Forum: Ruby on Rails DB Modelling the Rails way - Opinions??

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
Eric S. (Guest)
on 2006-01-02 03:43
(Received via mailing list)
Hi,
I'm trying to figure the most efficient way to model the following. I
can think of at least two ways to relate the tables but from a
client/server perspective! I'm wondering how to best (and
elegantly)relate them from an AR perspective.

A project has many people,
A person can work on many projects at any time,
A project has many roles,
A role is performed by a person,
A person may perform multiple roles,
An organisation has many people,
An organisation is a stakeholder (God, I hate that word - makes me feel
like Dracula surrounded!)in one or more projects,
A stakeholder has many roles within a project.

So one way I have

Projects HABTM Roles
Roles HABTM People
Organisation Has_Many People
An Organisation Belongs_to a Stakeholder
A Stakeholder HABTM Projects
A Stakeholder Has_Many Roles

Or

Projects HABTM People,
A Project has_many roles,
People HABTM Roles,
An Organisation has_many People,
An Organisation is a Stakeholder in a Project,
A Stakeholder has_many Roles in a Project.

I guess the outcome I'm after is a way to view this data from various
perspectives. For example, I have a project view that presents static
project data at the head of the screen with a set of tabs containing
partials with forms for editing stuff like e.g. People
Acting_For(Stakeholder), Acting_As (Role). Other perspectives would be
like seeing which organisations are doing what within any number of
projects - that sorta thing.

Whatya think?
Eric.
Gerard (Guest)
on 2006-01-03 13:40
(Received via mailing list)
Eric,

I don't comletely understand the definition of the entity Role. Possibly
usefull is to remember that when a project is closed or a person is
removed
(started working for another company) that the data is stil accessible.
To
simplify this. When a qoute or invoice is generated there's always a
copy
used of the contacts data. Because when that person doesn't work for a
company anymore and is removed I would still want to be able to view the
quote/invoice/whatever without getting 'nil' object errors.

Furthermore a look on what historical info you might save could possibly
help
as well on the relationships you want to maintain.

Looks like the 2nd one seems good (couldn't say why though). But how
does a
project have many roles. Doesn't a project have many people who, in
there
turn, have many roles within a project?

I'm on the virge of diving into a similar mather on my internal
administration
appliation and I must admit this fun stuff to chew on .. :-)

Hope (wonder if) it helps.

Regards,

Gerard.


On Monday 02 January 2006 02:10, Eric S. tried to type something
like:
> A person may perform multiple roles,
> An Organisation Belongs_to a Stakeholder
> A Stakeholder has_many Roles in a Project.
> Eric.
>
> _______________________________________________
> Rails mailing list
> removed_email_address@domain.invalid
> http://lists.rubyonrails.org/mailman/listinfo/rails

--
"Who cares if it doesn't do anything?  It was made with our new
Triple-Iso-Bifurcated-Krypton-Gate-MOS process ..."

My $Grtz =~ Gerard;
~
:wq!
Chris H. (Guest)
on 2006-01-03 15:40
(Received via mailing list)
I might suggest the following (and I am making the asusmption that the
relationships between projects, people and roles is unlimited

(untested)

people_projects_roles (join table between people and projects and roles)
----------
person_id
role_id
project_id

class Project < ActiveRecord::Base
  has_and_belongs_to_many :people, :join_table =>
"people_projects_roles"
  has_and_belongs_to_many :roles, :join_table => "people_projects_roles"
end

class Person < ActiveRecord::Base
  has_and_belongs_to_many :projects, :join_table =>
"people_projects_roles"
  has_and_belongs_to_many :roles, :join_table => "people_projects_roles"
end

class Role < ActiveRecord::Base
  has_and_belongs_to_many :people, :join_table =>
"people_projects_roles"
  has_and_belongs_to_many :projects, :join_table =>
"people_projects_roles"
end

now, this allows you to do things such as

project = Project.find(1) # "my project"

# all people who are associated with "my project" (any role)
project.people

# all roles associated with "my project"
project.roles

person = Person.find(1) # "John S."

