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Subject: RE: [xdi] proposal for binary data literal node
To make this work I think we need to first specify how a binary would be serialized in the XDI serialization protocol. Since that is based on JSON you either must use an encoding (i.e. data URL, or MIME), or have some part of multi-part message with the binary as a different MIME type. I think we need to specify how to handle binaries, but I don't think !! is the answer. I think specifying that the metadata always be loaded before the value or a literal is processed, may be the answer, which would allow our existing mechanisms for specifying the binary MIME type (we still don't have serialization finalized, currently encoding is used I believe by several of us). Kind regards, Bill Barnhill Booz Allen Hamilton - Belcamp,MD 1-443-924-0824| barnhill_william@bah.com -----Original Message----- From: xdi@lists.oasis-open.org [mailto:xdi@lists.oasis-open.org] On Behalf Of Michael Schwartz Sent: Friday, March 02, 2012 10:24 AM To: OASIS - XDI TC Subject: Re: [xdi] proposal for binary data literal node I want to stress that storage of binaries is not a niche use case. It doesn't matter what kind of implementation you are using--rdbms, ldap, or file system--you will want to treat binaries differently. An implementation detail is what do you do with the binaries, not whether you know if you have a binary. If we don't solve this, and we're stuck with some lame solutions like encoding binaries (i.e. like in SMTP), it would be a missed opportunity for the TC. How about a new type of arc: the "binary arc" ? See inline comments below. > > If for optimization purposes a server needs to know the data type of a > literal (binary, number, boolean, etc.), then it could either 1. > figure out the data type based on the dictionary, or I don't understand your suggestion here. How would a dictionary be helpful? How could you guarantee that the dictionary is known when you are parsing the XDI statements? > 2. require (as a policy) that clients add the literal together with > the metadata that specifies the data type no, per my previous comment, there is no guarantee the metadata would be loaded first. > > Markus > > On Fri, Mar 2, 2012 at 3:05 PM, Michael Schwartz <mike@gluu.org> wrote: > >> >> I think we need a way to differentiate binary literals if we want to >> support storage of binaries in the graph. And simply storing metadata >> is not sufficient because there is no guarantee that the metadata is >> created before the literal needs to be stored. Is there a solution? >> >> thx, >> >> Mike >> >> >> >> >> ------------------------------**--------------------- >> >> Michael Schwartz >> Gluu >> Founder / CEO >> mike@gluu.org >> +1 646-810-8761 >> >> >> On Thu, 1 Mar 2012, Drummond Reed wrote: >> >> Mike, the question you raised actually highlights a number of the >> key >>> reasons for the literal context proposal. Let me explain. >>> >>> First, per Markus' last point in his message, one primary purpose of >>> literal contexts is so an XDI processor always knows the type of the >>> literal node it is dealing with by the type of the literal context. >>> To use Mike's example, if "*logo" is defined as a literal context >>> containing a binary value (which has several semantic issues -- see >>> below), then @!1111*logo always identifies a single binary value. >>> >>> Secondly, it's a misunderstanding of literal contexts that there >>> could be two literal arcs. The whole idea of a literal context is >>> that it has a single literal arc. If the literal context is defined >>> as containing binary data, then that literal arc points to binary >>> data. If the literal context is defined as containing a number, then >>> the literal arc points to a number. >>> And so on. >>> >>> These are all controlled by XDI dictionary definitions, which is why >>> I think the XDI Dictionary spec is moving up in priority. >>> >>> Now, the semantic issues. First, @!1111*logo is semantically wrong >>> because uses a *name to identify a literal context defined in a >>> dictionary, and * is not the dictionary namespace. The dictionary >>> namespace is + (with the exceptions of a handful of special $words defined by the XDI TC). >>> >>> So it should be @!1111+logo. The second semantic issue is that +logo >>> should not be a literal context because