BIBI Configuration Generator¶

The BIBI Configuration Generator or BIBI Configuration Script is a Python module that generates Python transfer functions based on a BIBI Configuration in XML format according to BIBI Configuration File Format.

Why do we generate code for the BIBI Configuration?¶

In principal, there are two options of using the BIBI Configuration models, namely

1. Interpretation, i.e. we traverse the transfer functions each time we call them.

2. Compilation, i.e. we generate code in a lower abstraction from the transfer function model.

The advantages of interpretation are an easier implementation, better security and a higher interopability, i.e. it is easier to change the transfer function during a running simulation. Conversely, the advantage of a compilation is usually its better performance and lower memory consumption since it is not necessary to traverse a graph at runtime.

Since the performance of transfer functions is critical given that they are executed at every timestep and we do not want to support to change the transfer functions during a running simulation, we have decided for the compilation. The implementation effort is in a reasonable scale and the security is addressed below.

How do we compile the transfer functions?¶

At first, the XML file is loaded into memory using model representation classes as generated from pyxb (http://pyxb.sourceforge.net/ ), based on the XML Schema Document for the BIBI Configuration File Format (checked in into the Experiments repository). Then, this configuration model is transformed to Python code using Jinja2 templates. These generated files are then loaded into memory by using the RestrictedPython module.

The RestrictedPython essentially transforms the AST of the Transfer Function and allows users to plug in checks whether certain attributes may be accessed, whether certain modules may be loaded and so on. At the time of writing, we are not using any of these checks, so we basically allow whatever code the user has specified with one notable exception: RestrictedPython disallows any usage of double underscores __ as these can be a security hazard.