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XML 2007: Year in Review
Elliotte Rusty Harold, IBM developerWorks
2007 was a productive year for XML. The most sound and fury focused around the standardization of office document formats, a fight that even spilled over into the popular press. Who ever thought you'd be reading about ISO standards for XML formats in the Wall Street Journal? But if I had to pick the most important story of the year, I'd be hard pressed to choose between the continuing slow growth of XQuery, APP (Atom Publishing Protocol), and XForms. All have the potential to radically alter the software infrastructure that underlies the Web. XForms is a radically new client-development platform, XQuery is a radically new server-development platform, and APP connects them together. Of the three, XQuery is ready for serious production use today, and APP is gearing up. Atom Publishing Protocol (APP) began its life as a simple format for uploading blog entries to replace custom APIs like the MetaWeblog and WordPress APIs. But along the way, it turned into something much, much more. APP is nothing less than a RESTful, scalable, extensible, secure system for publishing content to HTTP servers. On one hand, it's a pure protocol, completely independent of any particular server or client. On the other hand, because it's nothing more than HTTP, it's easy to implement in existing clients and servers. The Web was originally intended to be a read-write medium. But for the first 15 years, most energy went into the reading half of that equation. Browsers got all the attention, while authoring tools withered on the vine. Page editors were generally poor and forced to tunnel through FTP to file systems. Only now, with APP, is the field opening up to editors that are as rich, powerful, and easy to use as the browsers. Some good server software, such as the eXist native XML database, has already started to take advantage of APP, and several clients are working on it. More will do so over the coming year. Publishing on the Web will finally become as straightforward as browsing it... XForms is running behind and may be a little late to the party, but I hope it gets there before the doors close. Either way, the future for XML on the Web looks brighter than ever.
See also: Atom references
Does XML Have a Future on the Web?
Michael Sperberg-McQueen, Messages in a Bottle
Earlier this month, the opening session of the XML 2007 conference was devoted to a panel session on the topic 'Does XML have a future on the Web?' [...] A lot depends on what we mean by 'the Web'. If we mean Web 2.0 Ajax applications, we may get one answer. If we mean the universe of data publicly accessible through HTTP, the answer might be different. But neither of these, in reality, is 'the Web'. If there is a single central idea of the Web, it's that of a single connected information space that contains all the information we might want to link to—that means, in practice, all the information we care about (or might come to care about in future): not just publicly available resources, but also resources behind my enterprise firewall, or on my personal hard disk. If there is a single technical idea at the center of the Web, it's not HTTP (important though it is) but the idea of the Uniform Resource Identifier, a single identifier space with distributed responsibility and authority, in which anyone can name things they care about, and use their own names or names provided by others, without fear of name collisions. Looked at in this way, 'the Web' becomes a rough synonym for 'data we care about', or 'the data we process, store, or manage using information technology'... There were something like two hundred people actively involved in the original design of XML, and among us I wouldn't be surprised to learn that we had a few hundred, or a few thousand, different goals for XML... One reason to think that XML has found broad uptake is the sheer variety of people complaining about XML and the contradictory nature of the problems they see and would like to fix. For some, XML is too complicated and they seek something simpler; for others, XML is too simple, and they want something that supports more complex structures than trees. Some would like less draconian error handling; others would like more restrictive schema languages. Any language that can accumulate so many different enemies, with such widely different complaints, must be doing something right. Long life to descriptive markup! Long life to XML!
