Martin Fowler gives a great example of describing the bounded context concept by the polyseme 'Meter' in the electric utility domain (https://martinfowler.com/bliki/BoundedContext.html) . Depending on the context, 'Meter' at least 3 meanings, which may result in 3 bounded contexts (BCs):
connection between the grid and a location -> lets call the corresponding BC 'geo';
connection between the grid and a customer -> lets call that BC 'customersupport';
the physical meter itself -> lets call that BC 'assetmanagement';
Lets say we want to design Open-Host services for exposing meter information for each bounded contexts: so a public API for meter in geo BC, a second one in customersupport BC and a third one in the assetmanagment BC.
In the electric utility domain we have a Common Information Model - CIM - (https://www.entsoe.eu/digital/common-information-model/) - which is the electric utility industry standard for data exchange, describing both syntax and semantics. For instance it has for entity 'Meter' a 'canonical' model, describing Meter with a global set of attributes that is bounded context independend so to say.
Should the public APIs we intend to design make use of the CIM model as the source model for the published language by selecting the right attributes from the canonical 'Meter' model? We can take the CIM 'Meter' model, select a subset of the relevant attributes according to the bounded contexts and publish the API in json or xml, based on the CIM model and decoupled from the BC application model.
Would this be a way to design Open-Host services for the Meter polyseme Martin Fowler is referring to?
Sure, you can have a grand unified model which encompasses a number of bounded contexts. Those contexts can effectively ignore the aspects of the unified model which don't really concern them (and even add their own attributes if it makes sense for their purposes).
It might get tricky if there's some aspect of the unified model which multiple bounded contexts are going to want to process updates for, but that can be worked around in various ways.
Would this be a way to design Open-Host services for the Meter polyseme Martin Fowler is referring to?
Open Host Service is a pattern involved in bounded context cooperation. The idea is to provide a stable API for your service, hiding implementation changes from clients to protect them. For instance, you could split your persistence into 2 databases and still expose a single unified interface. Using the CIM model for your service is a good way to ensure a stable API to your clients, using an open standard. However this has nothing to do with polysemes.
Polyseme is a concept where the same object can have different properties and meaning depending on the bounded context considered. For instance, in an ecommerce application, a product can have:
a color and size in the customization BC
a unit price and discount in sales BC
a count and size in storage BC
Size in customization and storage BC could have different meanings. Polysemes do not imply cooperation between these contexts, but is rather about splitting your model into distinct bounded contexts, so different business areas stop interfering with each other. This has to do with application architecture regarding RDBMS as write performance bottlenecks in monolithic applications. Why have your database read-lock your product price and discount information when the storage team update the count from their latest inventory ?
Quoting Martin Fowler:
In those younger days we were advised to build a unified model of the entire business, but DDD recognizes that we've learned that "total unification of the domain model for a large system will not be feasible or cost-effective". So instead DDD divides up a large system into Bounded Contexts, each of which can have a unified model - essentially a way of structuring MultipleCanonicalModels.
Here, he is explicitly referring to stuff like the CIM model when is writes about a unified model of the entire business. Basically, what is saying is that you should not use the whole CIM model for your contexts.
Should the public APIs we intend to design make use of the CIM model as the source model for the published language by selecting the right attributes from the canonical 'Meter' model? We can take the CIM 'Meter' model, select a subset of the relevant attributes according to the bounded contexts and publish the API in json or xml, based on the CIM model and decoupled from the BC application model.
The CIM model is designed for data exchange in this domain. It sounds like a good starting point for your Ubiquitous Language. However, if you don't need your overall system to comply with the CIM model standard, you should definitely split that into smaller bounded contexts.
Related
I've been reading Eric Evans' DDD: Tackling Complexity in the Heart of the Software and in the section in context maps, Evans cited an example of 2 bounded contexts (Booking context and Network Traversal Service) using a translator to integrate them.
If I understand correctly, when we create a model, we put everything into bounded contexts creating conceptual boundaries for the domain. My questions are:
If everything should be in a bounded context, where should the translator be located? In Evans' sample diagram, the translator is outside (in between) both bounded contexts.
Say we have a single team working on a ERP. Should the ERP be put in several bounded contexts or a single one only. Based on Evans' sample, the bounded contexts were devised so that multiple teams could work on their own model. But since this is a single team, wouldn't they benefit on a single model so integration wouldn't be an issue? Or did I understand this wrong?
