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RE: [higgins-dev] Higgins data model
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Hmmm, I thought that you were saying that the Tom object would have no
reference the link objects whatsoever. That the relationships would be
discovered by a query on an index specifying, in this case, from=Tom,
etc. This is what I thought you were saying would eliminate some of the
complexity since the Tom object would not have to be visited to remove a
relationship property. So, Jim's Case 1 is missing at least one step.
I can see how having a relationship object would be beneficial where
the same relationship exists among many objects ... maybe your
correction of my example is doubly linked and shouldn't be (Tom has
"hasRelationship" and Link 1a has "from") ... I'll add another child to
the mix in the example ... I'm out of sons but I'll pretend I got that
3rd child I always wanted, let's say another son ... Angus. ;)
Basically, I'd just eliminate the "from" property from the link.
Evan:
hasRelationship - Link2
Angus:
hasRelationship - Link2
Link 2:
to - Tom
type - son
Maybe this matches what Raj is trying to show in the diagram. Let me
map the example:
Digital Subject = Evan
IdRelation = IdRelationship2
Digital Subject = Angus
IdRelation = IdRelationship2
IdRelationship = IdRelationship2
relatedSubject = Tom
type = son
Digital Subject = Tom
IdRelation = IdRelationship1a
IdRelation = IdRelationship1b
IdRelation = IdRelationship1c
IdRelationship = IdRelationship1a
relatedSubject = Evan
type = parentOf
IdRelationship = IdRelationship1b
relatedSubject = Evan
type = legalGuardian
IdRelationship = IdRelationship1c
relatedSubject = Evan
type = soccerCoach
Is this right? So, if most of the relationships in the system are
unique, this could actually increase the complexity. If most of them
are shared, this could really decrease it. Now, if a "relateeSubject"
was added to IdRelationship, the "from" property from the original
example, the maintenance of the reference between related objects could
be eliminated. This may add another level of complexity not to mention
that I'm not sure how well this data model maps onto data models we want
to operate in. Did I get your intent correct Paul, Raj? If so, does
anyone care to map this to a directory model?
Tom
>>> "Paul Trevithick" <paul@xxxxxxxxxxxxxxxxx> 3/28/2006 4:26:27 pm
>>>
Tom wrote:
Let me see if I understand what you're proposing here with an example:
There is a Tom facet and an Evan facet. Tom has several relationships
to
Evan. Would these be represented in a single link object with
multiple
properties?
I was thinking quite the opposite. For each relationship that Tom has
with
Evan there would be a separate link object.
Perhaps
Link 1:
from - Tom
to - Evan
parentOf
legalGuardian
soccerCoach
Link 2:
from - Evan
to - Tom
son
So, rather than Tom having attributes which point to Evan or vice
versa, the
attributes (properties, sorry) of the link object hold the "pointers"
and
they are indexed for each of the specified relationships?
I was thinking that the object Tom has a set of relationships. In this
case
a set of three. So:
Tom:
hasRelationship - "Link 1a"
hasRelationship - "Link 1b"
hasRelationship - "Link 1c"
And the relationship link objects would be:
Link1a:
from - Tom
to - Evan
type - parentOf
Link1b:
from - Tom
to - Evan
type - legalGuardian
Link1c:
from - Tom
to - Evan
type - soccerCoach
Link2:
from - Evan
to - Tom
type - son
Notice that I snuck in the notion that links have a "type" property.
And I
think this should be a URI (just like an attribute).
Or would of the specified relationships be represented by another link
object? I see how this could be cleaner for indexing and deletion of a
link
but I also see some potential for additional complexity and potential
incongruency with other data models such as a directory.
I'm not sure if it's kosher to consider this when we're discussion a
conceptual model but I think it'd be helpful to work out a concrete
example
and then map it through to a directory data model as well as other
data
models we know we'll be dealing with.
Thanks,
Tom
>>> paul@xxxxxxxxxxxxxxxxx 3/28/2006 12:37:39 pm >>>
On your question about attributes vs. relationships in the M4 goals.
What's
driving things is a desire to consider the link between two objects to
itself be an object (with properties). If these link properties are
grouped
together and "attached to" the link itself management of links is
easier.
Imagine object A has a link to object B, and A also has a link to
object C.
And imagine that both links had a common property, "parentOf". Using
the
proposed approach we simply attach the parentOf property to each link
object. If we wish to delete a link, we delete the link and all of its
associated properties at the same time. If, on the other hand, we
flatten
the properties onto A, then we'd need to somehow index the two
parentOf
properties (of A) in order to distinguish them. To me using the link
object
as the indexing mechanism is cleaner.
Jim wrote:
The short answer to the question "how would JNDI represent the notion
of
IdFacet Relationships" would (I think) be to make them attributes.
Like IdFacets, a JNDI object has attributes. A class of attributes
would be
used as relationship attributes. The syntax of a relationship
attribute
would be described to have a field for the target facet (may be defined
to
have other fields as well). Specific instances of these attributes on
a
facet could be named differently (i.e. role, parent, affinity, etc.).
This begs another question:
In the M4 goals, IdFacetRelationships seem to be seen as separate from
Attributes. Why is this? I mean, why not just have attributes which
are
themselves relationships?
Jim
>>> "Paul Trevithick" <paul@xxxxxxxxxxxxxxxxx> 3/24/06 2:08:01 pm >>>
Task H6-03-24 of the Milestone 0.4 plan
(http://spwiki.editme.com/PlanM4) is
about "refining the Higgins data model". To support that work we've
begun
creating listing our goals (http://spwiki.editme.com/DataModelGoalsM4
(this
can be linked to from the main Higgins wiki page
http://spwiki.editme.com/Higgins).
Let me kick this off with a question:
It has been suggested that instead of creating our own model, we might
take
a look at using all or some of JNDI. Could someone explain how one best
use
JNDI to support our notion of "IdFacet Relationships" (see "IdFacet
Relationships" (currently item 9,10,11) here:
http://spwiki.editme.com/DataModelGoalsM4)?
