Re: R2RML draft - new introduction

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 
> <mailto: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
>
>
>
>