The *high level database interface* (HLDI) is needed to run biometric experiments using non-filelist databases (e.g. if one wants to use SQL-based database package).
This tutorial explains how to create a *high level* database
interface, using as an example ``bob.pad.*`` framework (e.g.
``bob.pad.face``). The process is similar for ``bob.bio`` frameworks,
e.g. ``bob.bio.face``, ``bob.bio.vein``). High level database interface
is a link between low level database interface/package (e.g. ``bob.db.replay``) and a
corresponding framework used to run biometric experiments (e.g.
``bob.pad.face``). Generally speaking, the low level interface has lot's
of querying options, which are not always used in the corresponding biometric
framework. High level interface only contains the functionality, which
is needed to run biometric experiments. This, must have functionality,
is defined in the corresponding base classes and is discussed next.
First thing you need to do is to create a ``*.py`` file containing
your high level implementation, for example:
``bob/pad/face/database/replay.py`` for the Replay database. This file
must be placed into corresponding biometric framework, which in this
case is ``bob.pad.face`` package. The file **must** contain the
implementation of two classes:
- ``<YourDatabaseName><Bio/Pad/Other>File``
- ``<YourDatabaseName><Bio/Pad/Other>Database``
For example, the names of the above classes for the *Replay* database used in
the ``bob.pad.face`` framework are: ``ReplayPadFile`` and
Do nothing. In this particular implementation the annotations are returned in the *File class above.
"""
return None
Instead, let's try to understand why the implementation looks like this. Again, the methods to be implemented are defined by the corresponding base class of our ``*Database`` class.
In the case of PAD ``*Database`` the inheritance structure is as follows:
For other biometric experiments it might look differently.
In the given example the behavior of the ``ReplayPadDatabase`` class is defined by the ``bob.pad.base.database.PadDatabase`` base class, which sates that two methods must be implemented in the high level database implementation: ``objects()`` and ``annotations()``. The ``objects()`` method returns a list of instances of ``ReplayPadFile`` class. The ``annotations()`` method is empty, since the developer of the code decided to return the annotations in the ``*File`` class. Note: you are not obliged to do it that way, it's just a matter of taste.
At this point, having all necessary classes in place, we are done with implementation of the high level database interface!
Just a few small things have to be done to register our high level interface in the corresponding biometric framework.
- First, import your package in the ``__init__.py`` file located in the folder containing the implementation of HLDI: ``from .replay import ReplayPadDatabase``
- Next, create an instance of the ``*Database`` class with default configuration. For example, for the ``ReplayPadDatabase`` class used in ``bob.pad.face`` framework, the default configuration file ``/bob/pad/face/config/database/replay.py`` is as follows:
.. code:: python
# The original_directory is taken from the .bob_bio_databases.txt file located in your home directory
original_extension = ".mov" # extension of the data files
database = ReplayPadDatabase(
protocol='grandtest',
original_directory=original_directory,
original_extension=original_extension,
training_depends_on_protocol=True,
)
- Finally, in the ``setup.py`` file of the corresponding biometric framework, add the entry pointing to your default configuration. In the case of observed PAD example the code is:
