2. --#PCDATA stands for qualified characters--> <! ELEMENT name (#PCDATA) > <! ELEMENT lessons (#PCDATA. XML is designed to replace HTML. Tags inside the PCDATA will be treated as markup and entities will. If the parentheses include the keyword #PCDATA or one of the other data types available in XML DTD, the element is a leaf node. The rules for mixed content models are similar to the element content as discussed in the previous section. technically qualifies as allowing mixed content, but does not allow any elements to be mixed in. The list of attributes that can appear within an element can also be specified . Elements that contain only other elements are said to have element content [Section 3. PCDATA stands for Parsed Character data. If the parentheses include names of other elements, these would be the children of the element in the tree structure. People's Commissariat of Defense (Russia) PCD. #PCDATA stands forparsed character data and symbolizes any sequence of general characters that does not contain any tag. For example, the file xhtml1-transitional. b. Raw Text:. PickStar provides the traditional Pick to Light benefits including a high level of accuracy, efficiency, and reliability at a much lower investment. Example. Syntax basics for writing DTD’s CDATA inside PCDATA. The GXSL class «pcdata» has no name and provides its own icon as shown in Figure 5. g. The PCDATA stands for parseable character data. Here PCDATA stands for parsed character data. Parsed data is the text between the start tag and the end tag of an XML element. Suggest new definition. For example, See the XML below. • Syntax • Following is a generic syntax for mixed element content − – <!ELEMENT elementname (#PCDATA|child1|child2)*> – ELEMENT is the element declaration tag. The rules for mixed content models are similar to the element content as discussed in the previous section. 2. Refer to one of the sources listed at the end of this chapter for more. Display Manager. • PCDATA – PCDATA stands for Parsed Character data. 4) Difference between Schema & DTD . PCDATA stands for “parsed character data”, and it refers to the text value of an element; “parsed” meaning that it can contain entities. DTD stands for document definition. markup and entities will be expanded. Provisional Committee on Development Agenda (WIPO) PCDA. Find the text that matches the value of the upc variable in the cd element. For example, the file xhtml1-transitional. PCDATA stands for parsed character data, that is, text that is not markup. Portable Code Domain Analyzer. DTDs are written in Extended Backus-Naur Form (EBNF). PCDATA means parsed character data, so in this case the declared element is allowed to have character data inside of it now ,you might be wondering if there is a way to define an element that has a CDATA section in it, which is unparsed. db #3 Use the supporting material to access the sensitive data. Simply put, PCDATA are data that are always recognized as markup. Create a title for a new HTML element. When defining a new XML language, you must specify its grammar — what tags are allowed, what child-tags they may (or, must) contain. Declarations of element type #PCDATA mean that XML Parsers will parse the text contents found between the start and end tags of an XML element that correspond to this DTD element. 1. Technology, Computer Science, Computing Suggest to this list Related acronyms and abbreviations Share PCDATA Meaning page What does PCDATA abbreviation stand. Cancer Gene Index elements not only contain child elements and text elements, but also information about. PCDATA stands for parsed character data, that is, text that is not markup. Document Types. PCDATA stands for parsed character data, that is, text that is not markup. It contains a list of legal elements and define the structure with the help of them. This means that the data is to be parsed by the XML parser. : 3) DTD doesn't support datatypes. Place this in a file quotations-xml. Like <BR/> in HTML. • It's the tag that is shown and also will be parsed (interpreted) by the program that reads the XML document. The other part consists of markup. That doesn't work, since XML recognizes the < as a potential start of a new tag. It is a text-based document and its extension is dot dtd (. txt) or view presentation slides online. What does PCDATA abbreviation stand for? List of 1 best PCDATA meaning form based on popularity. The tag (#PCDATA) stands for parsed character data, meaning that the data is taken from what is entered by the author of the document. Facts & Figures. • PCDATA stands for parsed character data, that is, text that is not markup. It is a set of markup affirmations that actually define a type of document for the SGML family, like GML, SGML, HTML, XML. The moniker PCDATA stands for pursuable character data. " A DTD defines the tags and attributes used in an XML or HTML document. This is the combination of (#PCDATA) and children elements. Elements that contain only other elements are said to have element content [Section 3. Author's Note: It is somewhat remarkable to think that this article, which appeared initially in the Winter 1997 edition of the World Wide Web Journal was out of date by the time the final XML Recommendation was approved in February. A name element contains an optional title element the question mark means the from COMPUTER S 123 at University of New Orleans<!ELEMENT myMessage ( #PCDATA )>]> The first myMessage is the name of the document type declaration. Within mixed content models, text can appear by itself or it can be interspersed between elements. FALSE. It is the good, old text that we write. Line 07 shows how to specify that an element not be allowed to have a body. 2. Or you can tell the XML parser to not parse your data by placing it in a CDATA section: <data><! [CDATA [a < b]]></data>. 