Answer 1.
 a. semi structured data 

 A Form of data which is not structured in the form of tables or conventional relational 
 databases formats. A semi-structured data model is a model where the data can typically 
 be organized as some kind of tree or graph and the contents of the nodes in the tree or 
 graph are not necessarily strictly typed. The nodes here could be tags.
 Example :
 <Students>
  <Student>
   <name>Bob</name>
   <id>777777777</id>
  </Student>
 </Students>

 b. DTD <!Element> tag

 It is a tag which is used to define XML elements which are building blocks of any XML 
 document. These can contain text, other elements, media, attributes, links, etc. These 
 elements appear as tags for the XML document. A simple format to use this tag is defined 
 below:
 <!ELEMENT element_name (list of names of child elements with their required necessity)>
 We can also provide SYSTEM location and the NotationName while defining an element.
 Example : (Example for both b and c is after c)

 c. DTD <!ATTLIST> tag

 It is a tag which is used to define the attributes list for a particular element which is 
 defined in the DTD. A simple format to use this tag is given below:
 <!ATTLIST element_name attribute_name_1 attribute_type [default_value] ... 
 attribute_name_n attribute_type [default_value]>
 Different attributes can be of different data types like CDATA, PCDATA, a set of values, 
 etc. The necessity of an attribute for the element can also be defined here, e.g. whether 
 one is required/optional/etc.

 Example for b and c part:
 <!DOCTYPE midterm [
 <!ELEMENT midterm (card*) >
 <!ELEMENT card (firstname) >
 <!ELEMENT firstname (#PCDATA)>
 <!ATTLIST card ID CDATA #REQUIRED>
 ]>

 A sample XML:

 <midterm>
    <card ID="013931476">
        <firstname>Sida</firstname>
    </card>
    <card ID="013931477">
        <firstname>Ishaan</firstname>
    </card>
    <card ID="013931478">
        <firstname>Parth</firstname>
    </card>
 </midterm>

 GROUP : Ishaan, Sida, Parth

 Question 5	

 Example xml file
 ----------------------------------------
 <business_card> 
 <name>Bob Bobber </name>
 <company position="ceo">Bob's Burgers </company>
 <address>777 San Jose, CA </address>
 <email>bob@burger.com</email>
 <phone_number> 777-7777 </phone_number>
 </business_card>

 Schema Oblivious mapping table creation
 ---------------------------------------
 CREATE TABLE NODE(
 ID CHAR(6) NOT NULL PRIMARY KEY,
 PARENT_ID CHAR(6),
 TYPE VARCHAR(9),
 LABEL VARCHAR(20),
 VALUE TEXT,
 FOREIGN KEY (PARENT_ID) REFERENCES NODE(ID) );
 CONSTRAINT CC1 CHECK(TYPE IN ("element", "attribute")) )

 PostgreSQL example of first insert.
 ------------------------------------
 INSERT INTO NODE(id, parent_id, "type", "label", "value") VALUES
 (1, NULL, 'element', business_card, NULL);

 Example Table
 -----------------------------------------------
 ID Parent_ID Type      Label        Value
 1 NULL      element business_card  NULL
 2  1        element name            Bob Bobber
 3  1        element company         Bob's Burgers
 4  3        attribute position      ceo
 4  1        element address          777 San Jose, CA 
 5  1        element email           bob@burger.com
 6  1        element phone_number    777-7777

 Question 8.
 Give a REST api that might be suitable for a stock quote web site,
 make sure it has an operation that can return daily stock prices for the last week. 
 Give an example JSON document that might be returned by this operation. 

 The following example returns the daily stock prices of stock id 7 for the time period starting from 09-28-2020 to 10-04-2020.
 GET Request :
 stocks/getQuote?id=7&freq=daily&startTime=09-28-2020&endTime=10-04-2020 

 Response JSON:
 {
   "id" : 7,
   "name" : "ABC",
   "quote" : [
     { 
       "date" : "09-28-2020",
       "price" : 166.08
     },
     { 
       "date" : "09-29-2020",
       "price" : 163.60
     },
     { 
       "date" : "09-30-2020",
      "price" : 165.26
     },
     { 
       "date" : "10-01-2020",
       "price" : 167.86
    },
     { 
       "date" : "10-02-2020",
       "price" : 168.08
     }
     ]
  }

 Explain how we might store a cache value of such a document using memcached. 
 (Say how to run a memcache server and how such a value could be stored using the memcache 
 protocol.)

