9.3Pool and Participant

A Pool is the graphical representation of a Participant in a Collaboration. A Participant (see page 113) can be a specific PartnerEntity (e.g., a company) or can be a more general PartnerRole (e.g., a buyer, seller, or manufacturer). A Pool MAY or MAY NOT reference a Process. A Pool is NOT REQUIRED to contain a Process, i.e., it can be a “black box.”

A Pool is a square-cornered rectangle that MUST be drawn with a solid single line (see Figure 9.2).

The label for the Pool MAY be placed in any location and direction within the Pool, but MUST be separated from the contents of the Pool by a single line.

If the Pool is a black box (i.e., does not contain a Process), then the label for the Pool MAY be placed anywhere within the Pool without a single line separator.

One, and only one, Pool in a diagram MAY be presented without a boundary. If there is more than one Pool in the diagram, then the remaining Pools MUST have a boundary.

The use of text, color, size, and lines for a Pool MUST follow the rules defined in “Use of Text, Color, Size, and Lines in a Diagram” on page 39.

Name

Figure 9.2 – A Pool

To help with the clarity of the Diagram, a Pool extends the entire length of the Diagram, either horizontally or vertically. However, there is no specific restriction to the size and/or positioning of a Pool. Modelers and modeling tools can use Pools in a flexible manner in the interest of conserving the “real estate” of a Diagram on a screen or a printed page.

A Pool acts as the container for the Sequence Flows between Activities (of a contained Process). The Sequence Flows can cross the boundaries between Lanes of a Pool (see page 304 for more details on Lanes), but cannot cross the boundaries of a Pool. That is, a Process is fully contained within the Pool. The interaction between Pools is shown through Message Flows.

Another aspect of Pools is whether or not there is any Activity detailed within the Pool. Thus, a given Pool MAY be shown as a “White Box,” with all details (e.g., a Process) exposed, or as a “Black Box,” with all details hidden. No Sequence Flows are associated with a “Black Box” Pool, but Message Flows can attach to its boundaries (see Figure 9.3).

Manufacturer

Figure 9.3 – Message Flows connecting to the boundaries of two Pools

For a “White Box” Pool, the Activities within are organized by Sequence Flows. Message Flows can cross the Pool boundary to attach to the appropriate Activity (see Figure 9.4).

Figure 9.4 – Message Flows connecting to Flow Objects within two Pools

A Collaboration can contain two (2) or more Pools (i.e., Participants). However, a Process that represents the work performed from the point of view of the modeler or the modeler’s organization can be considered “internal” and is NOT REQUIRED to be surrounded by the boundary of the Pool, while the other Pools in the Diagram MUST have their boundary (see Figure 9.5).