12 BPMN Notation and Diagrams

12.1 BPMN Diagram Interchange (BPMN DI)

12.1.1 Scope

This clause specifies the meta-model and schema for BPMN 2.0.2 Diagram Interchange (BPMN DI). The BPMN DI is meant to facilitate interchange of BPMN diagrams between tools rather than being used for internal diagram representation by the tools. The simplest interchange approach to ensure the unambiguous rendering of a BPMN diagram was chosen for BPMN DI. As such, BPMN DI does not aim to preserve or interchange any “tool smarts” between the source and target tools (e.g., layout smarts, efficient styling, etc.).

BPMN DI does not address or define the interchange of color information. The use of alternative colors in BPMN is non normative. The meaning or semantic of colors might vary from tool to tool or, from user to user, potentially leading to miss-interpretations.

BPMN DI does not ascertain that the BPMN diagram is syntactically or semantically correct.

12.1.2 Diagram Definition and Interchange

The BPMN DI meta-model, similar to the BPMN abstract syntax meta-model, is defined as a MOF-based meta-model. As such, its instances can be serialized and interchanged using XMI. BPMN DI is also defined by an XML schema. Thus its instances can also be serialized and interchanged using XML.

Both BPMN DI meta-model and schema are harmonized with a draft version of the OMG Diagram Definition (DD) standard. Annex B contains the relevant parts of the referenced DD specifications that were used as foundation for the BPMN DI model and schema. The provided DD contains two main parts: the Diagram Commons (DC) and the Diagram Interchange (DI). The DC defines common types like bounds and fonts, while the DI provides a framework for defining domain specific diagram models. As a domain specific DI, BPMN DI defines a few new meta-model classes that derive from the abstract classes from DI.

The focus of BPMN DI is the interchange of laid out shapes and edges that constitute a BPMN diagram. Each shape and edge references a particular BPMN model element. The referenced BPMN model elements are all part of the actual BPMN model. As such, BPMN DI is meant to only contain information that is neither present, nor derivable, from the BPMN model whenever possible. Simply put, to render a BPMN diagram both the BPMN DI instance(s) and the referenced BPMN model are REQUIRED.

From the BPMN DI perspective, a BPMN diagram is a particular snapshot of a BPMN model at a certain point in time. Multiple BPMN diagrams can be exchanged referencing model elements from the same BPMN model. Each diagram may provide an incomplete or partial depiction of the content of the BPMN model. BPMN DI does not ascertain that the BPMN diagram is syntactically or semantically correct.

As described in Clause 15, a BPMN model package consists of one or more files. Each file may contain any number of BPMN diagrams. The exporting tool is free to decide how many diagrams are exported and the importing tool is free to decide if and how to present the contained diagrams to the user.