|By Selim Mimaroglu||
|October 13, 2004 12:00 AM EDT||
This article looks in detail at how to generate XML data from your relational database. Although the examples were run on Oracle, very little of the code is Oracle specific. You can easily use all the ideas and examples presented here in other relational databases. We did this project at University of Massachusetts Boston as part of the Electronic Field Guide (EFG) project.
XML is the de facto standard for data exchange. It's simple, Unicode based, and platform independent. XML is a metadata language; it contains information about the data. All these features make it an attractive standard for exchanging data.
Why Generate XML from Relational Data?
Today most data (80% or more), is stored in relational databases such as Oracle, DB2, SQL Server 2000, and others. The Internet and Web services are present in our daily lives. A tremendous amount of data is transferred over the Internet between businesses. Data transfers may happen within a company, between different branches, or between different companies and individuals. No matter which of these situations applies to you, it's very likely that you will be asked to ship your data in XML, or that you are already doing it. Relational Database Management Systems (RDBMS) are still the best way to hold data in bulk. In the following paragraph we will give some information about our project and related resources that we used to provide relational data in XML.
Our XML project is part of the Electronic Field Guild (EFG). The EFG project is an object-oriented, Web-based database for the identification of species and recording of ecological observations. With funding from the National Science Foundation, this project is the result of the collaborative efforts between the Departments of Computer Science and Biology at the University of Massachusetts Boston. EFG queries the Integrated Taxonomic Information System (ITIS). On each query we only get a very small part of the ITIS database. XML can describe exactly what data it is delivering, and thus is the preferred format for the query results.
There are three ITIS branches: Canadian, Mexican, and U.S. U.S. ITIS provides the whole data in bulk (about 85MB), but, like many other organizations, it has been slow to join the modern trend to answer queries on it in XML format. Canadian ITIS provides query results in XML, but due to networking delays and some other problems, getting the result takes a long time. We decided to bring the whole database home and return the results of queries in XML format. We are using an RDBMS to store the bulk data. In the following paragraphs we will explain how to generate XML from this relational data.
This emerging standard enables us to generate XML fragments from relational data. Oracle and many other relational databases support the following standard SQL/XML functions. We will explain most of the SQL/XML functions, XMLElement, XMLAttributes, XMLForest, XMLAgg, and give an example for each.
As its name implies, this function generates an XML element. It takes an element name, an optional collection of attributes for the element, and zero or more arguments that make up the element content and returns an instance of type XMLType.
Table 1 is the schema of the "experts" table from our database. All the simple examples are related to this table, and Oracle was used for most cases.
Table 2 shows some of the data from the experts table.
WHERE expert_id BETWEEN 4 and 10;
XML2CLOB( XMLELEMENT(NAME "name", expert) )
WHERE expert_id BETWEEN 4 and 10
<name>Stotler, Raymond E.</name>
<name>Alfred L. Gardner</name>
<name>Steve J. Upton</name>
Here, name is the tag name; expert is the corresponding column name in the experts table. This query obtains the expert column value from the experts table and puts <name> and </name> tags around it.
This function simply creates attributes for an element. Listing 1 shows how it works.
Each name element has an id attribute. Each id attribute is obtained from the expert_id column value of the experts table. The XMLAttributes clause isn't used alone; it's used inside an XMLElement function. This makes sense since, in XML, an attribute is a name-value pair attached to the associated element's start tag.
The XMLForest() function produces a forest of XML elements from the given list of arguments. In other words, it produces many XML elements at a time.
In Listing 2, expert is the root element. The id, name, and info elements are children of expert element. The XMLForest function created three elements: the id element corresponds to expert_id column value; the name element corresponds to expert column value; and the info element corresponds to the exp_comment column value in experts table. Naming the elements in this function is accomplished by using AS keyword. For the first element it is expert_id as "id".
What if you don't specify an id (id = 6 in this example)? In this case you will have the appropriate XML fragment for each row.
XMLAgg() is an aggregate function that produces a forest of XML elements derived from a set of rows.
In Listing 3, there are five name elements as children of the experts root element. Without using XMLAgg() function it's impossible to have many name elements in a single XML document. If you don't use the XMLAgg() function and instead submit the query, you will get Listing 4.
That's not what we wanted. For this output, each experts element has only one name child element, and there are many experts elements. To combine information from multiple rows of the table we need to use the XMLAgg() function.
