Re: R2RML draft - new introduction

I don't think answers my question.

Just to make sure that I understand what is being proposed, I see as the
following:

Let R be a relational schema
Let V be a target vocabulary

R2R(R, V) = RDF graph

Is this correct?

Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Wed, Oct 13, 2010 at 1:50 PM, Souri Das <Souripriya.Das@oracle.com>wrote:

>  Not sure if you saw my earlier email ... I am including it here anyway,
> just in case:
> =====================
>
> Ashok's question is very important and the answer in our FPWD must be
> absolutely clear.
>
> I like the answer Richard came up with after discussing with Michael.
>
> We may want to consider a rephrasing like the following:
> "An RDB2RDF mapping may be used against a relational database only if the
> logical table(s) used in the mapping is (are) valid in that relational
> database."
>
> Also, there is an issue of privileges for actually using an RDB2RDF
> mapping:
> "A client connecting to the relational database, EITHER to materialize the
> RDF triples based upon an RDB2RDF mapping, OR to query via SQL query
> obtained via translation of a (end-user submitted) SPARQL query using an
> RDB2RDF mapping, must have sufficient privileges in the relational database
> to compute the logical table(s) specified in the mapping."
>
> Thanks,
> - Souri.
> =====================
>
>
> Juan Sequeda wrote:
>
> On Wed, Oct 13, 2010 at 1:11 PM, Richard Cyganiak <richard@cyganiak.de>wrote:
>
>> On 13 Oct 2010, at 15:12, ashok malhotra wrote:
>>
>>> How about "The input to an R2RML mapping is a Relational database which
>>> contains the data as well as the schema."
>>>
>>
>>  Well, the input can't be a database with *any* schema; it must be the
>> same schema that the mapping was written for. I'd like to make that as clear
>> as possible.
>>
>> How about this:
>>
>> “Every R2RML mapping is tailored to a specific database schema and target
>> vocabulary.
>
>
>  target vocabulary or vocabularies
>
>
>> The input to an R2RML mapping is a relational database that conforms to
>> the schema.
>
>
>  so you mean:
>
>  RDB and Vocabulary --> R2RML Mapping --> RDF
>
>  or is a R2RML mapping and input self:
>
>  RDB and Vocabulary and R2RML Mapping --> RDB2RDF System --> RDF
>
>
>
>> The output is an RDF dataset, as defined in SPARQL, that uses predicates
>> and types from the target vocabulary.”
>>
>> This is for the intro; in the later chapters there is more space to spell
>> it out in detail.
>>
>> Richard
>>
>>
>>
>>
>>
>>
>>  All the best, Ashok
>>>
>>> On 10/13/2010 4:01 AM, Richard Cyganiak wrote:
>>>
>>>> Ashok,
>>>>
>>>> On 12 Oct 2010, at 23:59, ashok malhotra wrote:
>>>>
>>>>> One question.  You say:
>>>>>
>>>>>  The input to an R2RML mapping is a relational database.
>>>>>>
>>>>>
>>>>> Is it a relational database or a relational database schema?
>>>>>
>>>>
>>>> Good question. I discussed this a bit with Michael this morning.
>>>>
>>>> Definition: An RDB schema consists of the table *declarations*, but it
>>>> does not include the actual *data* in the tables.
>>>>
>>>> Definition: A relational database on the other hand consists of both an
>>>> RDB schema, and data that populate the tables.
>>>>
>>>> The input to an R2RML mapping has to include the actual data, because
>>>> otherwise how could a transformed form of the data be part of the mapping's
>>>> output? So the input is indeed a relational database.
>>>>
>>>> On the other hand, an R2RML mapping is *specific* to an RDB schema. That
>>>> is, it only works with an input database that conforms to a certain schema
>>>> (contains certain tables and columns). Let's call that schema the “input
>>>> schema” of the mapping. One could then say that the input to a mapping is
>>>> any database that conforms to the input schema. In other word, the domain of
>>>> an R2RML mapping is the set of all databases that conform to the mapping's
>>>> input schema.
>>>>
>>>> I think the notion of an input schema is actually really valuable for
>>>> writing the spec. For example, it allows us to say things like, “the SQL
>>>> query in a TriplesMap MUST be a SELECT query that can be validly executed
>>>> over the input schema.”
>>>>
>>>> Richard
>>>>
>>>
>>
>>
>
>