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Mono is a project led by Novell (formerly by Ximian) to create an ECMA standard compliant .NET compatible set of tools, including among others a C# compiler and a Common Language Runtime. Mono can be run on Linux, FreeBSD, UNIX, Mac OS X, Solaris and Windows based computers.

Mono is dual licensed by Novell, similar to other products such as Qt and the Mozilla Application Suite. Mono's C# compiler and tools are released under the GNU General Public License (GPL), the runtime libraries under the GNU Lesser General Public License (LGPL) and the class libraries under the MIT License. These are all free software and open-source licenses and hence Mono is free and open-source software. Developers contributing source code to Mono must sign a copyright assignment allowing Novell to relicense the code under other licensing terms. This preserves Novell's ability under the dual license to commercially license Mono.For more information about the licensing, see Mono FAQ: Licensing

Microsoft has a version of .NET available for FreeBSD, Windows and Mac OS X called the Shared Source CLI (Rotor). Microsoft's shared source license is neither free software nor open-source and may be insufficient for the needs of the community (it explicitly forbids commercial use). The Mono project has many of the same goals as the Portable.NET project.

The Mono runtime contains just-in-time compilation (JIT) engine for a number of processors: x86, SPARC, PowerPC, ARM, S390 (in 32 bit and 64 bit mode), and x86-64, IA64 and SPARC for 64 bit modes. The runtime will perform a just-in-time compilation to the machine's native code and cached as the application runs. It is also possible to precache the native image before execution. For other supported systems not listed, an interpreter performs each byte code one by one without compiling the image to native code. In almost every condition the JIT method will outperform the interpreted method.

History

Miguel de Icaza became interested in .NET technology as soon as the .NET documents came out in December 2000. After looking at the byte code interpreter, he realized that there were no specifications for the metadata. In February 2001 de Icaza asked for the missing information on the metadata file format in the .NET mailing lists and at the same time started to work on a C# compiler written in C#, as an exercise in C#. In April 2001 ECMA published the missing file format, and at GUADEC (April 6 – April 8, 2001) de Icaza demonstrated the features of his compiler (which by then was able to parse itself).

Internally at Ximian there was much discussion about building tools to increase productivity: making it possible to create more applications in less time and therefore reduce time and cost of development. After a feasibility study, which clearly stated that it was possible to build the technology, Ximian reassigned staff from other projects and created the Mono team. Lacking the manpower to build a full .NET replacement on their own, they formed the Mono open source project, which was announced on July 19 2001 at the O'Reilly conference.

Almost three years later, on June 30, 2004 Mono 1.0 was released.

Mono Components

Mono consists of three groups of components: 1) core components; 2) Mono/Linux/GNOME development stack; and 3) the Microsoft compatibility stack.

The core components include the C# compiler, the virtual machine, and the base class libraries. These components are based on the Ecma-334 and Ecma-335 standards, allowing Mono to provide a standards compliant, free and open source CLI virtual machine.

The Mono/Linux/GNOME development stack provide tools for application development while leveraging existing GNOME and Free and Open Source libraries. These include: Gtk# for GUI development, Mozilla libraries for working with the Gecko rendering engine, Unix integration libraries, database connectivity libraries, a security stack, and the XML schema language RelaxNG. Gtk# allows Mono applications to integrate into the Gnome desktop as native applications. The database libraries provide connectivity to MySQL, SQLite, PostgreSQL, Firebird, Open Database Connectivity (ODBC), Microsoft SQL Server (MSSQL), Oracle, DB40, among many others. The Mono project tracks developing database components at its website.

The Microsoft compatibility stack provides a pathway for porting Windows .NET applications to Linux. This group of components include WebForms, ADO.NET, ASP.NET, and Windows.Forms, among others. As these components are not covered by ECMA standards, some of them remain subject to patent fears and concerns.

Framework Architecture

Class Library

The class library provides a comprehensive set of facilities for application development. They are primarily written in C#, but thanks to the Common Language Specification they can be used by any .NET language. The class library is structured into namespaces, and deployed in shared libraries known as assemblies. When we speak of the .NET framework, we are primarily referring to this class library.

Namespaces and assemblies
Namespaces are a mechanism for logically grouping similar classes into a hierarchical structure. This prevents naming conflicts. The structure is implemented using dot-separated words, where the most common top-level namespace is System, such as System.IO and System.NET (a complete list can be found in Mono Documentation). There are other top-level namespaces as well, such as Accessibility and Windows are examples. New namespaces can also be created prefixed with the organization.

Assemblies are the physical packaging of the class libraries. These are .dll files, just as (but not to be confused with) Win32 shared libraries. Examples of assemblies are mscorlib.dll, System.dll, System.Data.dll and Accessibility.dll. Namespaces are often distributed among several assemblies and one assembly can be composed of several files.

Common Language Infrastructure and Common Language Specification

The Common Language Infrastructure (CLI), or more commonly known as the Common Language Runtime, is implemented by the Mono executable. The runtime is used to execute compiled .NET applications. The common language infrastructure is defined by the ECMA standard ECMA-335. To run an application, you must invoke the runtime with the relevant parameters.

The Common Language Specification (CLS) is specified in chapter 6 of ECMA-335 and defines the interface to the CLI, such as conventions like the underlying types for Enum. The Mono compiler generates an image that conforms to the CLS. This is the Common Intermediate Language. The Mono runtime takes this image and runs it. The ECMA standard formally defines a library that conforms to the CLS as a framework.

Managed and Unmanaged Code

Within a native .NET/Mono application, all code is managed; that is, it is governed by the CLI's style of memory management and thread safety. Other .NET or Mono applications can use legacy code, which is referred to as unmanaged, by using the System.InteropServices libraries to create C# bindings. Many libraries which ship with Mono use this feature of the CLI, such as Gtk#.

Related projects

There exist lots of projects related to Mono that extend Mono and allows developers to use Mono in their development environment. These projects include:
  • Cocoa#, wrappers around the native Mac OS X toolkit (Cocoa).
  • Gecko#, bindings for embedding the layout engine used in Mozilla (Gecko).
  • Gtk#, C# wrappers around the underlying GTK+ and GNOME libraries, written in C.
  • Tao, a collection of graphics and gaming bindings

MonoDevelop: the Mono IDE

MonoDevelop is a free GNOME integrated development environment primarily designed for C# and other .NET languages such as Nemerle, Boo, and Java (via IKVM.NET). MonoDevelop was originally a port of SharpDevelop to Gtk#, but it has since evolved to meet the needs of Mono developers. The IDE includes class management, built-in help, code completion, Stetic (a GUI designer), project support, and an integrated debugger.

The MonoDoc browser provides access to API documentation and code samples. The documentation browser uses wiki-style content management, allowing developers to edit and improve the documentation.

Mono and Microsoft's patents

Mono implementation of those components of the .NET stack not submitted to the ECMA for standardization has raised some patent violation concerns. Particularly, discussion has taken place about whether Microsoft could destroy the Mono project through patent suits. The problematic parts are not the core technologies submitted to the ECMA or the Unix/Gnome-specific parts. The patent concerns primarily relate to technologies developed by Microsoft on top of the .NET Framework, such as ASP.NET, ADO.NET and Windows Forms, i.e. parts composing Mono's Windows compatibility stack. These technologies are today not fully implemented in Mono and not required for developing Mono-applications. 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.

Mono team patent strategy

The Mono team addresses the patent issues in the FAQ at the Mono website. The page states that the Mono team has a three-step strategy to deal with technologies subject to patent threats:
  1. Implement it by using another implementation technique and hence work around the patent.
  2. Remove the patent covered code
  3. Find prior art and make the patent invalid.

Of course, the first option is not always available. Some problems, such as those related to interoperability and communication, may only have a single solution. For this same reason, although the second option is always available, it may result in the development of a product which will not be usable as a .NET replacement. The third option is expensive, may not be possible, and involves a degree of luck (as in all patent interpretation suits).

Defensive patent strategy

Corporations with a vested interest in free and open source software developed a means to protect FOSS projects from the threats of patent suits by pooling patents into the Open Invention Network (OIN). The OIN is a company that acquires patents and offer them royalty free "to any company, institution or individual that agrees not to assert its patents against the Linux operating system or certain Linux-related applications".

The OIN has the Commerce One patents that cover web services, which potentially threaten anyone who uses web services. The OIN's founders intend for these patents to encourage others to join, and to discourage legal threats against Linux and Linux-related applications. Along with several other projects, Mono is listed as a covered project.

IBM, Novell, Philips, Red Hat, and Sony founded the OIN November 10, 2005.

Software developed with Mono

The following are programs that use the Mono API and C#.

See also

References

External links

International

Computing platforms | Free software | GNOME

Mono (platforma) | Mono (project) | Mono-Projekt | Proyecto Mono | Mono (informatique) | Mono (progetto) | Mono (ontwikkelplatform) | Mono (projekt) | Mono (projeto) | Mono | Mono (kehitysympäristö) | Mono | Mono

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Mono development platform".

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