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Re: [soapbuilders] Re: Sparse array interoperability

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  • Paul Kulchenko
    Hi, Andrew! I think question how sparse arrays look like and what they are is answered. Question for me is what sender expects to get from echoArray sending
    Message 1 of 60 , Sep 2, 2001
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      Hi, Andrew!

      I think question how sparse arrays look like and what they are is
      answered. Question for me is what sender expects to get from
      echoArray sending sparse array? Does he expects exactly the same
      sparse array back? If it's just an array with some gaps (whatever
      they are) can I fill them and return it as an usual array?

      Best wishes, Paul.

      --- Andrew Layman <mail@...> wrote:
      > I think we had a pretty good case made here that sparse arrays have
      > the
      > semantics described in DCE: transmission of parts, not all, of an
      > array. If
      > this is difficult to implement in some SOAP support libraries, I
      > recommend
      > that it would be better to omit sparse arrays from this round of
      > testing
      > rather than invent a novel interpretation of what a sparse array
      > is.
      >
      > Andrew Layman
      > http://strongbrains.com -- Resources for Self-Education
      > ----- Original Message -----
      > From: "NAKAMURA, Hiroshi" <nahi@...>
      > To: <soapbuilders@yahoogroups.com>
      > Sent: Sunday, September 02, 2001 8:37 PM
      > Subject: [soapbuilders] Re: Sparse array interoperability
      >
      >
      > Hi,
      >
      > > From: Rich Salz [mailto:rsalz@...]
      > > Sent: Saturday, September 01, 2001 9:41 AM
      >
      > > > Let me try to rephrase this. What you are saying is that the
      > sparse
      > > > array is the result of a "masking" operation of sorts on a
      > source
      > > > array?.
      > >
      > > Sort of.
      > >
      > > Think of it more like each side allocates the whole array, but
      > only part
      > > of it is transmitted at any one time.
      > >
      > > Using the "hello world" of web serivces: stock quotes.
      > >
      > > Client connects to server and sends up a list of 200 stocks it's
      > > interested in. It sends up an array of
      > <ticker,last-known-price>.
      > >
      > > Later on, client sends "gimme the big gainers" request. Server
      > sends
      > > down a sparse array of <ticker,last-known-price>. The client
      > > application can just unpack that array directly on top of the
      > client's
      > > previous copy, updating only the changed values. In this case,
      > sparse
      > > arrays are used for "transmitting delta's".
      > >
      > > Another application is search a huge crypto keyspace, or
      > SETI@HOME.
      > > Everyone gets an array with "the big picture," but each worker
      > machine
      > > gets a sparse array that has the set of data they are working on.
      > This
      > > used to be real popular in the early days of distributed
      > computing with
      > > RPC/mandelbrot demos.
      >
      > I'm using SOAP4R's sparse array for "poor-man's incremental
      > (differential) transmit" on a system. I could do it with
      > common XML instance + DOM programming, too. I agree that
      > conceptually SOAP sparse array is for these use.
      >
      > > > 5. Echo back as a sparse array.
      > > > int[1] = 1, int[3] = 2, size = 4
      > > > => int[1] = 1, int[3] = 2, size = 4
      > >
      > > I believe that yes, this is what you have to do. Unless of
      > course you
      > > change the WSDL array definition to have a default value.
      >
      > >From SOAP data model point of view, I agree with you. I
      > almost implemented in SOAP4R. But I thought that it might
      > be allowed to define limited use of sparse array in the
      > echo* application level. Reason:
      >
      > 1. It might be hard to accept in some language.
      > You cannot map ArrayOfInt to std::vector<int> directly in C++
      > even if you know a WSDL defines an element as 'ArrayOfInt'.
      >
      > 2. Few language supports sparse array in language level
      > (including Ruby.) So that language mapping is hard.
      > Possibility;
      >
      > Client SOAP node
      > --(sparse array)-->
      > Server SOAP node
      > --(common array with nil/Hash with length/etc)-->
      > echo application
      > <--(common array with nil/Hash with length/etc)--
      > Server SOAP node
      > <--(array/Map/etc)--
      > Client SOAP node
      >
      > SOAP4R can accept Option 5. Others: ?
      >
      > Regards,
      > // NaHi
      >
      >
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    • NAKAMURA, Hiroshi
      Hi Paul, ... In SOAP4R; Using low level API, user application gets an instance of SOAPArray class in either case of usual array/sparse array. Using high level
      Message 60 of 60 , Sep 4, 2001
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        Hi Paul,

