Parameters and FME

Parameters control how FME operates, and can be set by either the workspace author or the end user.

What are Parameters?

Parameters, in basic terms, are controls that define how FME operates; for example, how a Reader reads data, how a transformer transforms it, and how a Writer writes it. Almost every component in FME has parameters; of one type or another.

Types of Parameter

When looking at the types of parameter, it’s helpful to consider the types of people who use FME and their role in the process.

Workspace Authors are the people who design and create a workspace. They use FME Workbench and set parameters to control how the workspace runs.

Workspace Users are the people who make use of a workspace, without necessarily having created it first. The user might have very little knowledge of FME, and may never have used

FME Workbench, but they still may need to set parameters to control how the workspace runs. In light of these two roles, we can say there are two different types of parameter.

FME Parameters

FME parameters are those built into FME. They directly control a translation and can be found in various places, such as transformer dialogs or feature type dialogs. However, for the most part you will find all FME Parameters in the Navigator Window of FME.

Parameters:

• Overwrite Existing File: Yes
• Line Termination: System
• Write Last Line Terminator: Yes
• Character Encoding: SYSTEM
• Write UTF Byte Order Mark: Yes

Here, for example, are the FME Parameters for a text file Writer. They include options to overwrite or append to an existing text file, and the type of character encoding that should be used.

These are parameters the workspace author will use. The user is not expected to set these, because the user may have no experience of Workbench and not know where to find the parameter or how to set it.

For example, the author might decide that the Byte Order Mark should not be written in this output.

They double-click the parameter to open a dialog in which they can change the parameter value.

User Parameters

User Parameters are those that are created by an FME author for use by an FME user. In other words, they are a way for the end-user of the workspace to provide their input to a workspace.

User parameters appear in a special section of the Navigator window, labelled User Parameters. Here, for example, two user parameters are defined.

*User Parameters:

Published Parameters

• [SourceDataset_FILEGDB] Source Geodatabase: C:\FMEData2014\Data\Addresses\Addresses.gdb
• [DestDataset_TEXTLINE] Destination Text File: C:\FMEData2014\Output\GarbageSchedule.html

Each user parameter allows the end-user of a workspace to enter information. This may be through a simple dialog (in Workbench or the FME Quick Translator) or it might be through a web page on FME Server.

A user parameter is created by a workspace author by – in most cases – right-clicking on the User Parameters label in the Navigator window and choosing Add Parameter:

A dialog appears in which the author can define the parameter. In this case they are creating a parameter in which the user can enter their name:

Now when the end-user runs the workspace, they will be prompted to enter their name.

Using a User Parameter

Getting input from a user is pointless if it is not used, so it’s also necessary to actually do something with that input.

User parameters can be exploited in a number of places. Firstly they can be tied to an FME parameter (more information on that in the next section), but they can also be used to provide values to an attribute in a workspace.

For example, in this workspace a source dataset undergoes transformation and the output is flagged up with the name of the person who carried out the transformation (i.e. who ran the workspace);

The workspace author creates a user parameter for the user to enter their name (as in the previous screenshots) and then adds an AttributeCreator transformer to create the required output attribute.

In the FME parameters for the AttributeCreator, the author sets the value of the attribute to that provided by the user parameter:

Now when the workspace is run, the end user can enter their name into a text field, and have it entered into an attribute in the output.

Here we have a workspace that was created to translate a parks dataset from MapInfo to KML, plus also write an XML metadata file to show who translated the data and when.

At the moment, all of the XML metadata fields are hard-coded in an AttributeCreator transformer. We’ll need to create user parameters to take the place of these hard-coded values.

1) Start Workbench

Open the workspace C:\FMEData2015\Workspaces\DesktopAdvanced\Exercise1a-Begin.fmw.

Notice the transformers in the workspace.

The Sampler ensures that only one record is written to the output metadata, by discarding all but one feature.

The AttributeCreator creates a set of attributes and the DateFormatter formats the date attribute to an XML-compatible ISO format.

Open the parameters dialog for each transformer in turn. These are FME parameters, set by the workspace author and not available to the end-user.

Here are the parameters for the DateFormatter:

You can also find the same parameters in the Navigator window:

2) Change XML Writer Parameter

As a workspace author we need to change one of the Writer parameters. We don’t want the end-user to be setting this, so we’ll set it ourselves and not create a user parameter.

In the Navigator window locate the XML Writer. Expand the parameters list. Locate the parameter labelled Pretty Print and double-click on it.

In the dialog that opens, change the value to Yes and then click OK to close the dialog. We have now changed an FME parameter.

3) Create User Parameter

We now need to create some user parameters for the end-user to enter information into the workspace.

Firstly, locate the User Parameters section of the Navigator window, right-click on it, and choose the option to Add Parameter:

In the new dialog, select Text as the type of parameter to create (there will be more on parameter types in the next section). Each parameter needs a name, so call this one UserNameParam. Now enter a prompt, such as "Enter your name."

Click OK to close the dialog and create the parameter, which will now appear in the Navigator window.

4) Create Remaining User Parameters

Repeat the previous step twice more, this time creating parameters called UserEmailParam and UserCompanyParam.

The prompts should be “Enter your email address” and "Enter your company name."

When done the Navigator window looks like this:

5) Use User Parameter – Method 1

There are a number of ways to extract the value from a user parameter into a workspace. We’ll use a different way for each parameter, just to illustrate the different methods.

So, firstly open the parameters dialog for the AttributeCreator. This transformer is what currently creates the attributes for the output.

Click in the Value field for the AuthorName attribute. Click on the drop-down arrow, then select User Parameter > UserNameParam.

Once done the value field will change to a special icon and show the parameter that was chosen:

While in this dialog, click on the AuthorEmail and AuthorCompany fields, and press the minus button to delete them. That's just so we can demonstrate dealing with these a different way:

6) Use User Parameter – Method 2

A second way to extract the value from a user parameter is with a ParameterFetcher transformer.

Place a ParameterFetcher transformer (after the DateFormatter is fine). Open the parameters dialog.

Select UserEmailParam as the parameter to fetch. Enter AuthorEmail as the name of the target attribute:

7) Use User Parameter – Method 3

The final method to extract the value from a user parameter is with a schema attribute value.

To achieve this, locate the metadata feature type on the canvas and right-click the AuthorCompany attribute.

Then select the Edit Value option.

In the dialog that opens, you can enter a fixed (constant) value, but in our case we’ll click on the drop-down arrow, select User Parameters, and then select UserCompanyParam:

Click OK to close the dialog and the feature type should look like this. Notice how the attribute that has had its value set is now highlighted with a specific icon:

8) Save and Run Workspace

Save the workspace and then – as if you were the end-user – run it using Run > Prompt and Run.

When prompted enter your details into the fields that have been newly created:

Locate and open the XML file to ensure the contents have been inserted as expected: