Building on Eric Evans’ seminal book, 'Domain-Driven Design', Vaughn Vernon couples guided approaches to implementation with modern architectures, highlighting the importance and value of focusing on the business domain while balancing technical considerations. Ubiquitous Language is the term Eric Evans uses in Domain Driven Design for the practice of building up a common, rigorous language between developers and users. This language should be based on the Domain Model used in the software - hence the need for it to be rigorous, since software doesn't cope well with ambiguity.
Domain Driven Design is a methodology and process prescription for the development of complex systems whose focus is mapping activities, tasks, events, and data within a problem domain into the technology artifacts of a solution domain.The emphasis of Domain Driven Design is to understand the problem domain in order to create an abstract model of the problem domain which can then be implemented in a particular set of technologies. Domain Driven Design as a methodology provides guidelines for how this model development and technology development can result in a system that meets the needs of the people using it while also being robust in the face of change in the problem domain.The process side of Domain Driven Design involves the collaboration between domain experts, people who know the problem domain, and the design/architecture experts, people who know the solution domain. The idea is to have a shared model with shared language so that as people from these two different domains with their two different perspectives discuss the solution they are actually discussing a shared knowledge base with shared concepts.The lack of a shared problem domain understanding between the people who need a particular system and the people who are designing and implementing the system seems to be a core impediment to successful projects. Domain Driven Design is a methodology to address this impediment.It is more than having an object model. The focus is really about the shared communication and improving collaboration so that the actual needs within the problem domain can be discovered and an appropriate solution created to meet those needs.provides a brief overview with this comment:DDD helps discover the top-level architecture and inform about themechanics and dynamics of the domain that the software needs toreplicate. Concretely, it means that a well done DDD analysisminimizes misunderstandings between domain experts and softwarearchitects, and it reduces the subsequent number of expensive requestsfor change. By splitting the domain complexity in smaller contexts,DDD avoids forcing project architects to design a bloated objectmodel, which is where a lot of time is lost in working outimplementation details — in part because the number of entities todeal with often grows beyond the size of conference-room white boards.Also see this article which provides a short example.
The article provides the following thumbnail description of Domain Driven Design.Domain Driven Design advocates modeling based on the reality ofbusiness as relevant to our use cases. As it is now getting older andhype level decreasing, many of us forget that the DDD approach reallyhelps in understanding the problem at hand and design software towardsthe common understanding of the solution. When building applications,DDD talks about problems as domains and subdomains. It describesindependent steps/areas of problems as bounded contexts, emphasizes acommon language to talk about these problems, and adds many technicalconcepts, like entities, value objects and aggregate root rules tosupport the implementation.Martin Fowler has written a number of articles in which Domain Driven Design as a methodology is mentioned. For instance this article, provides an overview of the bounded context concept from Domain Driven Development.In those younger days we were advised to build a unified model of theentire business, but DDD recognizes that we've learned that 'totalunification of the domain model for a large system will not befeasible or cost-effective'. So instead DDD divides up a largesystem into Bounded Contexts, each of which can have a unified model -essentially a way of structuring MultipleCanonicalModels. You CAN ONLY understand Domain driven design by first comprehending what the following are:What is a domain?The field for which a system is built.
Airport management, insurance sales, coffee shops, orbital flight, you name it.It's not unusual for an application to span several different domains. For example, an online retail system might be working in the domains of shipping (picking appropriate ways to deliver, depending on items and destination), pricing (including promotions and user-specific pricing by, say, location), and recommendations (calculating related products by purchase history).What is a model?' A useful approximation to the problem at hand.' - Gerry SussmanAn Employee class is not a real employee. It models a real employee. We know that the model does not capture everything about real employees, and that's not the point of it. It's only meant to capture what we are interested in for the current context.Different domains may be interested in different ways to model the same thing.
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For example, the salary department and the human resources department may model employees in different ways.What is a domain model?A model for a domain.What is Domain-Driven Design (DDD)?It is a development approach that deeply values the domain model and connects it to the implementation. DDD was coined and initially developed by Eric Evans.Culled from. As in TDD & BDD you/ team focus the most on test and behavior of the system than code implementation.Similar way when system analyst, product owner, development team and ofcourse the code - entities/ classes, variables, functions, user interfaces processes communicate using the same language, its called Domain Driven DesignDDD is a thought process.