See also: the XML 2007 Conference session
First Public Working Draft for Delivery Context Ontology Specification
Rhys Lewis (ed), W3C Technical Report
Members of the W3C Ubiquitous Web Applications Working Group (UWA) have published a First Public Working Draft for "Delivery Context Ontology" and a Candidate Recommendation for "Delivery Context: Client Interfaces (DCCI) 1.0—Accessing Static and Dynamic Delivery Context Properties." The UWA Working Group focuses on extending the Web to enable distributed applications of many kinds of devices including sensors and effectors. Application areas include home monitoring and control, home entertainment, office equipment, mobile and automotive. (1) The new "Delivery Context Ontology" document provides a formal model of the characteristics of the environment in which devices interact with the Web. The delivery context includes the characteristics of the device, the software used to access the Web and the network providing the connection among others. The delivery context is an important source of information that can be used to adapt materials from the Web to make them useable on a wide range of different devices with different capabilities. The ontology is formally specified in the Web Ontology Language (OWL). This document describes the ontology and gives details of each property that it contains. The core, normative sections of this document are generated automatically from the ontology itself. (2) Implementations are now invited in connection with the "Delivery Context: Client Interfaces (DCCI) 1.0" Candidate Recommendation specification. This document defines platform and language neutral programming interfaces that provide Web applications access to a hierarchy of dynamic properties representing device capabilities, configurations, user preferences and environmental conditions. The key uses for DCCI are related to adaptation. One major use is in supporting devices that are capable of interaction with users in a variety of modalities. For example, a device may be able to interact visually, or using voice, depending on the user's current context. Another major use for DCCI relates to content adaptation for device independence. Materials to be used on a particular device may need to be tailored to take account of that device's particular capabilities.
See also: the DCCI specification
Information Model and XML Data Model for Traceroute Measurements
S. Niccolini, S. Tartarelli, J. Quittek, M. Swany (eds), IETF Internet Draft
The IESG has received a request from the IP Performance Metrics Working Group (IPPM) to consider "Information Model and XML Data Model for Traceroute Measurements" as a Proposed Standard. The IESG plans to make a decision in the next few weeks, and solicits final comments on this action. Substantive comments should be sent to the IETF mailing lists by 2008-01-15. Traceroutes are being used by lots of measurement efforts, either as an independent measurement or to get path information to support other measurement efforts. That is why there is the need to standardize the way the configuration and the results of traceroute measurements are stored. The standard metrics defined by IPPM working group in matter of delay, connectivity and losses do not apply to the metrics returned by the traceroute tool; therefore, in order to compare results of traceroute measurements, the only possibility is to add to the stored results a specification of the operating system and version for the traceroute tool used. This document, in order to store results of traceroute measurements and allow comparison of them, defines a standard way to store them using a XML schema. Section 7 contains the XML schema to be used as a template for storing and/or exchanging traceroute measurements information. The schema was designed in order to use an extensible approach based on templates (similar to how IPFIX protocol is designed) where the traceroute configuration elements (both the requested parameters, Request, and the actual parameters used, MeasurementMetadata) are metadata to be referenced by results information elements (data) by means of the TestName element (used as unique identifier). Currently Open Grid Forum (OGF) is also using this approach and cross-requirements have been analyzed. As a result of this analysis the XML schema is compatible with OGF schema since it was designed in a way that both limits the unnecessary redundancy and a simple one-to-one transformation between the two exist.
See also: IETF IP Performance Metrics (IPPM) WG
XML Schemas: Guaranteed Non-Interoperability as a Design Methodology?
Rick Jelliffe, O'Reilly Blog
The vogue quip that 'a camel is a horse designed by committee' probably makes more sense to people who don't live in a desert country. From here in Australia, camels seem to a very plausible design. It is the speaker, actually, who is wrong: what you need is a camel when you are in the desrt, a horse on the planes, a yak in the mountains, perhaps a porpoise in the sea, and an elephant in the jungle. The ongoing XML Schemas trainwreck shows little sign of improvement; that users have so repetitively stated their problem and received no satisfaction from the W3C shows how disenfranchised they are. I am thinking about these things again this week for three reasons... One positive thing that has come out has been the W3C Basic XML Schemas Databinding Patterns which lists various XPaths that databinding tools can have. It mentions how to use these in Schematron, which is good too... But it doesn't come up to the level of a profile. And, to be fair, the W3C Schema WG has also upgraded XSD to reduce some gotchas that have been reported, such as allowing unbounded on all groups.
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