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Joe, in bibframe, bf:carrierCategory has an expected value of bf:Category, so it can be a uri to an external bf:Category or a bf:Category [bf:categoryValue "string"]

Two examples:
---------------------------------
http://bibframe.org/tools/compare/bibid/2466523:

bf:Work	 bf:hasInstance [ a bf:Instance ;
    		                bf:carrierCategory [ a bf:Category ;
			                            bf:categoryValue "Microfiche" ] ;
...
]

---------------------------------


http://bibframe.org/tools/compare/bibid/16497758:

bf:Work	 bf:hasInstance [ a bf:Instance ;
		            bf:carrierCategory <http://id.loc.gov/vocabulary/carriers/nc> ;
....]
---------------------------------
Microfiche in the first instance is a valid rda carrier, but since it's coming from 710, there's no expression of the controlled list it's coming from ,so we don't assume it's the same as the 338, (which does say "rdacarrier" ) and we leave it as literal. 
In both cases, however, if you want the literal string, your system knows that carrierCategory follows the link (blank or not) to the Category, and reads the categoryValue. 

contentCategory and mediaCategory work the same way, and identifiers does or will.


Nate

-----------------------------------------
Nate Trail
Network Development & MARC Standards Office
LS/ABA/NDMSO
LA308, Mail Stop 4402
Library of Congress
Washington DC 20540


-----Original Message-----
From: Bibliographic Framework Transition Initiative Forum [mailto:[log in to unmask]] On Behalf Of Joseph Kiegel
Sent: Tuesday, March 31, 2015 1:22 PM
To: [log in to unmask]
Subject: Re: [BIBFRAME] BIBFRAME and RDA/RDF

I agree with your point about strings vs identifiers in RDA.  Depending whether rdaw:mediumOfPerformance contains a URI or a literal, it must be conditionally mapped to bf:musicMedium or bf:musicMediumNote.

However, while BIBFRAME properties have their ranges set either to a literal or a URI, the paired properties needed to cover both cases are not always defined.  For example, for rdam:mediaType, rdam:carrierType and rdae:contentType, the value may be either a literal or URI under RDA.  Of course, we would prefer URIs in linked data.  On the BIBFRAME side, the corresponding properties are mediaCategory, carrierCategory and contentCategory, all of which have a range of bf:Category.  Of the properties with a domain of bf:Category, we have only bf:categoryValue in which to put a value, and its range is a literal.  There is no bf:categoryUri with a domain of bf:Category and a range of rdfs:Resource, which is needed to contain category values when they are URIs.

The same thing is true with identifiers in BIBFRAME.  Conceivably, you could decompose identifier URIs into bf:identifierScheme (range: rdfs:Resource) and bf:identifierValue (range: rdfs:Literal), but that is doing it the hard way.  It would be better to have a property bf:identifierUri with a domain of bf:Identifier and a range of rdfs:Resource, which could contain an identifier expressed as a URI.  As it stands now, even bf:uri has to have a literal as its value.


Joe

--------------------------------------------------
From: "Karen Coyle" <[log in to unmask]>
Sent: Saturday, March 28, 2015 7:05 AM
To: <[log in to unmask]>
Subject: Re: [BIBFRAME] BIBFRAME and RDA/RDF

> Joseph, thanks for doing a comparison. Note that BF has about 400 
> properties, while RDA has nearly a thousand, so it is true that RDA is 
> more detailed that BF. However, RDA has virtually no class 
> relationships -- it's essentially a flat data space. This will have 
> implications for the use of RDA in actual systems, since class 
> relationships help you do things like "search all properties in the 
> title class."
>
> On 3/27/15 8:04 AM, Joseph Kiegel wrote:
>>
>>
>> Identifiers:
>> Under the influence of MARC, BIBFRAME has a large set of properties 
>> for identifiers while RDA is limited.
>
> The RDA rules often allow either strings or identifiers. RDA in RDF is 
> essentially silent in most cases on whether the value for a property 
> is expected to be a string or an identifier, and therefore it can 
> presumably be either. This, however, is highly problematic when 
> working with RDF data. In general, it's never good to not know what 
> kind of data to expect for a field in your metadata -- it complicates 
> input interfaces and the programs that use the data. However, if you 
> want to have the possibility in your data to accommodate both strings 
> and identifiers, you are kind of forced to create different properties 
> for those different choices, which would mean nearly doubling the 
> number of RDA properties. Although I find the use of blank nodes in BF 
> to be a complicating factor, I assume that in many cases those blank 
> nodes are there as a way around this string-vs-identifier problem, 
> allowing each statement to point to a blank node that can have either or both.
>
> To me this is evidence that we need to re-iterate back from our 
> attempts to create a viable RDF version of library data to the 
> cataloging rules, and create at least a subset of the rules that can 
> support a viable data format with clearly defined data values for each 
> property. The "string or identifier" in the rules just isn't workable in a data format.
>
> kc
>
>>
>> Subjects:
>> RDA is not yet able to express subject relationships (RDA chapters 
>> 33-37) and BIBFRAME has a mechanism for this.
>>
>> Holdings Information:
>> Although not fully elaborated, BIBFRAME has properties for holdings 
>> information while RDA has almost nothing.
>>
>>
>> RDA is richer than BIBFRAME
>>
>> Series:
>> RDA provides properties for all parts of series statements, while 
>> BIBFRAME has a single property:  series.
>>
>> Notes:
>> RDA has more properties for specific types of notes.  While BIBFRAME 
>> has note properties, the term "note" in a property name may mean 
>> simply that its range is a literal, e.g. findingAidNote, musicMediumNote.
>>
>> Technical Details of a Resource:
>> RDA has a large number of properties for technical details of 
>> resources such as polarity, playingSpeed, fileSize, etc.  It is not 
>> clear how BIBFRAME handles this type of information.
>>
>> Inverse Properties:
>> RDA provides inverse properties (e.g. animator and animatorOf) while 
>> BIBFRAME lacks them.
>>
>>
>
> --
> Karen Coyle
> [log in to unmask] http://kcoyle.net
> m: +1-510-435-8234
> skype: kcoylenet/+1-510-984-3600
>