Managing MDF 4 with ODS

One major result of an ASAM workshop held on May 12, 2016 at BMW was the agreement of all participating experts to further develop the standards MDF and ODS with the goal to make the data in MDF 4 files more easily accessible for ODS-compliant tools.

While currently it is possible to use MDF 3 files as binary mass data storage within ODS servers in the so-called “mixed mode”, that does not work “out-of-the-box” with MDF 4 files. Due to the more complex data filing structure of MDF 4 (e.g. data split across data block boundaries), the data first must be sorted to allow ODS servers an efficient access. However, this post-processing step is time-consuming and results in doubling the amount of storage capacity needed, since it is often necessary to keep the original files. Moreover, even with sorted data some extended functionalities of MDF 4 files remain problematic to map within ODS.

The attendees of the workshop have made some specific proposals for improvement in this respect. The proposal of Peak Solution was to introduce a layer of abstraction between ODS and the physical MDF 4 files.

The approach is to utilize a Virtual File System Server to represent the mass data of the MDF 4 files in a way that is compatible with the file interface already present in the ODS standard (the so-called “external component”). Thus, transparent (read-only) access to any MDF 4 file would be possible for all ODS servers (and all ODS-compliant applications in general) implementing the current ODS standard (5.3), without requiring MDF -specific importer tools or ODS standard extensions.

In this scenario, the Virtual File System Server’s responsibility is to create virtual files – according to the mass data file format (BTF) as described by the ODS standard – which contain the channel data from MDF 4 files. This includes also the handling of data type translation, conversions, data compression etc. In effect, since the logic for accessing a physical MDF 4 file is encapsulated in the Virtual File System Server, the ODS server itself need not have any knowledge of the data structure in the MDF 4 file nor deal with any aspect of the MDF 4 file format.

Important: The Virtual File System Server generates no physical files! The data and the associated directory structure is created in memory only. A file system interface (e.g., NFS) provides the necessary methods for that.

This intermediate layer would also allow both standards to be developed independently while ensuring that MDF 4 files can be seamlessly used as mass data files in ODS applications.

Currently Peak Solution prepares an ASAM project proposal for the implementation of this solution. In parallel, the ASAM experts will discuss other ideas in further workshops. A decision by the ASAM Technical Steering Committee (TSC) on the next steps is expected in mid-August 2016.

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