Re: [Tm4j-developers] Normalising ID and resourceID

[Gerd M. <ge...@sm...>]

> I've been reviewing the way in which TM4J's import and export functionality
> handles the resolution and normalisation of IDs and references and I would
> like to get feedback on my thoughts before implementing anything.
> 
> Firstly, all TopicMapObjects have two separate 'identifiers':
> 
>   ID property: Assigned by the import process.
>                Guarunteed to be unique across all objects in the same
> TopicMap
>                Should be stored as the ID only (not as a full URL)
> 
>   resourceID property: The URI of the XML element which gave rise to the
> creation
>                          of the object.
>                        Stored as a complete URI (many different topic map
> documents
>                          may contribute objects to a single TopicMap.
>                        May be NULL
>                        Guarunteed to be unique across all objects in the
> same TopicMap.
> 
> Then TopicMaps have three additional associated URIs:
> 
>   baseURL property: The URL which should be treated as the URL of the topic
> map in
>                       its entirety. All objects in the topic map can then be
>                       addressed as <baseURL>#<ID>.
>                     This is currently not a required property of the
> TopicMap, but
>                       it probably should be.
> 
>   xml:base : The (optional) value of the xml:base attribute of the
>                <topicMap> element.
>              Used only during parsing to resolve references to external
> documents.
> 
>   sourceURL: Not stored as a property of the TopicMap, but just used when
> parsing
>                a source document.
>              Used only during parsing to resolve the value of the id
> attribute
>                of an element into a full URI for storing as the resourceID
>                property of a TopicMapObject
>              Used to resolve references to external documents if baseURL is
> not
>                specified
> 
> Addressing into a topic map held in a TM4J system may require a
> backend-specific URI to identify the store. However, once a connection is
> made to a TM4J store, I think it should be possible to query the
> TopicMapProvider interface to retrieve a TopicMapObject by specifying a URL
> constructed of the baseURL property of the TopicMap and the ID of the object
> required.
> 
> What I have described in the foregoing is not exactly the way that TM4J
> behaves right now, partially because I didn't properly understand the
> purpose of xml:base and partly because before the Ozone implementation,
> there was no real need to consider a TM4J system that kept track of multiple
> topic maps simultaneously.
> 
> So, my questions to y'all are: Does this sound reasonable to everyone ? Is
> there something else missing from this list ?

One problem that I see is when to use the ID and when the resourceID.
I mean if I reference a topic in another topicmap I would write
<baseURL of th TM>#<ID of the topic>. But could it also be possible
to use the resourceID instead of the ID ? And if so, how do we
differentiate both versions or is this up to the target topic map ?

We could say the <baseURL>#<some id> means that <some id> is an ID
and <xml:base URL>#<some id> means that <some id> is a resourceID.
But the baseURL and <xml:base> can be the same, e.g. if there is
no <xml:base> in the XTM file. The solution could a different 
syntax for both versions, e.g. <baseURL>/ID#<some ID> references
the ID of topic and <baseURL>#<some ID> the resourceID.

We could also say that if there is a resourceID given by the XTM
file then the ID of the topic must be the same as the resourceID.
But then it will be hard to insure the uniqueness if the ID.

Best Regards,
Gerd

--
________________________________________________________________
Gerd Mueller                                    ge...@sm...     
SMB GmbH                                  http://www.smb-tec.com