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 It only means a number of other things: monochromatic (hence the
73 gray theme used in the Web site).
75 Q: When will you ship it?
77 A: We do not know when the code will be shipped. The more
78 contributions we get to the project, the sooner it will ship.
80 A rough estimate is that we might be able to run our C# compiler on
81 Linux by the end of the year. That means running the Windows
82 Executable generated by a Microsoft .NET compiler on the Linux
85 We expect that doing GUI applications will require more work on the
86 class libraries. That could take another six months.
88 Q: How can I contribute?
90 A: Check the <a href="contributing.html">contributing</a> section.
92 Q: You guys should innovate instead of copying.
94 A: In this particular case, we see a clear advantage in the platform
95 and we are interested in using the features of the CLI on open source systems.
97 We have decided that we should spend our limited resources towards
98 implementing an existing specification instead of designing and
101 Designing and implementing our own would be possible, but it doesn't make
102 sense to do that just because the specification comes from a
107 Q: Why is Ximian working on .NET?
109 A: We are interested in providing the best tools for programmers to
110 develop applications for Free Operating Systems.
112 For more information, read the project <a
113 href="rationale.html">rationale</a> page.
115 Q: Will Ximian be able to take on a project of this size?
117 A: Ximian will not be able to taken on the whole project on its own.
118 Mono will be a free software/open source community project, that is
119 the only way we can hope to implement something of this size. You
120 can <a href="contributing.html">contribute</a> to this effort.
122 Q: What pieces will Ximian be working on?
124 A: We will focus on building a development and execution
127 The idea is to get Mono to a state of that would allow
128 third parties to actually be able to use it real-world development.
130 Q: Why does Ximian even care?
132 A: We like the features that the CLI and its related technologies
133 bring to the table. An exciting addition to the developer toolkit.
134 The goal of Mono is to bring this technology to non-Windows
135 platforms (although we hope Mono will also run on Windows, for
136 debugging and comparative purposes).
141 Q: Will I be able to write proprietary applications that run with
144 A: Yes. The licensing scheme is planned to allow proprietary
145 developers to write applications with Mono.
147 Q: What license is Mono on?
149 A: The C# Compiler is released under the terms of the GPL. The class
150 libraries will be under the LGPL or the GPL with a special
151 exception. The runtime libraries are under the LGPL.
153 Since the LGPL is not suitable for embedded systems development, we
154 are also licensing the libraries under the GPL with the following exception:
156 If you link this library against your own program, then you do not
157 need to release the source code for that program. However, any
158 changes that you make to the library itself, or to any native
159 methods upon which the library relies, must be re-distributed in
160 accordance with the terms of the GPL.
162 This is similar in spirit to <a
163 href="http://www.gnu.org/software/classpath/classpath.html">GNU
166 Q: But in Object Oriented Programming I need to subclass your library
167 functions, does that mean that I am making modifications to your
168 library and hence I would have to distribute my sources under the
171 A: No. Object Oriented Programming in the class library is a well
172 understood interface barrier, so you can actually develop
173 proprietary applications with the Mono libraries.
175 Q: Will you accept code under the XXX License?
177 A: If the XXX License is compatible with the license we use in that
178 specific piece of code, then yes. If you want to use the BSD license, make
179 sure you use the BSD license without the advertisement clause (The
180 `Ousterhout License').
184 Q: If applications use Mono, does that mean that I have to pay a service fee?
186 A: No. Mono is not related to Microsoft's initiative of
187 software-as-a-service.
189 Q: If you implement .NET, will I depend on Microsoft Passport to run my software?
191 A: No. The .NET Framework is a runtime infrastructure and collection
192 of class libraries. Passport may be required to access certain web
193 services written for that framework, but only if the programmer
194 chooses Passport as the authentication mechanism.
196 Q: Is .NET just a bunch of marketing slogans?
198 A: Although the `.NET initiative' is still quite nebulous, The .NET Framework
199 has been available for some time. Mono is not an implementation of the .NET
200 initiative, just the development framework.