In question 2's case, if multiple bounded contexts, what if in implementation, we need a class from Accounting to be used in Payroll? I don't think we need a translator here but I'm not sure how to share the required class. Will just referencing the needed class from another bounded context be fine?
And lastly, how is a module in DDD related to a bounded context?
In an Infrastructure layer (outside the Domain), it's a technical detail.
A bounded context(BC) emerges from the Domain, that's why we identify them and not defining them. Once identified, if there are many BCs and there are developers available then the workload can be split so that the app can be developed faster. A single model is not advisable, you want a single domain model per BC and also a simplified read model for querying (CQRS).
I don't know but for me Payroll is part of Accounting, there aren't really 2 BC. Account is a BC, however other BC might need a Payroll but that definition is specific to the BC. And probably the definition is just really some data (a read model). Payroll behaviour should stay in Accounting. So you need to have clearly defined what each BC understands by "Payroll". Usually you'll have a domain service who will use concepts from both BC and which will use the 'translator'.
It isn't. A module just groups things together from a technical point of view. A BC is pretty virtual, you might choose to have a project or a module corresponding to one BC but that's your decision how to organize things.
If everything should be in a bounded context, where should the translator be located? In Evans' sample diagram, the translator is
outside (in between) both bounded contexts.
I think this question has no sense. Each BC is a boundary in wich a domain model exist, and the boundary is determined by the UL, each BC has its own UL. If you just create one model, you don't need translation. Instead of spliting a big model into several smaller ones, you are joining them.
Say we have a single team working on a ERP. Should the ERP be put in several bounded contexts or a single one only. Based on Evans'
sample, the bounded contexts were devised so that multiple teams could
work on their own model. But since this is a single team, wouldn't
they benefit on a single model so integration wouldn't be an issue? Or
did I understand this wrong?
I think you understood wrong. You split a single model into several BCs according to the UL, not to the available teams. Then if you don't have enough teams for the number of BCs created, a team will have to develop more than one BC. By the way, the opposite is not desirable, i.e., a BC shouldn't be developped by more than one team.
In question 2's case, if multiple bounded contexts, what if in implementation, we need a class from Accounting to be used in Payroll?
I don't think we need a translator here but I'm not sure how to share
the required class. Will just referencing the needed class from
another bounded context be fine?
You shouldn't reference a domain object of another BC. That BC should protect its domain model, that's the application layer for. The application layer expose DTOs, plain objects, it shouldn't expose the domain model to the outside world. What you are asking for is a shared kernel (a model shared by other BC).
And lastly, how is a module in DDD related to a bounded context?
A module is just a java package, useful for keeping together things that a related to each other. So you split the source code of a BC in modules. Do it according to the UL, not to technical aspects. For instance, a module for each aggregate, not a module for entities, another one for repositories, etc.
I've read Eric Evan's book and am reading Vaughn Vernon's book now. I'm in the second chapter where he talks about subdomains and bounded context and am thoroughly confused now.
From what I was able to distill, there should be a 1:1 relationship between a BC and an SD. However, I read in other places that this isn't necessarily the case.
Can someone explain to me the relationship between a BC and SD?
A subdomain is a part of your business. There are core domains, supporting domains and generic domains. Core domains are where the money is, supporting domains support your core business, and generic domains are the ones you need, but don't care a lot about, so you would probably buy them of the shelf. For an insurance company, the core domain is insurance, a supporting domain could be client portfolio, and a generic domain could be something like timesheets.
In general a bounded context is a boundary within which the ubiquitous language is consistent. In DDD walhalla each subdomain would live in its own bounded context. In reality however, there is legacy, there are packages that try to do everything at once... which will force all kinds of awkard relationships.
I try to explain these concepts with my understanding.
In DDD, everything should be communicated under ubiquitous language so the technical team and business team can use the same terms and have same views on the problems
Domain in DDD represent real problem in business. Such as: E commerce is a domain, Payroll system is a domain
Domain is divided into many sub domains, so each sub domains focus smaller problems. Such as: E commerce has many sub domains such as: Shopping Cart, Billing, Product Catalog, Customer Information...
Each sub domain should have explicit responsibilities so it has a boundary to limit their functionalities, the boundary will help sub domain focus to do only 1 thing and do well. This boundary is considered as bounded context of the sub domain. The bounded context will define:
How many domain models needed for the sub domain?
Which properties needed in the each model?
Which functionalities needed in sub domain?
