I would like to point there's already some kind of "textual representation" for ER that could have been ported to PlantUML. I have found a comprehensive document about it. In short, it could have been like this:
@startuml
' __ could signal the Primary Key (just a suggestion)
entity Bus (__reg_no, make, size, deck, no_of_pass)
entity Route (__route_no, avg_pass)
entity Driver (__emp_no, name, cell)
entity Stage (__stage_no)
entity Town (__name)
Bus m..1 Route : is serviced by
Route 1..m Stage : comprises
Driver m..1 : is allocated to
Stage n..m Town : Passes-though
Route n..m Town : Passes-though
@enduml
Which is more readable than the cryptic }|-|| (which is related to the drawn symbols, I know).
Also, the attributes can be written in a more classical way, less "java-ish", as shown in the entities declarations. I.e., the "Bus" entity would be shown as:
If attributes are listed and not hidden (`hide attributes`, i.e.) they could be also drawn following the ERD stadard, UseCase-like oval surrounding their entity, something like this:
NOTE: Since I used a Use-case diagram, I couldn't add the ERD symbols to the line ends.
And, just for completeness and drive the developers crazy, declare the relationships as diamonds if declared:
skinparam erdModel chen
etc.
But, just a thought. Document the current implementation would be nice enough. O:)
[NOTE 2: I admit I do not usually add the attributes in E-R diagrams...]