 video module we shall be looking at the concept of extensible markup language. Now I will be taking this video modules this sessions based on the syllabus of web 2.0 based on the syllabus of Sulapur University. So if you are really more interested you please go through the syllabus which will help you to be familiar with the course concepts. So these are the learning outcomes. Students will learn the basic concepts of XML as almost all the students know what is HTML. So I have tried to help you to understand what is the difference between HTML and XML. And also we shall be looking at how to construct XML documents. So what exactly is XML? XML stands for extensible markup language. Now let me tell you that XML is not a programming language. It is not a network module but it is a markup language just like HTML. It is used just to store meaningful data which can be used online. It can be transferred online. It can be converted to other transformations but it is used to store data. When it came into picture it highlighted the separation of document structure and document presentation. Mostly we see in while we write HTML documents we are concentrated and focused at document presentation but when XML came into picture so it highlighted the document structure and the format of the particular document. It promoted interoperability and portability also since web documents needs to be portable and XML brought about a document which was human as well as machine readable. So what are the advantages of using XML? First of all it is self-describing we can or the author or the programmer can write his or her tags and need not to stick to a particular standard formatted tags. This brings about flexibility according to the need of the application or need of the web document. This also brings about portability as I already mentioned earlier and it separates the logic from the presentation. So what are the core differences between XML and HTML? This is the full form of both the languages. HTML is used to format and display the data whereas we use XML to store as well as to transport the data. HTML tags are standard they are predefined whereas XML tags are custom made that is the coder can or the programmer can himself or herself define the tags and in XML documents can be structured logically according to the user that means according to as the user wants to structure the document he can do it whereas in HTML documents follow the standard structure format. There is no flexibility given to the user to structure his own document. So what are XML elements? It forms a basic basic thing of an XML doc and an XML element is any data represented from the elements start tag this is the start tag to the elements end tag. So my element here is name and I have encoded Rakesh as the name in the start tag and in the end tag. So name here is the tag starting tag slash name is the end tag and everything that comes here is an element. So I can also write the same element in a self which is also called as a self closing element I can start the name of the element and add a slash to it which says that it is a self closing element. So an element can contain text it can contain attributes what are attributes we shall see in the further slides. It can also contain nested element that is element within an element an element can hold another element as well or a mix or a combination of the above things. So these are the naming constraints that we have while we name the XML elements these these are case sensitive the names the element names are case sensitive they must start with a letter or underscore we cannot start them with XML keyword or with any digits they can contain letters digits hyphens underscores and periods and they cannot contain spaces this is very important to note that XML elements cannot be named with having spaces. So what are attributes? Attributes are designed to contain data related to a specific element for example say for example a person and his or her attribute is a gender. So you can specify the attribute of the person in the in the starting tag itself. So here I am starting the tag with person that is the name of the name of the element is person and here I am mentioning the attribute that is gender equals to in double codes female. Similarly one more example say for example we are designing an XML document for a mall say for example for a grocery mall. So you need to categorize the items. So the name of the element here is item and the attribute is category which holds the value grocery. So the value of the attribute is always given in double codes. So this is the XML tree structure how a particular XML document looks like. So this particular first line that you see here is the XML prologue or also we call as the pre-directives or the directives or a simple line which shows us that the following document is an XML document. It is an optional line for good programming standards if we are following the standard according to standard programming we should always write the first line and start with this particular line. Comments in XML are written like this you open the tag following with exclamation mark and two hyphens and your text and again closing with two hyphens and the closing tag. And here are the elements. So you start with a root element the child element and the subchild and so on and then you have you follow the proper nesting and then close it with the root tag itself. So this is a working example a simple example we are starting with the XML prologue. Students is the root element here. So I am basically taking us data or storing a data of some students here. So students with a capital S as you can see is the root element first student that is element with the tag student and the attribute is role which is having the value one. I have given a particular name tag holding the name Rakesh and department tag holding the department as CSE and after that I am closing the student tag or I am closing the student element. Now next student also the second student I am following with the same data here role has the attribute value of two name is Suresh department is IT and again I close the student tag. And in the end if you can clearly see I am closing the root node which is students. So here is a reflective question that I want you to think and answer go through this code find the errors in the XML code given below and answer wherever you find an error. So we shall scroll through the code here and see how where the errors have occurred here. If you have clearly seen the first error occurs in the attribute name of book element where the attribute names cannot have spaces between them. So there should be no space here in the attribute name accession number is an attribute name there should be no space here either you use underscore or completely take away the space but you cannot permit there the attribute name to hold a space. The second error occurs here where the excuse me the book the book closing tag is not marked with a slash. So book and not price book is having a error here. So the second error occurs here. The third error occurs here that the element name mentioned here is in different cases because we are starting with name with a with a small n and we're ending with a name with a capital N. So this is not permitted and the final solution for the XML document is here if you can just write it down in a text editor and open it using a browser web browser you will be able to see the XML document. So this is the assignment that I want you to do after watching this video. Write down a XML document for storing the following data for three computers. You need to use a particular element for brand name processor RAM space and HDT space and use computer as the root element. The second assignment that I want you to do is enumerate any two core differences between HTML and XML. These are the references that I used for these video sessions. Thank you very much.