4.2.3 Object Reference

When RESQML moved from a (mostly) hierarchical data model to an object-relationship model with top-level, stand-alone data objects, two new mechanisms were required (Figure 4.2.3-1):

• A way for data objects to reference one another, which is done using the DataObjectReference. (For more information on how data object references works, see 5.4 Specifying Relationships in RESQML .)

• A way to group data objects, which required additional reference mechanisms.

• Grouping data objects is done using the Energistics Packaging Conventions (EPC), which is a specialization of the Open Packaging Conventions (OPC).
• With EPC, most data is stored internal to the EPC package. However, some data may (or must) be stored externally to the package, including HDF5 files (HDF5 has been used by RESQML since v1 for optimized storage, retrieval and performance of large numeric data sets). EpcExternalPartReference and Hdf5Dataset are used for these external references.

• For more information on these EPC-related references, see the Energistics Packaging Conventions (EPC) Specification.

These mechanisms will be used across Energistics standards so have become part of Energistics Common Technical Architecture.

Figure 4.2.3-1 ObjectReference class (Energistics Common Technical Architecture).