程序代写代做 data science concurrency Java javascript html graph database Excel COMP20008

XML: eXtensible Markup Language
• A ‘meta’ mark-up language
• Extensible: user defined tags
• Facilitate better encoding of semantics

Subject guide in plain-text
Year of offer = 2019
Subject level = Undergraduate level 2 Subject code = COMP20008
Campus = Parkville
Availability = Semester 1, Semester 2

Subject guide in HTML

Subject guide in HTML – cont.

Subject guide in HTML – cont.

Subject guide in xml

XML syntax – well formed
• xml files must begin with declaration
• xml elements
• One root element
• Appropriately nested
• Start/end tags or Empty tags • Attributes in quotes
Parkville or • Case sensitive
• comments

XML syntax – cont.
• some characters have special meaning
• ‘<’ and ‘&’ are strictly illegal inside an element • all books & videos are now < AUD 10
• all books videos are now < AUD 10
• CDATA (character data) section may be used inside XML element to include large blocks of text, which may contain these special characters such as &, >
• •
&

Using HTML/XML (Python)
• For HTML scraping, the Beautiful Soup library is good
• For XML, a good library is http://lxml.de/
• Import the XML file into your program as a tree structure: import xml.etree.ElementTree as ET
tree = ET.parse(‘yourfile.xml’)
root = tree.getroot()
• Then loop through root with the various methods available: for child in root:
print child.tag, child.attrib

XML applications
• Mathematical Markup Language (MathML) • ChemML (Chemical Markup Language)
• RSS, SOAP, SVG, …

MathML example: markup an equation in terms of presentation and semantics
In MathML, x3+6x+6 is represented as

x 3
+
6 &InvisibleTimes; x
+
6

JavaScript Object Notation (JSON)
• JSON (www.json.org)
• Douglas Crockford (pretty much alone)
• c.f the development of XML by committee
• “Javascript: the good parts” • O’ Reilly, Yahoo Press

JSON
{ “Catalog”: [
{ “CD”: {
“title”: “Empire Burlesque”, “artist”: “Bon Dylan”,
“price”: {
”currency”: “USD”,
“value”: 10.90 },
“year”: 1985 }
},
{ “CD”: {
“title”: “Hide your heart”, “artist”: “Bonnie Taylor”, “price”: {
“currency”: “USD”, “value”: 9.90
},
“year”: 1988 }
} ]
}


Bob Dylan
10.90 1985


Bonnie Tyler
9.90 1988

JSON object example (cont. next slide)
{
“firstName”: “David”, “lastName”: “Lynn”, “isAlive”: true,
“age”: 25, “height_cm”: 167.6, “address”: {
“streetAddress”: “211 Fox Street”, “city”: “Greenville”,
“state”: “NH”,
“postalCode”: “80021”
},

JSON example (cont.)
“phoneNumbers”: [
{
“type”: “home”,
“number”: “315 555-1812” },
{
“type”: “office”,
“number”: “646 555-4567”
], }
“email”: “dlynn@nhs.net”
}

XML representation

David Lynn …..

…. dlynn@nhs.net

JSON syntax rules
• Object data is in name/value pairs “firstName”:”John”
• JSON values
•A number (integer or floating point)
•A string (in double quotes) •A Boolean (true or false)
•An array (in square brackets) •An object (in curly braces) •null

JSON syntax rules
• JSON Objects
{“firstName”:”John”, “lastName”:”Doe”}
• JSON Arrays “employees”:[
{“firstName”:”John”, “lastName”:”Doe”}, {“firstName”:”Anna”, “lastName”:”Smith”}, {“firstName”:”Peter”, “lastName”:”Jones”}
]
• These objects repeat recursively down a hierarchy as needed. • In terms of syntax that’s pretty much it!

Using JSON (Python)
import json
json.loads( ‘[“foo”,
{“bar”:
[“baz”, null, 1.0, 2]
} ]’)
json.dumps( [‘foo’,
{‘bar’:
(‘baz’, None, 1.0, 2)
} ]
– Load JSON format to Python Dictionary
)
– Convert to JSON format from Python Dictionary
Note: white space and indentation is for human purposes only!

JSON format (from json.org)

JSON format (json.org)

JSON compared to XML
• JSON is simpler and more compact/lightweight than XML; easy to parse.
• Common JSON application – read and display data from a webserver using javascript.
• https://www.w3schools.com/js/js_json.asp
• XML comes with a large family of other standards for querying and transforming (XQuery, XML Schema, XPATH, XSLT, namespaces, …)

JSON vs XML cont.
• XML allows complex schema definitions (via regular expressions) • allows formal validation
• makes you consider the data design more closely
• JSON is more streamlined, lightweight and compressed
• Which appeals to programmers looking for speed and efficiency • Widely used for storing data in noSQL databases

Exercise
Represent the following information in JSON
Homer Simpson
Grandpa Marge Lisa
Check it is well formed: http://jsonlint.com
Bart Duff

JSON: Summary
• JavaScript Object Notation
• Lightweight, streamlined, standard method of data exchange
• Originally designed to speed up client/server interactions: • By running in the client browser
• Native Javascript, so can be executed as code
• Can be used to represent any kind of semi structured data • Lacks context and schema definitions

Python libraries for JSON and XML
• json • lxml
XML, JSON, CSV and HTML conversion tools

What you should know
• Why do we have different data formats and why do we wish to transform between different formats?
• Motivation for using relational databases to manage information
• What is a csv, what is a spreadsheet, what is the difference?
• Difference between HTML and XML and when to use each
• Be able to read and write data in XML (elements, attributes)
• Be able to read and write data in JSON
• Difference between XML and JSON; applications where each can
be used.

Further reading
• Relational databases
Pages 403-409 of http://i.stanford.edu/~ullman/focs/ch08.pdf
• XML http://www.tei-c.org/release/doc/tei-p5-doc/en/html/SG.html