RE: EntityId decision analysis page (was RE: [higgins-dev]entityIDnot an

[David Kuehr-McLaren <dkuehrmc@xxxxxxxxxx>]

My vote on the 3 questions. I am assuming
that EntityId=CUID for this response.


> 1) Must an EntityId be an identifier (string)
or can it be a 
> collection of attributes (multi-part key)? (Higgins 1.0, only 
> supports the former.)

I prefer a multi-part key where the parts of the key
might also be unique in a context. An example is a EntityID made up of
a uniqueName, uniqueId, nativeName, nativeId. Any part of the of the Entity
ID could be used to identify the object. 

>  
> 2) Must an EntityId be exposed as an attribute
of an Entity, or is 
> it optional to do that?

Optional or not at all. If exposed as an attribute,
then it may require constraints, such as non-searchable attribute.  For
example LDAP DNs are not searchable. 

>  
> 3) Is the cardinality of EntityId 0..n or 0..1?

0..1 if the EntityId is mutlipart as in Q1.  0..n
if it is a string, and then it needs a type.


David 

David Kuehr-McLaren 
Tivoli Security 
919.224.1960 


higgins-dev-bounces@xxxxxxxxxxx wrote on 09/12/2008
03:39:40 PM:

> +1 that “Contextually Unique Identifier” (CUID) accurately captures
> the requirements for the value of the Context Data Model component
> currently called “EntityID”.
> So Jim, are you suggesting that we change “EntityId”
to “CUID”? Or 
> just that we just the term CUID when stating the requirements for
an
> EntityId value?
> Also, please feel free to weigh in on three other
questions I posed yesterday:
> 1) Must an EntityId be an identifier (string)
or can it be a 
> collection of attributes (multi-part key)? (Higgins 1.0, only 
> supports the former.)
>  
> 2) Must an EntityId be exposed as an attribute
of an Entity, or is 
> it optional to do that?
>  
> 3) Is the cardinality of EntityId 0..n or 0..1?
> =Drummond 
> 
> From: higgins-dev-bounces@xxxxxxxxxxx [mailto:higgins-dev-
> bounces@xxxxxxxxxxx] On Behalf Of Jim Sermersheim
> Sent: Friday, September 12, 2008 1:03 AM
> To: higgins-dev-bounces@xxxxxxxxxxx
> Cc: 'Higgins (Trust Framework) Project developer discussions'
> Subject: Re: EntityId decision analysis page (was RE: [higgins-dev]
> entityIDnot an attribute?)
>  
> Right, we talked about this on the dev call today.
 EntityID should 
> not be called "unique identifier" because that might imply
"globally
> unique".  What ppl have actually meant in the convo by "unique
> identifier" is "an identifier -- unique within the context
-- that 
> names the entity within that context". 
>  
> Our original term (CUID) was much better [Contextually
Unique Identifier]
> 
> >>> Anthony Nadalin <drsecure@xxxxxxxxxx> 09/11/08
8:32 PM >>>
> wiki is the pits
> 
> so a EntityID can't always be the unique identifier at best an 
> EntityID is a reference within a context only, Lets take a cell 
> phone, it has a unique identity of +015128380085 but that may not
> tell be how I reference this entity within a context.
> 
> Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122
> 
> [image removed] "Drummond Reed" ---09/11/2008 08:24:04 PM---I
took 
> the action item on the Higgins call today to parse the key questions
> being raised about EntityId on this thread into a d
> 
> [image removed] 
> From: 
> 
> [image removed] 
> "Drummond Reed" <drummond.reed@xxxxxxxxxxxx> 
> 
> [image removed] 
> To: 
> 
> [image removed] 
> "'Higgins (Trust Framework) Project developer discussions'"
> <higgins-dev@xxxxxxxxxxx> 
> 
> [image removed] 
> Date: 
> 
> [image removed] 
> 09/11/2008 08:24 PM 
> 
> [image removed] 
> Subject: 
> 
> [image removed] 
> EntityId decision analysis page (was RE: [higgins-dev] entityID not
> an attribute?) 
> 
> 
> 
> 
> I took the action item on the Higgins call today to parse the key
> questions being raised about EntityId on this thread into a decision
> analysis page on the Higgins wiki. I have posted this page at:
>  
> http://wiki.eclipse.org/EntityId_Requirements
>  
> …and placed a link to it on http://wiki.eclipse.
> org/Context_Data_Model_1.1_Open_Issues#Open_Issues.
>  
> The ideal way to proceed is for folks to post opinions to the page
> and then ping the list with a pointer. However, for those who prefer
> responding in email, following is the wikitext version of the page
> to which you can respond directly.
>  
> =Drummond 
> 
> == About ==
> This page is for discussing/documenting the terminology, 
> requirements, and design decisions for [[EntityId]]s.
>  
> == Content Data Model Requirements ==
