mono/web/faq

<a href="#basics">Basics</a><br>
<a href="#ximian">The Ximian Role in the Mono project</a><br>
<a href="#gnome">Mono and GNOME</a><br>
<a href="#gui">Building GUI applications with Mono</a><br>
<a href="#msft">Mono and Microsoft</a><br>
<a href="#pnpproject">Mono and the Portable.NET Project</a><br>
<a href="#webservices">Web Services</a><br>
<a href="#devel">Development Tools and Issues</a><br>
<a href="#java">Mono and Java</a><br>
<a href="#extending">Extending Mono</a><br>
<a href="#portability">Portability</a><br>
<a href="#reuse">Reusing Existing Code</a><br>
<a href="#gcc">Mono and GCC</a><br>
<a href="#performance">Performance</a><br>
<a href="#licensing">Licensing</a><br>
<a href="#patents">Patents</a><br>
<a href="#etc">Miscellaneous Questions</a><br>


<a name="basics"></a>
** Basics

Q: What is Mono exactly?

A: The Mono Project is an open development initiative sponsored by
   Ximian that is working to develop an open source, Linux-based
   version of the Microsoft .NET development platform.  Its objective
   is to enable Linux developers to build and
   deploy cross-platform .NET Applications.  The project will
   implement various technologies developed by Microsoft that have now
   been submitted to the ECMA for standardization.

Q: What is the difference between Mono and the .NET Initiative?

A: The ".NET Initiative" is a somewhat nebulous company-wide effort by
   Microsoft, one part of which is a cross-platform development
   framework.  Mono is an implementation of the development framework,
   but not an implementation of anything else related to the .NET
   Initiative, such as Passport, software-as-a-service, or
   corporate rebranding.

Q: What technologies are included in Mono?

A: Mono contains a number of components useful for building new
   software:

	<ul>
		* A Common Language Infrastructure (CLI) virtual
		  machine that contains a class loader, Just-in-time
		  compiler, and a garbage collecting runtime.

		* A class library that can work with any language
		  which works on the CLR.

		* A compiler for the C# language.  In the future we
		  might work on other compilers that target the Common
		  Language Runtime.
	</ul>


   Windows has compilers that target the virtual machine from <a
   href="http://msdn.microsoft.com/net/thirdparty/default.asp#lang">a
   number of languages:</a> Managed C++, Java Script, Eiffel,
   Component Pascal, APL, Cobol, Oberon, Perl, Python, Scheme,
   Smalltalk, Standard ML, Haskell, Mercury and Oberon.

   The CLR and the Common Type System (CTS) enables applications and
   libraries to be written in a collection of different languages that
   target the byte code

   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:
 
   <a href="http://www.dotnetexperts.com">http://www.dotnetexperts.com</a>

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: Will you offer an ECMA-compliant set of class libraries?

A: Eventually we will.  Our current focus is on interoperating
   with the Microsoft SDK, but we will also offer an ECMA compliant
   set of libraries. 

Q: What does the name "Mono" mean?

A: Mono is the word for `monkey' in Spanish. We like monkeys.

Q: Is Mono usable?

A: The JIT engine is usable on Intel x86 machines.  An interpreter
   can be used on other non-Intel x86 machines.  

   The class libraries are not yet mature enough to run real applications,
   but if you are interested in trying out Mono, you can definetly start
   testing things out as many programs run.

   The C# compiler has made significant progress, it can even compile
   itself now, but it can not yet be ran with our class libraries as
   they are missing some features. 

Q: When will you ship it?

A: It is premature to target a shipdate for the code, but we
   anticipate that it will be available some time in the middle of
   2002.

Q: How can I contribute?

A: Check the <a href="contributing.html">contributing</a> section. 

Q: Aren't you just copying someone else's work?

A: We are interested in providing the best tools for programmers to
   develop applications for Free Operating Systems.  We also want to help
   provide the interoperability that will allow those systems to fit in
   with other standards.

   For more background, read the <a href="http://www.go-mono.com/rationale.html">Mono
   Project white paper</a>.
   the project.


<a name="ximian"></a> 

** The Ximian Role in the Mono Project

Q: Why is Ximian working on .NET?

A: Ximian is interested in providing the best tools for programmers to
   develop applications for Free Operating Systems.  

   For more information, read the project <a
   href="rationale.html">rationale</a> page.

