Welcome parents in this video tutorial we will give introduction of D TD T TD stands for document type definition it defines the legal building blocks of XML document it defines the document structure with a list of legal elements and attributes a DTD can be declared inland inside an XML document or as an external reference now there is a.
Question why to use DTD so let’s talk about this with a DTD each of your examine files can carry a description of its own format with a DTD independent group of people can agree to use a standard.
DTD for interchanging data your application can you standard DTD to verify that the data you receive from the outside world is valid you can also use a DTD to verify your own data now let’s see various building blocks of XML document seen from a DTD point.
Of view all XML documents are made up of following building blocks first is the elements second is attributes third one is the entities fourth one is the EC data and last one is three data now let’s see.
Each one by one elements our main building blocks of both XML and HTML documents we have already seen elements in previous tutorials and everything in XML documents are elements attributes provide extra information about elements attributes are always placed inside the opening tag of an element we have already talked about attributes also entities some characters have special meaning in XML like.
The less than sign that defines the star of an XML tag so we cannot use this less than sign directly if you want to display less than sign in XML then we must have to use entity reference we have.
Already discussed about entity reference in previous videos for example if I want to display less.
Than sign then I have to write M % LT and : it will display less than sign now let’s talk about PC data PC data means parsed character data think of character data as the text.
Found between the start egg and the nth egg of an XML element fishy data is the text that will be passed by a parcel the text will be examined by the parser for entities and markup tags inside the text.
Will be treated as a markup and entities will be expanded however pass character data don’t contain any Amberson less than or greater than characters this needs to be represented by the entity reference now let’s talk about C data C data means character data C.
Data is text that will not be passed by a passer tags inside the text will not be treated as a markup and entity will not be expanded so this is all about introduction of DTD you must have knowledge or basic this introduction to proceed further in DTD so this is about introduction of TTT thank you.