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<== Date ==> <== Thread ==>

Subject: RE: Data Access Class Library Tutorial
From: "Liyu, Andrei" <[email protected]>
To: Jeff Hill <[email protected]>, [email protected]
Date: Wed, 23 Feb 2005 10:18:42 -0500
Jeff and Ralph,

	I hope I understood a little :)
	I had experience with OPC, DCOM and I suppose there are couple
interesting features in that protocol

- client does connections to server. Now CA does connection by PV name.
Sometimes it is suitable sometimes it is not suitable.
- when client read/write value there are two choice - access to real
value and access to according memory (reading - latest value, writing -
will wait next real write)

	About data type. It is fine that you would like to increase set
of types. I suppose any SCADA needs 
- set of simple types likes char, int, enum
- composition types array (which format?), structure
- raw block memory
It is fine that array can change volume on fly. I hope raw block memory
could do the same.

	For ALL: usually there are some types of manuals : introduction,
user, programmer, system. 

Thanks, Andrei.


-----Original Message-----
From: Jeff Hill [mailto:[email protected]] 
Sent: Tuesday, February 22, 2005 5:22 PM
To: [email protected]
Subject: Data Access Class Library Tutorial


Hello all,

Attached is the latest Data Access Class Library Tutorial for
your review. As described in previous talks given at user's group
meetings and at ICALEPCS by Ralph Lange and myself, the Data
Access interface and its associated support libraries were
designed and written for incorporation into future Channel Access
client and server interfaces. The work on a Data Access
implementation is in its 3rd generation. The next stage will be
to begin using it. The original CA client interface will of
course be preserved through use of Data Access interfaces for all
of the preexisting dbr_xxx types.

Thanks for your patience and consideration for our ideas in the
past, and thanks in advance for any time you can spare for
further comments.

Best regards,

Jeff Hill and Ralph Lange





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