Hello Dave, What pressure is there for core to constrain the use of rdf literals typed as xmlliteral?
I'd prefer to leave any such constraints to the domain specs Regards -ian ----- Original Message ----- From: Dave [[email protected]] Sent: 19/03/2010 13:26 AST To: [email protected] Subject: Re: [oslc-core] Need for an XML literal value type Arthur, thanks for your patience and good answers. I think I'm convinced. I do have a couple more questions for the WG: - Should we offer any guidance to folks who wish to store HTML5 or HTML 4.0.1 content as a property value? - Instead of an "XML Literal" value-type, what if we allowed only "XHTML Literal"? -- thus allowing literal XML only for rich text. Thanks, - Dave On Fri, Mar 19, 2010 at 12:30 PM, Arthur Ryman <[email protected]> wrote: > Dave, > > The data model that OSLC is adopting is RDF. We therefore need to define > how to represent RDF in various formats. There are some native RDF > formats, like N3 and Turtle - no problem there. For putting RDF in XML we > use RDF/XML which is just as much a standard as RDF itself. > > In RDF/XML, the way you include XML literal values is via the attribute > rdf:parseType="Literal" [1]. RDF defines a datatype for literal XML [2]. > This lets us put the angle brackets etc. in the RDF/XML document, and the > result is a well-formed XML document which is also RDF/XML valid, and we > can process the literal XML normally. > > When we define how to represent RDF as JSON, we need to define how to > represent the literal values. An XML literal would be encoded in JSON as a > string, but that string would be valid XML. What problem do you see in > having a JSON value that contains a valid XML string? > > Your proposal to use xsd:string for literal XML would require us to escape > all the parser-significant XML characters, which hides the fact that the > content is XML and defeats processing by standard XML tools (e.g XSLT) and > would make integration with other RDF data problematic, i.e. how would > other applications know that xsd:string values needs to be unescaped? How > would we distinguish strings that were plain text (and might contain angle > brackets) from text that was really esacped XML? > > The background for rich text is that many tools allow users to enter rich > text and include that in their resource representations. This is > especially important for Requirements tools where people do spend effort > to highlight text, e.g. in red, to indicate some semantics. The place > XHTML comes in is as an interchange format, i.e. OSLC resource should use > XHTML for rich text. Each tool must convert it's native format to XHTML > for purposes of interchange via OSLC resources. Uses would not type in > XHTML directly. They would use editors provided by the tools, and the > tools would convert it to XHTML for interchange. > > In the specific cases of dc:title and dc:description, we should use <span> > and <div> content respectively. A JSON client that received these literal > values can simply set or get this as DOM element content via the > innerHTML property. > > I'd be happy to have a telecon with you to discuss this further. > > [1] http://www.w3.org/TR/REC-rdf-syntax/#section-Syntax-XML-literals > [2] > http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#dfn-rdf-XMLLiteral > > Regards, > ___________________________________________________________________________ > > Arthur Ryman, PhD, DE > > > Chief Architect, Project and Portfolio Management > > IBM Software, Rational > > Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063 > Twitter | Facebook | YouTube > > > > > > > > From: > Dave <[email protected]> > To: > Arthur Ryman/Toronto/IBM@IBMCA > Date: > 03/19/2010 09:53 AM > Subject: > Re: [oslc-core] Need for an XML literal value type > > > > On Thu, Mar 18, 2010 at 10:40 PM, Arthur Ryman <[email protected]> wrote: >> Please explain why you are concerned. Literal XML is a standard feature > of RDF. > > Thanks for the helpful explanations, Steve, Ian and Arthur. > > I guess I still don't understand the need for XML literal in OSLC. > XHTML can be stored as a string -- so, what are the advantages of > storing it as literal XML? What specifically does XML literal buy us > over using a simple string? > > I'm concerned here because I'd like to see non-XML representations on > equal footing and I'd like to encourage folks to express things as > property values and not as XML constructs. Allowing literal XML could > open the door to XML content in places other than this XHTML case and > that could be an issue for JavaScript developers expecting JSON and > not wanting to ever have to parse XML. > > I also had concerns about embedding XML in property values because it > would result in invalid RDF/XML, but apparently the parse-type literal > makes this possible. Ian Green's comments seem to contradict this. Do > we have a definitive answer here? > > Thanks, > - Dave > > >> >> The pro for XML literal values is that we are using RDF in the way it > was >> designed. OSLC data may be combined with RDF data from other sources so > we >> should adhere to the standard. We do not want to create an OSLC dialect > of >> RDF. >> >> For rich text, we should adopt XHTML as the standard interchange format, >> and we should transfer it in RDF/XML as literal XML, not obfuscate it by >> turning it into a string. >> >> Many development tools capture rich text. Adopting a standard rich text >> format for OSLC, i.e. XHTML, simplifies processing (e.g. inclusion of > rich >> text in UIs, documents and reports) and interchange (so tools only have > to >> understand one format as opposed to understand RTF, HTML, etc.). XHTML > has >> a simpler syntax than HTML and is XML compliant so it can be readily >> processed by many XML technologies. >> >> In addition, there are other good reasons for using XML in general as > the >> value of a property, e.g. when there is an existing XML format, or when >> plain old XML is a more natural way to represent a literal value >> (otherwise you get an explosion of blank nodes). >> >> Regards, >> > ___________________________________________________________________________ >> >> Arthur Ryman, PhD, DE >> >> >> Chief Architect, Project and Portfolio Management >> >> IBM Software, Rational >> >> Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063 >> Twitter | Facebook | YouTube >> >> >> >> >> >> >> >> From: >> Dave <[email protected]> >> To: >> [email protected] >> Date: >> 03/18/2010 09:26 AM >> Subject: >> [oslc-core] Need for an XML literal value type >> Sent by: >> [email protected] >> >> >> >> I'm still a little concerned about adding XML literal as a value type >> and I'm trying to understand the pros and cons. The only justification >> that we have so far for adding an XML literal value is for storing >> XHTML data, which we need for rich text, but we can easily store XHTML >> data as a string. >> >> What specifically do we gain by putting XHTML content in-line in our >> RDF/XML and Atom XML representations? >> >> And conversely, what do we lose by not doing so? >> >> Also, does putting XHTML content in-line in RDF/XML result in valid >> RDF/XML? >> >> Thanks, >> - Dave >> >> _______________________________________________ >> Oslc-Core mailing list >> [email protected] >> http://open-services.net/mailman/listinfo/oslc-core_open-services.net >> >> >> >> > > > > _______________________________________________ Oslc-Core mailing list [email protected] http://open-services.net/mailman/listinfo/oslc-core_open-services.net
