- From: Steve Harris <steve.harris@garlik.com>
- Date: Thu, 10 May 2012 07:23:22 -0700
- To: Ivan Herman <ivan@w3.org>
- Cc: Richard Cyganiak <richard@cyganiak.de>, RDF Working Group WG <public-rdf-wg@w3.org>
I'm unsure about what the usecase is for (semi-)canonicalised equality. Can someone give me an example? Without that it's hard to know if we should be trying for full C14N, lexical comparison, or something in between. - Steve On 10 May 2012, at 01:28, Ivan Herman wrote: > Richard, > > I think this is the right approach, and I am in favour of doing it. However... > > http://www.w3.org/TR/html5/the-end.html#serializing-html-fragments > > does not seem to be 100% canonicalization algorithm. What I see right away is that it does not say anything about the order in which attributes should appear in the element (C14N requires them to be in alphabetical order). I have not checked all the details but that is enough to say that the canonical forms would not be enough to make a string comparison for equality. If so, what is the purpose of having it? > > Because, at the moment, I do not know of any work happening in HTML5 land in direction of HTML5 signature, I do not see that the concern of exact canonicalization will be on the agenda for the months/years to come. As a consequence, I would propose not to define any canonical form at all in this case, maybe adding a note that when that issue will be solved by the HTML5 community then this datatype might adopt that. > > Ivan > > > On May 10, 2012, at 02:32 , Richard Cyganiak wrote: > >> See below for a proposal for an HTML datatype. The lexical space is all Unicode strings (HTML5 explains how to parse any gunk into a DOM tree). The value space is normalized DOM DocumentFragments, like in the new rdf:XMLLiteral. The L2V mapping is HTML5's “fragment parsing algorithm”. The canonical mapping (from values to canonical lexical forms) is HTML5's “fragment serialization algorithm”. >> >> Like the new rdf:XMLLiteral (and all other datatypes), this datatype is entirely optional. >> >> Best, >> Richard >> >> >> == The rdf:HTML Datatype == >> >> RDF provides for HTML content as a possible literal value. This allows markup in literal values. Such content is indicated in an RDF graph using a literal whose datatype is a special built-in datatype rdf:HTML. >> >> rdf:HTML is defined as follows. >> >> === An IRI denoting this datatype === >> is http://www.w3.org/1999/02/22-rdf-syntax-ns#HTML. >> >> === The lexical space === >> is the set of Unicode strings. >> >> === The value space === >> is a set of DOM DocumentFragment nodes [DOM4:1]. Two DocumentFragment nodes A and B are considered equal if and only if the DOM method A.isEqualNode(B) [DOM4:2] returns true. >> >> === The lexical-to-value mapping === >> is defined as: >> >> 1. Let domnodes be the list of DOM nodes [DOM4:3] that result from applying the HTML fragment parsing algorithm [HTML5:1] to the literal's lexical form, without a context element. >> 2. Let domfrag be a DOM DocumentFragment [DOM4:1] whose childNodes attribute is equal to domnodes >> 3. Return domfrag.normalize() [DOM4:4] >> >> === The canonical mapping === >> defines a canonical lexical form [XMLSCHEMA11-2:1] for each member of the value space. The rdf:HTML canonical mapping is the HTML fragment serialization algorithm [HTML5:2]. >> >> NOTE: Any language annotation desired in the HTML content must be included explicitly in the HTML literal (@lang="…"). >> >> NOTE: RDF applications may use additional equivalence relations, such as that which relates an xsd:string with an rdf:HTMLLiteral corresponding to a single text node of the same string. >> >> == References == >> [DOM4:1] http://www.w3.org/TR/dom/#interface-documentfragment >> [DOM4:2] http://www.w3.org/TR/dom/#dom-node-isequalnode >> [DOM4:3] http://www.w3.org/TR/dom/#node >> [HTML5:1] http://www.w3.org/TR/html5/the-end.html#parsing-html-fragments >> [DOM4:4] http://www.w3.org/TR/dom/#dom-node-normalize >> [HTML5:2] http://www.w3.org/TR/html5/the-end.html#serializing-html-fragments >> [XMLSCHEMA11-2:1] http://www.w3.org/TR/xmlschema11-2/#dt-canonical-mapping > > > ---- > Ivan Herman, W3C Semantic Web Activity Lead > Home: http://www.w3.org/People/Ivan/ > mobile: +31-641044153 > FOAF: http://www.ivan-herman.net/foaf.rdf > > > > > > -- Steve Harris, CTO Garlik, a part of Experian 1-3 Halford Road, Richmond, TW10 6AW, UK +44 20 8439 8203 http://www.garlik.com/ Registered in England and Wales 653331 VAT # 887 1335 93 Registered office: Landmark House, Experian Way, NG2 Business Park, Nottingham, Nottinghamshire, England NG80 1ZZ
Received on Thursday, 10 May 2012 14:23:56 UTC