computer science

PureXML

PureXML is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand PureXML rather than just read about it. In short: pureXML is the native XML storage feature in the IBM Db2 data server. pureXML provides query languages, storage technologies, indexing technologies, and other features to support XML data. The word pure in pureXML was chosen to indicate that Db2 natively stores and natively processes XML data in its inherent hierarchical structure, as opposed to treating XML data as plain text or converting it into a relational form…

Key takeaways

PureXML belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PureXML to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PureXML from memory before moving on to harder problems.

Reference excerpt

pureXML is the native XML storage feature in the IBM Db2 data server. pureXML provides query languages, storage technologies, indexing technologies, and other features to support XML data. The word pure in pureXML was chosen to indicate that Db2 natively stores and natively processes XML data in its inherent hierarchical structure, as opposed to treating XML data as plain text or converting it into a relational format.

Technical information Db2 includes two distinct storage mechanisms: one for efficiently managing traditional SQL data types, and another for managing XML data. The underlying storage mechanism is transparent to users and applications; they simply use SQL (including SQL with XML extensions or SQL/XML) or XQuery to work with the data. XML data is stored in columns of Db2 tables that have the XML data type. XML data is stored in a parsed format that reflects the hierarchical nature of the original XML data. As such, pureXML uses trees and nodes as its model for storing and processing XML data. If you instruct Db2 to validate XML data against an XML schema prior to storage, Db2 annotates all nodes in the XML hierarchy with information about the schema types; otherwise, it will annotate the nodes with default type information. Upon storage, Db2 preserves the internal structure of XML data, converting its tag names and other information into integer values. Doing so helps conserve disk space and also improves the performance of queries that use navigational expressions. However, users aren't aware of this internal representation. Finally, Db2 automatically splits XML nodes across multiple database pages, as needed. XML schemas specify which XML elements are valid, in what order these elements should appear in XML data, which XML data types are associated with each element, and so on. pureXML allows you to validate the cells in a column of XML data against no schema, one schema, or multiple schemas. pureXML also provides tools to support evolving XML schemas. IBM has enhanced its programming language interfaces to support access to its XML data. These enhancements span Java (JDBC), C (embedded SQL and call-level interface), COBOL (embedded SQL), PHP, and Microsoft's .NET Framework (through the DB2.NET provider).

History pureXML was first included in the DB2 9 for Linux, Unix, and Microsoft Windows release, which was codenamed Viper, in June 2006. It was available on DB2 9 for z/OS in March 2007. In October 2007, IBM released DB2 9.5 with improved XML data transaction performance and improved storage savings. In June 2009, IBM released DB2 9.7 with XML supported for database-partitioned, range-partitioned, and multi-dimensionally clustered tables as well as compression of XML data and indices.

Competition

Db2 is a hybrid data server—it offers data management for traditional relational data, as well as providing native XML data management. Other vendors that offer data management for both relational data and native XML storage include Oracle with its 11g product and Microsoft with its SQL Server product. pureXML also competes with native XML databases like BaseX, eXist, MarkLogic or Sedna.

Books IBM International Technical Support Organization (ITSO) has published the following books, which are available in print or as free e-books:

DB2 9: pureXML Overview and Fast Start DB2 9 pureXML Guide The following books are also available for purchase:

DB2 pureXML Cookbook: Master the Power of IBM Hybrid Data Server

Education and training The following pureXML classroom and online courses are available from IBM Education:

Query and Manage XML Data with DB2 9. IBM course CG130. Classroom. Duration: 4 days. Query XML Data with DB2 9. IBM course CG100. Classroom. Duration: 2 days (first 2 days of CG130). Managing XML Data in DB2 9. IBM course CG160. Classroom. Duration: 2 days (last 2 days of CG130). DB2 pureXML. IBM Course CT140. Self-paced study plus Live Virtual Classroom.

Worked examples

Example 1 — a first encounter with PureXML

Start with the simplest possible case. Write down what PureXML claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PureXML before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PureXML ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PureXML

In research: PureXML appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PureXML in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PureXML is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data management, Data modeling, IBM Db2, so understanding it makes those chapters shorter.
In everyday life: Look for PureXML outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study PureXML in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PureXML means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PureXML out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PureXML in simple terms?

Why does PureXML matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PureXML?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PureXML.