builder.addElement(Contributor.KEY);
builder.addElement(Source.KEY);
builder.addElement(BatchId.KEY);
builder.addElement(BatchInterrupted.KEY);
builder.addElement(BatchOperation.KEY);
builder.addElement(BatchStatus.KEY);
// Register adaptations.
TextContent.registerMetadata(registry);
OtherContent.registerMetadata(registry);
OutOfLineContent.registerMetadata(registry);