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In computing, the System Object Model (SOM) is an
object-oriented Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
shared library In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subro ...
system developed by IBM. DSOM, a distributed version based on
CORBA The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between sys ...
, allowed objects on different computers to communicate. SOM defines an interface between programs, or between libraries and programs, so that an object's interface is separated from its implementation. SOM allows classes of objects to be defined in one programming language and used in another, and it allows libraries of such classes to be updated without requiring client code to be recompiled. A SOM library consists of a set of classes, methods, static functions, and data members. Programs that use a SOM library can create objects of the types defined in the library, use the methods defined for an object type, and derive subclasses from SOM classes, even if the language of the program accessing the SOM library does not support class typing. A SOM library and the programs that use objects and methods of that library need not be written in the same programming language. SOM also minimizes the impact of revisions to libraries. If a SOM library is changed to add new classes or methods, or to change the internal implementation of classes or methods, one can still run a program that uses that library without recompiling. This is not the case for all other
C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
libraries, which in some cases require recompiling all programs that use them whenever the libraries are changed, known as the
fragile binary interface problem {{Citations missing, date=May 2009 The fragile binary interface problem or FBI is a shortcoming of certain object-oriented programming language compilers, in which internal changes to an underlying class library can cause descendant libraries or pr ...
. SOM provides an
application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...
(API) that gives programs access to information about a SOM class or SOM object. Any SOM class inherits a set of virtual methods that can be used, for example, to find the class name of an object, or to determine whether a given method is available for an object.


Applications

*
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
*
OpenDoc OpenDoc is a defunct multi-platform software componentry framework standard created by Apple in the 1990s for compound documents, intended as an alternative to Microsoft's proprietary Object Linking and Embedding (OLE). It is one of Apple's e ...
SOM was intended to be used universally from IBM's mainframe computers right down to the desktop in
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
, allowing programs to be written that would run on the desktop but use mainframes for processing and data storage. IBM produced versions of SOM/DSOM for OS/2,
Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
and various
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
flavours (notably IBM's own
AIX Aix or AIX may refer to: Computing * AIX, a line of IBM computer operating systems *An Alternate Index, for a Virtual Storage Access Method Key Sequenced Data Set * Athens Internet Exchange, a European Internet exchange point Places Belgi ...
). For some time after the formation of the
AIM alliance The AIM alliance, also known as the PowerPC alliance, was formed on October 2, 1991, between Apple, IBM, and Motorola. Its goal was to create an industry-wide open-standard computing platform based on the POWER instruction set architecture. It ...
, SOM/DSOM was also used by
Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...
for similar purposes. It was most widely used in their
OpenDoc OpenDoc is a defunct multi-platform software componentry framework standard created by Apple in the 1990s for compound documents, intended as an alternative to Microsoft's proprietary Object Linking and Embedding (OLE). It is one of Apple's e ...
framework, but saw limited use in other roles as well. Perhaps the most widespread uses of SOM within IBM were in later versions of OS/2, which used it for most code, including the
Workplace Shell The Workplace Shell (WPS) is an object-oriented desktop shell (also called desktop environment) produced by IBM's Boca Raton development lab for OS/2 2.0. It is based on Common User Access and made a radical shift away from the Program Manager ...
. Object REXX for OS/2 is able to deal with SOM classes and objects including WPS. SOMobjects were not completely shut down by IBM. They were ported to OS/390, and are still available on this OS. One can read documentation on IBM website. In 1996 Tandem Computers Inc. obtained SOMobjects technology. Tandem was sold to Compaq, Compaq was sold to Hewlett-Packard. NonStop DOM and some other technologies eventually merged into NonStop CORBA, but current documentation of NonStop products does not contain signs of SOM technology still powering NonStop products.