Q: Will Ximian be able to take on a project of this size?  

A: Of course not. Ximian a supporter of the Mono project, but the only way
   to implement something of this size is for the entire free software
   community to get involved. Visit the <a href="contributing.html">contributing</a> 
   page if you'd like to help out.

Q: What pieces will Ximian be working on?

A: We will devote most of our resources to work on the pieces which are
   on the critical path to release a development and execution
   environment. Once the project is at a stage where it is useful in
   the real world, it will achieve a critical mass of developers to
   improve it further.

Q: Will Ximian offer Mono commercially?

A: When Mono is ready to be shipped Ximian will offer a commercial
   support and services for Mono. 

Q: Will you wait until Mono is finished?

A: Mono will ship on various stages as they mature.  Some people
   require only a subset of the technologies, those will ship first.

   More advanced features will take more time to develop.  A support
   timeline will be available in June 2002.

<a name="gnome"></a> 
** Mono and GNOME

Q: How is Mono related to GNOME?

A: In a number of ways.  This project was born out of the need of
   providing improved tools for the GNOME community, and will use
   existing components that have been developed for GNOME when they
   are available.  For example, we plan to use Gtk+ and Libart to
   implement Winforms and the Drawing2D API and are considering
   GObject support.

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 now?

A: It is still far to early for discussions of "switching over."  No
   pieces of Mono will be ready within the next six months, and a
   complete implementation is roughly 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 would be the "backend" for various classes.

Q: Will Mono include compatibility with Bonobo components? What is the
   relationship between Mono and Bonobo?

A: Yes, we will provide a set of classes for implementing and using
   Bonobo components from within Mono.  Mono should allow you to write
   Bonobo components more easily, just like .NET on Windows allows you
   to export .NET components to COM.

Q: Does Mono depend on GNOME?

A: No, Mono does not depend on GNOME.  We use a few packages produced by
   the GNOME team like the `glib' library.  

Q: But will I be able to build GNOME applications?

A: Yes, we will enable people to write GNOME applications using Mono.

<a name="gui"></a>
** GUI applications

Q: Will Mono enable GUI applications to be authored?

A: Yes, you will be able to build GUI applications.  Indeed, that is our
   main focus.  We will provide both the Windows.Forms API and the Gtk# API.

Q: What is the difference between Gtk# and System.Windows.Forms?

A: Gtk# is a set of bindings for the Gtk+ toolkit for C# (and other
   CIL-enabled languages).  System.Windows.Forms is an API defined
   by Microsoft to build GUI applications.

Q: Will I be able to run my smart clients on systems powered by Mono?

A: As long as your applications are 100% .NET and do not make use
   of P/Invoke to call Win32 functions, your smart client applications
   will run on Mono platforms.

<a name="msft"></a>
** Mono and Microsoft

Q: Is Microsoft helping Ximian with this project?

A: No. Ximian CTO Miguel de Icaza had a friendly conversation with
   Microsoft software architect David Stutz, but that's about the
   extent of the contact. Microsoft is interested in other
   implementations of .NET and are willing to help make the ECMA spec
   more accurate for this purpose.

   Ximian representatives have also spoken with Sam Ruby at the ECMA
   TG3 committee to discuss the same issues.

Q: Is Microsoft or Corel paying Ximian to do this?

A: No.

Q: Do you fear that Microsoft will change the spec and render Mono
   useless?

A: No.  Microsoft proved with the CLI and the C# language that it was
   possible to create a powerful foundation for many languages to
   interoperate.  We will always have that.  

   Even if changes happened in the platform which were undocumented,
   the existing platform would a value on its own.

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.

Q: If my applications use Mono, will I have to pay a service fee?

A: No.  Mono is not related to Microsoft's initiative of
   software-as-a-service.

Q: Is the Mono Project is related to the Microsoft Hailstorm effort?  Is
   Ximian endorsing Hailstorm?  

A: No.  The Mono Project is focused on providing a compatible set of
   tools for the Microsoft .NET development platform.  It does not
   address, require, or otherwise endorse the MS Passport-based
   Hailstorm single sign-on system that is part of Windows XP and
   other services.

Q: Will Mono or .NET applications depend on Microsoft Passport?

A: No. MS Passport is unrelated to running .NET compatible applications
   produced with the Mono tools.  The only thing you will need is a
   just-in-time compiler (JIT).