Ex: Shopping Cart sub domain needs models: Cart, Product, Customer Info... and contains functions to perform CRUD on the cart. Notes: The Product and Customer model in the Shopping Cart sub domain maybe not the same with the models in Product Catalogs and Customer Profiles sub domain, they just contain necessary properties to display on Shopping Cart.
Vaughn Vernon in his “Implementing Domain-Driven Design” book states that “the subdomains live in the problem space and the bounded contexts in the solution space”
Imagine a software that is being developed to support a dentist. A dentist has two problems: fixing patients’ teeth and making appointments for the patients. Fixing teeth is the core domain and making appointments is a supporting subdomain. In the core domain the medical staff cares about a patient’s dental history, can they handle general anesthesia or not, what their current problem is, etc. In the subdomain the staff (not necessarily medical staff) cares about a patient’s contact information, a date and a time that best suits both the doctor and the patient, the type of dental work needed, etc. Both domains need a model of a patient, but that model will depend on the bounded context we put in place to ensure the correct information and features are available when solving the problems of each domain.
read https://robertbasic.com/blog/bounded-contexts-and-subdomains/
Rereading the Booking Context from the blue book 18 times helped me finally get a handle. http://codeidol.com/csharp/domain-driven-design/Maintaining-Model-Integrity/Bounded-Context/
This article helped as well: http://gorodinski.com/blog/2013/04/29/sub-domains-and-bounded-contexts-in-domain-driven-design-ddd/
Here is my understanding, I would use the Hospital example to elaborate the concepts and deep dive into how is BC is different than Subdomain and why they can be a case where there is no 1:1 relationship between them
Example
Imagine we are making software for a Hospital, in which we have identified 3 subdomain
Health Care (Core domain, where they actually want to cure the patient)
Invoice (Supporting domain focused on invoicing)
Knowledge (Generic domain, where doctors maintain procedures on how to operate on a patient for a particular disease)
Now we know that Bounded Contexts are boundaries under which terms
have a very well-defined meaning. So let us apply those in Subdomains
Let's consider the term. Patient. What are the things that you think about when hearing the term patient?
Their current symptoms
Past medical records
Allergies
How about their bill-paying credibility? Current outstanding balance? Didn't think of it? The reason is you were thinking in the core subdomain space of Health Care. The bill-paying credibility makes sense only when you shift to the Invoice subdomain.
What we understand from this is the Patient term is inside a Bounded Context, its a boundary inside a subdomain where it has a very specific meaning
The reason it said
BC is in solution/implementation/programming space and not in business
space
is because here we decide what fields and behaviors should be part of the Patient model
In the core domain space, you might represent Patient it like this
class Patient {
List<Allergy> alergies;
List<MedicalRecord> records;
Age age;
boolean isAllergicTo(Allergy allergy)
boolean canTakeLocalAnesthesia()
}
Whereas in the Invoicing subdomain you might want to represent it like this
class Patient {
CreditCard creditCard;
CreditScore creditScore;
Bill currentBill;
void charge(Amount amount)
}
Similarly, the term Cure in the Health Core subdomain, would have the operations that were/are_to_be performed on a patient to cure the disease whereas in the Knowledge subdomain it would contain information about Symptoms, Diagnosis tests, Prescription suggestions, that go along with a disease.
You can now see the Health Care subdomain has multiple BCs and under a BC each term has a very specific meaning thus supporting the Ubiquitous Language
Please check this link it will help you,
Bounded Context or Context?
The term Context is a general description of a grouping of concepts, the term Bounded Context is more specific – a Bounded Context is an area of your application which has explicitly defined borders, has its own Model, and maintains its own code. Within the Bounded Context everything should be strictly consistent.
Usually, we can use the terms Context and Bounded Context interchangeably, though I tend to talk in terms of Context about the business side of things, and the term Bounded Context about the technical implementation.
In a very short and simple sentence, we can say: subdomains are part of the problem space and are chosen by The Business whereas bounded contexts are software boundaries defined by engineers.
First. The official definitions from the Blue Book is:
Domain: A sphere of knowledge, influence, or activity.
Bounded context: The delimited applicability of a particular model. Bounded contexts gives team members a clear and shared
understanding of what has to be consistent and what can develop
independently.
Note that those concepts exists by themselves before any architecture design or line of code is written down.
DDD is about having a domain model shared by business people and programmers that is reflected in source code. But with medium or bigger organisations it is not practical to have a single model. It is better to divide and conquer because:
Different areas have different needs, cultures, jargon, etc. Sometimes the same concept has different terms or viceversa.
Creating a big meeting to make people agree is costly and it is really hard to agree in something at this scale for so many people.
The cognitive load of developing an enterprise-wide mega application. Better to implement a components that can assigned to smaller teams.
So you reduce the domain modelling to an specific an concrete bounded contexts. This has the advantage of also reducing the complexity. But what if the same concept is used in several contexts? This leads me to the second question:
There should be a 1:1 relationship between a BC and an SD. However, I
read in other places that this isn't necessarily the case.
No. There is no need. Here is an example from Martin Fowler: the products and customers subdomains are shared by the sales and support bounded contexts.
Of course you try to select bounded contexts as loosely coupled as possible. But just as when you separate modules in an app there is a minimum level of coupling to make the connection. So, the same concept is modelled differently in each context (Multiple Canonical Models). This can be implemented in code by adding an Anti-Corruption-Layer that translates between models.
Moving to a single bounded context is not just a matter of software design. It would require modifying the mental model of business and this is hard. Also, people sometimes have simpler views of a domain because it reduces the complexity and their cognitive load.
Concrete example:
In this talks from DDD Europe they have an example from Amazon:
The sub-domain term Book has a very different model in different bounded contexts:
In the Catalog bounded context: Picture, title, authors, rating...
In the Shipping bounded context: Dimensions, weight, international restrictions
In the Search inside bounded context: full-text content, copyright dealing policy
So Amazon may have very complex sub-domains with lots of attributes:
Books: isbn, title, number of pages)
Clothing: size, colour, material
Computers: cpu, graphic card, hard-drive, ram
But only some of them would be relevant in different subdomains.
Let me add a diagram with a more global example
Extra resources:
"Bounded Contexts" Talk by Eric Evans in DDD Europe 2020
DDD Crew: repo resources
Virtual DDD community
Vaughn Vernon states in his book “Implementing Domain-Driven Design” the following:
"It is a desirable goal to align Subdomains one-to-one with Bounded Contexts." Page 57
A model's boundary, the bounded context, can contain ideas from various subdomains. Or a single subdomain might be represented by a number of bounded contexts. The ideal scenario would be one bounded context for one subdomain. If you are able to define multiple bounded context for a subdomain, that sometimes leans you into realizing that the subdomain is not fine-grained, and maybe the subdomain could be distilled into separated subdomains.
The other way around could also be justified, when you had multiple subdomain aspect covered in one BD, because e.g. that was pragmatic to do so.
More specifically, when the subdomain is generic, and the generic solution is easy to integrate, it may be more cost-effective to integrate it in each of the bounded contexts locally.
An example is a logging framework; it would make little sense for one of the bounded contexts to expose it as a service, as the added complexity of integrating such a solution would outweigh the benefit of not duplicating the functionality in multiple contexts.
When two different languages talking the same or similar thing, the thing is referred in 2 different contexts. You can translate the thing in 2 context in certain extents.
Similarly a term could have different meaning in different departments. in that case different context explain the term differently. Translation between two to some extent maybe possible.
Instead of saying “Bounded context” maybe try saying “bounded world”
My understanding about sub-domain and bounded context is-
Each subdomain represents a specific area of knowledge or responsibility within the overall domain, and each subdomain may have one or more responsibilities associated with it. In some cases responsibilities can split across multiple subdomains. Considering all theses issues, it can be useful to draw logical boundaries to separate those responsibilities and maintain consistency and transactional integrity.
Bounded contexts in Domain-Driven Design (DDD) are used to define these logical boundaries and provide a way to manage the complexity of large and complex systems by dividing them into smaller, more manageable parts. By using ubiquitous language we can ensure that the concepts and rules of that context are clearly understood and communicated within the development team. So we draw that boundary based on the uses language in that particular context.
So, in summary, a subdomain represents a specific area of knowledge or responsibility within the overall domain, and bounded contexts are used to manage the complexity of large systems by creating logical boundaries around specific areas of responsibility, and using a specific language, or ubiquitous language, to ensure clear communication and understanding of the concepts and rules within that context.
Bounded context ensure us that one responsibility doesn't blend with another one and finally prevent us from introducing complexity and confusion. In that sense it is very similar with SRP of SOLID
When you are developing an architecture in OO/DDD style and modeling some domain entity e.g. Order entity you are putting whole logic related to order into Order entity.
But when the application becomes more complicated, Order entity collects more and more logic and this class becomes really huge.
Comparing with anemic model, yes its obviously an anti-pattern, but all that huge logic is separated in different services.
Is it ok to deal with huge domain entities or i understand something wrong?
When you are trying to create rich domain models, focus entities on identity and lifecyle, and thus try to avoid them becoming bloated with either properties or behavior.
Domain services potentially are a place to put behavior, but I tend to see a lot of domain service methods with behavior that would be better assigned to value objects, so I wouldn't start refactoring by moving the behavior to domain services. Domain services tend to work best as straightforward facades/adaptors in front of connections to things outside of the current domain model (i.e. masking infrastructure concerns).
You can also put behavior in Application services, but ask yourself whether that behavior belongs outside of the domain model or not. As a general rule, try to focus application services more on orchestration-style tasks that cross entities, domain services, repositories.
When you encounter a bloated entity then the first thing to do is look for sets of cohesive set of entity properties and related behavior, and make these implicit concepts explicit by extracting them into value objects. The entity can then delegate its behavior to these value objects.
Since we all tend to be more comfortable with entities, try to be more biased towards value objects so that you get the benefits of immutability, encapsulation and composability that value objects provide - moving you towards a more supple design.
Value objects enable you to incorporate a more functional style (eg. side-effect-free functions) into your domain model and thus free up your entities from having to deal with the complexity of adding complicated behavior to the burden of managing identity and lifecycle. See the pattern summaries for entities and value objects in Eric Evan's http://domainlanguage.com/ddd/patterns/ and the Blue Book for more details.
When you are developing an architecture in OO/DDD style and modeling
some domain entity e.g. Order entity you are putting whole logic
related to order into Order entity. But when the application becomes
more complicated, Order entity collects more and more logic and this
class becomes really huge.
Classes that have a tendency to become huge, are often the classes with overlapping responsibilities. Order is a typical example of a class that could have multiple responsibilities and that could play different roles in your application.
Given the context the Order appears in, it might be an Entity with mutable state (i.e. if you're managing Order's commercial condition, during a negotiation phase) but if you're application is managing logistics, an Order might play a different role: and an immutable Value Object might be the best implementation in the logistic context.
Comparing with anemic model, yes its
obviously an anti-pattern, but all that huge logic is separated in
different services.
...and separation is a good thing. :-)
I have got a feeling that the original model is probably data-centric and data serving different purposes (order creation, payment, order fulfillment, order delivery) is piled up in the same container (the Order class). Can't really say it from here, but it's a very frequent pattern. Not all of this data is useful for the same purpose at the same time.
Often, a bloated class like the one you're describing is a smell of a missing separation between Bounded Contexts, and/or an incomplete Aggregate separation within the same bounded context. I'd have a look to:
things that change together;
things that change for the same reason;
information needed to fulfill behavior;
and try to re-define aggregate boundaries accordingly. And also to:
different purposes for the application;
different stakeholders;
different implicit models/languages;
when it comes to discover the involved contexts.
In a large application you might have more than one model, thus leading to more than a single representation of a single domain concept, at least for concepts that are playing many roles.
This is complementary to Paul's approach.
It's fine to use services in DDD. You will commonly see services at the Domain, Application or Infrastructure layers.
Eric uses these guidelines in his book for spotting when to use services:
The operation relates to a domain concept that is not a natural part of an ENTITY or VALUE OBJECT.
The interface is defined in terms of other elements in the domain model
The operation is stateless
What are DDD recommendations for inter-domain referencing design?
Should I try to connect them as "Matryoshka" (put one into another) or it is better to create upper-level "inter-domain" business service?
P.S. Crossing this smooth water, I was unable to find anything useful to read in the Internet, and have started thinking that for this kind of things exist better term than "inter-domain referencing"... Am I right?
DETAILS:
I have two models/business services.
Semantically first domain (A) is CRM with sell/maintenance process for our goods, second domain (B) is "design" data of our goods. We have two view points on our goods: from seller perspective and from engineer perspective.
Actually each model is effective ORM (Object-Relational Mapping) tool to the same database.
There are some inter-domain activities e.g. validations (e.g. sometimes we can sell things to smb. only if some engineering rules are valid).
From developer's point of view I have two clear possibilities (reference B in A or create new cross reference domain/service C ). But from designer perspective I am lost in understanding what kind of Business Service I have when I compose business logic from two different domains.
