Continue with Making Subgraph Configurable.

To export an attribute of a component as a parameter of subgraph, choose the attribute of a component of subgraph and use the Export as subgraph parameter button.

The following window opens, where you can set the parameter properties.

The public parameter then appears as a subgraph component attribute under its respective group of properties.

One public parameter can be used in more components of the same subgraph. For example two Filter components can share the filter expression exported from a subgraph component as a public parameter.

Any existing public graph parameter can be used as an attribute value of components in a subgraph.

To use an existing public parameter as a value of an attribute of a component choose the attribute and use the Use parameter as value button.

Input and output ports of a subgraph can be marked as optional. It lets you create a component with ports that do not require a connected edge.

It can be set up in Outline within a subgraph. Right click the port inOutline and choose the corresponding option.

You can set up optional ports from Context menu in the subgraph editor too. Move the mouse cursor on the optional port and right click to open the Context menu.

This way is available only if there is an edge connected to the port.

There are three options:

You can use Optional ports to conditionally enable or disable a component within subgraph. See Enable/Disable Component.

You can set up color for the subgraph component arising from the subgraph. The subgraph can be assigned to the category of components (Readers, Writers, etc.). The subgraph component will have the color of the assigned category.

To set up the category, right click on the subgraph component, select Open subgraph, and in the Properties Tab select Subgraph  Category.

Subgraph can have own icon assigned. Three sizes of icons can be defined:

To define the path to the icon, right click on the subgraph component, select Open Subgraph and go to Subgraph section on the Properties.

Suggested place for subgraph icons is in ${PROJECT}/icons.

As an icon,.png and.gif files can be used.

Continue with Developing and Testing Subgraphs.

Note, that subgraph elements, like graph parameters, connections, etc., are independent of graph elements of parent graph. There is no connection between them like inheritance. If you need some elements of parent subgraph, map it using the Input mapping or Output mapping attributes.

A subgraph can define explicit metadata in its definition and propagate them to the SubgraphOutput component. When the subgraph is used in a parent graph, these metadata will be propagated via subgraph’s output edge to the parent graph.

Typical use-case is a reader subgraph that not only reads a data source, but also provides metadata of the data source (e.g. orders). In the example below, we define explicit metadata on the output of SpreadsheetDataReader component for records containing orders. Metadata on the output of the Filter component are set to be auto-propagated, which propagates the orders metadata to the output of the subgraph (as defined by SubgraphOutput). When using such a subgraph in a parent graph, the orders metadata are auto-propagated on the output of the subgraph.

Subgraph can require specific metadata when used in a parent graph by defining explicit metadata on the outputs of SubgraphInput. When the subgraph is used, its input metadata in the parent graph must match the metadata defined inside the subgraph.

Typical use-case is a writer subgraph that requires some specific metadata (e.g. customers) to store records in a service. In the example below, we explicitly define customers metadata on the output of the SubgraphInput. When the subgraph is used, its input metadata in the parent graph must match the customers metadata.

Subgraph can be quite generic and not specify any explicit metadata, only use auto-propagated metadata. The subgraph will acquire metadata from its parent graph.

To develop and test such a subgraph, we recommend that you define explicit metadata in the Debug Input (or Debug Output) section of the subgraph. These metadata will make the subgraph valid for testing it.

Typical use-case is a generic filter graph that performs filtering on specific (or user defined) fields, and copies all other fields. In the example below, all edges of the subgraph body are set to be auto-propagated. When the subgraph is used in a parent graph, the customers metadata are propagated through the subgraph.

For details on metadata propagation, see also Auto-propagated Metadata.