2]. PCDATA stands for Parsed Character Data and is the way you specify non-markup text in your DTDs. You can use it to avoid XML escaping special characters. Question 7. e. All of the SGML delimiters listed in the table of delimitersare recognized in PCDATA. In addition to element names, the special symbol #PCDATA is reserved to indicate character data. Rajeev. Pueblo Chemical Depot Activity. PCDATA stands for “parsed character data”, and it refers to the text value of an element; “parsed” meaning that it can contain entities. Elements that contain both other elements and #PCDATA are said to have mixed content. html from CS NETWORKS at Modern Academy In Maadi. 2. c. Students also studiedDocument Types. PCDATA is the text that will be. PCDATA stands for Parsed Character Data. If the parentheses include names of other elements, these would be the children of the element in the tree structure. 1]. PCDATA is the text that a parser must read from. The text consists of a stream of lines. SAX doesn’t provide object model for you, therefore here we have to create our own custom object model and write a Event handler class that listens to SAX Events and does element to object mapping. – PCDATA is the text that will be parsed by a parser. XML is case sensitive. PCDATA stands for Parsed Character Data and is the way you specify non-markup text in your DTDs. It is derived from S tandard G eneralized M arkup L anguage (SGML). Parsed Character Data) Empty element, no content. types. #PCDATA stands for parsed character data and means the element can contain text. XML is a markup language much like HTML. 4/1/99 cps616xmlapril99 njm@npac. PCDATA stand for Parsed Character Data. What does XML parser do? Answer : An XML parser basically checks whether a document is following XML standard or not. What we are now saying is that an element called wml can only have a card in it. Save File Dumping and Injection is available here. Well-formed vs. When defining a new XML language, you must specify its grammar — what tags are allowed, what child-tags they may (or, must) contain. PCDATA: (Parsed Character Data): XML parsers are used to parse all the text in an XML document. The qapair element consists of a question element followed by an answer element. Share PCDATA Meaning page. Students also studiedWhy such a convoluted rule for the head tag Why not just write ELEMENT head from COE coe at University Of the City of Manila (Pamantasan ng Lungsod ng Maynila)PCDATA stands for parsed character data, which includes regular text characters except <, &, or the sequence ]]>. !ELEMENT note defines that the note element must contain four elements: "to,from,heading,body". Within mixed content models, text can appear by itself or it can be interspersed between elements. b. Exercise 10: Generating XML. Some characters like (<, >,&, “, ‘ ) which been indicated in XML morphology should be changed by so-called forms so-called entity references to. 7. Hence, if a DTD element declaration contains the #PCDATA value, it suggests that this element can contain both text and child elements. Document Type Definition (DTD) IST 421 Spring 2004 Lecture 6What file stands out as being likely to contain sensitive data? We have to visit directory “/assets”. PCDATA stands for Parsed Character Data and is the way you specify non-markup text in your DTDs. The parser will process any tags it finds and replace entity references with their actual values. A DTD defines the structure and the legal elements and attributes of an XML document. 2]. CB - Control blocks related to failing task; DM - Data management control blocks (DEB, DCB, IOB) for the task; ENQ - Global resource serialization control blocks for the task; ERR -. This is the combination of #PCDATA and children elements. The * signifies that there can be 0 or more player. This is what the above ch06-wonders. Question 7. For example, if we wanted to turn the example well-formed XML document we have just seen into a valid document, we would insert a line which would look like <!DOCTYPE people someDTDspec >PCDATA stands for parsed character data. ; XML documents can contain international characters. In part 2 you will learn about the components of XML documents seen from a DTD perspective, and how to use them for the markup declarations in the DTD. This type of DTD is declared outside the XML file with a separate file. PCData Back This tool has the impressive restoring ability to create the exact same user accounts and restore data directly from a different volume or from Windows. Example: Norwegian øæå or French êèé. PCDATA stands for Parsed Character Data and is the way you specify non-markup text in your DTDs. All of the SGML delimiters listed in the table of delimitersare recognized in PCDATA. Instructions also. PCDATA stands for data of the Parsed Character. 