How do you model roles / relationships with Domain Driven Design in mind?
- by kitsune
If I have three entities, Project, ProjectRole and Person, where a Person can be a member of different Projects and be in different Project Roles (such as "Project Lead", or "Project Member") - how would you model such a relationship?
In the database, I currently have the following tablers: Project, Person, ProjectRole Project_Person with PersonId & ProjectId as PK and a ProjectRoleId as a FK Relationship.
I'm really at a loss here since all domain models I come up with seem to break some "DDD" rule. Are there any 'standards' for this problem?
I had a look at a Streamlined Object Modeling and there is an example what a Project and ProjectMember would look like, but AddProjectMember() in Project would call ProjectMember.AddProject(). So Project has a List of ProjectMembers, and each ProjectMember in return has a reference to the Project. Looks a bit convoluted to me.
update
After reading more about this subject, I will try the following: There are distinct roles, or better, model relationships, that are of a certain role type within my domain. For instance, ProjectMember is a distinct role that tells us something about the relationship a Person plays within a Project. It contains a ProjectMembershipType that tells us more about the Role it will play. I do know for certain that persons will have to play roles inside a project, so I will model that relationship.
ProjectMembershipTypes can be created and modified. These can be "Project Leader", "Developer", "External Adviser", or something different.
A person can have many roles inside a project, and these roles can start and end at a certain date. Such relationships are modeled by the class ProjectMember.
public class ProjectMember : IRole
{
public virtual int ProjectMemberId { get; set; }
public virtual ProjectMembershipType ProjectMembershipType { get; set; }
public virtual Person Person { get; set; }
public virtual Project Project { get; set; }
public virtual DateTime From { get; set; }
public virtual DateTime Thru { get; set; }
// etc...
}
ProjectMembershipType: ie. "Project Manager", "Developer", "Adviser"
public class ProjectMembershipType : IRoleType
{
public virtual int ProjectMembershipTypeId { get; set; }
public virtual string Name { get; set; }
public virtual string Description { get; set; }
// etc...
}
