XML Attributes and Elements

Question 1

What does XML stand for

Answer 1

eXtensible Markup Language (similar to HTML)

Question 2

XML is designed to

Answer 2

support documents that contain structured information. It is commonly used for data interchange and data storage

Question 3

What format was used before XML

Answer 3

CSV (comma separated values)

Question 4

Problems associated with no standards for data interchange include:

Answer 4

Difficult to read, Hard to validate, Error prone

Question 5

XML Code Example:

Answer 5

Question 6

How is XML similar to HTML

Answer 6

they both came from SGML - standard generalized markup language

Markup language: the markup is separate from the content

Question 7

HTML example

Answer 7

Question 8

Well-Formed XML must have

Answer 8

a corresponding end tag for all of its start tags. Nesting of elements within each other in an XML document must be proper. For example,

<Order><id>12</id></Order>

is a correct way of nesting and

<Order><id>12</Order><id>id> is not

In each element two attributes must not have the same value. Example:
<Quantity>12</Quantity> is correct
<Quantity unit="in" unit'="lg">/Quantity> is incorrect

-Markup characters must be properly specified.
-An XML document can contain only one root element. So the root element of an XML document is an element that is preset only once in an XML document, and it does not appear as a child element within any other element.
-There are additional rules for well-formed XML documents as well https://www.w3resource.com/xml/well-formed.php for more info
</id></id></Order>

Question 9

Parts of an XML Document - XML Declaration

Answer 9

Optional but recommended
-Version number: Required if declaration is present, often it is 1.0
-Encoding: Optional, XML parsers usually detect UTF-8 and UTF-16

<?xml version=”1.0” encoding = “utf-8”?>

Question 10

Parts of an XML Document - XML Elements:

Answer 10

Hierarchical with start and end tags

<Item>Food Processor</Item>

Question 11

Parts of an XML Document - XML Attributes:

Answer 11

Attributes appear in the start tag and must have a unique name. Attribute value must be enclosed in quotes

<Quantity>.
</Quantity>

Question 12

Parts of an XML Document - Comments:

Answer 12

Comments cannot appear above the XML declaration and may span multiple lines. Provides extra information about the document.

<! - - This is a comment - - >

Question 13

Parts of an XML Document - CDATA:

Answer 13

This is raw character data and allows the use of non-ascii characters.

<![CDATA[
Can use different characters for a description&raquo_space;&laquo_space;& and reserved characters
] ]>

Question 14

Attributes Versus Elements

Answer 14

There are no rules when to use attributes versus elements, but many developers follow guidelines; for example, using elements for data and attributes for information that is peripheral or incidental to the data.
-Use elements instead of attributes
-Metadata should be stored as attributes
-Use an attribute if it influences and element value
-Do not use an attribute that influences another attribute
-Instead of using multiple attributes consider using child elements

Child Elements

<person>
<firstname>Ben</firstname>
<lastname>Solo</lastname>
<age>25</age>
</person>

One Attribute

<person>
<firstname>Ben</firstname>
<lastname>Solo</lastname>
</person>

All attributes

<person></person>

Question 15

XML Element Relationships (with example)

Answer 15

Children are elements directly beneath a parent element. <book><title><author><year><price> are all children of <bookstore>.</bookstore></price></year></author></title></book>

Question 16

XML Ancestors and Descendants

Answer 16

A descendant element is one that is contained within another element. For example,

<Items> is a child of <Order>
<Items> elements are children of <Items>

<Item> is a descendent of <Order>

<Order> is an ancestor of <Item>

EML Example:

</Item></Order></Order></Item></Items></Items></Order></Items>

Question 17

XML Namespaces

Answer 17

Namespaces are used to provide different elements and attributes within an XML document to prevent name conflicts.

Namespace is a URL http://mycompany.com/order
in this example but does not have to be a URL

Namespaces are reserved attributes:
“xmins” or “xmins:”

You can provide a default namespace to a specific element such as the Order element

All elements and attributes are in the http://mycompany.com/order namespace because it applies to Order and all of its descendants

Question 18

XML Prefixes

Answer 18

All elements and attributes that are prefixed with”it:” are part of the xmins:it=http://mycompany/item namespace

The order ID element and the Item ID element are different namespaces. So the elements are uniquely identified.