Creating hierarchical data is easy. Listing 5 shows you how to do this. You can use this idea in similar queries. This example involves the taxonomic_units table, which stores data about species, phyla, etc., i.e. nodes in the tree of life. Note the select within the select, to run through the inner loop.
I hope these examples have convinced you that it's possible to generate XML that obeys any XML Schema or DTD. You can use these functions, nested in each other, to display any kind of parent-child relation. Another such query could display all the experts for each taxon.
This is easy! You can start using these functions as soon as you finish reading this article. Being flexible adds value to this approach. An important point that's worth mentioning is that all the work is done inside the database by using the SQL/XML functions. In the Oracle case, all the work is done in the XML DB Engine. This is much faster and more efficient than doing the work outside the database. Another approach would be to get the data from the database and tag it outside the database for creating XML. This is possible but less efficient, more time consuming. The following are more advanced topics, such as XMLType View and XML Schema validation.
A view is a table that results from a subquery, but which has its own name and can be treated in most ways as if it were an ordinary table. Thus a view table is a logical window on selected data from the base tables and other views. XMLType views wrap the relational data in XML formats. In other words you can have a virtual XML file over your relational data inside the database. We can treat this new view as XML, and use XML specific operations on it, such as XPath and XQuery. These types of operations will be converted to corresponding SQL; this is known as query rewrite. You can create this view by using SQL/XML functions. Our SQL, which generates an XMLType view is shown in the source code, create.sql, online at www.syscon.com/xmlj/sourcec.cfm. Below is a simpler example, for better understanding.
SQL> CREATE OR REPLACE VIEW expert_view of XMLTYPE WITH OBJECT ID (EXTRACT(sys_nc_rowinfo$,[email protected]').getnumberval()) AS SELECT XMLELEMENT("experts", XMLAGG( XMLELEMENT("expert", XMLATTRIBUTES(expert_id as "id"), expert))) FROM experts WHERE expert_id BETWEEN 4 and 10; View created.
This is how the view looks when you query it. This XMLType view is created over the experts table. The data displayed comes from the underlying relational table.
SQL> SELECT * FROM expert_view; SYS_NC_ROWINFO$ <experts> <expert id="4">Stotler, Raymond E.</expert> <expert id="5">Alfred L. Gardner</expert> <expert id="6">Steve J. Upton</expert> <expert id="8">Wayne Starnes</expert> <expert id="10">Lynne Parenti</expert> </experts>
It's possible to use XPath expressions on this view. Following is a query that has an XPath expression. This query extracts the value of an expert element that has an id attribute equal to 4.
SQL> SELECT extract(value(x), '/experts/expert[@id=4]') FROM expert_view x;
<expert id="4">Stotler, Raymond E.</expert>
First Step: Register an XSD
You can validate an XMLType instance against XML Schema Documentation (XSD) in Oracle. First, register the XSD in Oracle. Next, call a function that does the validation. There are several functions in Oracle for accomplishing this. Listing 6 is the only one shown, for simplicity.
This will register the XSD and name it as expert_view.xsd. You can name it anything you want of course.
Second Step: Validation
This section introduces isSchemaValid (argumet1, argument2). The first argument is the name of the registered XSD. The second argument is the name of the root element in the specified XSD. XSD can have more than one root. If the XML document (x in this case) is valid, this isSchemaValid returns 1.
SQL> select x.isSchemaValid('expert_view.xsd', 'experts') from expert_view x;
Putting It Together
For our project we generated XML that obeys our XML Schema Documentation (XSD)[itis.xsd]. Our SQL is shown in the source code for this article (available online at www.sys-con.com/xmlj/sourcec.cfm). It will output all the data in XML. As you can see, this query is significantly nested and long, but it's easy to understand (I hope). There are a few more functions in this query that we would like to mention: trim() simply gets rid of the white space in an entry and the to_char() function is used to change the date format. For example, to_char(v.up date_date, 'YYYY-MM-DD') will display the date as something like 2004-04-23. This is somewhat important because the date format in the database doesn't match the date format of the XML Schema.
In this project we deliver XML through a search server. Using this server, you can query the database by tsn, which is identical to the identification number of a taxonomic unit. e.g. a particular animal or plant. For this part of the project we used:
- Sun Enterprise 250 Server: 2 X UltraSPARC-II 400MHz, 2GB memory, SCSI disks
- Sun Solaris Operating System 5.8
- Oracle 9.2i
- JAVA 1.4.2
- Java Database Connectivity (JDBC) inside JavaBeans for connecting to and querying the database. We preferred the Oracle thin driver to the oci driver.
- JavaServer Pages (JSP) at the user interface level
- Tomcat 5.0.12
- Use Oracle Connection Pool
- Turn off the auto commit feature
- Use predefined column types in the select statement.
If you are not already doing so, you will probably be delivering your data in XML format soon. Keep in mind that most data resides in relational databases so generating XML from relational databases will be a very common task. Many of the database vendors, such as Oracle and DB2, provide the SQL/XML function support to make this task easier. SQL Server 2000 adds a new clause, the FOR XML clause, to the SELECT statement, which instructs SQL Server to return the result of a query in XML format.
Based on our experiments, generating XML data inside the database is fast; it took an average of 0.032 seconds per taxon query. Storing your data without the start and end tags is space efficient. Relational databases are very mature about storing, querying, and retrieving data quickly and efficiently. There has been over 20 years of work done in these technologies.
For larger projects, having XMLType views over the relational tables is advantageous. It gives you the chance to query the data using XPath and XQuery besides SQL.
In this article we provided some insight about SQL/XML functions, mentioned the benefits of storing data in relational databases, and explored the benefits of using XMLType views over relational data. For more detailed information about SQL/XML functions, check your database documentation.
So, you bought into the current machine learning craze and went on to collect millions/billions of records from this promising new data source. Now, what do you do with them? Too often, the abundance of data quickly turns into an abundance of problems. How do you extract that "magic essence" from your data without falling into the common pitfalls? In her session at @ThingsExpo, Natalia Ponomareva, Software Engineer at Google, will provide tips on how to be successful in large scale machine lear...
Apr. 30, 2016 10:00 PM EDT Reads: 1,058
In his session at @ThingsExpo, Chris Klein, CEO and Co-founder of Rachio, will discuss next generation communities that are using IoT to create more sustainable, intelligent communities. One example is Sterling Ranch, a 10,000 home development that – with the help of Siemens – will integrate IoT technology into the community to provide residents with energy and water savings as well as intelligent security. Everything from stop lights to sprinkler systems to building infrastructures will run ef...
Apr. 30, 2016 05:30 PM EDT Reads: 698
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
Apr. 30, 2016 04:45 PM EDT Reads: 609
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
Apr. 30, 2016 04:45 PM EDT Reads: 1,049
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at 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. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus inter...
Apr. 30, 2016 04:45 PM EDT Reads: 1,012
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, will discuss how research has demonstrated the value of Machine Learning in delivering next generation analytics to im...
Apr. 30, 2016 04:15 PM EDT Reads: 1,664
There is an ever-growing explosion of new devices that are connected to the Internet using “cloud” solutions. This rapid growth is creating a massive new demand for efficient access to data. And it’s not just about connecting to that data anymore. This new demand is bringing new issues and challenges and it is important for companies to scale for the coming growth. And with that scaling comes the need for greater security, gathering and data analysis, storage, connectivity and, of course, the...
Apr. 30, 2016 03:15 PM EDT Reads: 742
This is not a small hotel event. It is also not a big vendor party where politicians and entertainers are more important than real content. This is Cloud Expo, the world's longest-running conference and exhibition focused on Cloud Computing and all that it entails. If you want serious presentations and valuable insight about Cloud Computing for three straight days, then register now for Cloud Expo.
Apr. 30, 2016 02:30 PM EDT Reads: 1,704
IoT device adoption is growing at staggering rates, and with it comes opportunity for developers to meet consumer demand for an ever more connected world. Wireless communication is the key part of the encompassing components of any IoT device. Wireless connectivity enhances the device utility at the expense of ease of use and deployment challenges. Since connectivity is fundamental for IoT device development, engineers must understand how to overcome the hurdles inherent in incorporating multipl...
Apr. 30, 2016 02:15 PM EDT Reads: 1,449
SYS-CON Events announced today that Stratoscale, the software company developing the next generation data center operating system, will exhibit at 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. Stratoscale is revolutionizing the data center with a zero-to-cloud-in-minutes solution. With Stratoscale’s hardware-agnostic, Software Defined Data Center (SDDC) solution to store everything, run anything and scale everywhere...
