The best way to prepare for an interview is by practicing. But what if you don’t know what questions will be asked in advance? We’ve compiled a list of XPath Interview Questions that you can use to practice before your next interview.
An XML document is structured with nodes that are organized hierarchically, and it’s easiest to navigate the hierarchy using the XPath language.
1. What is XPath?
Ans. XPath is a powerful language for navigating and searching XML data. XPath syntax resembles traditional Unix-style file path expressions, with the exception that they are used to navigate nodes in an XML document instead of files on disk.
2. What is an XPath Expression?
Ans. An expression is a combination of keywords, operators, variables, and parentheses that are used to select nodes from XML documents or data sets.
3. What is the difference between an XPath expression and an XSLT transformation?
Ans. An XPath expression selects nodes from XML documents or data sets, whereas an XSLT transformation applies stylesheets to transform XML documents into HTML webpages.
4. What is the difference between a node and an element?
Ans. A node represents one XML document within the root node of an XML hierarchy. Elements represent parts that belong to nodes in the hierarchy. For example, “title” can be found as a node, and “title” can also be found as an element.
5. What is the difference between a text node and other types of nodes?
Ans. A text node is just that – it contains textual content in XML documents such as plain English words or sentences. Text nodes are used to store data within the root node (elements) and can be found nested within other nodes.
6. What are some examples of XPath?
Ans. The best way to answer this is with an example:
//title/text() – This would return all of the text nodes that are nested within “title” and we can assume there are a lot more XPaths.
/rootnode[child-of=parent]/* – The first part in brackets tells us where to start looking within the hierarchy, and the asterisk (*) tells us to include all of those nodes.
/root node[child-of=’parent’]/* – This XPath would show you how many times “parent” exists in the document.
7. What is an XML Schema?
Ans. An XML schema defines what valid documents are allowable for an XML document.
XML Schema is a language-independent way of specifying the structure and semantics of an XML document.
An example would be:
<?xml version=”” xmlns=”” encoding=’utf-16″?>” – This tells us that we’re using UTF-16 for our text, with no end tag needed.
8. What are the advantages of XPath?
Ans. XPath is a simple language that can be learned in minutes. It’s also very intuitive as it only requires you to identify the node or location within an XML document, and then provide what action should take place. Finally, XPaths doesn’t require any coding skills, so people with limited technical experience can use it.
9. What are the different types of XPath?
Ans. There are three main types:
- Positional XPath: This is the simplest and most common form of XPath. It uses a string to define an element by its position in the XML hierarchy, starting with “//”.
- Relative XPaths: These paths start out with “/” instead of “//”, indicating where they are relative from their parent node.
- Axis XPath: These paths use the different axes to navigate, such as “child” and “parent”. This type of XPath is a bit more complicated than other types.
10. What is an XPath query?
Ans. An XPath query allows you to select nodes from a document by applying expressions. For example, you can ask for all of the elements with a “text” tag and then filter by opening tags.
An XPath query is more complex than an XPath location path because it requires some form of logic or searches to identify what nodes are desired. Queries use full expressions that result in boolean values – true/false – which return nodes when the condition is satisfied.
11. List different types of XPath operators.
Ans. There are five types of operators:
- Arithmetic Operators – These include + (addition), – (subtraction), and *(multiplication).
- Comparison Operators – These include =, >, >=, <=.
- Logical Operators- these generally occur in a conditional statement such as “if” or “else.” They also return boolean values.
- Text Operators- these operators are used to return text values, such as “text(), substring()”.
- XPath Functions – These allow you to apply a function to the nodes that meet certain criteria. For example: length().
12. What is an XML document?
Ans. An XML document describes data using markup tags in order for it to be understood by humans and machines alike. This may include anything from formatting content or even styling webpages with CSS stylesheets. By design, all well-formed XML documents must have a root node containing at least one element.
13. Where do you use XPath?
Ans. XPath is used in navigating data within and between XML documents in order to create a new document. XPath queries can be applied as part of the “xpath()” function, which selects nodes based on their position or value (and then performs an action).
14. Explain atomic value in XPath?
Ans. An atomic value is the simplest form of data that can be used in XPaths. It’s a single word or number, which accepts no modifiers and cannot be broken down any further.
15. What is an attribute in XPath?
Ans. An attribute is a property that provides information about an element. For instance, attributes can provide metadata about when the XML document was created or what its name should be. Attribute names are always followed by “:”, and they have to come before any other text within the node’s location path.
16. What is a primary axis in XPath?
Ans. A primary axis is a way in which XPaths are read. It can be either an “ancestor” or a “descendant.”
17. What is the difference between ancestor and descendant primaries?
Ans. Ancestors represent nodes that come before another node, while descendants represent those that come after it. As such, ancestors will always return nodes of a higher hierarchy while descendants return nodes that are lower in the XML tree.
The ancestor primary can only be used to go up one level, while descendant primaries allow you to go down at any depth. For example: “//book/chapter” is an ancestor axis and it will always point upwards from chapter node (child) to book node (parent).
The descendant primary can be used to go up or down the tree, such as “//chapter/section” which points upwards from section node (child) to chapter node (parent), or “//book/chapter” which points downwards.
18. What does it mean when you see a slash in XPath?
Ans. A slash indicates that we’re splitting an item into two parts – one on each side of the slash. It’s called a selector or a node test operator.
19. How does the “//” signify in XPath?
Ans. The double slashes are called an axis and signify that we’re navigating this path from the root document to find all of its child elements. It’s also used as a delimiter for items in lists or arrays – like when you see it between the quotation marks in the XPath string.
20. What is a sibling node?
Ans. A Sibling node refers to an element that shares both its parent and its name with another, different XML node on the same level of hierarchy. For example: if you have a node named “text” and the XML document has one element on the same level like that, it would be a Sibling to it.