202 Q: What is a 100% .NET application?
204 A: A `100% .NET application' is one that only uses the APIs defined
205 under the System namespace and does not use PInvoke. These
206 applications would in theory run unmodified on Windows, Linux,
207 HP-UX, Solaris, MacOS X and others.
209 Q: But Microsoft will release a port of the real thing under the
210 `Shared Source' license, why bother with anything else?
212 A: The Shared Source implementation will not be usable for commercial
213 purposes. We are working towards an implementation that will grant
214 a number of rights to recipients: use for any purpose,
215 redistribution, modification, and redistribution of modifications.
217 This is what we call <a
218 href="http://www.gnu.org/philosophy/free-sw.html">Free Software</a>
222 Q: Is this a free implementation of Passport?
224 A: No. Passport is part of Microsoft's Hailstorm initiative. Mono
225 is just a runtime, a compiler and a set of class libraries.
227 Q: Will the System.Web.Security.PassportIdentity class, mean
228 that my software will depend on Passport?
230 A: No. That just means that applications might use that API to
231 contact a Passport site.
233 As long as your application does not use Passport, you will not
236 It might even be possible to implement that class with
237 a set of dummy functions, or use an alternate Passport implementation.
239 We do not know at this time whether the Passport protocol is
240 documented and whether we will be able to talk to
243 Q: But that must mean that you are tied to Passport!
245 A: All the contrary. The implementation could keep the interface (for
246 the sake of simplicity, lets say it implements the method `Login'
249 We could implement `Login' and `GetUserName' by talking to XNS or
250 any other decentralized systems. Or any other system that the
251 industry standarizes on.
253 Q: What is your opinion?
255 A: You can read my personal <a href="passport.html">opinion on
258 Q: Will Mono running on Linux make Passport available for Linux?
260 A: The Passport toolkit for Linux-based web servers is available from
263 Again, Mono has nothing to do with Passport.
267 Q: Will Mono allow me to run Microsoft Office on Linux?
269 A: No, it will not. Microsoft Office is a Windows application. To
270 run Windows applications on Intel Unix systems refer to <a
271 href="http://www.winehq.com">the Wine Project</a>
275 Q: How is this related to GNOME?
277 A: In a number of ways:
279 * Mono will use existing
280 components that have been developed for GNOME when it makes
281 sense. For example on X systems, we will use Gtk+ and
282 Libart to implement Winforms and the Drawing2D API.
284 For database access, we will use LibGDA (not really
285 depending on GNOME, but related to).
287 * This project was born out of the need of providing improved
288 tools for the GNOME community.
290 * We would like to add support to our CLR implementation to
291 deal with GObjects (in GNOME 1.x, they are called
292 GtkObjects), and allow Mono developers to provide GObjects
293 or use and extend existing GObjects.
295 Q: Has the GNOME Foundation or the GNOME team adopted Mono?
297 A: Mono is too new to be adopted by those groups. We hope that the
298 tools that we will provide will be adopted by free software
299 programmers including the GNOME Foundation members and the GNOME
302 Q: Should GNOME programmers switch over to Mono?
304 A: Mono will not be ready even within the next six months, and a
305 complete implementation is probably one year away.
307 We encourage GNOME developers to continue using the existing tools,
308 libraries and components. Improvements made to GNOME will have an
309 impact on Mono, as they will provide the "backend" for various
312 Q: Will Mono include compatibility with Bonobo components?
314 A: Yes, we will provide a set of classes for implementing and using
315 Bonobo components from within Mono.
317 Q: Does Mono replace Bonobo?
319 A: Bonobo is very focused on cross-application component reuse. Mono
320 will provide a Bonobo framework to allow you to develop Bonobo
321 components and use Bonobo components on Unix.
323 Mono should allow you to write Bonobo components more easily, just
324 like .NET on Windows allows you to export .NET components to COM.
328 Q: Is Mono a way of running Java applets?
334 Q: Is Mono just a new way of writing Web Services?
338 Q: If this implements the SDK classes, will I be able to write and
339 execute .NET Web Services with this?
