Universal Network Objects
Universal Network Objects (UNO) is the component model used in the OpenOffice.org and LibreOffice computer software application suites. It is interface-based and designed to offer interoperability between different programming languages, object models and machine architectures, on a single machine, within a LAN or over the Internet.
Users can implement or access UNO components from any programming language for which a language binding exists. Complete UNO language bindings exist for C++ (compiler-dependent), Java, Object REXX, Python, and Tcl . Bindings allowing access, but not writing, to components exist for StarOffice Basic, OLE Automation and the .NET Common Language Infrastructure.
Universal Network Objects operate within the UNO Runtime Environment (URE).
UNO for function-calling 
Examples: an external program can export an ODT file as a PDF file, or import and convert a DOCX, calling LibreOffice by the UNO interface. Another external program can access a cell and formulas from LibreOffice Calc file.
UNO for Add-Ons 
Programmers can write and integrate their own UNO components to LibreOffice. Those components can be added to the LibreOffice menus and toolbars; we call them "Add-Ons". The Add-Ons can extend the functionality of LibreOffice.
The integration of new components is supported by some tools and services. The three main steps are as follows:
- Register the new components within LibreOffice. This can be accomplished using the tool
- Integrate the new components as services. The ProtocolHandler and JobDispatch services assist you.
- Change the user interface (menus or toolbars). This can be done almost automatically by writing an XML text file that describes the changes.
Application example: jOpenDocument.
- Loeschky, Dieter; Shanmugam Senthil (2001). "Universal I18n Framework for Office Applications: Technical Overview" (PDF). Palo Alto: Sun Microsystems. pp. 1–26 . Retrieved 2010-05-18.
- Docvert project, new version implemented with Python and XSLT.
- JODConverter project implemented as Java jODconverter and Python pyODconverter
- See http://help.libreoffice.org/Common/Integrating_new_UNO_components
- UNO Development Kit project page
- Overview and technical details
- Java overview-summary
- OpenOffice.org Software Development Kit
- ODF Toolkit: Transition Steps
- Developer's Guide
- http://api.libreoffice.org/docs/tools.html (see unoexe and unopkg)
Language bridges (native for Java and Python):