FW: [dais-wg] A simple Data Access service

[Savas Parastatidis]

Dear all,

This is my 3rd attempt to sending the files... I just realised that the
other messages were failing silently to appear due to the zip
attachments...

You can download an updated version of the files from here:

http://savas.parastatidis.name/dais/dais2.zip (this link is not
permanent and it will disappear after a few weeks or so).

Here are some changes to the files since my original post (copied from
one of my failed posts)...

I have an updated version of the WSDL and XSD files. This time, I have
included a 'Delete' message to demonstrate how one could include
DAIS-specific 'lifetime' management capabilities. It took me a great one
line of code to implement this functionality :-)))

The WSDL operation expects the name of the data resource to delete.
Extending this to support multiple or no data resource names is trivial.

 

Talk to you all this afternoon (or morning to some).

Regards,
--
Savas Parastatidis
http://savas.parastatidis.name
 

> -----Original Message-----
> From: owner-dais-wg at ggf.org [mailto:owner-dais-wg at ggf.org] On Behalf
Of
> Savas Parastatidis
> Sent: Tuesday, April 19, 2005 12:25 AM
> To: dais-wg at gridforum.org
> Subject: [dais-wg] A simple Data Access service
> 
> Dear all,
> 
> Please allow me to contribute to the discussions the metadata for a
> simple data access service that I put together in a couple of hours.
The
> service is based on approach 4 which was discussed at the
teleconference
> last week. It uses only WS-I Basic Profile specs (apart from the
> 'resolve' response message which returns the XML representing a
> WS-Addressing EPR).
> 
> I have implemented two WSDL portTypes: DaisCore and DaisRelational. I
> have exposed them as two ports of the same service (the wsdl:service
> element) but the messages from the two namespaces could have been
> included in the same portType. As a result, only one port would have
> been necessary. This is an implementation detail.
> 
> The DaisCore portType is supposed to provide access to the wrapped
DBMS.
> It can return Properties (the XML Schema of the properties document is
> visible to the consumers) and it can resolve names of data resources
to
> EPRs.
> 
> The DaisRelational portType describes the messages supported for
> relational data resources. It allows SQL queries to be sent and a)
> either a WebRowSet is returned or b) a name to a WebRowSet data
> resource. I have included a WebRowSetCount message which, given a name
> for a data resource, will result in a message with the number of rows
in
> the rowset to be returned. Other relational-related messages can also
be
> provided. You'll also notice that I have a RelationalProperties
message.
> This is to allow for relational-specific properties to be returned
> together with the DaisCore properties. The two could be different if
> necessary.
> 
> If the name for the data resource in the WebRowSetCount message is
made
> optional, then the same message could be used with WSRF. The
difference
> would be that an EPR would be required. I think such an approach can
act
> as a bridge between approaches 3 and 4.
> 
> Messages for the lifetime management of the data resource created from
> the ExecuteSqlResultByRef message would have to be defined. WSRF
> implementations won't need such messages.
> 
> The attached WSDL and schema files were automatically created from my
> implementation. They should work with any WS-I-compliant tooling.
> However, if there are any mistakes, this is because I had to clean
them
> up from policy-related metadata and format them for readability.
> 
> The cool thing about the implementation is that it only uses something
> between 100-200 lines of code. I use a hashtable to maintain the
> resulting data resources from the queries although a database could
> easily be used as well in order to allow for scalability of the
> implementation.
> 
> Please note that I don't make a distinction between type 2 and type 3
> resources. If you feel strongly about making the distinction at the
> portType-level, I am open to suggestions.
> 
> The service uses SQL Server 2005 beta 2 at the backend (although any
> other DB could have been used) and exposes the SLOAN Digital Sky
Survey
> (SDSS) database. Unfortunately, I can't deploy the service anywhere
for
> you to try since the necessary tools are only installed on my laptop
and
> I don't have another machine at the University from which I can make
the
> service available :-( I'll see if something can be done though.
> 
> Let me know what you think.
> 
> Best regards,
> --
> Savas Parastatidis
> http://savas.parastatidis.name
> 
> 
>