Rose Metadata¶

Metadata can be used to provide information about settings in Rose configurations.

It is used for:

Documenting settings.
Performing automatic checking (e.g. type checking).
Formatting the rose config-edit GUI.

Metadata can be used to ensure that configurations are valid before they are run and to assist those who edit the configurations.

The Metadata Format¶

Metadata is written in a rose-meta.conf file. This file can either be stored inside a Rose configuration in a meta/ directory, or elsewhere outside of the configuration.

The rose-meta.conf file uses the standard Rose configuration format.

The metadata for a setting is written in a section named [section=setting] where setting is the name of the setting and section is the section to which the setting belongs (left blank if the setting does not belong to a section).

For example, take the following application configuration:

rose-app.conf¶

[command]
default=echo "Hello ${WORLD}."

[env]
WORLD=Earth

If we were to write metadata for the WORLD environment variable we would create a section called [env=WORLD].

meta/rose-meta.conf¶

[env=WORLD]
description=The name of the world to say hello to.
values=Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

This example gives the WORLD variable a title and a list of allowed values.

Metadata Commands¶

The rose metadata-check command can be used to check that metadata is valid:

$ rose metadata-check -C meta/

The configuration can be tested against the metadata using the -V option of the rose macro command.

For example, if we were to change the value of WORLD to Pluto:

$ rose macro -V
Value Pluto not in allowed values ['Mercury', 'Venus', 'Earth', 'Mars', 'Jupiter', 'Saturn', 'Uranus', 'Neptune']

Metadata Items¶

There are many metadata items, some of the most commonly-used ones being:

title: Assign a title to a setting.
description: Attach a short description to a setting.
type: Specify the data type a setting expects, e.g. type=integer.
length: Specify the length of comma-separated lists, e.g. length=: for a limitless list.
range: Specify numerical bounds for the value of a setting, e.g. range=1, 10 for a value between 1 and 10.

For a full list of metadata items, see rose-meta.conf[SETTING].

Practical

In this practical we will write metadata for the application-tutorial app we wrote in the Rose application practical.

Create a Rose application called metadata-tutorial.

Create a new copy of the application-tutorial application by running:
```
rose tutorial metadata-tutorial ~/rose-tutorial/metadata-tutorial
cd ~/rose-tutorial/metadata-tutorial
```
View the application in rose config-edit.

The rose config-edit command opens a GUI which displays Rose configurations. Open the metadata-tutorial app:
```
rose config-edit &
```
Tip

Note rose config-edit searches for any Rose configuration in the current directory. Use the -C option to specify another directory.

In the panel on the left you will see the different sections of the rose-app.conf file.

Click on env, where you will find all of the environment variables. Each setting will have a hash symbol (#) next to its name. These are the comments defined in the rose-app.conf file. Hover the mouse over the hash to reveal the comment.

Keep the rose config-edit window open as we will use it throughout the rest of this practical.
Add descriptions.

Now we will start writing some metadata.

Create a meta/ directory containing a rose-meta.conf file:
```
mkdir meta
touch meta/rose-meta.conf
```
In the rose-app.conf file there are comments associated with each setting. Take these comments out of the rose-app.conf file and add them as descriptions in the metadata. As an example, for the INTERVAL environment variable you would create a metadata entry that looks like this:
```
[env=INTERVAL]
description=The interval between forecasts.
```
Longer settings can be split over multiple lines like so:
```
[env=INTERVAL]
description=The interval
           =between forecasts.
```
Once you have finished save your work and validate the metadata using rose metadata-check:
```
rose metadata-check -C meta/
```
There should not be any errors so this check will silently pass.

Next reload the metadata in the rose config-edit window using the Metadata ‣ Refresh Metadata menu item. The descriptions should now display under each environment variable.

Tip

If you don’t see the description for a setting it is possible that you misspelt the name of the setting in the section heading.
Indicate list settings and their length.

The DOMAIN and WEIGHTING settings both accept comma-separated lists of values. We can represent this in Rose metadata using the rose-meta.conf[SETTING]length setting.

To represent the DOMAIN setting as a list of four elements, add the following to the [env=DOMAIN] section:
```
length=4
```
The WEIGHTING and WIND_CYCLES settings are different as we don’t know how many items they will contain. For flexible lists we use a colon, so add the following line to the [env=WEIGHTING] and [env=WIND_CYCLES] sections:
```
length=:
```
Validate the metadata:
```
rose metadata-check -C meta/
```
Refresh the metadata in the rose config-edit window by selecting Metadata ‣ Refresh Metadata. The three settings we have edited should now appear as lists.
Specify data types.

Next we will add type information to the metadata.

The INTERVAL setting accepts an integer value. Add the following line to the [env=INTERVAL] section to enforce this:
```
type=integer
```
Validate the metadata and refresh the rose config-edit window. The INTERVAL setting should now appear as an integer rather than a text field.

In the rose config-edit window, try changing the value of INTERVAL to a string. It shouldn’t let you do so.

Add similar type entries for the following settings:

integer settings real (float) settings

INTERVAL WEIGHTING

N_FORECASTS RESOLUTION

Validate the metadata to check for errors.

In the rose config-edit window try changing the value of RESOLUTION to a string. It should be marked as an error.
Define sets of allowed values.

We will now add a new input to our application called SPLINE_LEVEL. This is a science setting used to determine the interpolation method used on the rainfall data. It accepts the following values:
- 0 - for nearest member interpolation.
- 1 - for linear interpolation.
Add this setting to the rose-app.conf file:
```
[env]
SPLINE_LEVEL=0
```
We can ensure that users stick to allowed values using the values metadata item. Add the following to the rose-meta.conf file:
```
[env=SPLINE_LEVEL]
values=0,1
```
Validate the metadata.

As we have made a change to the configuration (by editing the rose-app.conf file) we will need to close and reload the rose config-edit GUI. The setting should appear as a button with only the options 0 and 1.

Unfortunately 0 and 1 are not particularly descriptive, so it might not be obvious that they mean “nearest” and “linear” respectively. The rose-meta.conf[SETTING]value-titles metadata item can be used to add titles to such settings to make the values clearer.

Add the following lines to the [env=SPLINE_LEVEL] section in the rose-meta.conf file:
```
value-titles=Nearest,Linear
```
Validate the metadata and refresh the rose config-edit window. The SPLINE_LEVEL options should now have titles which better convey the meaning of the options.

Tip

The rose-meta.conf[SETTING]value-hints metadata option can be used to provide a longer description of each option.
Validate with rose macro.

On the command line rose macro can be used to check that the configuration is compliant with the metadata. Try editing the rose-app.conf file to introduce errors then validating the configuration by running:
```
rose macro -V
```

`integer` settings	`real` (float) settings
`INTERVAL`	`WEIGHTING`
`N_FORECASTS`	`RESOLUTION`