Welcome!

Related Topics: Industrial IoT, Microservices Expo

Industrial IoT: Article

Index XML Documents with VTD-XML

How to turn the indexing capability on in your application

VTD+XML in 30 Seconds
Allowing XML parsing to be decoupled from application logic, the key in the example above is the index file "po.vxl," which conforms to the VTD+XML spec. What is VTD+XML? Since VTD-XML's internal representation of XML infoset is inherently persistent, VTD+XML, as the name suggests, is simply the binary packaging format that combines VTD records, LCs entries, and XML into a single file. The detailed technical spec can be found at http://vtd-xml.sourceforge.net/persistence.html.

A Simple Example
This section gets down to the nitty-gritty of the specification by manually composing, byte-by-byte, a VTD+XML index. For the sake of simplicity, this example chooses to index a simple XML document containing a single child-less root element whose parsed representation doesn't have location cache entries. This example also assumes a big-endian byte order (as in Java) and UTF-8 document encoding (the default character set). The name space awareness is set to false.

<root/>

The first four-byte word of the corresponding index file is 0x0102A000 containing:

  • The VTD+XML version number (0x01) in the first byte
  • The character encoding format (0x02) in the second byte (Jimmy1)
  • The name space awareness, word length of LC entries in the last level, byte endian-ness of the platform, and VTD version as encoded in various bit fields in the third byte (0xA0)(Jimmy2)
  • The document depth (0x0 as the root element has no child)(Jimmy3)

    The second four-byte word has the value of 0x00040001 containing:

  • The number of LC levels supported by the VTD-XML implementation in the upper 16 bits (0x0004 in big endian)(Jimmy4)
  • The root element index value in the lower 16 bits (0x0001 in big endian)(Jimmy5)
The next four four-byte words are reserved and set to zero.
The byte order of all the ensuing 32-bit or 64-bit words is platform-dependent and specified in the third byte of the VTD+XML spec. The next eight-byte words indicate the size (in bytes) of the XML document, which equals seven in this example. Immediately following (0x3C726F6F742F3E00) is the byte content of the XML rounded up to an integer multiple of eight bytes by padding zero to the end.

The remaining part of VTD+XML index consists of multiple adjacent segments each containing an eight-byte word (0x0000000000000002 indicating the VTD record or LC entry count) followed by the actual content of the VTD records or LC entries. The first eight-byte word (0x000000000000000002) indicates that there are two VTD records that are 0xDFF0000000000000 and 0x0000000400000001.

The remaining three eight-byte words all have the value of zero indicating that the location caches in level one, two, and three have zero entry in the VTD+XML index.

As the final output, the VTD+XML index for "<root/>" is 88-bytes long and looks like the following hex:

0x0102A00000040001 0x0000000000000000
0x0000000000000000 0x0000000000000007
0x3C726F6F742F3E00 0x0000000000000002
0xDFF0000000000000 0x0000000400000001
0x0000000000000000 0x0000000000000000
0x0000000000000000

Benefits and Limitations
Because VTD+XML straightforwardly combines VTD and XML, it inherits all the benefits of VTD-XML parsing. When compared with existing XML indices (e.g., various pure-binary XML indices modeling labeled, ordered tree etc.), VTD+XML possesses many unique technical benefits:

•  General Purpose - Before VTD+XML, most native XML indices only optimize specific types (e.g., the axis) of Xpath lookups. If an input query differs slightly from the index type, the query execution still has to resort to expensive parsing. Due to this limitation, many native XML databases today require users to create multiple indices, one for each input query type so users can benefit from those indices. The problem is that XML database applications usually serve many types of queries that are unpredictable and complex in nature, often rendering the benefits of indexing insignificant. In comparison, VTD+XML is the first index that completely eliminates the cost of XML parsing and predictably speeds up any type of XPath query. It also works with namespaces exceptionally well.
•  Human Readable - VTD+XML is also the first human-readable XML index. You can actually open it in a text editor to examine the XML text. Figure 1 is what "po.vxl" looks like in "vim." More than just a nice property, VTD+XML's human-readability offers distinct advantages over pure binary indexing schemes. Everything else being equal, keeping XML in its original format avoids the processing cost of converting to and from any binary formats. Moreover, what if your applications just wants to modify the XML payload, such as inserting into it a chunk of XML text extracted out of another SOAP message? What's the point of converting XML to binary formats? In a service-oriented heterogeneous environment, maintaining XML in its original format automatically retains the openness and interoperability. It just seems to me that the only loss-less equivalent of XML is XML itself, no less.


  • More Stories By Jimmy Zhang

    Jimmy Zhang is a cofounder of XimpleWare, a provider of high performance XML processing solutions. He has working experience in the fields of electronic design automation and Voice over IP for a number of Silicon Valley high-tech companies. He holds both a BS and MS from the department of EECS from U.C. Berkeley.