343 When the project is finished, you will be able to use the same
344 technologies that are available through the .NET Framework SDK on
345 Windows to write Web Services.
349 A: Soup is a library for GNOME applications to create SOAP server and
350 SOAP clients. You can browse the source code for soup using <a
351 href="http://cvs.gnome.org/bonsai">GNOME's Bonsai</a>
355 A: Yes. The CLI contains enough information about a class that
356 exposing it to other RPC systems (like CORBA) is really simple, and
357 does not even require support from an object.
359 We will be implementing CORBA interoperation as an extension to the
360 Mono classes so that we can integrate with Bonobo, just like
361 Microsoft provides COM interoperation classes and support
364 Q: Can I serialize my objects to other things other than XML?
366 A: Yes, although the serializing tools have not yet been planned, and
367 you would probably have to implement them yourself.
371 Q: Will it be possible to use the CLI features without using bytecodes
374 A: Yes. The CLI engine will be made available as a shared library.
375 The garbage collection engine, the threading abstraction, the
376 object system, the dynamic type code system and the JIT will be
377 available for C developers to integreate with their applications if
380 Q: Will you have new development tools?
382 A: Hopefully Free Software enthusiasts will contribute tools to
383 improve the developer environment. These tools could be developed
384 initially using Microsoft implementation of the CLI and then
385 executed later with Mono.
389 Q: What about using Java? After all there are many languages that
392 A: You can get very good tools for doing Java development on free
393 systems right now. <a href="http://www.redhat.com">Red Hat</a> has
394 contributed a <a href="http://gcc.gnu.org">GCC</a> <a
395 href="http://gcc.gnu.org/java">frontend for Java</a> that can take
396 Java sources or Java byte codes and generate native executables; <a
397 href="http://www.transvirtual.com">Transvirtual</a> has implemented
398 <a href="http://www.kaffe.org">Kaffe</a> a JIT engine for Java;
399 Intel also has a Java VM called <a
400 href="http://www.intel.com/research/mrl/orp">ORP</a>.
402 The JVM is not designed to be a general purpose virtual machine.
403 The Common Intermediate Language (CIL), on the other hand, is
404 designed to be a target for a
405 wide variety of programming languages, and has a set of rules
406 designed to be optimal for JITers.
409 Q: What kind of rules make the Common Intermediate Language useful for
412 A: The main rule is that the stack in the CLI is not a general purpose
413 stack. You are not allowed to use it for other purposes than
414 computing values and passing arguments to functions or return
417 At any given call or return instruction, the types on the stack
418 have to be the same independently of the flow of execution of your
421 Q: I heard that the CIL is ideal for JITing and not efficient for
422 interpreters, is this the case?
424 A: The CIL is better suited to be JITed than JVM byte codes, but you
425 can interpret them as trivially as you can interpret JVM byte
428 Q: Could Java target the CLI?
430 A: Yes, Java could target the CLI. We have details on a <a
431 href="ideas.html#guavac">project</a> that someone could take on to
436 Q: Would you allow other classes other than those in the
439 A: Yes. The Microsoft class collection is very big, but it is by no
440 means complete. It would be nice to have a port of `Camel' (the
441 Mail API used by Evolution inspired by Java Mail) for Mono
444 You might also want to look into implementing CORBA for Mono. Not
445 only because it would be useful, but because it sounds like a fun
446 thing to do, given the fact that the CLI is such a type rich
449 For more information on extending Mono, see our <a
450 href="ideas.html">ideas</a> page.
452 ** Mono and portability
454 Q: Will Mono only work on Linux?
456 A: Currently, we are doing our work on Linux-based systems and
457 Windows. We do not expect many Linux-isms in the code, so it
458 should be easy to port Mono to other UNIX variants.
460 Q: What about Mono on non X-based systems?
462 A: Our main intention at Ximian is to be able to develop GNOME
463 applications with Mono, but if you are interested in providing a
464 port of the Winform classes to other platforms (frame buffer or
465 MacOS X for example), we would gladly integrate them, as long
466 they are under a Free Software License.
468 ** Reusing existing Code
470 Q: What projects will you reuse or build upon?
472 A: We want to get Mono in the hands of programmers soon. We are
473 interested in reusing existing open source software.
