<XML/> without the X
The return of {{Textual}} markup

Dave Beckett
www.dajobe.org
Yahoo! Inc.

This talk is personal opinion. I am not speaking on behalf of Yahoo!

Slides presented using Slidy by Dave Raggett

Overview

Textual Formats

Textual Formats are

Markup that is
NOT (SGML, HTML or XML markup)

Early Web was built on Text

† (yes some binary formats and protocols still exist in such things as X.509 certificates, but they remain horrible)

Two Types of Web Markup

  1. Presentational Markup
  2. Descriptive or Semantic Markup

XML is...

  1. a web data format
  2. a web document markup format
    ... sort of, if you ignore that most of the web is HTML Tag Soup
  3. a protocol when XML documents are exchanged over a network

let's concentrate on #1

XML for Web Data

XML Rocks

XML Sucks

Goals of Textual Formats

  1. Human readable and human writable
  2. Simple

These are very different from the requirements for XML.

Applications of Web Textual Formats

Main Uses of Web Textual Formats in 2007

Supporting Rich Web Applications
Asynchronous, continuous connections
Small data packets
Between browser client and website HTTP server
Providing Data for HTTP Web Services
Enabling (lowercase) web services: not WS-deathstar
GETting data

Trends in Use of Textual Formats

When Textual Formats Go Bad

When Textual Formats Go Bad: Unicode

XML always had this and requires support for it.

When Textual Formats Go Bad: Extension Mechanisms

Extending a format includes:

Textual formats

XML's X is eXtensible and it has attributes, elements and namespaces. must ignore also often used (outside XML formats based on validation).

When Textual Formats Go Bad: Proliferation of similar alternatives

At least there is only one XML†

† (ignoring XML 1.1 which has little traction)

When Textual Formats Go Bad: Used beyond their sweet spot

The sweet spot for JSON is serializing simple data structures for transfer between programming languages. If you need more complex data structures (maybe with some kind of schema for validation), use XML
Simon Willison, http://simonwillison.net/2006/Dec/20/json/

When Textual Formats Go Bad: ESPECTOOLARGE

$ lynx -dump http://yaml.org/spec/current.html | wc -w
30862
$ lynx -dump http://www.w3.org/TR/REC-xml/ | wc -w
19526
$ lynx -dump http://www.w3.org/TR/REC-xml-names/ | wc -w
3955

When Textual Formats Go Bad: Not thinking big

Often missing the technology needed for bigger projects and problems:

XML has a mature namespaces specification, must ignore and inclusion mechanisms.

When Textual Formats Go Bad: Validation

XML has many choices here such as none, DTD, WXS, RelaxNG, ... to declare constraints and to share them.

When Textual Formats Go Bad: Tools

Some of the textual formats can be baroque to deal with
Complex syntax detail and whitespace rules (YAML, Wiki, iCalendar, vCard, programming languages)
Each format needs its own tools
For example there are no JSON databases, standard JSON query languages, out of the box JSON APIs in standard SDKs for all major programming languages and operating systems.
If they even exist, they are all add-ons.

XML is a single common format and for tool support beats all textual format tools combined. It's syntax detail is widely implemented.

When Textual Formats Go Bad: Performance: Speed and Size

When Textual Formats Go Bad: Whitespace with semantics

<rant>What is this, the 1950s when where you punched a hole in a card at a column number mattered? </rant>

Culprits: make(1), YAML, Ruby, Python, FORTRAN 77

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
d e f   l e p p a r d ( y e a r ) :
    i f   y e a r   = =   2 0 0 7 :
        p r i n t   " t h i s   i s  s i l l y "

Case Study 1: The Turtle RDF syntax

Main RDF Syntaxes

RDF Syntax: a way to write the RDF triples data model

RDF/XML: W3C Recommended XML syntax
OK for computers but has it's own pros and cons.
See several other talks
N-Triples: simplest textual format for RDF
Parsimonious but verbosius: 
<http://www.dajobe.org/foaf.rdf#i> <http://xmlns.com/foaf/0.1/homepage> <http://www.dajobe.org/> .
Still used in tests for OWL, SPARQL, GRDDL, ...
Definitive but very verbose way to write down any RDF

