Calligra provides a framework that all components build on. Through this framework high integration is achieved. It is possible to develop your own component that integrates as well.
Despite offering so many components, Calligra is lightweight, fast and has a rather low memory footprint. This is also achieved because Calligra builds on KDE, a powerful application development framework.
A goal of Calligra is also to not overload the user interface with features that are hardly needed. This results in a lean and mean user interface that lets you do your work efficiently.
Being lightweight can at times also mean that that very particular special functionality you need is not there. In this case you can always add the functionality yourself by extending Calligra. Extra features can always be made available through additional plugins or scripts, thus keeping Calligra itself lightweight.
Calligra offers a wide range of components, covering most of the home and business office needs. Additional features can always be implemented through scripts, plugins or even whole components based on the Calligra framework.
It is a major importance for any office suite to adhere to established standards. Especially on the file format level to allow seamless document exchange with other office suites. This also avoids vendor lock-in, which is especially important for companies and also for individuals.
For this reason Calligra has adapted the OASIS OpenDocument format as native file format.
Since Calligra builds on KDE all the features you would expect from a KDE application are also available in Calligra. This includes D-Bus, KParts, Flake, Desktop Integration, Configurability and so on. All this makes the look and feel of Calligra very familiar and really integrates Calligra into the desktop environment, thus allowing seamless workflows.