Custom Transformer Types

There are two types of custom transformers.

An embedded transformer is one whose definition is stored in the workspace itself. Each instance of the custom transformer refers to that embedded definition. Only the workspace in which the definition is embedded has access to that custom transformer.

A linked transformer is one whose definition is stored outside of the workspace, in its own file. Each instance of the custom transformer is linked to that definition. Any workspace can have access to that custom transformer.

On a workspace canvas, embedded transformers are identified by their green color, while linked transformers are colored cyan:

Linked vs. Embedded Transformers

Both types of transformers can be used in an FME workspace, and there are various advantages and disadvantages to each type.

Embedded Transformers

Embedded transformers are easier to manage, need no external files, and their definition is embedded into the workspace. They are particularly useful for tidying a workspace but also work for employing advanced functionality like parallel processing.

However, sharing and re-use of content are not as simple with an embedded transformer. The custom transformer cannot easily be shared with other users, unless they are given a copy of the same workspace, and it is not easy to maintain a consistent definition among several users.

Linked Transformers

Linked transformers are perhaps a little harder to manage. They exist as a file (.fmx) outside of the workspace, which is less convenient, and when used to employ advanced functionality such as loops they can be more complex.

However, a linked custom transformer is a little easier to edit (you open the .fmx file rather than the .fmw file) and is much easier to share among users. Not only can the file be given to any FME author to use, but any number of authors can actually point their FME to the same custom transformer file.

Sharing the same file is useful because any changes made to the definition are automatically propagated to all workspaces that use it.

FME Lizard says…

Like embedded transformers, linked transformers also show up in the transformer gallery and Quick Add dialog. Also notice that they have a special icon to signify that you are about to use a linked version, rather than the embedded: