Miscellaneous Published Parameters

Self-Serve parameters can include any regular parameters, not just ones that are specific only to a Data Download setup

Any parameter in FME can be published and presented to the user as a choice to be made when running a workspace. They don’t have to be specifically related to the Data Download service.

Finding a Parameter

Parameters are located in the Navigator window (usually on the left-hand side of FME Workbench).

As you can see, there are parameters for the source data location (1) and the destination data dataset (2), which is the one that the Data Download service overrides. There are also general Reader and Writer parameters (3) and parameters for transformers (4)

Publishing a Parameter

Parameters are published by right-clicking on them and choosing “Create User Parameter”.

For example, here a workspace author is about to publish a parameter on the LabelPointReplacer transformer.

When the workspace is run the end-user will now be able to decide what size they want labels to appear as.

The author gets to choose the type of parameter (in this case a floating point number), the user prompt, and the default value.

Using a Parameter

A User Parameter that is published becomes available to the end-user at run-time.

In FME Workbench, you would select Run > Prompt and Run from the menubar, to see these parameters. There is also a toolbar button and a keyboard shortcut (Ctrl+R).

In FME Server, these parameters become available on the Configuration page of a service, as seen in the Chapter 2 exercises.

Key Parameter Types

Two key parameter types for a self-serve setup are “Choice with Alias” and “Scripted”.

Choice with Alias parameters are where the user is presented with a choice, each of which returns a different value to FME.

For example, here the author wishes the user to select the height of labels to be created in the output dataset.

The user is presented with the list of (more intuitive) options on the right, but the value returned to FME will be the (more useful) number on the left.

This parameter type is also very useful for some Data Download specific tasks, as we’ll see shortly.

Scripted parameters are a way to incorporate a Python or Tcl script into the generation of a parameter value.

This script can include references to other user parameters, meaning one parameter value can be calculated based on the value of another. Parameters referred to in the scripts are generally published parameters that accept input from the user.

So, user input can be accepted from one parameter, and this input processed using a script, in order to produce the actual information required by the workspace.

The Data Download system from Exercise 3b works, but could be improved upon. In particular, it would be helpful for users to be able to choose the resolution and compression of the imagery they are downloading.

1. Create a Published Parameter for Resolution

Start FME Workbench (if necessary). Open the workspace from Exercise 3b (or the start workspace for this exercise).

Locate the User Parameters section of the Navigator window. Right-click on the header for this section and choose Add Parameter.

This opens the Add/Edit User Parameter dialog. In this dialog enter the following values:

Type Integer

Name Resolution

Published Yes (Checked)

Optional No (Unchecked)

Prompt Image Resolution (1-50)

Default Value 5

2. Apply Parameter to RasterResampler

Having created the parameter we can get input from the end-user, but, as-yet, the workspace isn’t doing anything with that input. We must now apply the input to the transformers.

Click the cog wheel icon to open the parameters dialog for the RasterResampler transformer.

Notice that the X and Y Cell Spacing is currently hard-coded as 5.

Click the drop down arrow to the right of the X Cell Spacing parameter. Choose User Parameter > Resolution. This will apply the Resolution parameter you just created to this transformer.

Repeat the action for the Y Cell Spacing parameter.

The transformer X/Y Cell parameters will now look like this:

3. Create a Published Parameter for JPEG Compression

Now we will create a parameter for the user to control the JPEG compression amount.

Open the properties dialog of the AirphotoMosiac feature type. Click on the Format Parameters tab.

Click the drop down arrow beside Compression Level and choose User Parameter > Create User Parameter.

Change the prompt to JPEG Compression (0-100) and leave the default at 28.

4. Test your Workspace in FME Workbench

Save the workspace as Exercise3c.fmw.

As workspaces get more complex it is always a good idea to test them first in FME Desktop before publishing to FME Server. Use the menu Run - Prompt and Run (or Cntrl+R) to see the parameters which are now available. You should see your new parameters.

Click the file browse button and select some neighboring image files, for example 06-07-LM.tif and 06-07-NO.tif.

Enter some extreme values for your new parameters so it will be obvious that the output has been changed, for example:

Image Resolution 50

Compression Level 100

Click OK to run the workspace.

Check the output; you should have a single very low resolution, poor quality image.

If you ever need to change the parameter prompts or defaults then browse to the parameters in the Navigator window and right-click the one you want to change. Select Edit Definition and this will open a dialog in which to update the definition.

5. Publish the Workspace

Use the publish wizard to publish your workspace to FME Server. You don’t need to upload any data (assuming you uploaded it in the earlier exercises), but be sure you check Data Download Service in the last window.

6. Run Data Download Using New Parameters

Acting as a user now, visit the Web User Interface and navigate to your workspace: Workspaces > Training > Exercise3c.fmw > Data Download

Notice your new parameters are now shown automatically in the web form.

As before, select some or all of the source image files under Browse Resources.

Scroll down and enter reasonable values for the Image Resolution and the JPEG Compression. Click Run Workspace on the bottom of the form.

7. Download the Output

The Success page will appear with a link to download the data. Download and extract the zip file contents to ensure it includes an image based on the specifications you entered in the web form.

Congratulations! You now have a Data Download Service where your customers can choose the resolution and compression for imagery they want to access.