Fading away

With the "death" of OS/2 in the mid-1990s, the ''
raison d'être Raison d'être is a French expression commonly used in English, meaning "reason for being" or "reason to be". Raison d'être may refer to: Music * Raison d'être (band), a Swedish dark-ambient-industrial-drone music project * ''Raison D'être' ...
'' for SOM/DSOM largely disappeared; if users would not be running OS/2 on the desktop, there would be no universal object library anyway. In 1997, when
Steve Jobs Steven Paul Jobs (February 24, 1955 – October 5, 2011) was an American entrepreneur, industrial designer, media proprietor, and investor. He was the co-founder, chairman, and CEO of Apple; the chairman and majority shareholder of Pixar; a ...
returned to Apple and ended many development efforts including Copland and
OpenDoc OpenDoc is a defunct multi-platform software componentry framework standard created by Apple in the 1990s for compound documents, intended as an alternative to Microsoft's proprietary Object Linking and Embedding (OLE). It is one of Apple's e ...
, SOM was replaced with
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
already being in use in
OPENSTEP OpenStep is a defunct object-oriented application programming interface (API) specification for a legacy object-oriented operating system, with the basic goal of offering a NeXTSTEP-like environment on non-NeXTSTEP operating systems. OpenStep was ...
(to become Mac OS X later). SOM/DSOM development faded, and is no longer actively developed, although it continues to be included and used in OS/2-based systems such as
ArcaOS ArcaOS is an operating system based on OS/2, developed and marketed by Arca Noae, LLC under license from IBM. It was codenamed Blue Lion during its development. It builds on OS/2 Warp 4.52 by adding support for new hardware, fixing defects and l ...
. Despite effective death of OS/2 and OpenDoc, SOM could have yet another niche: Windows and
cross-platform In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software r ...
development. SOM 3.0 for WinNT was generally available in December 1996. The reasons for not advancing in these directions go beyond market adoption problems. They involve opportunities missed by IBM, and destructive incompatible changes: * The first version of VisualAge C++ for Windows was 3.5. It was the first and the last version to support SOM. It had SOM 2.1 bundled in and Direct-to-SOM support in the compiler. Versions 3.6.5 and later had no trace of SOM. * SOMobjects largely relied on
makefile In software development, Make is a build automation tool that automatically builds executable programs and libraries from source code by reading files called ''Makefiles'' which specify how to derive the target program. Though integrated develo ...
s. VisualAge C++ 4.0 introduced .icc projects and removed icc.exe and ilink.exe command line compiler and linker from supply. It is impossible to build any SOM DTK sample out of box with VAC++ 4.0. VisualAge C++ comes with its own samples, but there are no .icc SOM samples even in VAC++ 4.0 for OS/2. vacbld.exe, the only command line compilation tool, doesn't support SOM. * VisualAge C++ bundled-in Object Component Library (OCL) was not based on SOM. It was probably meant to be ported to SOM using C++ Direct-to-SOM mode, but in VAC v3.6.5 this mode was abandoned, and OCL has no SOM interface so far. * Near the end of the 1990s, IBM shut down SOMobjects download sites and never put them back online. SOM 3.0 DTK for WinNT can't be found on IBM FTP, despite much other legacy stuff lying around freely. Despite general availability of SOM 3.0 for WinNT, it was nearly impossible to locate until the end of 2012. * Finally, IBM never open-sourced SOM (as done to Object REXX), despite several articles and petitions.


Alternative implementations

Two projects of open-source SOM implementations exist. One is Netlabs Object Model (NOM), which is technically the same, but binary incompatible. Another is somFree, which is a
clean room design Clean-room design (also known as the Chinese wall technique) is the method of copying a design by reverse engineering and then recreating it without infringing any of the copyrights associated with the original design. Clean-room design is usefu ...
of IBM SOM, and binary compatible.


Comparison of support for compiled class libraries

Historically, SOM was compared to Microsoft's Component Object Model (COM) by IBM. However, from some points of view there is no place for COM at all. From the point of view of release to release transformations, COM is on procedural level, thus, the table 1 in RRBC article (''Release-to-Release Binary Compatibility'' referenced earlier) does not contain COM column at all. Instead, SOM is being compared to: * compiled
Smalltalk Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by Alan Ka ...
* compiled
Common Lisp Object System The Common Lisp Object System (CLOS) is the facility for object-oriented programming which is part of ANSI Common Lisp. CLOS is a powerful dynamic object system which differs radically from the OOP facilities found in more static languages such as ...
(CLOS) * generic
C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
* SGI Delta/C++ * Sun Object Binary Interface *
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
*
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
Most information in this table is still applicable to modern versions (as of 2015), except Objective-C 2.0 getting so called non-fragile instance variables. Some solutions remained experimental: SGI Delta/C++ or Sun OBI. Most approaches based on one programming language were phased out or were never used actively in the same way. For instance, Netscape Plugin Application Programming Interface (
NPAPI Netscape Plugin Application Programming Interface (NPAPI) was an application programming interface (API) of the web browsers that allows plugins to be integrated. Initially developed for Netscape browsers, starting in 1995 with Netscape Navigato ...
) browser plugins were written using Java API initially (LiveConnect), but
Java Virtual Machine A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describes ...
(JVM) was later excluded from the chain. It can be seen as Java replaced with Cross Platform Component Object Model (
XPCOM Cross Platform Component Object Model (XPCOM) is a cross-platform component model from Mozilla. It is similar to Microsoft Component Object Model (COM) and Common Object Request Broker Architecture (CORBA). It features multiple language bindings ...
).
Common Lisp Object System The Common Lisp Object System (CLOS) is the facility for object-oriented programming which is part of ANSI Common Lisp. CLOS is a powerful dynamic object system which differs radically from the OOP facilities found in more static languages such as ...
(CLOS) and Smalltalk are not known as being chain links like Java in LiveConnect.
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
is also not known much in this role and not known to be marketed this way, but its runtime is one of the most friendly to similar use cases. Generic C++ is still being used in Qt and the K Desktop Environment (
KDE KDE is an international free software community that develops free and open-source software. As a central development hub, it provides tools and resources that allow collaborative work on this kind of software. Well-known products include the ...
). Qt and KDE are notable for describing efforts it takes to maintain binary compatibility without special support in development tools.
GObject The GLib Object System, or GObject, is a free software library providing a portable object system and transparent cross-language interoperability. GObject is designed for use both directly in C programs to provide object-oriented C-based APIs ...
only aimed to avoid dependence on C++ compiler, but RRBC issues are the same as in generic C++. Without special runtime many other programming languages will have the same issues, e.g.,
Delphi Delphi (; ), in legend previously called Pytho (Πυθώ), in ancient times was a sacred precinct that served as the seat of Pythia, the major oracle who was consulted about important decisions throughout the ancient classical world. The oracle ...
,
Ada Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, ...
. It can be illustrated by so-called ''unprecedented approach'' it took to produce Delphi 2006 binary compatible Delphi 2007 release
How to add a "published" property without breaking DCU compatibility
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
is the most promising competitor to SOM (although not being actively marketed as multi-language platform), and SOM should preferably be compared to Objective-C as opposed to COM as it happened historically. With non-fragile instance variables in Objective-C 2.0 it is the best alternative amongst actively supported.
COM Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level d ...
,
XPCOM Cross Platform Component Object Model (XPCOM) is a cross-platform component model from Mozilla. It is similar to Microsoft Component Object Model (COM) and Common Object Request Broker Architecture (CORBA). It features multiple language bindings ...
are being used actively, but they only manage interfaces, not implementations, and thus are not on the same level as SOM,
GObject The GLib Object System, or GObject, is a free software library providing a portable object system and transparent cross-language interoperability. GObject is designed for use both directly in C programs to provide object-oriented C-based APIs ...
and
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
.
Windows Runtime Windows Runtime (WinRT) is a platform-agnostic component and application architecture first introduced in Windows 8 and Windows Server 2012 in 2012. It is implemented in C++ and officially supports development in C++ (via C++/WinRT, C++/CX or ...
under closer look behaves much like COM. Its metadata description is based on .NET, but since WinRT does not contain special runtime to resolve RRBC issues, like in Objective-C or SOM, several restrictions had to be applied that limit WinRT on procedural level:
Type System (C++/CX)
: A ref class that has a public constructor must be declared as sealed, to prevent further derivation.
Windows Runtime Components - Windows Runtime Components in a .NET World
: Another restriction is that no generic public classes or interfaces can be exposed. Polymorphism isn’t available to WinRT types, and the closest you can come is implementing WinRT interfaces; you must declare as sealed any classes that are publicly exposed by your Windows Runtime Component.


