This is an interesting thread, and one that I might be able to provide some input to...
The logical data model (or Entity Relationship Diagram) is supposed to be a model that describes the primary business concepts and relationship between those concepts from a business perspective; it contains entities, attributes, and relationship described in business language. Because a fully normalized entity relationship model is very similar to a first cut physical model, many people in technology confuse the two. The first cut physical model is a platform specific implementation of a logical model, it contains tables, columns and referential integrity frequently following the naming and abbreviation standards for that database platform.
Typically logical models are created and maintained by data management professionals with the title of Information Architect, Data Architect, Data Modeler or Data Analyst.
The physical model is maintained by a Data Base Administrator in most shops...and then they move into the actual tuning and denormalization that is required for physical implementation.
There are a number of decent online "self-training" courses for data modeling techniques that a Business Analyst can use to develop solid data requirements which are the input to a data model. In some shops a BA may do some of the modeling; in others the DA is responsible for creating the data model deliverable.
In a more object oriented environment, you can think of the entity-relationship diagram as the data structure that documents the relationships between persistent data....
I hope this gives you a bit more clarity about the use of an entity-relationship model as well as different areas of the data management practice.
There is an organization that supports data management professionals www.dama.org as well as an online newsletter that typically includes information on data modeling related topics www.tdan.com. The certifications for this practice include CDMP (Certified Data Management Professional) and CBIP (Certified Business Intelligence Professional) are administered by www.iccp.org.
Best of luck,
Loretta
CCP, CBIP, CDMP - Mastery level.