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: If Microsoft will release a port of their .NET platform under the
   `Shared Source' license, why should I bother with anything else?

A: The Shared Source implementation will be expensive and its uses
   will be tightly restricted, especially for commercial use. We are
   working towards an implementation that will grant a number of
   important rights to recipients: use for any purpose,
   redistribution, modification, and redistribution of modifications.

   This is what we call <a
   href="http://www.gnu.org/philosophy/free-sw.html">Free Software</a>

Q: Is Mono a free implementation of Passport?

A: No. 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.  Applications may use that API to contact a Passport site, but
   are not required to do so.

   As long as your application does not use Passport, you will not
   need Passport.  

Q: Will Mono running on Linux make Passport available for Linux?

A: No.  However, the Passport toolkit for Linux-based web servers is
   available from Microsoft.

Q: Will Mono allow me to run Microsoft Office on Linux?

A: No, it will not.  Microsoft Office is a Windows application.  To
   learn more about running Windows applications on Intel Unix systems
   refer to <a href="http://www.winehq.com">the Wine Project</a>.

<a name="pnpproject"></a>
** Mono and Portable.NET

Q: What are the differences between Mono and Portable.NET?

A: Most of Mono is being written using C#, with only
   a few parts written in C (The JIT engine, the runtime, the
   interfaces to the garbage collection system).  The Portable.NET
   Project is using C for development.

<a name="webservices"></a>
** Web Services

Q: How is Mono related to Web Services?

A: Mono is only related to Web Services in that it will implement the
   same set of classes that have been authored in the .NET Framework
   to simplify and streamline the process of building Web Services.

   But most importantly, Mono is an Open Source implementation of the
   .NET Framework.

Q: Can I author Web Services with Mono?

A: You will be able to write Web Services on .NET that run on Mono and
   viceversa. 

Q: If Mono implements the SDK classes, will I be able to write and
   execute .NET Web Services with it?
   
A: Yes.  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?  Can I use Soup without Mono?

A: Soup is a library for GNOME applications to create SOAP servers and
   SOAP clients, and can be used without Mono.  You can browse the
   source code for soup using <a
   href="http://cvs.gnome.org/bonsai">GNOME's Bonsai</a>.

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.

Q: Will Mono use ORBit?

A: No. Mono will be using a new implementation of CORBA that isn't still started. 

<a name="devel"></a>
** Development Tools and Issues

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: With any luck, Free Software enthusiasts will contribute tools to
   improve the developer environment.  These tools could be developed
   initially using the Microsoft implementation of the CLI and then
   executed later with Mono.

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: Is it true that the CIL is ideal for JITing and not efficient for
   interpreters?

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. 

<a name="java">
** Mono and Java
   
Q: Why don't you use 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.  <a href="http://www.redhat.com">Red Hat</a> has
   contributed a <a href="http://gcc.gnu.org">GCC</a> <a
   href="http://gcc.gnu.org/java">frontend for Java</a> that can take
   Java sources or Java byte codes and generate native executables; <a
   href="http://www.transvirtual.com">Transvirtual</a> has implemented
   <a href="http://www.kaffe.org">Kaffe</a> a JIT engine for Java;
   Intel also has a Java VM called <a
   href="http://www.intel.com/research/mrl/orp">ORP</a>.

   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: Could Java target the CLI?

A: Yes, Java could target the CLI.  We have details on a <a
   href="ideas.html#guavac">project</a> that someone could take on to
   make this happen.  

   Microsoft has an implemenation of the Java language called J# that
   can target the CIL execution engine. 

Q: Is it possible to write a JVM byte code to CIL convertor?

A: Yes, it is possible.  Here are a few starting point:

	<ul>
        	* A byte code representation is really a flattened forest of
          	  trees.  Look at the Mono JIT engine to see how we compute
          	  the basic blocks (this is used to figure out the "trees").

          	  The forest is just an array of trees.

          	  Indeed, run the JIT engine with -d (mono -d prog.exe) and
          	  you will see how these trees look like.

            	  You will have to do something similar for Java.

        	* Each "forest of trees" has a meaning.  This meaning can now
          	  be translated into the equivalent "meaning" in CLR-land.
	</ul>

<a name="extending"></a>
** 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 <a
   href="ideas.html">ideas</a> page.

Q: Do you plan to Embrace and Extend .NET?

