Re: [model] section 3.2.4 Metadata

You could as well ask "where are the formal semantics of an LFB class 
defined?"  After all, the CE has to understand what the FE will do 
when asked to put an instance of an LFB class on a data path.

The decision we took was to not formally define semantics.  Semantics 
are defined textually.
This is true of LFB operations.  It is also true of meta-data 
semantics.  Typically, some LFB will produce the meta-data, with text 
indicating that the meta-data is some result of manipulating a field 
in a packet, or an entry in a table provided by the CE, or ...
(Yes, there is room for ambiguity.  Writers of the text describing 
LFB classes need to do their best to make sure the English is clear.)
And another LFB might indicate that it uses some piece of meta-data 
as an index in a table.

The CE is responsible for making use of these things in a consistent fashion.
And no, that is not automatic.  the expectation is that writers of 
CEs, in writing the logic to translate user policy into LFB 
configurations will address how the meta-data is to be used, in 
accord with the LFB Class definitions.

Formality isn't going to help much.

Yours,
Joel

At 03:03 PM 12/28/2006, Jamal Hadi Salim wrote:
>My question was:
>Assume two LFBs LFBa and LFBb defined by two different writers were to
>operate on the same metadatum, lets say LFBa would create it (the
>operation is WRITE) and that LFBb would reference it (the operation is
>READ).
>Then the author of LFBa would need to formally define the metadatum s/he
>creates. How is this "formally definition" achieved?
>If it is in the LFB definition, then doesnt the schema need to have a
>construct for it?
>I could imagine just putting a comment/documentation in the definition
>which says that the LFB will create the metadata under certain
>conditions. If this is the envisioned path then what is the point of
>explicitly defining formal operations like WRITE or READ in?
>How does LFBb know that it can only READ but not modify the metadatum
>etc? A secret handshake will do too ;->