Hi Laszlo -
On Thu, 14 Sep 2006, Dobos, Laszlo wrote:
> I just ran through the document quickly, because I was interested in the Web
> Service issues. I'm pretty sure that from the scientific view the data model
> is very well designed, and your work on collection and organizing the
> enourmous number of different metadata fields is appreciated, but I've found
> some problems that may cause trouble in a web service aware application.
These look like very good pointers about how to serialize using XML in a SOAP context, which will come up in some applications. My main comment about the Spectrum DM though, is that for an object of this complexity (also for VOTable, FITS, etc.) we would want to use a document-oriented interface. That is, rather than expose a Spectrum serialization directly in SOAP, we would pass the XML version of Spectrum as a string or other blob, much as we would for the other document formats such as VOTable or FITS. A SOAP interface to SSA could use conventional SOAP encoding for the query input parameters, but the query response or spectrum object would be passed back as a blob (or maybe just directly as a MIME-type identified response).
Hence it is not clear that compatibility of a complex model such as Spectrum with SOAP is an issue. The biggest difference between the JHU spectrum services and the DAL approach is probably this document-centric versus SOAP/RPC approach. The document-centric approach is admittedly more complex, but is required to support multiple data formats (including non-XML ones), and has other advantages such as separating the object code from the specific interface or protocol used.