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XML metadata interchange (XMI)

XML Metadata Interchange (XMI) implements an open exchange format for metadata in distributed software structures based on the Extensible Markup Language (XML) that is independent of manufacturers and middleware.

As the figure shows, it covers a wide range of applications. One of the primary goals of XMI is to enable the easy exchange of metadata between modeling tools and metadata repositories - each based on OMG standards - in distributed heterogeneous environments. With XMI, the definition for a so-called stream-based exchange format has been created. Due to the generic format, a multitude of different models can thus be transferred.

Exchange with XMI

Exchange with XMI

The development of XMI

The beginnings of XMI go back to 1998, when the first proposal was submitted to the Object Management Group (OMG) by various companies, including IBM and Oracle. IBM also implemented the first XMI toolkit in July 1999, followed by version 1.1 of the standardization by the OMG in 2000 - meanwhile version 2.1.1 is available, the specification of which can be viewed in detail at the link below. This chronology is particularly worth mentioning because with version 2.0 elementary features were standardized for the further spread of the exchange format:

  • Complex processing of graphical UML notations,
  • support of the W3C Schema Description,
  • Xlinks links were implemented,
  • Meta Object Facility (MOF) and UML Profiles were integrated,
  • Additional meta models are available.
The characteristics of XMI are summarized below in an overview:

  • XML technology for mapping - mapping - objects and their relationships to each other.
  • An object model, such as a database schema or a class schema in UML, is mapped to XML in a standardized way while preserving the relationships between the objects.
  • The mapping between the meta language of the object model - for example UML to XML - must be defined. The OMG specification MOF2XMI is a concrete example.
  • During transformation - also known as serialization - XML DTD or XML Schema is used to transfer and check the data stream.
  • This also makes it possible to store, read or even generate objects and object hierarchies in XMI documents at runtime.
  • XMI often serves as a standardized exchange format of UML models between different tools - which internally have a proprietary representation of the UML models.
  • XMI is thus an important exchange format in the context of model-driven software development (MDSD).
The advantages of an exchange format like XMI are obvious:

  • Use of the Internet and development with existing industry standards such as XML, UML or MOF,
  • XMI is easily integrated by vendors into current products,
  • barriers between incompatible applications and repositories are overcome.
For larger models, exporting the entire model to an XMI file is often impractical because

  • the export and import times are too long,
  • the file sizes are unwieldy,
  • an incremental approach is not possible.

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Englisch: XML metadata interchange - XMI
Updated at: 17.11.2013
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Translations: DE