I recently listened to the show #369 of .Net Rocks! And read the reaction of Frans Bourma (LLBLGenPro) on the subject.
I wanted to react and give my views on the subject.
For an overview of what Object Relational Mapping is, please read my previous post on the subject.
This post assumes that the reader will already have the knowledge of the Microsoft Entity Framework concepts. If it is not the case please read the ADO.NET Entity Framework Overview as a pre-requisite.
Quick introduction to the Microsoft Entity Data Model (EDM)
The MS Entity Framework is composed of several parts, one of which is the Entity Data Model (EDM). The EDM is used for modelling at a conceptual level the business space, and actually corresponds to the "object space" of the Object/Relational mapping. The EDM is the model describing the set of objects mapped to relational tables on the database side. Then comes the mapping layer, being the bridge or glue between the EDM, or "object side" and the tables in your relational database. Finally, the Object Relational Mapping engine does the trick to manipulate data, persist changes to the database and feed the EDM objects at runtime. An important aspect that will be essential for the main subject of the post is the following: the EDM model is decoupled from the mapping layer and from the ORM engine. In other words the EDM model has no knowledge that there is a mapping and an ORM engine at all, and can be used or re-used without the presence of the mapping and ORM engine. This is an essential pattern for working in a remote/disconnected scenario where a service is responsible for manipulating and persisting data (and thus is using the mapping layer and ORM engine), and the client solely use the data provided by the services, through the form of EDM objects, with no knowledge on how and where the data is stored. Please note that there is nothing conceptually new here and this is the basis of most existing ORM tools of the market, adapted to the Microsoft terminology.
So now that the introduction is made, here comes the main subject of this post.
The Microsoft Entity Framework entering the ORM tools market
For what I've understood from the .Net Rocks podcast, Microsoft could be having more interest on the EDM model than on the ORM engine. You could imagine that this is because they did not manage to catch-up with the existing ORM tools maturity or for a more strategic reason, but that's out of subject here.
Fact is they are many ORM vendors, doing and mastering this job for years and being very mature. The EDM specifically could be on its side more interesting for MS because it is platform oriented and could become a new Microsoft standard, ideal for making applications inter-communicate though this EDM full object oriented, strongly typed object model. Let be clear: the Entity Framework is not a platform, however the Entity Framework and more specifically the EDM model can become an important glue element of the Microsoft platform, becoming the de-facto standard for inter-connecting Microsoft applications and services and any third party application wanting to leverage the EDM opportunity and offer a communication interface to the outer world though EDM entities.
A new business opportunity for third party vendors?
What I would extrapolate from Stephen Forte talk in the podcast (and that engages only me) is that there is an opportunity for ORM vendors to build on top of EDM and provide advanced and efficient ORM engine core functionalities: a third party ORM engine replacing the Microsoft one, manipulating and persisting data all through EDM entities. There is also an opportunity for Microsoft Partners to build tools or designers that could assist creating a EDM model and map it to the database + making use of an ORM engine (being the Microsoft one or any other "EDM Compliant" ORM engine). In this scenario, third parties ORM vendors would be using the EDM as the data model used to manipulate, transfer data, between applications and services. Another clarification: the EDM is indeed not a new, revolutionary concept, and every ORM tool in the market is including such a concept: the entities model is indeed the actual object oriented side of the object/relation mapping layer and is an essential part of any ORM tool.
Closer look on the EDM on a broader picture
The EDM model becomes a data contract in the WCF sense, making easier and efficient to exchange data between systems, regardless of where the underlying data is stored and whether or not we are using ORM engine to concretely retrieve these EDM entities. For instance you could most probably use and EDM model to represent data in an inter-application communication scenario and not link to any database in the back-end. The EDM and the Entity Framework ORM engine are loose-coupled and you can use one or the other independently. Well at least you can use the EDM independently from the EF ORM engine, I am not too sure of the opposite.
And the EDM is even more than just a data contract: it comes with tools and will probably come with more. One is the Entity SQL, based on SQL syntax oriented toward object queries on the EDM model. And again this is nothing new: for instance Llblgen provides a full framework around its entity model, adding extra functionalities as compared to a basic object model or to any model you could build from scratch by hand, in a reasonable amount of time.
So back to the point: using the EDM as a data contract, it removes the need for applying a DTO pattern for interoperability between systems and especially when exposing services and wanting to make your clients unaware and decoupled from your inner implementation and especially from the ORM tool you are using. Well to be more precise: if the EDM becomes a "Microsoft standard", any one agreeing on that could consume a service delivering EDM entities. But you should be aware that the interoperability will anyway not be complete as using EDM will probably tight you to the Microsoft platform and "Microsoft Entity Framework aware" clients. I will write another post about the DTO pattern in a SOA world and when to use or not use it. DTO is yet another mapping layer and one can wonder why after mapping from the relational world to the object world we still need another translation. My recommendation would be that one should not introduce another mapping layer is there is no absolute need for it. You might need it or might absolutely want to forget about it, depending on the scenario you're in, there is no single solution to all problems.
So is the Entity Data Model much bigger than a just an ORM?
So Yes, for what the EDM is concerned and what you can hear in the podcast as being "more than just ORM", you can achieve the same result with other ORM tool and I am actually doing it on my projects with the LLBLGen Pro generated entities model layer. What however the EDM might provide as a plus in the future is integration in the whole MS suite and become the missing glue link to seamlessly connect systems though the strongly type, object oriented EDM data model. Well let´s be more precise: the missing link in systems based on Microsoft tools and technology.
So to insist on this point, I can understand Frans Bourma when he is reacting strongly on the sentence "The EF is much more than an ORM" because no, there is no magic and what MS say they can do with the entity framework and the EDM could be achieved with another ORM tool and its own entity model. It is just after all a matter of convention and all actors standardizing on the same framework (and for instance here the EDM part of entity framework). But Yes MS can bring something more with the EDM that goes beyond the ORM aspect, just by the fact that they can push for using the EDM as the data contract layer for all of their products. They can do it because they own the product! And this is what makes the idea powerful: for instance when a company start investing in Microsoft, it usually spread the whole SI and range of applications: start installing MS servers and desktops windows OS and you end up using Exchange server and SharePoint server and office and more and more, rather that competing products. And why? Just because all integrate so well: it is all coming for a single vendor who actually makes the integration of all its range of applications as easy and straight-forward as possible! Same thing can happen with the EDM on a more technical, low level I must say, but following the same driving idea.
To conclude …
To conclude, what I can foresee is that what will bring most to Microsoft strategically speaking is the EDM layer of the Entity Framework. Because this it becomes part of the communication layer, behind the data container for interconnecting the various MS applications. Then how the ORM engine is internally implemented is not of so much importance. And I guess they will be more than happy at Microsoft if a third party ORM engine could be used, and build on top of the EDM and proving very efficient. It will just go in their direction of promoting the entity framework and especially the EDM layer and through the EDM the maturity of their platform and catalogue of products and they will be in a position to market and sell how easy interconnecting them is.
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