 Connect to the memcached server using the following command :
 memcached -l 127.0.0.1 -p 11211
 where -l is the location of the server and -p specifies the port to connect to .
 
 To store the value of the JSON in a memcached server we use the text protocol. 
 Set the key-value record as :
 set 7 0 0 10
 09-28-2020, 166.08 
 The command should return STORED if successful.

 Question 3	
 
 SAMPLE XML DOCUMENT
 <Businesscards>
	<BusinessCard>
		<Name>
			<Firstname>Bob</Firstname>
			<LastName>Kanagavel</Lastname>
		</Name>
		<Designation>Product Manager</Designation>
		<Company>RP Inc</Company>
		<Phone>7799578901</Phone>
		<Email>Bob.kanagavel@rpi.com</Email>
		<Address>RP INC , 4, Washington Square, San Jose, CA</Address>
	</BusinessCard>
 </Businesscards>

 XPath Expression :	
 
 Returns all bussiness cards with last name containing 'Kanagavel' and address 
 contains 'San Jose'
 
 doc(“businesscards.xml”)//Businesscard/Name[contains(Lastname,‘Kanagavel’)] | 
 //Businesscard[contains(Address,’San Jose’)]

 DOM API

 The Document Object Model API for XML Processing is a tree based API that 
 represents an XML Document as a tree in internal memory. DOM provides various 
 classes and method for navigating through the tree and to do various operations 
 such as adding, moving, or removing elements from the tree. As the whole document 
 is held in memory at one time, it often uses a lot of space for larger documents.

 For Example Consider the following XML Document,

 <note>
  <to>Bob</to>
  <from>Bill</from>
 </note>

 DOM Would render the document in memory in the following tree structure,

             Document—note—to—Bob
                        |
                      from— Bill 

 SAX API 

 The Simple API for XML API is an event based XML Processing API that represents an 
 XML document as a stream of events. This stream can be directly passed on to the 
 application which will use an event handler to process the event. So access with 
 SAX is more path-in-tree-like than whole tree-like. Since no tree is built it 
 tends to use less memory than DOM. SAX tends to be good for simple sequential 
 operations on a document or for random access to a part of a document, but it 
 performs worse if you need to do have data manipulation.

 SAX would render the XML document from the DOM example as follows,

 start document
 start element: note
 start element: to
 text: Bob
 end element: to
 start element: from
 text: Bill
 end element: from
 end element: note
 end document 

 Question 2	
 
 XML Schema card
 <?xml version="1.0"?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

 <xs:element name="business_card">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="company-name" type="xs:string"/>
      <xs:element name="name" type="xs:string"/>
      <xs:element name="designation" type="xs:string"/>
      <xs:element name="email" type="xs:string"/>
      <xs:element name="phone" type="xs:string"/>
      <xs:element name="address" type="xs:string"/>
    </xs:sequence>
  </xs:complexType>
 </xs:element>

 </xs:schema>
 
 Sample XML Document
 <?xml version="1.0" encoding="UTF-8"?>
 <?xml-stylesheet type="text/xsl" ?>
 <business_card xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://somewhere.com card.xsd">
    <name> Bob </name>name>
    <designation> Developer </designation>
    <email> bob77777@gmail.com</email>
    <phone>777777777</phone>
    <address>dummy_address</address>
 </business_card>

 XSLT card
 <?xml version="1.0"?>

 <xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

 <xsl:template match="business_card">
  <html>
            <head>
                <head>
                    <link rel="stylesheet" type="text/css"/>
                </head>
                <title>Cart</title>
            </head>
            <body>
                <h1>Business Card for Company: <xsl:value-of 
 select="/business_card/@company-name"/></h1>
                <p><xsl:value-of select="/business_card/@name"/></p>
                <p><xsl:value-of select="/business_card/@designation"/></p>
                <p><xsl:value-of select="/business_card/@email"/></p>
                <p><xsl:value-of select="/business_card/@phine"/></p>
                <p><xsl:value-of select="/business_card/@address"/></p>
            </body>
        </html>  
    </xsl:template>
 </xsl:template>

 </xsl:stylesheet>

 GROUP : Ishaan, Sida, Parth