PalmSource announced it is releasing its recently created software library known as libsqlfs, under a Lesser General Public License (LGPL). Created as part of the ACCESS Linux Platform (ALP), the libsqlfs library is an add-on to the popular SQLite package. The libsqlfs software library was designed to provide a more flexible and convenient way to implement an Open Mobile Alliance-Device Management (OMA-DM) compliant registry.

OMA-DM is a key specification for mobile phones and devices, and it defines a common set of system settings for cell phones. This specification requires support for secure settings, whose access must be limited to applications with specific credentials.

Such a service must also allow keys to be organized in a hierarchy like pathnames in a file system. PalmSource engineers concluded that a simpler way to meet these needs was to write a library that supported the POSIX file system semantics on an SQL database. This combines the benefits of a real database, such as transactions and concurrency control, with SQL access to file system metadata.

"The motivation for creating a file system-to-database-file bridge originated with our need for ALP to be able to store and retrieve application and system preferences," said Michael Kelley, senior vice president of engineering at PalmSource. "We evaluated what is available today and decided to write a software library specifically to address this issue."

"PalmSource built a tremendously strong community around Palm OS," commented Bill Weinberg, Senior Analyst, Open Source Development Lab (OSDL). "Today, their creation of the Linux-based ALP platform and opening up libsqlfs (and other projects) demonstrates their capability to build communities around embedded software, and their commitment to free open source software."

An adjunct to the open source SQLite database software, the libsqlfs library, developed by PalmSource, provides an easy way for applications to put an entire read/write file system into a relational database as a single file in the host file system. Such a file system can easily be moved around, backed up or restored as a single file. In addition, the file system in a single database file can be more space efficient than many small individual files. Unlike other space-efficient alternatives such as cramfs*, the libsqlfs software library supports write access to the files.

A registry built using the libsqlfs software library can accommodate small preference values such as a number, and large binary objects such as a video clip. The library provides a generic file system layer that maps a file system onto an SQLite database, and supports POSIX file system semantics.