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

[David Kuehr-McLaren <dkuehrmc@xxxxxxxxxx>]

> Another question is this:  Is the EntityID
of an Entity immutable?  
> I believe it must be as soon as we start tying policy to EntityIDs.
> Either that, or we need to require a way to ensure referential 
> integrity for places where EntityIDs are stored in policy statements.

> 

My vote on 1.) was multipart where the decomposition
could contain both mutable (uniqueName) and immutable (uniqueId) parts.
They both have their use cases. 

If the EntityID is a string, then 1..n is needed to
accomodate mutable, immutable types and if the id can be used in other
protocols (compatability with legacy systems).  

David 

David Kuehr-McLaren 
Tivoli Security 
919.224.1960 


higgins-dev-bounces@xxxxxxxxxxx wrote on 09/12/2008
05:57:09 PM:

> On #2 I vote no -- it's not required to be an attribute however 
> there's no requirement that restricts its value from also being 
> reflected in an attribute. 
> 
> On #3, I vote 0..1 (where entities which are missing an entityID can
> only be used as "blank entities".   The other use case
is where one 
> performs a search and receives one or more Entities that are 
> nameless.  Do people want/need that to happen? 
> 
> On #1... I dunno.  I tend to want simple. 
> 
> Another question is this:  Is the EntityID of an Entity immutable?
 
> I believe it must be as soon as we start tying policy to EntityIDs.
> Either that, or we need to require a way to ensure referential 
> integrity for places where EntityIDs are stored in policy statements.

> 
> Jim
> 
> >>> "Drummond Reed" <drummond.reed@xxxxxxxxxxxx>
09/12/08 1:39 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 
> 
> _______________________________________________ 
> 
> higgins-dev mailing list
> higgins-dev@xxxxxxxxxxx
> https://dev.eclipse.org/mailman/listinfo/higgins-dev 
> _______________________________________________
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