475 Q: What about Intel's research JIT framework, ORP?
477 A: At this time, we are investigating whether we can use elements of
478 ORP for Mono. ORP is a research JIT engine that has a clear
479 defined API that splits the JIT from the GC system and the actual
480 byte code implementation. It is a research product.
482 Q: What about using GNU Lightning?
484 A: We are also researching <a
485 href="http://www.gnu.org/software/lightning/lightning.html">GNU
488 <a name="ximian-and-microsoft">
489 ** Ximian and Microsoft
491 Q: I read that Microsoft is helping out Ximian, is this true?
493 A: Initial contact between David Stutz and Miguel de Icaza happened.
494 It was a friendly conversation. Microsoft is interested in other
495 implementing .NET and are willing to help make the ECMA spec more
496 accurate for this purpose.
498 We were initially contacted by Sam Ruby at the ECMA TG3 committee
499 to discuss the same issue. And we are glad to have good contacts
500 to ask questions about the specs.
502 Q: Is Microsoft paying Ximian to do this?
504 A: No, we are doing this for purely selfish reasons. We are upgrading
505 our development platform to build better applications on Unix and other
508 Q: Do you fear that Microsoft will change the spec and render Mono useless?
510 A: No. Microsoft proved with the CLI and the C# language that it was
511 possible to create a powerful foundation for many languages to
512 interoperate. We will always have that.
514 Even if changes happened in the platform which were undocumented
515 (which is very unlikely), the existing platform has a value on its
518 Miguel once explained its motivation for working on Mono to Dave
519 Winer, and his mail got posted <a
520 href="http://scriptingnews.userland.com/stories/storyReader$1275">here</a>
522 Q: Didn't Miguel de Icaza say that `Unix Sucks'?
524 A: Yes, he did, as a catch phrase in his opening remark on the Ottawa
525 Linux Symposium. His talk focused on various ways to improve Unix.
527 There is a paper describing some ways to improve Unix at:
529 <a href="http://primates.ximian.com/~miguel/bongo-bong.html">
530 http://primates.ximian.com/~miguel/bongo-bong.html</a>
532 Q: Didn't Ximian's Miguel work for Microsoft?
534 A: Actually, Nat Friedman (Ximian's co-founder) did work as an
535 intern for Microsoft for one summer but Miguel did not.
537 Q: Did Nat and Miguel meet at Microsoft?
539 A: They met online on the Linux IRC network; They met in person for
540 the first time in 1997.
542 ** Mono and Microsoft
544 Q: How can you expect Mono to compete with Microsoft, wont this
545 require an effort too large?
547 A: You are right. Mono will never become a reality without the help
548 of other contributors. Ximian is a small company that can not
549 finish Mono alone. We will be working with members of the
550 community to deliver the product.
552 Q: Is Microsoft and Corel involved in the Mono implementation?
556 Q: Are you writing Mono from the ECMA specs?
558 A: yes, we are writing them from the ECMA specs and the published
559 materials in print about .NET
561 Q: What happens if Microsoft `Embraces and Extends' the CLI standard
562 and keeps Mono out of the play?
564 A: There are various explanations to this question. The first one is
565 that the benefits that you can get from the CLI are going to be
566 there with or without `embracing and extending'. We might not be
567 able to run every .NET Windows application on Mono. But remember:
568 it was already easy for someone to just use PInvoke to tie their
569 application to Windows.
571 The bottom line is that the advantages of having a CLI runtime will
572 be with us, no matter if Microsoft forks their version to be
575 Q: What if Microsoft changes the interface, and all of a sudden
578 A: If they change their released API, every application that was
579 developed against it will break.
581 That being said, Microsoft have a pretty good record of keeping
582 backwards binary compatibility.
586 Q: What is the difference between CLR (Common Language Runtime) and
587 CLI (Common Language Infrastructure)?
589 A: CLI is the specification of an execution system. The Microsoft
590 implementation of this specification is named CLR.
