- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Thu, 14 Oct 2010 15:17:37 +0100
- To: Souri Das <Souripriya.Das@oracle.com>
- Cc: Juan Sequeda <juanfederico@gmail.com>, ashok.malhotra@oracle.com, RDB2RDF WG <public-rdb2rdf-wg@w3.org>
Souri, On 13 Oct 2010, at 19:50, Souri Das wrote: > 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." These should definitely go in, but not in the introduction, but in a later chapter. Richard > > 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 >> >> >> >> >
Received on Thursday, 14 October 2010 14:18:11 UTC