> In terms of the underlying graph model, following is a summary of
> the abstract requirements derived in a recent (2008-09-11) thread
on
> the email list. The first step is determining if there is consensus
> about these requirements. '''Please post a note with your wiki 
> signature if you disagree with any of the following:'''
>  
> # An [[Entity]] is a node in the graph described by the Higgins 
> [[Context Data Model]]. The CDM needs a consistent way of 
> representing arcs referencing that node.
> # There MAY be 0..n such arcs referencing the node. (0 is possible
> for blank nodes.)
> # An arc MAY theoretically be represented as either:
> ## A unique identifier.
> ## A set of [[Attribute]]s of that [[Entity]], none of which itself
> is required to be a unique identifier.
> # If the arc is represented as a unique identifier:
> ## It MUST be locally unique within the [[Context]], and it MAY be
> globally unique across all [[Context]]s).
>  
> == Higgins API Requirements ==
> The second step, based on the above requirements, is answering the
> following questions with respect to the Higgins API. '''Please post
> your votes/answers (with your wiki signature).'''
>  
> === #1: Unique Identifier vs. Attribute Set ===
> Should the Higgins API constrain an [[EntityId]] to be a unique 
> identifier, or can it be a set of [[Attribute]]s?
>  
> === #2: Representation of an EntityId as a Unique Identifier ===
> If an [[EntityId]] is a unique identifier, should this be represented
as:
> # A type of [[Attribute]]?
> # A separate property of an [[Entity]] that MAY be exposed as an 
> [[Attribute]]?
> # Inherent in the definition of an [[Entity]]?
>  
> === #3: Cardinality ===
> What is the cardinality of [[EntityId]]? (The answer may depend on
> the answer to #2.)
> # 0..n?
> # 0..1?
> # 1 (whose value may be null)?
>  
> 
> From: higgins-dev-bounces@xxxxxxxxxxx [mailto:higgins-dev-bounces@xxxxxxxxxxx
> ] On Behalf Of Anthony Nadalin
> Sent: Thursday, September 11, 2008 7:36 AM
> To: Higgins (Trust Framework) Project developer discussions
> Cc: higgins-dev; higgins-dev-bounces@xxxxxxxxxxx
> Subject: Re: [higgins-dev] entityID not an attribute?
>   
> So there are a couple of things here, we have
always talked about 
> the EntityID as being a reference to the Entity and not the unique
> identifier. There are many ways to reference an Entity, so I don't
> believe that this is limited to 0..1. I also believe that the 
> EntityID encapsulates a given set of attributes.The unique 
> identifier is only has to be unique within a context. So I believe
> that the unique identifier is an attribute, not a way to reference
the Entity.
> 
> Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122
> 
> [image removed] Paul Trevithick ---09/10/2008 05:51:39 PM---Raj has
> suggested the need to clarify the language here. So here is a 
> restatement. Additions in red. Substitutions in blue. All 
>  
> 
> [image removed] 
> From: 
> 
> [image removed] 
> Paul Trevithick <paul@xxxxxxxxxxxxxxxxx> 
> 
> [image removed] 
> To: 
> 
> [image removed] 
> higgins-dev <higgins-dev@xxxxxxxxxxx> 
> 
> [image removed] 
> Date: 
> 
> [image removed] 
> 09/10/2008 05:51 PM 
> 
> [image removed] 
> Subject: 
> 
> [image removed] 
> Re: [higgins-dev] entityID not an attribute? 
> 
> 
> 
> 
> 
> Raj has suggested the need to clarify the language here. So here is
> a restatement. Additions in red. Substitutions in blue. All defined
> terms in initial caps.
> 
> Background: We remain committed to these two principles:  
> ·    An Entity has 0..1 unique identifier
(called an EntityId) (...
> and we expect almost all Entities will have an EntityId).  
> ·    [Raj: you asked about why this
EntityId is optional. The 
> answers are (1) that our “complex” Attributes have values that are
> themselves Entities and we didn’t want to require developers to 
> explicitly “name” these values (especially in situations where there
> was no need for N>1 Entities to share (link to the same) 
> value/Entity and (2) we need this in order that our model remain a
> pure super-set of RDF/OWL (and thus allows IdAS to losslessly 
> “adapt” the Semantic Web (including all Linked Data).] 
> ·    An Entity has 0..N Attributes
some of which may be used singly 
> or in combination to identify an Entity or a set of Entities within
a Context.
> ·    [Raj: To date we have decided
not to define an explicit 
> “Identifier” Attribute type. The reason for not defining it is twofold:
First