67. A DTD can be declared inline in your XML document, or as an external reference. • CDATA – CDATA: (Unparsed Character data): CDATA contains the text which is not parsed further in an XML document. PCDATA stands for parsed character data, which is roughly similar to a string data type. An element is everything from the element's start tag to the element's end tag: <firstName>John</firstName> <lastName>Smith</lastName> In DTD, we declare element as follows: <!ELEMENT firstName (#PCDATA)> <!ELEMENT lastName (#PCDATA)> Here PCDATA stands for parsed character data. Here are some basic rules about PCDATA: PCDATA is a string of characters and XHTML entities. 2. dtd available at through the XHTML 1. Think of character data as the text found between the start tag and the end tag of an XML element. The following is an example of a DTD used for defining an automobile:Parsed Character Data (PCDATA) is a data definition that originated in Standard Generalized Markup Language (SGML), and is used also in Extensible Markup Language (XML) Document Type Definition (DTD) to designate mixed content XML elements. #PCDATA is often (but not always) used for leaf elements. 2]. An element that is defined to contain PCDATA can't contain any other element (no sub-tags). 2]. It defines the rules for all the attributes and elements in a XML document. PCDATA is the text that will be parsed by a parser. We provide services to students and learners by presenting the latest, effective and comprehensive video lectures, notes, and. For example, the definition for burns might be <!ELEMENT burns (#PCDATA | quote)*>When a message is parsed by the generic XML parser, the relevant part of the message tree looks like this (assuming that there are no carriage returns or white space between tags):C. An element that is defined to contain PCDATA can't contain any other element (no sub-tags). The tag (#PCDATA) stands for parsed character data, meaning that the data is taken from what is entered by the author of the document. Place #PCDATA in DTD mixed Content. Example: <!ELEMENT name. Find the upc attribute that matches the value of the upc variable. S. : XSDs are written in XML. B. Declarations of element type #PCDATA mean that XML Parsers will parse the text contents found between the start. For example, the definition for burns might be <!ELEMENT burns (#PCDATA | quote)*>PCDATA: (Parsed Character Data): XML parsers are used in an XML document to interpret all of the data. 0 specification page, formally defines the grammar for the XHTML 1 web markup. CDATA also means character data. A DTD can be declared inside an XML document as inline or as an. Question 7. Expert Help. , if the document is properly marked up according to XML syntax rules. An XML document which is well-formed and meets the definitions in a DTD or schema isThis is the DTD <!-- Root element article should contain the elements in parenthesis in that order. DTD Introduction 2. – Headquartered in the Netherlands, Pcdata also has a dedicated sales and support office for the North. CDATA will not be parsed or shown. • #PCDATA stands for parsed character data and means the element can. Such a content model is called mixed. If the DTD is included in your XML source file, it should be wrapped in a DOCTYPE definition with the following syntax:Chapter 27 XML: Extensible Markup Language Chapter Outline Introduction Structured, Semi structured, and Unstructured Data. (Recall that “pre” stands for pre-formatted and is also used for displaying quoted material. The PCDATA stands for parseable character data. This is the combination of (#PCDATA) and children elements. We can supply DTD in separate file as well as in same XML file. This is what the above ch06-wonders. It refers to text data in an XML document that has been parsed by the XML parser. Validates a document against its model, i. Both 1 and 2. 