Neil, Thank you very much for forwarding the previous correspondence on to Mike. I'm going to be trying to create a federated query across DCQL and OGSA-DAI in the next month or so. I'll have more details at that point.
Mike, thanks for your input. -Ron On Fri, May 23, 2008 at 8:46 AM, neil p chue hong <[EMAIL PROTECTED]> wrote: > Hi, > > In followup to this query: > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf > Of Ron Price > > Sent: 16 May 2008 22:38 > > Subject: [gt-user] federated query across ogsa-dai and dcql resources > > > > Is it possible to do a federated query when some data services use > OGSA-DAI and some use DCQL? > > > > a message was sent directly to Ron as follows (copied here for archiving to > the lists as Mike Jackson is not a member of the lists). I should add that > another good place to ask these queries is the [EMAIL PROTECTED] > list. > > Cheers, > neil > > > -- > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > > ---------- Forwarded message ---------- > Date: Wed, 21 May 2008 10:54:19 +0100 (BST) > From: Mike Jackson <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Cc: Mike Jackson <[EMAIL PROTECTED]>, [EMAIL PROTECTED] > Subject: Re: FW: [gt-user] federated query across ogsa-dai and dcql > resources > > > Hi Ron, > > Your query was forwarded to me by a colleage - Neil Chue Hong - so I'll try > to > answer. > > We've never heard of CQL or DCQL until now. I see from the CaGrid Wiki (via > Google) they're both XML-based query languges based on querying data with > respect to its UML information model and are used to submit queries to data > services. > > In theory it should be possible to run queries over federations of OGSA-DAI > and > DCQL services. You'd need some "layer" or components to manage this. In > particular, there needs to be: > > -A common query language for the federated resources, or using an > existing query language. I'll call this L. > -A common data format for query results, or using an existing > data format. I'll call this D. > > and components to: > > -Convert queries in L into OGSA-DAI workflows. > -Convert queries in L into DCQL queries. > -Submit OGSA-DAI workflows, representing queries, to OGSA-DAI data > services. > -Convert data from OGSA-DAI services into format D. > -Submit DCQL queries to DCQL services. > -Convert data from DCQL services into format D. > -Join the data, expressed in format D, from the different services. > > i.e. > > -L-> Translator -DAI workflow-> > DAI service <-> database > <-D- Translator <-DAI response- > Client > -L-> Translator -DCQL-> > DCQL service <-> database > <-D- Translator -DCQL response- > > So basically, components to translate queries, submit queries, translate > data > and combine data. As I said, in theory it's possible. How much effort it > would > take in practice however would depend upon the ease of identifying the best > choice for L and D above. > > OGSA-DAI would be one framework in which such a layer could be implemented > since it is designed with the intent of accessing and integrating data from > distributed heterogeneous databases. > > Another alternative would be to devise a DCQL compliant presentation layer > (data service) for OGSA-DAI which could convert DCQL queries to OGSA-DAI > workflows. This means that OGSA-DAI servers would be used identically to > DCQL > compliant services. > > i.e. > > -DCQL-> > -DAI workflow-> > DAI DCQL service DAI core <-> DB > <-DAI response- > <-DCQL response- > Client > -DCQL-> > DCQL service <-> DB > <-DCQL response- > > I hope these are clear. If you need any more information please ask. > Likewise, > it would be of interest to us if you could send more details as to what you > have in mind, if you can. > > Cheers, > > mike > > -- Thanks, Ron Price 801.560.2305
