
521 A: I would love to see this, specially since GCC supports this same
522 feature for Java Byte Codes. You could use the metadata library
523 from Mono to read the byte codes (ie, this would be your
524 "front-end") and generate the trees that get passed to the
527 Ideally our implementation of the CLI will be available as a shared
528 library that could be linked with your application as its runtime
531 Q: But would this work around the GPL in the GCC compiler and allow
532 people to work on non-free front-ends?
534 A: People can already do this by targeting the JVM byte codes (there
535 are about 130 compilers for various languages that target the JVM).
537 Q: Why are you writing a JIT engine instead of a front-end to GCC?
539 A: The JIT engine and runtime engine will be able to execute CIL
540 executables generated on Windows.
544 Q: Is Mono part of the GNU project?
546 A: Mono is a Ximian project, that is also part of the GNU project.
548 ** Mono and Portability
550 Q: Will Mono work on other variants of Unix?
552 A: Yes. We do not expect to add any gratuitous incompatibilities.
554 Q: Will Mono run on Windows?
556 A: Hopefully yes. Currently some parts of Mono only run on Windows
557 (the C# compiler is a .NET executable) and other parts have only
558 been compiled on Linux, but work on Windows with Cygwin.
560 Q: Will Mono depend on GNOME?
562 A: It will depend only if you are using a particular assembly (for
563 example, for doing GUI applications). If you are just interested
564 in Mono for implementing a `Hello World Enterprise P2P Web
565 Service', you will not need any GNOME component.
569 Q: How fast will be Mono?
571 A: We can not predict the future, but a conservative estimate is that
572 it would be at least `as fast as other JIT engines'.
574 Now, wishfully thinking I hope that we will ship various JITs with
575 Mono just like Microsoft has done. A fast JITer when maximum
576 performance is not needed, but fast load times are important; And
577 an optimizing JITer that would be slower at generating code but
578 produce more optimal output.
580 The CIL has some advantages over the Java byte code: it is really
581 an intermediate representation and there are a number of
582 restrictions on how you can emit CIL code that simplify creating
585 For example, on the CIL the stack is not really an abstraction
586 available for the code generator to use at will: it is just a way
587 of creating a postfix representation of the parsed tree. At any
588 given call point or return point, the contents of the stack are
589 expected to contain the same object types independently of how the
590 instructions was reached.
592 ** Assorted questions
594 Q: You say that the CLI allows multiple languages to execute on the
595 same environment. Isn't this the purpose of CORBA?
597 A: CORBA can be used for this purpose, but think of CORBA mostly as a
598 inter-process (local machine or remote machine) communication
601 Think of the CLI to be targeted to interoperation of languages in
602 the same process, and CORBA as being a nifty addition for
605 Sure, we have used CORBA for in-proc components, but the lack of an
606 ABI for in-proc components does not translate into a good framework