Comparison to COM

SOM is similar in concept to COM. Both systems address the problem of producing a standard library format that can be called from more than one language. SOM can be considered more robust than COM. COM offers two methods of accessing methods onto an object, and an object can implement either one of them or both. The first one is dynamic and
late binding In computing, late binding or dynamic linkage—though not an identical process to Dynamic linker, dynamically linking imported code Library (computing), libraries—is a computer programming mechanism in which the Method (computer programming), ...
(
IDispatch IDispatch is the interface that exposes the OLE Automation protocol. Extending IUnknown, it is one of the standard interfaces that can be exposed by COM objects. COM distinguishes between three interface types: ''custom'' that are VTABLE-based I ...
), and is language-neutral similar to what is offered by SOM. The second, called a Custom Interface, is using a function table which can be built in C but is also directly compatible with the binary layout of the virtual table of C++ objects in Microsoft's C++ compiler. With compatible C++ compilers, Custom Interfaces can therefore be defined directly as pure virtual C++ classes. The resulting interface can then be called by languages that can call C functions through pointers. Custom Interfaces trade robustness for performance. Once an interface is published in a released product, it can not be changed, because client applications of this interface were compiled against a specific binary layout of this interface. This is an example of the
fragile base class The fragile base class problem is a fundamental architectural problem of object-oriented programming systems where base classes ( superclasses) are considered "fragile" because seemingly safe modifications to a base class, when inherited by the ...
problem, which can lead to
DLL hell In computing, DLL Hell is a term for the complications that arise when one works with dynamic-link libraries (DLLs) used with Microsoft Windows operating systems, particularly legacy 16-bit editions, which all run in a single memory space. DLL Hel ...
, as a new version of a shared library is installed and all programs based on the older version can stop functioning properly. To prevent this problem, COM developers must remember to never change an interface once it is published, and new interfaces need to be defined if new methods or other changes are required. SOM prevents these issues by providing only late binding, to allow the run-time linker to re-build the table on the fly. This way, changes to the underlying libraries are resolved when they are loaded into programs, although there is a performance cost. SOM is also much more robust in terms of fully supporting a wide variety of OO languages. Whereas basic COM essentially defines a cut-down version of C++ to program to, SOM supports almost all common features and even some more esoteric ones. For instance SOM supports
multiple inheritance Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit features from more than one parent object or parent class. It is distinct from single inheritance, where an object or ...
,
metaclass In object-oriented programming, a metaclass is a class whose instances are classes. Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances. Not all object-oriente ...
es and
dynamic dispatch In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time. It is commonly employed in, and considered a prime characteristic of, object-oriented ...
ing. Some of these features are not found in most languages, which had led most SOM/COM-like systems to be simpler at the cost of supporting fewer languages. The full flexibility of multi-language support was important to IBM, however, as they had a major effort underway to support both
Smalltalk Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by Alan Ka ...
(
single inheritance Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit features from more than one parent object or parent class. It is distinct from single inheritance, where an object or ...
and
dynamic dispatch In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time. It is commonly employed in, and considered a prime characteristic of, object-oriented ...
) with
C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
(
multiple inheritance Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit features from more than one parent object or parent class. It is distinct from single inheritance, where an object or ...
and fixed dispatch). The most notable difference between SOM and COM is support for inheritance—COM does not have any. It might seem odd that Microsoft produced an object library system that could not support one of the most fundamental concepts of OO programming; the main reason for this is that it is difficult to know where a base class exists in a system where libraries are loaded in a potentially random order. COM demands that the programmer specify the exact base class at compile time, making it impossible to insert other derived classes in the middle (at least in other COM libraries). SOM instead uses a simple algorithm, looking for potential base classes by following the inheritance tree and stopping at the first one that matches; this is the basic idea behind inheritance in most cases. The downside to this approach is that it is possible that new versions of this base class may no longer work even if the
API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
remains the same. This possibility exists in any program, not only those using a shared library, but a problem can become very difficult to track down if it exists in someone else's code. In SOM, the only solution is extensive testing of new versions of libraries, which is not always easy. While SOM and COM were contrapositioned by IBM, they were not mutually exclusive. In 1995 Novell contributed ComponentGlueComponentGlue(tm) Provides Full Interoperability with OLE, OCX Controls
/ref> technology to
OpenDoc OpenDoc is a defunct multi-platform software componentry framework standard created by Apple in the 1990s for compound documents, intended as an alternative to Microsoft's proprietary Object Linking and Embedding (OLE). It is one of Apple's e ...
for Windows. This technology provided different means to integrate between COM- and SOM-based components. In particular, SOM objects can be made available to OLE2 applications by either late binding bridge (based on IDispatch) or COM interfaces having higher performance. In essence, SOM classes are implementing COM interfaces this way. The flexibility offered by SOM was considered worth the trouble by almost all , but similar systems, such as
Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...
'
Distributed Objects Everywhere Distributed Objects Everywhere (DOE) was a long-running Sun Microsystems project to build a distributed computing environment based on the CORBA system in the 'back end' and OpenStep as the user interface. First started in 1990 and announced soon th ...
, also supported full inheritance.
NeXT Next may refer to: Arts and entertainment Film * ''Next'' (1990 film), an animated short about William Shakespeare * ''Next'' (2007 film), a sci-fi film starring Nicolas Cage * '' Next: A Primer on Urban Painting'', a 2005 documentary film Lit ...
's
Portable Distributed Objects Portable Distributed Objects (PDO) is an application programming interface (API) for creating object-oriented code that can be executed remotely on a computer network, network of computers. It was created by NeXT Computer, Inc. using their OpenStep ...
avoided these issues via a strong versioning system, allowing library authors to ship new versions along with the old, thereby guaranteeing
backward compatibility Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
for the small cost of disk space.