A: Embracing a good technology is good.  Extending technologies in
   incompatible ways is bad for the users, so we do not plan on 
   extending the technologies.

   If you have innovative ideas, and want to create new classes, we 
   encourage you to make those classes operate correctly well in both
   Mono and .NET

<a name="portability"></a>
** 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 an open source license.  

Q: Will Mono run on Windows?

A: We hope so.  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 components.

<a name="reuse"></a>
** 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 clearly
   defined API that splits the JIT from the GC system and the actual
   byte code implementation.

Q: What about using GNU Lightning?

A: We are also researching <a
   href="http://www.gnu.org/software/lightning/lightning.html">GNU
   Lightning</a>.

<a name="gcc"></a>
** Mono and GCC

Q: Are you working on a GCC front-end to C#? A GCC backend that will
   generate CIL images? What about making a front-end to GCC that
   takes CIL images and generates native code?

A: We are currently seeking volunteers for those projects.
   Visit the <a href="contributing.html">contributing</a> section if
   you are interested.

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: We want the JIT engine and runtime engine because they will be able
   to execute CIL executables generated on Windows, and so no recompilation 
   will be necessary.

<a name="performance"></a>
** Performance

Q: How fast will Mono be?

A: We can not predict the future, but a conservative estimate is that
   it would be at least `as fast as other JIT engines'.

   We would like to ship various JIT engines with Mono, just like
   Microsoft has done with their .NET development platform. We could
   provide a faster, JIT for fast load times but lower performance,
   and an and an optimizing JIT 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.  Rather, it is 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
   instruction was reached.

<a name="licensing"></a>
** Licensing

Q: Will I be able to write proprietary applications that run with
   Mono?

A: Yes.  The licensing scheme is planned to allow proprietary
   developers to write applications with Mono.
   
Q: What license or licenses are you using for the Mono Project?

A: The C# Compiler is released under the terms of the <a 
   href="http://www.opensource.org/licenses/gpl-license.html">GNU GPL</a>.  The runtime
   libraries are under the <a
   href="http://www.opensource.org/licenses/lgpl-license.html">GNU
   Library GPL</a>.  And the class libraries are released
   under the terms of the <a
   href="http://www.opensource.org/licenses/mit-license.html">MIT X11</a>
   license.

Q: I would like to contribute code to Mono under a particular
   license. What licenses will you accept?

A: We will have to evaluate the licenses for compatibility first,
   but as a general rule, we will accept the code under the same
   terms of the "container" module. 

<a name="patents></a>
** Patents

Q: Could patents be used to completely disable Mono (either submarine
   patents filed now, or changes made by Microsoft specifically to
   create patent problems)?

A: No.  First, its basic functional capabilities have pre-existed too
   long to be held up by patents.  The basic components of Mono are
   technologically equivalent to Sun's Java technology, which has been
   around for years.  Mono will also implement multi-language and
   multi-architecture support, but there are previous technologies
   such as UCSD p-code and ANDF that also support multiple languages
   using a common intermediate language.  The libraries are similar
   to other language's libraries, so again, they're too similar to
   be patentable in large measure.

   However, if Microsoft does patent some technology, then our plan is
   to either (1) work around it, (2) chop out patented pieces, (3) 
   find prior art that would render the patent useless.
 
   Not providing a patented capability would weaken the
   interoperability, but it would still provide the free software /
   open source software community with good development tools, which
   is the primary reason for developing Mono.  

<a name="etc"></a> **
Miscellaneous Questions

Q: You say that the CLI allows multiple languages to execute on the
   same environment.  Isn't this the purpose of CORBA?

A: The key difference between CORBA (and COM) and the CLI is that the
   CLI allows "data-level interoperability" because every
   language/component uses the same data layout and memory management.

   This means you can operate directly upon the datatypes that someone
   else provides, without having to go via their interfaces.  It also
   means you don't have to "marshall" (convert) parameters (data
   layouts are the same, so you can just pass components directly) and
   you don't have to worry about memory managment, because all
   languages/components share the same garbage collector and address
   space.  This means much less copying and no need for reference
   counting.

Q: Will you support COM?

A: The runtime will support XPCOM on Unix systems and COM on Windows.
   Most of the code for dynamic trampolines exists already.

Q: Will Ximian offer certifications on Mono or related technologies?. 

A: It's possible. But there is no plan about this. So the short answer is no.