Re: [Forces-protocol] Data Encoding

"Weiming Wang" <wmwang@mail.hzic.edu.cn> Wed, 17 November 2004 14:56 UTC

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From: "Weiming Wang" <wmwang@mail.hzic.edu.cn>
To: <hadi@znyx.com>
References: ocaldomain><009e01c4cb24$ba144bd0$020aa8c0@wwm1> <1100610279.1152.33.camel@jzny.localdomain>
Subject: Re: [Forces-protocol] Data Encoding
Date: Wed, 17 Nov 2004 22:48:16 +0800
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Cc: Avri Doria <avri@acm.org>, Steve Blake <slblake@petri-meat.com>, "Joel M. Halpern" <joel@stevecrocker.com>, Dong Ligang <donglg@mail.hzic.edu.cn>, "Khosravi, Hormuzd M" <hormuzd.m.khosravi@intel.com>, "\(Ram Gopal \)" <ram.gopal@nokia.com>, forces-protocol@ietf.org, Patrick Droz <dro@zurich.ibm.com>, zsolt@modularnet.com, David.Putzolu@intel.com, Robert Haas <rha@zurich.ibm.com>
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Jamal,

----- Original Message -----
From: "Jamal Hadi Salim" <hadi@znyx.com>

> Weiming,
>
> You introduce two things below:
> 1) content based access aka associative
> 2) operations of such contents (AND, OR are the two i see you using)
>
> We havent discussed those. But this is a good point as any to start.
>
> Lets talk about one issue at a time
[Weiming] I just think they(content based and index based) are so tightly tied
that we may have to consider it simulteneously.
>
> There is a TLV "KEY_INFO" Which has in its value a KEY that could be a
> the ID and KEY_DATA to be the value. If we allow to have multiple of
> these in a path-data then we can have complex operations.
> With that in mind, let me move to the rest of your email and use this to
> address your examples.
[Weiming]My thought on this is, we do not have to recognize if it is a KEY or
not. It's just a kind of element in a path.
>
> >
> On Mon, 2004-11-15 at 10:06, Weiming Wang wrote:
> > Jamal,  Joel as well,
> >
> > Good, I'l try to follow the example in the doc. I'm just trying to raise
some
> > question in the line actually trying to show my view further.
> >
> > To summarize, I strongly believe the Data field should allow IDs other than
pure
> > values. I think in the examples Jamal also has shown some cases where Data
are
> > not pure values (including index, field ids).
> >
>
> I think this should be available but optionaly i.e you could have
> simple, BLOCK or KEY based accesses. It may also be ok to have a mixture
> of all 3.
>
> > Regarding using Data encoding without IDs,  I really have a feeling that it
is
> > more dangerous than with IDs. Note one bit error produced by programmer
(e.g.,
> > mistaken one u32 to u64 and another u64 to 32) will result in the total
failure
> > for the whole Data and the error is hard to be debugged (no IDs to verify
it).
> > One more question is the appearing sequence also become important with this
> > approach, which makes the FE model schema sequence sensetive. This is really
> > inconvenient.
> >
>
> I dont see how. The path is still composed of IDs and subscripts/indices
>
> > I'm trying to add Steve and Zsolt in the list (but seems Steve's server
always
> > takes my post as spam:( .  ).
> >
> > Cheers,
> > Weiming
> > ---------------------
> > OPER_TLV : = <PATH-DATA>
> > PATH-DATA := flags IDcount <IDs> [BLOCK_OR_KEY_NOTATION] [DATA]
> > [Weiming]Why don't we just set the PATH as a TLV?
> >
> > -> IDs := a series of 32bit IDs (whose size is given by IDcount) defining
the
> > path.
> > [Weiming] Obviously, we need a flag to indicate the ID being
index(subscript) or
> > field ID as
> >     ID:= flag(1bit)  Index(31bit) | fieldID(31bit)
> >     flag:=0(fieldID) | 1(index)
> > [/Weiming]
> >
>
> Lets defer your idea of decomposing the ID above for now. I think we can
> still achieve the goals without it.
[Weiming]By separate the fieldIDs from Indexes, as Joel just proposed? I just
have a worry on this expression. Pls see my reply to Joel.
>
> > Assume LFB with following attributes
> >
> > foo1, type u32, ID = 1
> >
> > foo2, type u32, ID = 2
> >
> > table2: type array, ID = 4
> >  elements are:
> >  j1, type u32, ID = 1
> >  j2, type u32, ID = 2
> > [Weiming] Let me add one more field as
> >  j3, type u32, ID=3
> >
> > Then, very often, we may have operations as:
> >
> > 1) delete(or get ) all entries with j1=100, and j2=200 (note j3 is not
cared)
>
> Can be done as follows:
>
> Path = 4
> TLV, T = KEY_INFO, Length = 4+8
> KEY = 1 // j1
> KEY_DATA = 100
> TLV, T = KEY_INFO, Length = 4+8
> KEY = 2 // j2
> KEY_DATA = 200
[Weiming]I have to say above format only applies to where KEY is only with one
ID. In reality, the KEY refered here is actually a subpath, which may also have
multiple levels, like j2.g3 .
>
> The above is an && operation of the two keys. Not sure how to do ||
> cleverly
>
> Other
> Of course we could make KEY_DATA a TLV so we can have variable sized
> DATA for a KEY, eg to repeat above:
>
> Path=4
> T=KEY_INFO, length = 4 + xx
>    T=1,  Length= 4 + 4 // 1 is ID for j1
>    V = 100
>    T=2, L = 4 + 4
>    V = 200
>
> The above wastes 4 bytes per value because of TLV and is clearly more
> complex to parse, but we could say thats the cost of doing this.
[Weiming]This still applies to where KEY is with one ID, not with multiple level
IDs as 1.2.

