Hello Dana
A ERD is simply a class diagram with a specific profile (Crow's foot notation, stereotypes for primary/foreign keys, triggers and constraints are represented as operations etc.) Anything you can do with a ERD you can also do with a class diagram (there's whole books on this subject on Amazon).
I remember years back the OMG looking into requests to adopt ERDs and concluding that UML already has full capability to do what ERDs do, so nothing to be gained. The main issue is programmers proficient in UML not liking data modelers proficient in ERD and very much vice versa (look up "object impedance").
Anyways a data model (in whatever notation, class diagram or ERD) is an excellent way to capture requirements because you can efficiently and precisely rationalize key concepts (entities and attributes), business rules (relationships and cardinality; also datatypes and domain checks) and other qualities into one simple model that can summarize hundreds of different requirements from dozens of business processes and IT systems.
The best way to learn how to do it is to pick a methodology and practice, practice practice. Most methodologies recommend PLAIN TEXT to capture requirements, then transfer the text to comments on said entities, attributes and relationships. Sparx tagged values and CSV import/export make this very convenient.
Good luck!
Phew. Going directly from requirements to a data model is like having the cake from the flour on the table. Requirements -> Use Cases -> Conecptional Class Model -> Concrete Class Model/Data Model would be the way to go.
q.
In this case, the customer has provided a specification of what data is to be in the database. This task is to simply produce a conceptual data model representation of that specification and the tracing to requirements (specification) is to make sure I have full coverage.
I am curious about "Conceptual Class Model" versus ERD Diagrams in EA. In the past, I have done my data modelling in Class Models but coming back to the tool after about 5 years I discover the ERD Diagram feature. To be honest, I am not quite sold on the ERD Diagram yet. Is there a good resource on the pros and cons of each approach and when/why to choose one over the other?