Click here to close now.


Industrial IoT Authors: Elizabeth White, Liz McMillan, Pat Romanski, Pete Waterhouse, Glenn Rossman

Related Topics: Industrial IoT

Industrial IoT: Article

Use a Native XML Database for Your XML Data

Deciding when an XQuery-based native XML database is better than an SQL database

Developers tend to use the most familiar technologies. For data storage, that is the relational database. During design it's easy to see tables of data everywhere; however, not everything is relational in nature. When dealing with XML data or data easily expressed as XML, XQuery-based native XML databases (NXDs) present a viable and cost-effective alternative to relational databases, file system storage, or custom developed storage implementations. So, when is it time to consider an NXD?

Can native XML databases really provide a better answer for your data storage needs? In this article we'll examine some guidelines to help answer that question.

When to Consider a Native XML Database

  1. Do you have thousands of XML files?
  2. Is your XML data larger than 200MB?
  3. Are you trying to build a hierarchy into tables?
  4. Could your data change over time?
  5. Have you spent more that $100 on books explaining SQLXML?
The File System Isn't a Database
The first two questions are practical in nature. If estimates indicate more than 1000 XML files or 200MB of XML data exist, the file system isn't the right tool for the job. File systems are not built to manage large numbers of files in a single directory or huge directory hierarchies. Managing concurrency, out of disk space conditions, and other common problems will plague your application unless you use a database.

Naturally Hierarchical
The third reason to consider an NXD really has to do with the impedance mismatch between relational databases and XML data. Fundamentally, XML data is hierarchical and is a poor match for a relational database's rows and columns. Relational databases have always had a hard time modeling hierarchies. You'll find dozens of workarounds for this, but no real simple and efficient solution. Any XML-to-relational mapping tool will have to pick one of these techniques and manage this common case as best as possible. Regardless of the solution, performance will suffer. The end result will also be more brittle over time. Changing the structure of the data - which is easy, natural, and useful to do in XML - forces a redesign of the relational database and changes to the mapping layer. A single mapping mistake could completely skew an entire data set. As an XML document structure changes over time, it's possible for attributes to become elements, and vice versa. Over time, incremental changes to the logical structure of the XML data can force physical changes to the database, and wholesale dump and reload may be required of the relational system to keep pace.

Structured Yet Flexible Data
The fourth question suggests that requirements change over time, something true of most real world business systems. Once a relational database schema has been set in stone, only the database administrator (DBA) is qualified to change it without disrupting services. The contract between a relational database and the program that use it becomes the weakest link in the system. As requirements change, the DBA will spend endless hours mitigating the issues that arise. Contrast that with XML databases. XML is both structured and flexible. Even XML documents conforming to a DTD or XML Schema maintain a high degree of flexibility when compared to relational schemas. Most NXDs will optionally validate document structure. Even when document validation is not enforced, XML documents maintain a high degree of implicit structure. Therefore in either case, XML documents are flexible and structured and as a result the contract between the database and the programs using it is not brittle. It can withstand change without requiring a DBA.

Data Mapping Is Wasted Time, Money, and Effort
The last question is really a reality check. Take a second to consider the amount of time and money you've spent trying to make a solution workable. The best thing you can do when digging a hole is to stop digging and get out of the hole. With that in mind, let's look at SQLXML. If you need to mix and match SQL data and XML data, it's not a horrible way to go. However, if you view it as a way to squeeze XML into a relational system in which you've already invested, you might want to reconsider. You are going to pay a performance penalty for every document stored in terms of CPU and memory. Your ability to query, index, and optimize will be impacted as well. Executing XQuery against XML data mapped into relational tables will be hindered by the non-native storage format. An optimized native XML database won't have the same penalty.

Let's take a look at how to use an NXD to learn more about its advantages over a relational database.

Examples and Code
Berkeley DB XML is an open source XQuery implementation built atop the Berkeley DB transactional database system. It supports optimized XML storage, XQuery query planning, massive scale and concurrency, and is available for download as source code for multiple platforms and as a Windows installer from Sleepycat Software ( Berkeley DB XML has also been integrated with Stylus Studio if you're more comfortable using an IDE for development. Berkeley DB XML is readily available to anyone, so we'll use it for the following examples.

First let's create an in-memory container for XML documents. Follow along using the "dbxml" command line provided with Berkeley DB XML.

dbxml> createContainer ""
dbxml> putDocument myDoc <names><name>joe</name><name>fred</
dbxml> query collection('')/names/name[.='joe']
dbxml> print
Line 1 creates the container, while line 2 places a simple document into the container. The third line performs a query on the container returning each document that matches the XPath query /names/name[.=joe]. Finally it displays what we returned by the query statement.