> , the distinction between an Identifier and an Attribute has so far
> proved impossible to agree on. Second, Context Provider developers
> are free to create their own Attribute Definitions and thus a 
> developer could define their own “Identifier” sub-Attribute] 
> 
> The proposal remains:  
> ·    To no longer consider the one,
optional EntityId as an Attribute. 
> ·    To have an IdAS getEntityId()
method to return this EntityId 
> (or return null if it doesn’t exist) whereas other getAttribute 
> methods return Attributes/values 
> ·    NOTE: CP developers remain free
to present the EntityId value 
> as the value of some Attribute type that they define and use within
> their Context 
> 
> With the above clarified and annotated definitions, I’m interested
> to hear Tony’s, Raj’s and anyone else’s reactions.
> 
> -Paul
> 
> 
> On 9/9/08 1:20 PM, "Nataraj Nagaratnam" <natarajn@xxxxxxxxxx>
wrote: 
> Yea, there seems to be disconnect here with usage
of the term 
> 'identifier' (or Id).  
> The statement "An Entity has 0..N Attributes
some of which may be 
> used as identifiers" tells me that there is more than one 
> identifier, and then the statement "An Entity has 0..1 EntityId"
> says that there is one identifier (as i think "EntityId"
means 
> "Entity Identifier"). This seems to be contradicting statements
in 
> some sense, and maybe the cause of disconnect here. 
> 
> So how about this..  
> · An Entity has 0..N Attributes 
> · An Entity has 1 UniqueIdentifier within a given context. 
> 
> Then it makes the calculation of uniqueIdentifier to be relevant to
> the Entity within a given context; this way, we leave attributes as
> they are - if we end up using those attributes to 
> identify/search/lookup an entity, then fine but uniqueness is not
> guaranteed. Wrt those attributes that are used to search/lookup,..
> maybe we don't need to designate those attributes to be identifiers
> in a formal manner in the data model?
> 
> So proposal can be
> To have an IdAS getUniqueEntityId() method to return a unique 
> identifier within the context of that entity, whereas other 
> getAttribute methods return Attributes/values
> 
> another comment - do we really want entities without unique 
> identifiers at all?
> 
> Regards,
> Raj
> 
> 
> 
> [image removed] Anthony Nadalin---09/09/2008 12:40:37 PM---OK, So
> not sure I agree
> 
> [image removed] 
> From:[image removed] 
> Anthony Nadalin/Austin/IBM@IBMUS 
> [image removed] 
> To:[image removed] 
> "Higgins \(Trust Framework\) Project developer discussions"
<
> higgins-dev@xxxxxxxxxxx> 
> [image removed] 
> Cc:[image removed] 
> higgins-dev <higgins-dev@xxxxxxxxxxx>, higgins-dev-bounces@xxxxxxxxxxx
> [image removed] 
> Date:[image removed] 
> 09/09/2008 12:40 PM 
> [image removed] 
> Subject:[image removed] 
> Re: [higgins-dev] entityID not an attribute? 
> 
> 
> 
> 
> 
> OK, So not sure I agree
> 
> I believe that there are 0..N EntityIDs and the EnitityID job is to
> encapsulate the referenced attributes, thus there may be multiple
EntityIDs.
> 
> Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122
> 
> [image removed] Paul Trevithick ---09/09/2008 10:56:26 AM---Just to
> make sure we’re all discussing the right proposal. Let me back up
a 
> bit here and restate it:
> [image removed] 
> From:[image removed] 
> Paul Trevithick <paul@xxxxxxxxxxxxxxxxx> 
> [image removed] 
> To:[image removed] 
> higgins-dev <higgins-dev@xxxxxxxxxxx> 
> [image removed] 
> Date:[image removed] 
> 09/09/2008 10:56 AM 
> [image removed] 
> Subject:[image removed] 
> Re: [higgins-dev] entityID not an attribute? 
> 
> 
> 
> 
> 
> Just to make sure we’re all discussing the right proposal. Let me
> back up a bit here and restate it:
> 
> Background: We remain committed to these two principles: 
> · An Entity has 0..1 EntityId (...and we expect
almost all Entities 
> will have an EntityId) 
> · An Entity has 0..N Attributes some of which may be used as 
> identifiers (that is, these attributes may singly or in combination
> uniquely identify an Entity within its Context) 
> 
> The proposal is: 
> · To no longer consider the one, optional EntityId
as an Attribute. 
> · To have an IdAS getEntityId() method to return this EntityId (or
> return null if it doesn’t exist) whereas other getAttribute methods
> return Attributes/values 
> · NOTE: CP developers remain free to present the EntityId value as
> the value of some Attribute type that they define and use within their
Context
> 
> -Paul
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