[Pharo-project] I need some advice (was Re:
[squeak-dev] Organising
and Documenting Micro-Universes in Squeaksource)
Göran Krampe
goran at krampe.se
Fri Mar 20 10:08:40 UTC 2009
Hi!
Stéphane Ducasse wrote:
> Hi goran
>
> I did not get at all why you need a new format.
> Without self.
> I think that if you want adoption of deltastream do not mix them with
> a file format.
I am sorry, perhaps you haven't followed the reasoning, a quick recap:
1. Deltas are not bound to a specific format on disk. You can store them
in any way you like. They are "self contained object graphs" in the
image and can trivially be serialized.
2. Matthew made a format called "Interleaved ChangeSet" which combines
binary data with the chunk format meaning that a Delta can be stored
both as a changeset (loosing lots of info) and a Delta embedded inside
it. This means an old image can "file it in" just like a cs.
3. I think the Interleaved format is a bit too complex and while it is
"cool" I don't think the use case is *that* important (being backward
compatible for images that don't know what a Delta is). It is probably
simpler to include easy conversion delta2cs and cs2delta. These
conversions are not lossless however.
4. Since I wanted a readable, simple, fast, editable, and secure format
for Deltas - I came up with Tirade. Chunk format is readable, simple and
editable but it is not fast nor secure. It is also less "declarative" in
nature IMHO.
Tirade is well defined, small and simple. The Tirade package is just a
few classes and it is intended to work in "all Squeaks" - no
dependencies on any advanced stuff.
Tirade is a "data format" - it is NOT "Smalltalk code", it just happens
to match a lot of syntax and concepts. It is "merely" a sequence of
keyword messages with "data" as arguments (String, Symbol, Arrays,
Associations and Numbers - nested however you like). That is it. No
assignment, no variables, no globals, no expressions etc etc. It is NOT
Smalltalk. Adding "self" to it has no purpose, well, the ONLY purpose
would be to make it "look" like Smalltalk.
Now... this is repeating stuff I have already written elsewhere - but
there ya go. :)
regards, Göran
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