That's all quite useful, but let's say that you need to access your XML storage programmatically. Because Berkeley DB XML is a library, and as such is linked into your application just as any other library would be, it does not incur the overhead of client/server communication. You interact with Berkeley DB XML using one of the supported language APIs. The primary one is C++, as the product is written in C++. Java, Python, Perl, PHP, and TCL are all supported API languages. Many other languages are supported by third parties and are readily available on the Internet.

With that in mind, let's next try some simple C++ code that calls for the same thing as the dbxml commands used in the previous example (see Listing 1).

The underlined sections of the code relate back to the first example. The first underlined section creates a container. This container is called 'test.dbxml,' and is on disk, and rather than in memory. The next underlined section places the same simple XML document into the new container. The last underlined section issues the query, and the while loop equates to the print statement. Put it all together and you have essentially the same result as before. In Java the code looks much the same; again the underlined areas are the common key sections of code (see Listing 2).

As you can see, the API is fairly straightforward and similar across languages. You'll note that the C++ and Java examples create a database on disk rather than in memory simply by giving the container a name.

Let's move back to the dbxml shell and try a more complicated example. This time let's add a few documents, so we can explore the performance of the system.

First let's populate an imaginary parts database.

dbxml> createContainer parts
Creating document storage container
That created an empty container and opened it as the default container in the shell. We can now use the putDocument command to run our XQuery and insert the sample data.

More Stories By Gregory Burd

Gregory Burd is the Product Manager for Sleepycat Software, now a part of Oracle. Prior to Sleepycat, he was on the business team at KnowNow, a Kleiner Perkins startup in the San Francisco Bay Area. He has many years of software development and product leadership within companies such as JavaSoft, a division of Sun Microsystems, Marble Associates, a consulting company, and NeXT Computer, now part of Apple Computer.

More Stories By Kimbro Staken

Kimbro Staken is an independent consultant, author, and open source developer specializing in technologies for XML data management. He is one of the primary developers of the dbXML Core Open Source native XML database and a cofounder of the XML:DB Initiative.

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.