RDF Syntaxes Timeline

Turtle – the Terse RDF Triple Language

N-Triples is too verbose for humans, so extend it but:

  1. Add to the syntax only what was useful for people
  2. Remain within the RDF data model
  3. Only add abbreviations to:
    1. reduce verbosity
    2. remove duplication
    3. add convenience

Giving N-Triples+ or Turtle – the Terse RDF Triple Language

Turtle Abbreviations 1

  1. Prefixed names (Verbosity) to make the URIs shorter 
    <http://www.dajobe.org/foaf.rdf#i> foaf:homepage <http://www.dajobe.org/> .
  2. Allow relative URIs (Verbosity) 
    <#i> foaf:homepage </> .
  3. Abbreviate repeated triple subjects (Verbosity, Duplication) 
    <#i> foaf:homepage </> ;
     foaf:name "Dave Beckett" .
  4. Abbreviate repeated triple subjects and predicates (Verbosity, Duplication) 
    <#i>
  foaf:homepage </> ;
  foaf:name "Dave Beckett" ,
            "David Beckett" .

Turtle Abbreviations 2

  1. Blank Nodes (Duplication) 
    <#i>
  foaf:knows [
    a foaf:Person;
    foaf:name "Edd Dumbill";
  ]
  2. RDF Collections (Verbosity, Convenience) 
    <#i>
  tenthings:ihateaboutyou (
    "I hate the way you talk to me, and the way you cut your hair."
    "I hate the way you drive my car."
    "I hate it when you stare."
    # 7 more
   ) .
  3. Common Data Types and Predicates (Convenience)
  4. Long strings (Convenience) allow """-multi-line quoting

Turtle: Summary

i.e. It is time to standardise this.

Case Study 2: Designing a new textual format: RDF-JSON

RDF-JSON

Purpose: to better enable rich web applications using RDF

RDF-JSON - Triples-Centric Style

(based on the SPARQL Serializing SPARQL Query Results in JSON, W3C WG Note, 2006-10-04)

{
  "subject" : {
    "value" : "http://www.dajobe.org/foaf.rdf#i",
    "type" : "uri"
  },
  "predicate" : {
     "value" : "http://xmlns.com/foaf/0.1/homepage",
     "type" : "uri"
   },
   "object" : {
     "value" : "http://www.dajobe.org/",
     "type" : "uri"
   }
}

Boy, that's pretty verbose. It's N-Triples again!

RDF-JSON - Resource Centric

{
  "prefixes" : {
    "rdf" : "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "foaf" : "http://xmlns.com/foaf/0.1/",
    ...
  },

  "http://www.dajobe.org/foaf.rdf#i" : {
    "rdf:type" : [ { "value" : "http://xmlns.com/foaf/0.1/Person", "type" : "uri" } ] ,
    "foaf:homepage" : [ { "value" : "http://www.dajobe.org/", "type" : "uri" } ] ,
    "foaf:name" : [ { "value" : "Dave Beckett", "type" : "literal" } ],
    ...
  },

Actually this looks more like Turtle or RDF/XML

RDF-JSON - Exhibit Style

{
  "items" : [
    {
      "label" : "i",
      "name"  : "Dave Beckett",
      ...
    }
  ],
  "types" : {
    "Person" : {
      "uri" : "http://xmlns.com/foaf/0.1/Person"
    }
  },
  "properties" : {
    "name" : {
      "uri"       : "http://xmlns.com/foaf/0.1/name",
      "valueType" : "item"
    },
    ...
  }
}

Plug: For more on Exhibit see XML-powered Exhibit: A Case Study of JSON & XML Coexistence by Chimezie Ogbuji of Cleveland Clinic Foundation at 16:00 TODAY in the Applications track.

RDF-JSON - Choices

Clearly more work needs to be done here

Conclusions

Thanks

Questions?

Slides (to appear at):
http://www.dajobe.org/talks/200705-textual/

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