Syntax - Mabel

Question 1

Name some common character encodings

Answer 1

ASCII
ISO Latin 1
(a.k.a. ISO-8859-1)
UTF-8
UTF-16

Question 2

What constraints are dropped when we denormalise data?

Answer 2

• Relational integrity - identical support
• Atomic integrity/first normal form - flat rows (atomic integrity, which is also the first normal form),
• Domain integrity - homogeneous data types within a column

Question 3

Give examples of structured, semi-structured and unstructured data

Answer 3

• Structured - Relational Tables
• Semi-Structured - XML/JSON
• Unstructured - Text

Question 4

Explain the concept of well-formedness using an example

Answer 4

A well-formed XML, it means that it can be successfully opened by an editor as XML, and recognised as being that language

Question 5

Which 6 building blocks make up JSON?

Answer 5

• String: Delimited with “, backslash escaping syntax is supported. Unicode characters are represented by \u and the unicode code point.
• Number: There are no size limits, numbers can be written as floating point numbers, integers and in scientific notation, e.g. -1.23E+5.
• Boolean: true and false
• Null: null
• Array: An ordered list of zero or more values that can be any type, denoted by square brackets with comma-separated elements
• Object: A collection of name-value pairs where the names (keys) are strings, denoted by cury braces. Trailing commas are not allowed as well, duplicate keys should not be used.

Question 6

Is a leading + allowed for numbers in JSON?

Answer 6

a leading + is not allowed. Also, a leading 0 is not allowed except if the integer part is exactly 0 (in which case it is even mandatory, i.e., .23 is not a well-formed JSON number literal)

Question 7

Is [] a valid array in JSON?

Answer 7

Yes

Question 8

What types can JSON keys be?

Answer 8

Only strings

Question 9

Is {} a valid object in JSON?

Answer 9

Yes

Question 10

Must keys be unique within an object?

Answer 10

Technically no
The JSON standard recommends for keys to be unique within an object, as some parsers may reject this

Question 11

What does an XML element look like?

Answer 11

In XML, an element consists of an opening tag and a closing tag and contains potentially more XML: < foo>[more XML]< / foo>

Question 12

How can empty XML elements be shortened?

Answer 12

< bar/> can be used which is equivalent to < bar>< /bar>

Question 13

Attributes

Answer 13

Attributes are key value pairs, duplicate keys are not allowed. The quotes are always needed, but single and double quotes can be used: < a attr=”value”/>