        > From: Paul Kulchenko [mailto:paulclinger@...]
        > Sent: Tuesday, September 04, 2001 9:13 AM

        > > I do not think so. If sparse array is not interoperable
        > > with usual array, it does not have to be an array.

        > If this is correct then question is "how"? How usual array should
        > look like in this case? In my current implementation, sparse array is
        > the same as array with undef/null elements, but I'm not sure it's
        > correct.

        In SOAP4R;

        Using low level API, user application gets an instance of
        SOAPArray class in either case of usual array/sparse array.
        Using high level API, user application gets an instance of
        common Array class in Ruby in either case. Sparse array is
        the same as usual array with nil elements in high level API.
        User application which wants to use sparse array must use
        low level API.

        So I must build echo interop server using low level API
        when the interop echo R2 application adopts Option 5.

        > > We sometimes want the array including indeterminate elements
        > > (such as VARIANT ARRAY with many Empty in COM, array with
        > > many undef-s in Perl). We can reduce transmitted data
        > > using Sparse array to pass these type of array. I believe
        > > SOAP authors introduce Sparse array for this purpose.

        > how implementation should look like in this case? Would you scan
        > EVERY array to check how many nulls are there? Would you allow user
        > (who doesn't care about it) tell that he want to have "sparse" array
        > on wire? It does make sense ONLY if there is already some type in a
        > language that implements sparse arrays. But I do not expect SOAP
        > processor to be so smart and choose between array and sparse array
        > checking number of empty elements.

        In SOAP4R, SOAP node knows whether it is an usual array or
        sparse array. When receiving an array, with "offset" or
        "position" attribute, SOAP4R recognize it as a sparse array.
        When sending an array, user application must define it as
        a sparse array by low level API.

        I mean, SOAP4R consider a partial array with "offset" as a
        sparse array. It could be an error under lexical context
        of SOAP spec, but I think these 2 special arrays is for the
        same purpose.

        > > > It's very similar to difference between multidimensional arrays
        > > and
        > > > arrays of arrays. Will you accept array of arrays as echo for
        > > > multidimensional array?
        > > I disagree here. Common array and Sparse array have same
        > > type of content (arrayType). 1D-Array and 2D-Array have
        > > different arrayType.
        > That's true. My point was different. They look different on wire, but
        > they are the same in some languages (Perl for example). So, you're
        > saying that they are indeed different and you do NOT accept one as
        > echo for another one. That's similar to my point about sparse arrays.
        > Ther MAY look the same as usual array in your language, but they are
        > different. Looks like I'm the only one who support this point of view
        > ;).
        >
        > Let me summarize. This discussion was started from echoArray problem
        > when you send sparse array and I send back usual array where omitted
        > elements are nulls. How correct is it? Definitely what I'm sending
        > back IS NOT a sparse array. So what? Is it proper echo? Andrew's
        > point was that sparse array and array with nulls ARE NOT the same. In
        > theory (sorry, Andrew ;)). How about practice? If I CANNOT echo usual

        In SOAP data model level, we know we cannot define how we
        should do, don't we? In the R2 echo application level, we
        are discussing how we should do for testing inteoperability
        in a most effective way, I think.

        Someone like Option 5, someone like Option 1. I can accept
        Option 5. Which do you like?

        Options:
        http://groups.yahoo.com/group/soapbuilders/message/5128

        Regards,
        // NaHi

        PS. I'm sorry if I'm blunt because of my poor English...
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