Apr. 30, 2016 01:15 PM EDT Reads: 1,527
The increasing popularity of the Internet of Things necessitates that our physical and cognitive relationship with wearable technology will change rapidly in the near future. This advent means logging has become a thing of the past. Before, it was on us to track our own data, but now that data is automatically available. What does this mean for mHealth and the "connected" body? In her session at @ThingsExpo, Lisa Calkins, CEO and co-founder of Amadeus Consulting, will discuss the impact of wea...
Apr. 30, 2016 01:15 PM EDT Reads: 656
Angular 2 is a complete re-write of the popular framework AngularJS. Programming in Angular 2 is greatly simplified – now it's a component-based well-performing framework. This immersive one-day workshop at 18th Cloud Expo, led by Yakov Fain, a Java Champion and a co-founder of the IT consultancy Farata Systems and the product company SuranceBay, will provide you with everything you wanted to know about Angular 2.
Apr. 30, 2016 12:45 PM EDT Reads: 1,696
SYS-CON Events announced today that Men & Mice, the leading global provider of DNS, DHCP and IP address management overlay solutions, will exhibit at 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. The Men & Mice Suite overlay solution is already known for its powerful application in heterogeneous operating environments, enabling enterprises to scale without fuss. Building on a solid range of diverse platform support,...
Apr. 30, 2016 12:00 PM EDT Reads: 2,289
You deployed your app with the Bluemix PaaS and it's gaining some serious traction, so it's time to make some tweaks. Did you design your application in a way that it can scale in the cloud? Were you even thinking about the cloud when you built the app? If not, chances are your app is going to break. Check out this webcast to learn various techniques for designing applications that will scale successfully in Bluemix, for the confidence you need to take your apps to the next level and beyond.
Apr. 30, 2016 11:30 AM EDT Reads: 1,465
We’ve worked with dozens of early adopters across numerous industries and will debunk common misperceptions, which starts with understanding that many of the connected products we’ll use over the next 5 years are already products, they’re just not yet connected. With an IoT product, time-in-market provides much more essential feedback than ever before. Innovation comes from what you do with the data that the connected product provides in order to enhance the customer experience and optimize busi...
Apr. 30, 2016 11:15 AM EDT Reads: 883
SYS-CON Events announced today that Ericsson has been named “Gold Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. Ericsson is a world leader in the rapidly changing environment of communications technology – providing equipment, software and services to enable transformation through mobility. Some 40 percent of global mobile traffic runs through networks we have supplied. More than 1 billion subscribers around the world re...
Apr. 30, 2016 11:00 AM EDT Reads: 865
Increasing IoT connectivity is forcing enterprises to find elegant solutions to organize and visualize all incoming data from these connected devices with re-configurable dashboard widgets to effectively allow rapid decision-making for everything from immediate actions in tactical situations to strategic analysis and reporting. In his session at 18th Cloud Expo, Shikhir Singh, Senior Developer Relations Manager at Sencha, will discuss how to create HTML5 dashboards that interact with IoT devic...
Apr. 30, 2016 11:00 AM EDT Reads: 913
Artificial Intelligence has the potential to massively disrupt IoT. In his session at 18th Cloud Expo, AJ Abdallat, CEO of Beyond AI, will discuss what the five main drivers are in Artificial Intelligence that could shape the future of the Internet of Things. AJ Abdallat is CEO of Beyond AI. He has over 20 years of management experience in the fields of artificial intelligence, sensors, instruments, devices and software for telecommunications, life sciences, environmental monitoring, process...
Apr. 30, 2016 11:00 AM EDT Reads: 881
Digital payments using wearable devices such as smart watches, fitness trackers, and payment wristbands are an increasing area of focus for industry participants, and consumer acceptance from early trials and deployments has encouraged some of the biggest names in technology and banking to continue their push to drive growth in this nascent market. Wearable payment systems may utilize near field communication (NFC), radio frequency identification (RFID), or quick response (QR) codes and barcodes...
Apr. 30, 2016 10:00 AM EDT Reads: 703
SYS-CON Events announced today that Fusion, a leading provider of cloud services, will exhibit at 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. Fusion, a leading provider of integrated cloud solutions to small, medium and large businesses, is the industry's single source for the cloud. Fusion's advanced, proprietary cloud service platform enables the integration of leading edge solutions in the cloud, including cloud...
Apr. 30, 2016 09:45 AM EDT Reads: 2,553