5(b) specifies that a stock_quotes element has zero or more stock_quote elements as its children, while a stock_quote element has four elements symbol, price, change,andvolume, occurring in this order. Compare that with CDATA, where the characters are not to be parsed by the XML, XHTML, or HTML parser. DTD Introduction. (< will be changed to <, <p> will be taken to mean a paragraph tag, etc). dtd extension It is used to define the structure of XML document. PCDA. So PCDATA, the Parsed Character Data is nothing special. This means that it is just a string of characters without any special formatting or markup. PCDATA is the text that will be parsed by a parser. Finally, you may see hyphens and zeros. The DTD defines the constraints on the structure of an XML document. Similarly, for attributes — what attributes are required on certain tags (like “ img ” tags must have a “ src ” attribute and otherwise be empty), and what the allowed values are for attributes. Simply speaking, PCDATA stands for Parsed Character Data. 2. Same attribute in different elements. An element that is defined to contain PCDATA can't contain any other element (no sub-tags). Document Types. • Syntax • Following is a generic syntax for mixed element content − – <!ELEMENT elementname (#PCDATA|child1|child2)*> – ELEMENT is the element declaration tag. technically qualifies as allowing mixed content, but does not allow any elements to be mixed in. 0 Recommendation at the W3C defines a CData Section as fellows: Definition: CDATA sections may occur anywhere character data may occur; they are used to escape blocks of text containing characters which would otherwise be recognized as markup. That means the characters are to be parsed by the XML, XHTML, or HTML parser. For example, the definition for burns might be<!ELEMENT element_4 (#PCDATA)> <!ELEMENT element_5 ANY> DOCTYPE Declaration & DTDs : The document type (DOCTYPE) declaration consists of an internal, or references an external Document Type Definition (DTD). PCDATA stands for Parsed Character Data and is the way you specify non-markup text in your DTDs. pdf), Text File (. The text consists of a stream of lines. DTD. 00 out of 1. It is actually possible to specify that an element can contain both PCDATA and other elements. This is the lightest-weight solution, and is suitable for the homework assignment. You can also define (#CDATA), this stands for character data. Rajeev. If the parentheses include names of other elements, these would be the children of the element in the tree structure. It is derived from S tandard G eneralized M arkup L anguage (SGML). 1]. The term #PCDATA stands for Parsed Character Data, which refers to the text in an XML document which will be parsed by an XML parser. (< will be changed to <, <p> will be taken to mean a paragraph tag, etc). In other words you can say that a parsed character data means the XML parser examine the data and ensure that it doesn't content entity if it contains that will be. EMPTY means the element is an empty element. Tags inside the PCDATA will be treated as markup and entities will be expanded. In other terms, you can assume that a parsed character data implies. #PCDATA stands for Parsed Character data. Namespaces are not supported by DTDs. PCDATA stands for “parsed character data”, and it refers to the text value of an element; “parsed” meaning that it can contain entities. PCDATA stands for Parsed Character Data. This definition appears very rarely and is found in the following Acronym Finder categories: Information technology (IT) and computers; Link/Page Citation Abbreviation Database Surfer. CDATA inside PCDATA. The tag (#PCDATA) stands for parsed character data, meaning that the data is taken from what is entered by the author of. types. The purpose of a DTD is to define the legal building blocks of an XML document. When defining a new XML language, you must specify its grammar — what tags are allowed, what child-tags they may (or, must) contain. PCDATA stands for Parsed Character data. !ELEMENT from defines the from element to be of type "#PCDATA". Character data (CDATA) is just like PCDATA, except the parser will not expect child XML content to be embedded in it. Simply speaking, PCDATA stands for Parsed Character Data. Otherwise, your software might stop working because of validation errors. A DTD allows you to create rules for the elements within your XML documents. While the AdaBoost model identifies the shortcomings by using high weight data points, gradient. ). A DTD is a simple text file that contains the instructions for the elements contained within the corresponding XML document. ˘ˇ ˘ˆ ˙˘˘˙ ˙ ˝˙˘˘˙˛ ˚ ˜ !˛ " ! Table of contents Table of contents Target audience for this paper Summary/objectiveXML stands for eXtensible Markup Language. PCDATA stands for “parsed character data”, and it refers to the text value of an element; “parsed” meaning that it can contain entities. It declares all of the document's element typesglossary, children element types, and. PCDATA stand for Parsed Character Data. Create a Tcl program that queries the quotations table, produces an XML document in the preceding form, and returns it to the client with a MIME type of "application/xml". Elements that contain both other elements and #PCDATA are said to have mixed content [Section 3. 