  Almost all groups involved in linear collider detector studies have their own
simulation software framework. Using a common persistency scheme would allow to
easily share results and compare reconstruction algorithms. We present such a
persistency framework, called LCIO (Linear Collider I/O). The framework has to
fulfill the requirements of the different groups today and be flexible enough
to be adapted to future needs. To that end we define an `abstract object
persistency layer' that will be used by the applications. A first
implementation, based on a sequential file format (SIO) is completely separated
from the interface, thus allowing to support additional formats if necessary.
The interface is defined with the AID (Abstract Interface Definition) tool from
freehep.org that allows creation of Java and C++ code synchronously. In order
to make use of legacy software a Fortran interface is also provided. We present
the design and implementation of LCIO.
