17. Parameterized attributes

17.1. Introduction

To get the point of parameterized attributes begin with an example : the /electromagneticSource/planeWave definition.

We have seen that a plane wave is defined by some attributes and a magnitude arraySet :

data.h5
`-- electromagneticSource
    `-- planeWave
        `-- $a-plane-wave[@xo=0.0
            |             @yo=0.0
            |             @zo=0.0
            |             @theta=0.0
            |             @phi=0.0
            |             @linearPolarization=0.0]
            `-- magnitude[@floatingType=arraySet]

All attributes are simple :

• the physical nature is given by Amelet HDF
• the unit is fixed
• the value is a scalar

However, it could happen someone would like to define a plane wave with varying parameters :

• theta and/or phi could take their values in an interval [0, PI] because a module can take into account several directions of propagation in a single simulation
• Make the origin point move during a simulation

For these reasons, Amelet HDF offers a flexible way to override attributes definition without blurring the simplicity of the format.

17.2. The _param group

Given a simple attribute of the above example, @xo for example, we want it to take many values. The solution is to create a _param group in electromagneticSource/planeWave/a-plane-wave element and add an xo floating type arrayset to _param

data.h5
`-- electromagneticSource
    `-- planeWave
        `-- a-plane-wave[@yo=0.0
            |            @zo=0.0
            |            @theta=0.0
            |            @phi=0.0
            |            @linearPolarization=0.0]
            |-- magnitude[@floatingType=arraySet]
            `-- _param
                `-- xo[@floatingType=arraySet]
                    |-- data[@physicalNature=length
                    |        @unit=meter]
                    `-- ds
                        `-- dim1[@physicalNature=time
                                 @unit=second]

The element a-plane-wave/_param/xo simply overrides the definition a-plane-wave/@xo.

The general rule is that

a container’s attribute can be overridden by adding an element with the same name to the ``_param`` group child of the container.