75) fi/catalog/cd [@upc=fi + upc + fi] means. PCDATA stands for parsed character data. a. The rules for mixed content models are similar to the element content as discussed in the previous section. The moniker PCDATA stands for parseable character data . For example, "©" is XHTML entity referring to the. Similarly, for attributes — what attributes are required on certain tags (like “ img ” tags must have a “ src ” attribute and otherwise be empty), and what the allowed values are for attributes. Question 6. They can be added to them but it really is a hack and you need to take a great deal of care in order to make them work. lt!ELEMENT element (PCDATA)gt ; The keyword PCDATA stands for parsed-character data and is any well-formed text string. (#PCDATA) stands for parsed character data. The WDDX DTD allows for multiple encodings of binary data. Examination question paper: May 2018 Module code: Component number: CS5004 003 Module title: Emerging Programming Platforms and Technologies Module leader: Dr. Line 07 shows how to specify that an element not be allowed to have a body. A DTD can be declared inside an XML document as inline or as an external recommendation. When you are experimenting with XML, or when you are working with small XML files, creating DTDs may be a waste of time. DTDs check vocabulary and validity of the structure of XML documents against grammatical rules of appropriate XML language. contain text. The division into lines has no significance apart from indicating a word end. Predefined Character Data; Parsed Character Data; Pure Character Data; None of the given; Which of the following is used to retrieve data from XML documents?Elements with Children (sequences) Elements with one or more children are declared with the name of the children elements inside parentheses: When children are declared in a sequence separated by commas, the children must appear in the same sequence in the document. For example, "©" is HTML entity referring to the copyright character: "©". The DTD can also define multiple ENTITY types - & and similar. It is a language (not> a programming language) that uses the markup and can extend. The rules for mixed content models are similar to the element content as discussed in the previous section. Elements that contain only other elements are said to have element content [Section 3. Tags inside the CDATA text are not treated as markup and. PCDATA stands for parsed character data, that is, text that is not markup. The moniker PCDATA stands for parseable character data . parsed character data, or text. PCDATA stands for Parsed Character data. Similarly, for attributes — what attributes are required on certain tags (like “ img ” tags must have a “ src ” attribute and otherwise be empty), and what the allowed values are for attributes. It is the normal data stored in any XML file that will be parsed by an XML parser. You can use it to avoid XML escaping special characters. Elements that contain both other elements and #PCDATA are said to have mixed content [Section 3. It indicates. An element that is defined to contain. 2]. Parsed Character Data (PCDATA) is a data definition that originated in Standard Generalized Markup Language (SGML), and is used also in Extensible Markup Language (XML) Document Type Definition (DTD) to designate mixed content XML elements. Sub elements An element that contains sub elements is described thus: <!ELEMENT car (brand, type) > <!ELEMENT brand (#PCDATA) > <!ELEMENT type (#PCDATA) >-16-This means that the element car has two subtypes: brand and type. The term enterprise references playback a vitalities role in PCDATA. Syntax <!ELEMENT elementname (#PCDATA|child1|child2)*> • PCDATA is the text that is not markup. Elements with both element content [Section 3. ( < will be changed to. 3) Why we use Schema. This is the combination of (#PCDATA) and children elements. Looking for online definition of PCDATA or what PCDATA stands for? PCDATA is listed in the World's most authoritative dictionary of abbreviations and acronymsWhat does PCDATA stand for? What does PCDATA mean? This page is about the various possible meanings of the acronym, abbreviation, shorthand or slang term: PCDATA. XML is the data standard for many industries, from tech to health to business. ==If it exists, it must come first in the document==. 10 19 Document Type Definition (DTD) Well-formedness (basic requirement of an XML document) doesn’t mean that the data is useful or even correct, e. This means not merely a string of characters, but some entities that may have to be escaped or interpreted by the parser (browser) to have special meaning. For an external document file on your own computer, you can use SYSTEM Start your xml file with a DOCTYPE specifying where the dtd is found, e. For machine-oriented records formats this generally means the data that comes directly. The list of attributes that can appear within an element can also be specified via the keyword !ATTLIST. That means the characters are to be parsed by the XML, XHTML, or HTML parser. – Head office in the Netherlands, Pcdata also has a dedicated sales and support office for the North American. Raw Text: Character Data Looking for the definition of PCDATA? Find out what is the full meaning of PCDATA on Abbreviations. XML: #PCDATA GXSL: Figure 5: GXSL icon for the «pcdata»-class In addition to element type declarations, a DTD may PCDATA stands for Parsed Character data. What does XML parser do? Answer: An XML parser basically checks whether a document is following XML standard or not. Elements that contain only other elements are