# all projects assocated with "John S."
person.projects

# all roles assocated with "John S."
person.roles

role = Role.find(1) # "programmer"

# all projects with a "programmer" role
role.projects

# all people with a "progammer" role
role.people


now say you want to add John as a "manager" (id = 2) role to Project 10

john = Person.find_by_name("John")
manager = Role.find_by_name("Manager")
project.find(10)

with this information, you could do it several different
ways...depending on
the situation

project.people.push_with_attributes(john, :role_id => manager.id)
project.roles.push_with_attributes(manager, :person_id => john.id)
john.projects.push_with_attributes(project, :role_id => manager.id)
john.roles.push_with_attributes(manager, :project_id => project.id)
role.projects.push_with_attributes(project, :person_id => john.id)
role.people.push_with_attributes(john, :project_id => project.id)

each of these accomplish the same thing, they add John as a Manager to
Project 10

now, as far as organisation/projects/roles go, that sounds strange (not
being critical)...can an organisation have the same roles as a person?
i
would assume that organisations have different roles than people so you
will
want to setup a separate "org roles" table to manage those.

can an organisation be involved in many projects and can a project have
many
organisations (stakeholders)?  if so, then i would setup another join
table
between organisations/projects/org roles and follow the same idea as
above

now, one thing i would be concerned about is corss referencing (not sure
the
proper term).  you have people associated with projects, organisations
assocated with projects and people associated with organisations...this
can
get messy when you want to start limiting who can do based upon their
other
associations (ie, given a project/organisation association, can only
people
associated with the same organisation be assocated with that project?)

hope this helps.
Eric S. (Guest)
on 2006-01-03 23:53
(Received via mailing list)
Hi Chris,
Thanks for your input. You've hit the nail squarely on the head (ouch).
The relationship between Projects, Roles and People is to be unlimited
for exactly the reasons you have pointed out - brilliantly I might add.
As to Organisations - the relationship there is simply to define a
broader role - Client, Contractor, etc. that People act_for. In practice
this level of flexibility might be overkill - but I want it there - just
in case :~) As I said in response to Gerard(to whom I replied before
reading your post) - on paper this looks kinda scary

Thanks Again,
Eric.
Gerard (Guest)
on 2006-01-04 01:33
(Received via mailing list)
Eric / Chris,

@Chris: Cudo's to you Chris!

@Eric: Having gone through Chris' email. I must say now it doesn't just
look
scary on paper .. :-)

Being a Rails fan for a couple of weeks I'm not fully up to speed on the
proper, and more important failsafe, OO programming. Nevertheless .. I
did
another post on a model I'm chewing on, on which I would like some
reponse. I
think, IMHO, I've got the model covered for now (never now what's around
the
corner). I'm just somewhat insecure on programming around it. But I
guess
there's just one lesson .. Practice!

Should you or Chris have some comments, they would be appreciated.

Regards,

Gerard.


On Tuesday 03 January 2006 22:49, Eric S. tried to type something
like:
> Thanks Again,
> > person_id
> > "people_projects_roles" has_and_belongs_to_many :roles, :join_table =>
> >
> >
> >
> > project.people.push_with_attributes(john, :role_id => manager.id
> > <http://project.id>)
> > many organisations (stakeholders)?  if so, then i would setup another
> >
> >     (started working for another company) that the data is stil
> >     as well on the relationships you want to maintain.
> >
> >      > Hi,
> >      > A project has many roles,
> >      > So one way I have
> >      > Projects HABTM People,
> >      > People
> >      > _______________________________________________
> >
> >
> Rails mailing list
> removed_email_address@domain.invalid
> http://lists.rubyonrails.org/mailman/listinfo/rails

--
"Who cares if it doesn't do anything?  It was made with our new
Triple-Iso-Bifurcated-Krypton-Gate-MOS process ..."

My $Grtz =~ Gerard;
~
:wq!
Rebus M. (Guest)
on 2006-01-19 13:32
Hi,

If using proposed solution by Chris, have can you paginate for example
person.projects with a condition like roles = 'editors'?

Rebus
This topic is locked and can not be replied to.