V4 2nd Design Meeting Notes

2nd Design Meeting (APS) - Notes

Who is the customer?

As there are no big machines coming up and lots of existing installations, V4 will be targeting the whole community.

Compatibility and conversion issues

V4 will not support 68k processors under Tornado2, only under RTEMS. (There might be memory footprint issues, though.)

Lower limit: 8MB/68k or 16MB/coldfire - i.e. must support small and embedded systems.

Gateways will be used to convert CA connections between V3 and V4 within one system.

We should provide a set of asara records (asara = as similar as reasonably achievable) providing V3 behaviour that can be used for automatic conversion of existing V3 databases.

DBD syntax and generation

Building blocks

It seems wrong to have real C++ declarations within the dbd file. The interface definitions should rather reside in a separate header file. (That way it would be easier to e.g. have the interfaces in different languages.)

Declarations of fields and views

The V3 prompt declaration will be replaced by a "hint" or "help" text that can be applied to any entity defined in the dbd language (not just fields). Tools may use that text to display bubble help or similar things.

The V3 group declaration will be replaced by views that can be used by the configuration tool to group things into hierarchies.

Hierarchies

Jeff envisions a "global" hierarchical namespace, where a request for quad4.ps2.current.analogValue.val would be answered by a "virtual" record that forwards and collects things from different records. Such a virtual could reside on a different node. It is unclear, who or how such a record would be written.

V3 compatibility records will define views like

view (HIHI) {
    property (....)
}

so that clients can still use the old syntax of <recordName>.<fieldName> to access fields.