@ThingsExpo Stories
I recently attended and was a speaker at the 4th International Internet of @ThingsExpo at the Santa Clara Convention Center. I also had the opportunity to attend this event last year and I wrote a blog from that show talking about how the “Enterprise Impact of IoT” was a key theme of last year’s show. I was curious to see if the same theme would still resonate 365 days later and what, if any, changes I would see in the content presented.
Apps and devices shouldn't stop working when there's limited or no network connectivity. Learn how to bring data stored in a cloud database to the edge of the network (and back again) whenever an Internet connection is available. In his session at 17th Cloud Expo, Ben Perlmutter, a Sales Engineer with IBM Cloudant, demonstrated techniques for replicating cloud databases with devices in order to build offline-first mobile or Internet of Things (IoT) apps that can provide a better, faster user experience, both offline and online. The focus of this talk was on IBM Cloudant, Apache CouchDB, and ...
Microservices are a very exciting architectural approach that many organizations are looking to as a way to accelerate innovation. Microservices promise to allow teams to move away from monolithic "ball of mud" systems, but the reality is that, in the vast majority of organizations, different projects and technologies will continue to be developed at different speeds. How to handle the dependencies between these disparate systems with different iteration cycles? Consider the "canoncial problem" in this scenario: microservice A (releases daily) depends on a couple of additions to backend B (re...
With all the incredible momentum behind the Internet of Things (IoT) industry, it is easy to forget that not a single CEO wakes up and wonders if “my IoT is broken.” What they wonder is if they are making the right decisions to do all they can to increase revenue, decrease costs, and improve customer experience – effectively the same challenges they have always had in growing their business. The exciting thing about the IoT industry is now these decisions can be better, faster, and smarter. Now all corporate assets – people, objects, and spaces – can share information about themselves and thei...
Two weeks ago (November 3-5), I attended the Cloud Expo Silicon Valley as a speaker, where I presented on the security and privacy due diligence requirements for cloud solutions. Cloud security is a topical issue for every CIO, CISO, and technology buyer. Decision-makers are always looking for insights on how to mitigate the security risks of implementing and using cloud solutions. Based on the presentation topics covered at the conference, as well as the general discussions heard between sessions, I wanted to share some of my observations on emerging trends. As cyber security serves as a fou...
Discussions of cloud computing have evolved in recent years from a focus on specific types of cloud, to a world of hybrid cloud, and to a world dominated by the APIs that make today's multi-cloud environments and hybrid clouds possible. In this Power Panel at 17th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the importance of customers being able to use the specific technologies they need, through environments and ecosystems that expose their APIs to make true change and transformation possible.
There are over 120 breakout sessions in all, with Keynotes, General Sessions, and Power Panels adding to three days of incredibly rich presentations and content. Join @ThingsExpo conference chair Roger Strukhoff (@IoT2040), June 7-9, 2016 in New York City, for three days of intense 'Internet of Things' discussion and focus, including Big Data's indespensable role in IoT, Smart Grids and Industrial Internet of Things, Wearables and Consumer IoT, as well as (new) IoT's use in Vertical Markets.
Container technology is shaping the future of DevOps and it’s also changing the way organizations think about application development. With the rise of mobile applications in the enterprise, businesses are abandoning year-long development cycles and embracing technologies that enable rapid development and continuous deployment of apps. In his session at DevOps Summit, Kurt Collins, Developer Evangelist at, examined how Docker has evolved into a highly effective tool for application delivery by allowing increasingly popular Mobile Backend-as-a-Service (mBaaS) platforms to quickly crea...
The Internet of Things (IoT) is growing rapidly by extending current technologies, products and networks. By 2020, Cisco estimates there will be 50 billion connected devices. Gartner has forecast revenues of over $300 billion, just to IoT suppliers. Now is the time to figure out how you’ll make money – not just create innovative products. With hundreds of new products and companies jumping into the IoT fray every month, there’s no shortage of innovation. Despite this, McKinsey/VisionMobile data shows "less than 10 percent of IoT developers are making enough to support a reasonably sized team....
The cloud. Like a comic book superhero, there seems to be no problem it can’t fix or cost it can’t slash. Yet making the transition is not always easy and production environments are still largely on premise. Taking some practical and sensible steps to reduce risk can also help provide a basis for a successful cloud transition. A plethora of surveys from the likes of IDG and Gartner show that more than 70 percent of enterprises have deployed at least one or more cloud application or workload. Yet a closer inspection at the data reveals less than half of these cloud projects involve production...
As organizations realize the scope of the Internet of Things, gaining key insights from Big Data, through the use of advanced analytics, becomes crucial. However, IoT also creates the need for petabyte scale storage of data from millions of devices. A new type of Storage is required which seamlessly integrates robust data analytics with massive scale. These storage systems will act as “smart systems” provide in-place analytics that speed discovery and enable businesses to quickly derive meaningful and actionable insights. In his session at @ThingsExpo, Paul Turner, Chief Marketing Officer at...
Internet of @ThingsExpo, taking place June 7-9, 2016 at Javits Center, New York City and Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 18th International @CloudExpo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo New York Call for Papers is now open.
We all know that data growth is exploding and storage budgets are shrinking. Instead of showing you charts on about how much data there is, in his General Session at 17th Cloud Expo, Scott Cleland, Senior Director of Product Marketing at HGST, showed how to capture all of your data in one place. After you have your data under control, you can then analyze it in one place, saving time and resources.
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound cha...
We are rapidly moving to a brave new world of interconnected smart homes, cars, offices and factories known as the Internet of Things (IoT). Sensors and monitoring devices will touch every part of our lives. Let's take a closer look at the Internet of Things. The Internet of Things is a worldwide network of objects and devices connected to the Internet. They are electronics, sensors, software and more. These objects connect to the Internet and can be controlled remotely via apps and programs. Because they can be accessed via the Internet, these devices create a tremendous opportunity to inte...
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Day 2 Keynote at 17th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, wil...
Cloud computing delivers on-demand resources that provide businesses with flexibility and cost-savings. The challenge in moving workloads to the cloud has been the cost and complexity of ensuring the initial and ongoing security and regulatory (PCI, HIPAA, FFIEC) compliance across private and public clouds. Manual security compliance is slow, prone to human error, and represents over 50% of the cost of managing cloud applications. Determining how to automate cloud security compliance is critical to maintaining positive ROI. Raxak Protect is an automated security compliance SaaS platform and ma...
SYS-CON Events announced today that Kintone has been named "Bronze Sponsor" of SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. kintone promotes cloud-based workgroup productivity, transparency and profitability with a seamless collaboration space, build your own business application (BYOA) platform, and workflow automation system.
Today air travel is a minefield of delays, hassles and customer disappointment. Airlines struggle to revitalize the experience. GE and M2Mi will demonstrate practical examples of how IoT solutions are helping airlines bring back personalization, reduce trip time and improve reliability. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Dr. Sarah Cooper, M2Mi’s VP Business Development and Engineering, explored the IoT cloud-based platform technologies driving this change including privacy controls, data transparency and integration of real time context with p...
Just over a week ago I received a long and loud sustained applause for a presentation I delivered at this year’s Cloud Expo in Santa Clara. I was extremely pleased with the turnout and had some very good conversations with many of the attendees. Over the next few days I had many more meaningful conversations and was not only happy with the results but also learned a few new things. Here is everything I learned in those three days distilled into three short points.