said to have element content [Section 3. #PCDATA stands forparsed character data and symbolizes any sequence of general characters that does not contain any tag. Expand full name of PCDATA. To declare the. In XML, PCDATA stands for "parsed character data": basically text. CDATA is not processed so what you put in is essentially what you get out. Elements that contain only other elements are said to have element content [Section 3. PCDATA stands for parsed character data, that is, text that is not markup. – Headquartered in the Netherlands, Pcdata also has a dedicated sales and support office for the North. What does PCDATA actually mean? Find out inside PCMag's comprehensive tech and computer-related encyclopedia. PickStar by Pcdata is an easy-to-implement Pick to Light system which can be implemented in many different operations and order-picking environments. What does XML parser do? Answer: An XML parser basically checks whether a document is following XML standard or not. Sorted by: 1. PCDATA stands for Parsed Character data. b. Let us try to understand this with the help of an example. unstructured data • Relational databases are highly structured • All data resides in tables • You must define schema before entering any data 2 Answers. Similarly, for attributes — what attributes are required on certain tags (like “ img ” tags must have a “ src ” attribute and otherwise be empty), and what the allowed values are for attributes. PCDATA means parsed character data. PCDATA stands for "Parsed Character Data. Let us try to understand this with the help of an example. Elements that contain both other elements and #PCDATA are said to have mixed content [Section 3. This is used to solve the inclusion of the mathematical term in the XML document. The book has two sections called 'Preface' and 'First and only chapter' respectively, the second of which has two subsections. Any elements defined in a DTD can be used in these documents, along with the predefined tags and attributes that are part of each markup language. ) XML does . B. Select a course code for Subjective Questions: ACC311 CS001 CS101 CS201 CS301 CS607 CS701 CS702 CS703 CS704 CS707 CS708 CS710 CS711 CS718 CS721 CS724 ECO401 ECO403 ENG101 ENG301 MGT703 MTH501 STA301. Norman Walsh. An XML document can have only a limited number of child elements. End Declaration − Finally, the declaration section of the DTD is closed using a closing bracket and a closing angle bracket (]>). XHTML entities are escape sequences used to refer to special characters that are not so easy to enter them in a text document. Which document is used to define the style of an XML document?ELEMENT is element declarations, PCDATA is the parsed character data which are parsed by the XML parsers. In addition to element names, the special symbol #PCDATA is reserved to indicate character data. XML Character data (CDATA) is defined as Blocks of texts and a type of XML Node recognized by the mark-up languages but are not parsed by the parsers. For example, See the XML below. PCDATA stands for Parsed Character DATA. dtd” file. g. Instructions in a DTD include what elements are used, whether these elements contains parsed character data ( #PCDATA), or other elements, or both. PCDATA is the text that will be parsed by a parser. DTD: Element declaration An element can contain other elements <student> <firstName>John</firstName> <lastName>Smith</lastName> <email> [email protected] </email> </student> In DTD, we declare as follows: <!ELEMENT student (firstName,lastName,email)> It means, the. PCDATA. The moniker PCDATA stands for parseable character data . Compare that with CDATA, where the characters are not to be parsed by the XML, XHTML, or HTML parser. Here are some basic rules about PCDATA: PCDATA is a string of characters and XHTML entities. <!DOCTYPE ancient_wonders SYSTEM "wonders. Note that there is no notion of a “chapter” as. For example, "©" is XHTML entity referring to the copyright character: "©". Similarly, for attributes — what attributes are required on certain tags (like “ img ” tags must have a “ src ” attribute and otherwise be empty), and what the allowed values are for attributes. If you have problems with PCEdit, go check out RAM2Sav. 13 TYPES OF ELEMENT CONTENT. 2. Program Change Decision/Division. It can be used to validate the length of the binary object after decoding. #PCDATA is often (but not always) used for leaf elements. PCDATA stands for 'parseable character data', in plain terms, character strings (text) that can contain markup (elements). 2. There are 4 content models defined for XHTML elements: 1. The above line in your DTD allows the name element to contain non-markup data in your XML document:PCData stands for "Parsed Character Data". This portion of the XML document contains textual data marked up by tags. Syntax DTD: Stands for "Document Type Definition. Defining Web Document Types. PCDATA. XHTML entities are escape sequences used to refer to special characters that are not so easy to enter them in a text document. DTD stands for Document Type Definition. Well-formed vs.