As far as I know, DDD has no strict rules for 'inter-domain' referencing. At the end of the day your domain model will have to reference basic Java or .NET classes. Or it may reference specialized date/time or graph library (aka 'Generic Domain').
On the other hand DDD has a concept of Bounded Context. And it has quite a few patterns that can be applied when you work at the boundaries of the system. For example 'Anticorruption Layer' can be used to isolate you from legacy system. Other integration styles can be used depending on how much control you have over external code, team capabilities etc.
So there is probably no need to introduce artificial glue layer if you just dealing with two subdomains in one Bounded Context. Might also be worth reading Part 4 of DDD book (Strategic Design).
UPDATE:
Based on the information you provided, it looks like you only have one Bounded Context. You don't seem to have 'linguistic clashes' where the same word have two different meanings. Bounded Context integration patterns are most likely not applicable to your situation. Your Sales domain can reference Products domain directly. If you think of Products domain being more low-level and Sales being high level you can use Dependency Inversion Principle. Define an interface like ProductCompatiblityValidator in Sales and implement it in Products domain. And then inject the actual implementation at the application layer. This way you will not have a direct reference from Sales to Products.
In addition to what Dmitry has already said...
I think of any code that crosses bounded contexts as application layer code. I would have that application layer code reference domain types from both contexts (and their repositories) but not have two domains reference each other. I think it's OK to have business logic in an application layer if it specifically crosses domain boundaries and is unit-testable.
If you really have a hierarchy, then it would be OK to have the the more concrete subdomain reference the more abstract domain. However, I would be careful if this causes you to need to have domain objects reference repositories of any type. Pulling objects out of of a repository is rarely a true domain concept. Referencing repositories is best done in an application layer that sits a layer above the domain model.
Of course this is all as much art as science. I'd try modeling a thin slice of your application a couple different ways and see what friction you run into with each approach.
What is the difference between a domain model and a data model?
A datamodel is a design model that only describes data and it's relations. The model contains entities, but they are described in terms of what data they own not how they act on this data or what their responsibilities are.
An domain model on the other hand, is a conceptual model used in analysis of a problem domain. It describes the domain in terms of entities that have relations, data and behaviour. It describes the responsibilities of those entities as relevant for understanding the problem domain.
BTW an excelent and very short introduction to UML is:
UML Distilled: A Brief Guide to the Standard Object Modeling Language
A data model is focused on the DB schema definition, including tables, columns, and relationships.
A domain model is focused on the business domain, including concepts (classes of objects), behavior (methods/logic), and relationships.
In both cases, the cardinality is used for relationships (e.g. 1:1, 1:Many, 0:Many, ...).
That said, you would ideally like the data model and domain model to be closely related, i.e. a Person with name, ... and a MailingAddress, ... relates to a PERSON table with a NAME column and a FK to a MAILING_ADDR table entry. You have to decide where logic is hosted - in the objects in the software system vs. in the DB via procedures, triggers, and such.
I think it's important to provide some clarity here for posterity.
A data model is a design for how to structure and represent information. By structure, I mean concerns like "fifth normal form". By representation, I mean choosing a computer serialization, such as integer, floating point, or string.
The term domain model actually has two conflated meanings.
A model of essential characteristics of real or imaginary things in the world. In this kind of model, classes represent human conceptualizations and instances are things in the world. For example, a "Person" class would have instances including you and me, and an essential characteristic might be that every Person has a mother. This kind of model is often called an conceptual ontology or concept model and is intended to provide meaning.
A model of required information about things in the world, usually with some system in mind. In this kind of model, classes represent information that must be stored about things in the world. For example, a "Person" class would have instances representing required information about you and me, such as first name, last name, date of birth, current height, and current weight. This information often does not include all essential characteristics, such as our mothers, because, for the purposes of a particular system, that information is not required. This kind of model is often called an information model, conceptual data model, or operational ontology.
Both the UML and OWL languages can be used to represent either kind of domain model. Both can be considered analysis models, as they are used to analyze a domain. One is used to understand things in a domain, the other is used to gather requirements to build a particular software or database system for things in a domain. Both are necessary, and, unfortunately, they are usually conflated such that people building an analysis model are themselves confused about what they are modeling!
I think that domain model and data model are now pretty much the same with new top down modelling technologies. I mean that you can model in a class diagram and only add database stereotypes in your diagram. If you use the tool that I use then your ejb3 annotation would be immediately synchronized with your code. The next step is only to use a mapper to create your database. This technology only works with Java