592 Unless we come up with our own acronym, we could just call ours
593 also CLR, just because it would do exactly the same thing the
594 Microsoft implementation does.
599 Q: Should someone work on a GCC front-end to C#?
601 A: I would love if someone does, and we would love to help anyone that
602 takes on that task, but we do not have the time or expertise to
603 build a C# compiler with the GCC engine. I find it a lot more fun
604 personally to work on C# on a C# compiler, which has an intrinsic
607 We can provide help and assistance to anyone who would like to work
610 Q: Should someone make a GCC backend that will generate CIL images?
612 A: I would love to see a backend to GCC that generates CIL images. It
613 would provide a ton of free compilers that would generate CIL
614 code. This is something that people would want to look into
615 anyways for Windows interoperation in the future.
617 Again, we would love to provide help and assistance to anyone
618 interested in working in such a project.
620 Q: What about making a front-end to GCC that takes CIL images and
621 generates native code?
623 A: I would love to see this, specially since GCC supports this same
624 feature for Java Byte Codes. You could use the metadata library
625 from Mono to read the byte codes (ie, this would be your
626 "front-end") and generate the trees that get passed to the
629 Ideally our implementation of the CLI will be available as a shared
630 library that could be linked with your application as its runtime
633 Again, we would love to provide help and assistance to anyone
634 interested in working in such a project.
636 Q: But would this work around the GPL in the GCC compiler and allow
637 people to work on non-free front-ends?
639 A: People can already do this by targeting the JVM byte codes (there
640 are about 130 compilers for various languages that target the JVM).
642 Q: Why are you writing a JIT engine instead of a front-end to GCC?
644 A: The JIT engine and runtime engine will be able to execute CIL
645 executables generated on Windows.
647 ** Mono and Portability
649 Q: Will Mono work on other variants of Unix?
651 A: Yes. We do not expect to add any gratuitous incompatibilities.
653 Q: Will Mono run on Windows?
655 A: Hopefully yes. Currently some parts of Mono only run on Windows
656 (the C# compiler is a .NET executable) and other parts have only
657 been compiled on Linux, but work on Windows with Cygwin.
659 Q: Will Mono depend on GNOME?
661 A: It will depend only if you are using a particular assembly (for
662 example, for doing GUI applications). If you are just interested
663 in Mono for implementing a `Hello World Enterprise P2P Web
664 Service', you will not need any GNOME component.
668 Q: How fast will be Mono?
670 A: We can not predict the future, but a conservative estimate is that
671 it would be at least `as fast as other JIT engines'.
673 Now, wishfully thinking I hope that we will ship various JITs with
674 Mono just like Microsoft has done. A fast JITer when maximum
675 performance is not needed, but fast load times are important; And
676 an optimizing JITer that would be slower at generating code but
677 produce more optimal output.
679 The CIL has some advantages over the Java byte code: it is really
680 an intermediate representation and there are a number of
681 restrictions on how you can emit CIL code that simplify creating
684 For example, on the CIL the stack is not really an abstraction
685 available for the code generator to use at will: it is just a way
686 of creating a postfix representation of the parsed tree. At any
687 given call point or return point, the contents of the stack are
688 expected to contain the same object types independently of how the
689 instructions was reached.
692 ** Mono and Portable.NET
694 Q: What are the differences between Mono and Portable.NET?
696 A: Most of Mono is being written using C#, the only pieces written in
697 C are those who have to absolutely be built using C (The JIT
698 engine, the runtime, the interfaces to the garbage collection
701 The C# compiler and the tools will become reusable C# components.
703 Portable.NET is building its components out of C pieces.
705 ** Assorted questions
707 Q: You say that the CLI allows multiple languages to execute on the
708 same environment. Isn't this the purpose of CORBA?
710 A: The key difference between CORBA (and COM) and the CLI is that the
711 CLI allows "data-level interoperability" because every
712 language/component uses the same data layout and memory management.
714 This means you can operate directly upon the datatypes that someone
715 else provides, without having to go via their interfaces. It also
716 means you don't have to "marshall" (convert) parameters (data
717 layouts are the same, so you can just pass components directly) and
718 you don't have to worry about memory managment, because all
719 languages/components share the same garbage collector and address
720 space. This means much less copying and no need for reference