See also

* Component Object Model *
GObject The GLib Object System, or GObject, is a free software library providing a portable object system and transparent cross-language interoperability. GObject is designed for use both directly in C programs to provide object-oriented C-based APIs ...
*
Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
*
XPCOM Cross Platform Component Object Model (XPCOM) is a cross-platform component model from Mozilla. It is similar to Microsoft Component Object Model (COM) and Common Object Request Broker Architecture (CORBA). It features multiple language bindings ...
*
Windows Runtime Windows Runtime (WinRT) is a platform-agnostic component and application architecture first introduced in Windows 8 and Windows Server 2012 in 2012. It is implemented in C++ and officially supports development in C++ (via C++/WinRT, C++/CX or ...


References


External links

* tp://ftp.software.ibm.com/publications/clubod/som30/index.html IBM SOMobjects Developer's Toolkit Version 3.0 for Windows NT, OS/2 Warp, and AIX Documentation {{OS/2
System Object Model In computing, the System Object Model (SOM) is an Object-oriented programming, object-oriented shared library system developed by IBM. DSOM, a distributed version based on CORBA, allowed objects on different computers to communicate. SOM defin ...
SOM Object-oriented programming
System Object Model In computing, the System Object Model (SOM) is an Object-oriented programming, object-oriented shared library system developed by IBM. DSOM, a distributed version based on CORBA, allowed objects on different computers to communicate. SOM defin ...