I read this a while ago but it seems somewhat relevant recently.
The Vietnam of Computer Science "Although it may seem trite to say it, Object/Relational Mapping is the Vietnam of Computer Science. It represents a quagmire which starts well, gets more complicated as time passes, and before long entraps its users in a commitment that has no clear demarcation point, no clear win conditions, and no clear exit strategy."
"Developers simply give up on objects entirely, and return to a programming model that doesn't create the object/relational impedance mismatch. While distasteful, in certain scenarios an object-oriented approach creates more overhead than it saves, and the ROI simply isn't there to justify the cost of creating a rich domain model. ([Fowler] talks about this to some depth.)"
Fowler's piece I believe is, "GetterEradicator" which links to "Tell, Don't Ask", which makes an important point about Design by Contract, "According to Design by Contract, as long as your methods (queries and commands) can be freely intermixed, and there is no way to violate the class invariant by doing so, then you are ok. But while you are maintaining the class invariant, you may have also dramatically increased the coupling between the caller and the callee depending on how much state you have exposed."
"Developers simply give up on relational storage entirely, and use a storage model that fits the way their languages of choice look at the world."
"Developers simply accept that it's not such a hard problem to solve manually after all, and write straight relational-access code to return relations to the language, access the tuples, and populate objects as necessary."
"Developers simply accept that there is no way to efficiently and easily close the loop on the O/R mismatch, and use an O/R-M to solve 80% (or 50% or 95%, or whatever percentage seems appropriate)..."
"Developers simply accept that this is a problem that should be solved by the language, not by a library or framework...bring relational concepts (which, at heart, are set-based) into mainstream programming languages, making it easier to bridge the gap between "sets" and "objects". Work in this space has thus far been limited, constrained mostly to research projects and/or "fringe" languages, but several interesting efforts are gaining visibility within the community, such as functional/object hybrid languages like Scala or F#, as well as direct integration into traditional O-O languages, such as the LINQ project from Microsoft for C# and Visual Basic. One such effort that failed, unfortunately, was the SQL/J strategy; even there, the approach was limited, not seeking to incorporate sets into Java, but simply allow for embedded SQL calls to be preprocessed and translated into JDBC code by a translator."
"Developers simply accept that this problem is solvable, but only with a change of perspective. Instead of relying on language or library designers to solve this problem, developers take a different view of "objects" that is more relational in nature, building domain frameworks that are more directly built around relational constructs."