Re: Questions regarding best practice: Use fragments as entity identifiers

Looks pretty good, have a couple of suggestions below...

- Steve Speicher


On Sat, Aug 17, 2013 at 12:46 PM, Ashok Malhotra
<ashok.malhotra@oracle.com>wrote:

>  Cody:
> I took a crack at rewriting paras 3, 4 and 5
>
> I think we need to make explicit the relationship of the fragments to the
> main document.
>
> -------------------------------------------------
>
> In expressing Linked Data Platform Resources in RDF, fragments are useful
> because they can be expressed as relative URIs on the document describing
> them. This is particularly handy for describing resources that are
> sub-resources of the same parent document.
>
I'm not sure we have a concept of sub-resources.  Perhaps it would best to
say something like "describing multiple LDPRs whose representations are
within a single document."

>  First, it provides the convenience and efficiency of brevity. Suppose,
> for example that you want to describe the resources foo, bar and baz which
> are contained in the same resource. Since serving all of the descriptions
> in a
>
What does "in the same resource" mean here?  I believe you mean either
"same RDF resource" or better perhaps "same document".


> single document is a acceptable, we can mint relative URIs within the
> document using the fragment identifier (<#foo>, <#bar> and <#baz>). The
> full URI is assumed to be the base URI, plus the hash mark, and the
> fragment identifier.
>
> Second, it can help avoid complexities inherent with other approaches.
> Achieving the same result  using
> three independent dereferenceable URIs could be more involved, because
> you'd need to create and publish multiple documents, perhaps also having to
> setup 303 redirects.
>
> All the best, Ashok
> On 8/16/2013 4:45 PM, Cody Burleson wrote:
>
> OK, guys, here's my crack at it. I'm not sure the value is as clearly
> stated as it can be, but... I kind of struggled with it.
>
> Please let me know if you think it can be improved:
>
> 2.6 Use fragments as object identifiers
>
> The fragment identifier introduced by a hash mark *#* is the optional
> last part of a URI for an object, which is typically used to identify a
> subordinate or related object.
>
> Take the URI, http://www.example.com/products#item10245, for example. The
> base URI is the part preceding the hash mark,
> http://www.example.com/products, and the fragment identifier is the part
> that follows, item10245.
>
> In the RDF expressing Linked Data Platform Resources, fragments are useful
> because they can be expressed as relative URIs on the document describing
> them. This is particularly handy for describing a handful of resources that
> are frequently used together.
>
> First, it provides the convenience and efficiency of brevity. Suppose, for
> example that you want to describe the resources foo, bar and baz. Since
> serving all of the descriptions in a single document is a acceptable, we
> can mint relative URIs within the document using the fragment identifier (
> <#foo>, <#bar> and <#baz>). The full URI is assumed to be the base URI,
> plus the hash mark, and the fragment identifier.
>
> Second, it can help avoid certain complexities inherent with other
> approaches. Achieving the same result (three dereferenceable URIs) could be
> more involved, because you'd need to create and publish multiple documents,
> perhaps also having to setup 303 redirects.
>
> *See also:*
>
> Cool URIs for the Semantic Web <http://www.w3.org/TR/cooluris>
>
>    - http://www.w3.org/TR/cooluris/#hashuri
>    - http://www.w3.org/TR/cooluris/#choosing
>
> Axioms of Web Architecture, URI References: Fragment Identifiers on URIs<http://www.w3.org/DesignIssues/Fragment.html>
> http://www.w3.org/DesignIssues/Fragment.html
>
> Dereferencing HTTP URIs<http://www.w3.org/2001/tag/doc/httpRange-14/2007-05-31/HttpRange-14>
> http://www.w3.org/2001/tag/doc/httpRange-14/2007-05-31/HttpRange-14
>
>
>
> On Wed, Aug 14, 2013 at 6:47 PM, Richard Cyganiak <richard@cyganiak.de>wrote:
>
>> On 14 Aug 2013, at 23:39, Cody Burleson wrote:
>>
>> > Team,
>> >
>> > I could use a little help fleshing out a spot in the LDP Best Practices
>> and Guidelines.
>> >
>> > One of the recommendations in the Deployment Guide was written in the
>> wiki as follows:
>> >
>> > ---
>> > Use fragments as entity identifiers
>> >
>> > Fragments are nice because they can be expressed as relative URIs on
>> the document describing them.
>> > ---
>> >
>> > I'm not sure who first wrote that, but if you could provide me with
>> more detail, it would be helpful. Or anybody, for that matter.
>>
>>  It may have been me.
>>
>> Scenario:
>>
>> - You want to describe a number of resources (say: foo, bar and baz)
>> - You need to mint URIs for these resources
>> - Putting all the descriptions into a single document (say: <
>> http://example.com/stuff.ttl>) is acceptable
>>
>> Then minting hash URIs is a very convenient approach. Simply use <#foo>,
>> <#bar> and <#baz>. The result are nice dereferenceable URIs, <
>> http://example.com/stuff.ttl#foo> and so on.
>>
>> Thanks to the logic of URI resolution, the simple local identifier <#foo>
>> gets turned into a globally unique ID. It becomes globally unique by being
>> qualified with the URI of the document it is used in.
>>
>> With other approaches, achieving the same result (three dereferenceable
>> URIs) would probably be more involved, because you'd need to create and
>> publish multiple documents, perhaps set up 303 redirects and whatnot.
>>
>> The sweet spot for this approach is for a handful of resources that
>> frequently are used together. That's why most RDFS vocabularies and OWL
>> ontologies use this approach.
>>
>> Relevant W3C references:
>> http://www.w3.org/TR/cooluris/#hashuri
>> http://www.w3.org/TR/cooluris/#choosing
>>
>> Best,
>> Richard
>>
>>
>> >
>> > I understand the use of fragments in RDF. It's how I define properties
>> on an Instance in OWL, for example. If I have a representation of a Person
>> (Instance of Person), the fragment #hasName represents the hasName property
>> of that Person which may or may not be defined in the same RDF document.
>> >
>> > But is it really a Best Practice? Or simply a Guideline? There is some
>> somewhat confusing debate on the web.
>> >
>> > Also, can you represent why it is a useful practice using an example
>> representation of a resource?
>> >
>> > What do you think we really need to say here to make this point a
>> little more meaningful?
>> >
>> >
>> >
>> > --
>> > Cody Burleson
>> >
>>
>>
>
>
> --
> Cody Burleson
> Enterprise Web Architect, Base22
> Mobile: +1 (214) 537-8782
> Skype: codyburleson
> Email: cody@base22.com
> Blog: codyburleson.com
>
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