ISO 11179 defines relationship as "connection among model elements". It is a simple definition, yet with profound usages in the SHARE MDR. We use relationships to impose constraints between asset types. For instance, a variable metadata element (MDE) may only be represented by 1 value domain (VD). We use relationships to represent collections and their members. Examples: A domain-level metadata element set (MDES), which is a collection entity, may contain multiple variable MDE asset members; or, a class-level MDES may contain multiple domain MDES. We also use relationships to express hierarchies. The SHARE Stack diagram does a great job illustrating the hierarchy among various asset types for SDTM. As you can tell by now, we don't take relationships lightly.
We used the SDTM metadata spreadsheet posted on the CDISC website to formulate the baseline content. During our recent quality sweep, we realized some relationships didn't look right and sometimes were missing. Take Findings About, for example. Findings About was shown as a class at the same level of the 3 general observations classes. Further, domain FA was a member of the Findings class.
Before
After
Some relationships for SDTM can be less than easy to discern from the PDF documents (normative documents). The team has done a fabulous job making them explicit and correct in SHARE so that the standard will become less esoteric, expressing expert knowledge as metadata.