    Comments (0)

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    Latest Stories
    This session will provide an introduction to Cloud driven quality and transformation and highlight the key features that comprise it. A perspective on the cloud transformation lifecycle, transformation levers, and transformation framework will be shared. At Cognizant, we have developed a transformation strategy to enable the migration of business critical workloads to cloud environments. The strategy encompasses a set of transformation levers across the cloud transformation lifecycle to enhance ...
    Your job is mostly boring. Many of the IT operations tasks you perform on a day-to-day basis are repetitive and dull. Utilizing automation can improve your work life, automating away the drudgery and embracing the passion for technology that got you started in the first place. In this presentation, I'll talk about what automation is, and how to approach implementing it in the context of IT Operations. Ned will discuss keys to success in the long term and include practical real-world examples. Ge...
    The challenges of aggregating data from consumer-oriented devices, such as wearable technologies and smart thermostats, are fairly well-understood. However, there are a new set of challenges for IoT devices that generate megabytes or gigabytes of data per second. Certainly, the infrastructure will have to change, as those volumes of data will likely overwhelm the available bandwidth for aggregating the data into a central repository. Ochandarena discusses a whole new way to think about your next...
    So the dumpster is on fire. Again. The site's down. Your boss's face is an ever-deepening purple. And you begin debating whether you should join the #incident channel or call an ambulance to deal with his impending stroke. Yes, we know this is a developer's fault. There's plenty of time for blame later. Postmortems have a macabre name because they were once intended to be Viking-like funerals for someone's job. But we're civilized now. Sort of. So we call them post-incident reviews. Fires are ne...
    Whenever a new technology hits the high points of hype, everyone starts talking about it like it will solve all their business problems. Blockchain is one of those technologies. According to Gartner's latest report on the hype cycle of emerging technologies, blockchain has just passed the peak of their hype cycle curve. If you read the news articles about it, one would think it has taken over the technology world. No disruptive technology is without its challenges and potential impediments t...
    Hackers took three days to identify and exploit a known vulnerability in Equifax’s web applications. I will share new data that reveals why three days (at most) is the new normal for DevSecOps teams to move new business /security requirements from design into production. This session aims to enlighten DevOps teams, security and development professionals by sharing results from the 4th annual State of the Software Supply Chain Report -- a blend of public and proprietary data with expert researc...
    CloudEXPO New York 2018, colocated with DevOpsSUMMIT and DXWorldEXPO New York 2018 will be held November 12-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI and Machine Learning to one location.
    CloudEXPO | DevOpsSUMMIT | DXWorldEXPO are the world's most influential, independent events where Cloud Computing was coined and where technology buyers and vendors meet to experience and discuss the big picture of Digital Transformation and all of the strategies, tactics, and tools they need to realize their goals. Sponsors of DXWorldEXPO | CloudEXPO benefit from unmatched branding, profile building and lead generation opportunities.
    DXWorldEXPO LLC announced today that Nutanix has been named "Platinum Sponsor" of CloudEXPO | DevOpsSUMMIT | DXWorldEXPO New York, which will take place November 12-13, 2018 in New York City. Nutanix makes infrastructure invisible, elevating IT to focus on the applications and services that power their business. The Nutanix Enterprise Cloud Platform blends web-scale engineering and consumer-grade design to natively converge server, storage, virtualization and networking into a resilient, softwar...
    The digital transformation is real! To adapt, IT professionals need to transform their own skillset to become more multi-dimensional by gaining both depth and breadth of a wide variety of knowledge and competencies. Historically, while IT has been built on a foundation of specialty (or "I" shaped) silos, the DevOps principle of "shifting left" is opening up opportunities for developers, operational staff, security and others to grow their skills portfolio, advance their careers and become "T"-sh...
    Lori MacVittie is a subject matter expert on emerging technology responsible for outbound evangelism across F5's entire product suite. MacVittie has extensive development and technical architecture experience in both high-tech and enterprise organizations, in addition to network and systems administration expertise. Prior to joining F5, MacVittie was an award-winning technology editor at Network Computing Magazine where she evaluated and tested application-focused technologies including app secu...
    DXWorldEXPO LLC announced today that Big Data Federation to Exhibit at the 22nd International CloudEXPO, colocated with DevOpsSUMMIT and DXWorldEXPO, November 12-13, 2018 in New York City. Big Data Federation, Inc. develops and applies artificial intelligence to predict financial and economic events that matter. The company uncovers patterns and precise drivers of performance and outcomes with the aid of machine-learning algorithms, big data, and fundamental analysis. Their products are deployed...
    ICC is a computer systems integrator and server manufacturing company focused on developing products and product appliances to meet a wide range of computational needs for many industries. Their solutions provide benefits across many environments, such as datacenter deployment, HPC, workstations, storage networks and standalone server installations. ICC has been in business for over 23 years and their phenomenal range of clients include multinational corporations, universities, and small busines...
    This sixteen (16) hour course provides an introduction to DevOps, the cultural and professional movement that stresses communication, collaboration, integration and automation in order to improve the flow of work between software developers and IT operations professionals. Improved workflows will result in an improved ability to design, develop, deploy and operate software and services faster.
    Headquartered in Plainsboro, NJ, Synametrics Technologies has provided IT professionals and computer systems developers since 1997. Based on the success of their initial product offerings (WinSQL and DeltaCopy), the company continues to create and hone innovative products that help its customers get more from their computer applications, databases and infrastructure. To date, over one million users around the world have chosen Synametrics solutions to help power their accelerated business or per...