it is not a single defined >>> datatype. >>> +logo >>> should be a supertype that has defined subtypes. In other words, the >>> dictionary defintion should say +logo/$is$a/+image, and (among other >>> options) +$image/$a/$a$xsd$jpeg. So if the binary you wanted was a >>> JPEG, then the address would be: >>> >>> 1. @!1111+logo$a$xsd$jpeg <== canonical JPEG version of the logo >>> (zero-or-one) >>> 2. @!1111+logo/$a$xsd$jpeg <== (note the slash) relational arc >>> pointing >>> >>> to all the JPEF versions of the logo (zero-or-more) >>> >>> So it is the dictionary-defined $jpeg, and not +logo (and >>> definitely not >>> *logo) that is the XRI literal context storing the binary data. And >>> because the $dictionary will define $jpeg as a JPEG binary, any time >>> an XDI processor sees $jpeg as the literal context, it knows the >>> value is a JPEG. >>> >>> I'll put this on the agenda for tomorrow's call (even though Mike >>> won't be there). >>> =Drummond >>> >>> On Thu, Mar 1, 2012 at 4:35 PM, Michael Schwartz <mike@gluu.org> wrote: >>> >>> >>>> Markus, >>>> >>>> Thanks for the quick response! >>>> >>>> 1. Yes, you could have both a ! and !! arc, why not? It doesn't >>>> seem inherently problematic to me. >>>> >>>> 2. yes, you're right I forgot the / for the literal arc :) >>>> >>>> 3. !! was just an idea... it could be something else. >>>> >>>> 4. Its useful to be able to differentiate binary data from other >>>> types of data because there persistence strategy varies greatly. >>>> >>>> >>>> - Mike >>>> >>>> >>>> >>>> >>>> 1. Could you have BOTH a binary and a non-binary literal in a context? >>>> >>>>> I.e. >>>>> have a ! arc and a !! arc. >>>>> If not, will the server throw an error if you already have one >>>>> literal and try to add the other one? >>>>> >>>>> 2. In your example, wouldn't the XRI actually be @!1111*logo/!! >>>>> instead of @!1111*logo!! ? >>>>> >>>>> 3. Something is bothering me about the fact that !! is two subsegments. >>>>> I >>>>> am worried it will result in ambiguity in one way or the other. >>>>> >>>>> 4. I don't understand why you can't load the metadata together >>>>> with the literal, to figure out whether it is binary or not. >>>>> Wasn't this the whole point of what Drummond called "literal contexts"? >>>>> >>>>> Markus >>>>> >>>>> On Thu, Mar 1, 2012 at 9:49 PM, Michael Schwartz <mike@gluu.org> wrote: >>>>> >>>>> >>>>> XDI TC: >>>>>> >>>>>> I'm attaching a proposal to represent binary literal values as "!!" >>>>>> >>>>>> So, for example, the XRI for a my company's logo might be : >>>>>> @!1111*logo!! >>>>>> >>>>>> The fact that the image is a binary can't be represented in the >>>>>> metadata, because it is not known which will be loaded first, the >>>>>> literal node, or the metadata about the literal node. >>>>>> >>>>>> This is a critical issue to optimize persistence of binary >>>>>> objects, which need to be indexed differently. >>>>>> >>>>>> I'd like to fast track this because we need to store binaries as >>>>>> part of the oxPlus demo :) >>>>>> >>>>>> Thoughts? >>>>>> >>>>>> thx, >>>>>> >>>>>> - Mike >>>>>> >>>>>> >>>>>> ------------------------------****----------------------------**- >>>>>> -** >>>>>> --------- >>>>>> To unsubscribe, e-mail: >>>>>> xdi-unsubscribe@lists.oasis-****open.org<http://open.org> >>>>>> <xdi-unsubscribe@**lists.oasis-open.org<xdi-unsubscribe@lists.oas >>>>>> is-open.org> >>>>>>> >>>>>> >>>>>> For additional commands, e-mail: xdi-help@lists.oasis-open.org >>>>>> >>>>>> >>>>>> >>>>> ------------------------------****----------------------------** >>>> --**--------- >>>> To unsubscribe, e-mail: >>>> xdi-unsubscribe@lists.oasis-****open.org<http://open.org> >>>> <xdi-unsubscribe@**lists.oasis-open.org<xdi-unsubscribe@lists.oasis >>>> -open.org> >>>>> >>>> >>>> For additional commands, e-mail: xdi-help@lists.oasis-open.org >>>> >>>> >>>> >>> >> ------------------------------**------------------------------**----- >> ---- To unsubscribe, e-mail: >> xdi-unsubscribe@lists.oasis-**open.org<xdi-unsubscribe@lists.oasis-op >> en.org> For additional commands, e-mail: >> xdi-help@lists.oasis-open.org >> >> > --------------------------------------------------------------------- To unsubscribe, e-mail: xdi-unsubscribe@lists.oasis-open.org For additional commands, e-mail: xdi-help@lists.oasis-open.org
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