Cheers,
Weiming

>
>
> > 2) modify entry with index=10 to j1=100, and j2=200 (note j3 is not to be
> > changed)
> >
>
> Can use one of those two schemes above.
>
> > If we allow field ID in Data, this can be expressed easily. I just see some
> > difficulty using the encoding you and Joel proposed. For 2) you may say it
can
> > be done by using two separate Path-data, but I just think this way is very
> > tedious, saying if we have 10 fields more. If we allow field ID in data, it
can
> > be tidily expressed.
> > [/Weiming]
> >
>
> I think what you have described is content based schemes - which is not
> exclusive. Both schemes need to be supported.
>
> > table1: type array, ID = 3
> >  elements are:
> >  t1, type u32, ID = 1
> >  t2, type u32, ID = 2  // index into table 2
> >
> > [Weiming] I think a compund structural type is very common, which should be
> > instanced  in the example.  Let me show one as:
> >
> > foo3, type structure, ID=5
> > {
> >     s1, type u32, ID=1
> >     s2, type structure, ID=2
> >     {
> >         g1, type u32, ID=1
> >         g2, type u32, ID=2
> >     }
> >  }
> >
> > For this type, we then may also have very common operations as:
> >         Modify s1 to 100 and g1 to 200.
> > I also see some tidious problem if we don't allow field ID in the DataTLV.
> > [/Weiming]
>
> We could add that as another example; Lets come back to it when we have
> solved some of the basic stuff
>
> > 1) To get foo1
> > Path IDs = 1
> >
> > Result:
> > Path = 1, DATA_TLV with value of foo1
> >
> > 2) to set foo2 to 10
> > Path IDs = 2
> > DATA_TLV: L = 4+4, V=10
> >
> > 3) To dump table2 (get)
> > Path = 4
> >
> > Result:
> > Path = 4
> > DATA_TLV, Length = 4 + (#of entries in table2)(8+4)
> > This is followed by data of the form:
> > subscript,j1value,j2value (subscript is 4 bytes, j1 + j2 is 8 bytes)
> >
> > Note the above allows for holes in subscripts, i.e if subscript is
> > not in use it doesnt take space
> > [Weiming] Note that some tables may or may not have subscript, above format
will
> > then result in ambiguity in semantics. If we uniformly ask IDs in Data, no
such
> > problem then.
>
> Forget about IDs for a second - I dont think we need them for this
> specific case - and make a recommendation about how to word this.
[Weiming]It's true to express above with IDs are more bits consuming. Actually
I'm not vitally against not using IDs in values, just a little worry that it may
also be complex to do with pure heap values, just considering above j1 is
another compond structure rather than an atomic one. We need to verify more to
see the practicability.

Cheers,
Weiming
>
> Again, to reiterate both content and the other schemes need to be
> supported.
>
> cheers,
> jamal
>
>
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