XML: Basic Concepts

Extensible Markup Language, abbreviated XML, describes a class of data objects called XML documents and partially describes the behavior of computer programs which process them. XML is an application profile or restricted form of SGML, the Standard Generalized Markup Language. By construction, XML documents are conforming SGML documents.

It is called extensible because it is not a fixed format like HTML (a single, predefined markup language). Instead, XML is actually a `metalanguage' - a language for describing other languages - which lets you design your own customized markup languages for limitless different types of documents. XML can do this because it's written in SGML, the international standard metalanguage for text markup systems (ISO 8879).

XML is primarily intended to meet the requirements of large-scale Web content providers for industry-specific markup, vendor-neutral data exchange, media-independent publishing, one-on-one marketing, workflow management in collaborative authoring environments, and the processing of Web documents by intelligent clients. It is also expected to find use in certain metadata applications. XML is fully internationalized for both European and Asian languages, with all conforming processors required to support the Unicode character set in both its UTF-8 and UTF-16 encodings. The language is designed for the quickest possible client-side processing consistent with its primary purpose as an electronic publishing and data interchange format.

XML documents are made up of storage units called entities, which contain either parsed or unparsed data. Parsed data is made up of characters, some of which form the character data in the document, and some of which form markup. Markup encodes a description of the document's storage layout and logical structure. XML provides a mechanism to impose constraints on the storage layout and logical structure. A software module called an XML processor is used to read XML documents and provide access to their content and structure. It is assumed that an XML processor is doing its work on behalf of another module, called the application. This specification describes the required behavior of an XML processor in terms of how it must read XML data and the information it must provide to the application.

This summary in 10 points attempts to capture enough of the basic concepts.

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Language work

The Passive

Passive are very common in			PROLOG	were	designed	for
technical writing where we are more			research into Artificial Intelligence.
interested in facts, processes, and			Present Perfect:		Computers	and
events than in people. We form the			microchips have become part of our
passive by using the appropriate			everyday lives: We visit shops and
tense of the verb to be followed by			offices which have been designed
the past participle of the verb we are			with the help of computers, we read
using. For example:			magazines	which	have	been
Active			produced on computers.
			Past Perfect: By this time
1. The	CPU	processes	Microsoft made its operating system
instructions. (simple present)			Windows 95, graphic user interface

2.Charles Babbage invented the had widely been used by Macintosh.

computer. (simple past)	Present	Continuous:		BASIC
Passive	enables the user to interact with the
1. Instructions are processed by	program while it is being executed,
the CPU. (simple present)	which means that data can be input
2. The computer was invented	while the program is running.
by Charles Babbage. (simple	Past Continuous:		All	computers
past)	were being brought to a virtual
Passive verb forms:	standstill by the mysterious bug.
	Future Simple: If the market for
Present Simple: When a particular	possible	computers	grows, prices
program is run, the data is processed	will be reduced.
by the computer very rapidly.	Future Perfect: By the year 2030
Past Simple: In the 1970s, new	human labour in industry will have
languages such as LISP and	been replaced by robots.

Task 7. Rewrite the following sentences using the Passive.

1.Last Thursday we appointed a new system analyst.

2.Portable PCs will be replacing desktop PCs in a few years time.

3.They have fully computerized the factory.

4.Smith Ltd is supplying our company with computers.

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5.Professor Niklaus Wirth and his colleagues developed the Pascal language.

6.No-one has seen the Senior Programmer since the day of the exhibition.

7.They program the computer to warn users before it deletes information.

8.They are installing the new computer system next month.

9.The computer didn’t carry out the instructions because of a syntax error.

10.We’ll complete the testing of the new computer program by next week.

11.Computer Services Engineer Technician has been restoring the data for several hours.

12.She offered me the job as a hardware engineer but I refused it.

13.We use computers to process our sales information.

14.Local businesses have provided technical support.

15.The CPU processes instructions.

16.Governments can take measures against computer crime.

17.Software manufactures will have made hundreds of new programs by this time next year.

18.Scientists may discover new electronic components.

Task 8. Here is the beginning of a report of an experiment. Rewrite it, putting verbs in the passive where appropriate and making any other necessary changes.

I conducted the test in the college library to minimize noise. I took the students out of their normal lessons and I tested them in groups of four. I carried out all the tests in January 1996. The test consisted of two components. First, I showed the students a design (I presented it in Chapter 3) and I asked them to describe what they saw. I tape recorded all their answers. I then gave them a set of anagrams (words with jumbled letters) which I instructed them to solve in as short time as possible. I remained in the room while the students did this…

Task 9. Fill in the gaps in the following sentences using the appropriate form of the verbs in brackets.

1.The first digital computer …… (build) by the University of Pennsylvania in 1946.

2.Instructions written in a high-level language …… (transform) into machine code.

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3.The operating system is always present when a computer …… (use).

4.The contractor who had developed a computerized circulation system inserted a logic bomb that would disable the system on a certain date unless the contractor …… (pay).

5.All computer languages must …… (translate) into binary commands.

6.A new version of TurboPascal …… (just/release).

7.In the next century, computers …… (program) in natural languages like English or French.

8.All the activities of the computer system …… (coordinate) by the central processing unit.

9.By 2020, new technology …… (revolutionize) communications.

10.Previously those business presenters who wanted to make an impression handed round copies of reports that …… (professionally/ produced).

11.During that period, enormous advances …… (make) in computer technology.

12.In some modern systems information ….. (hold) in optical disks.

13.Software can …… (hold) in the memory of the computer or …… (record) on floppy disk.

14.Microsoft …… (find) on the basis of the development of MS/DOS.

15.As the MT systems designed for diffusion purposes are computationally very heavy, they …… (develop) on mainframes.

16.The interface is called WIMP: Window, Icon, Mouse and Pointer and software products for the Macintosh …… (design) to take full advantage of its features using this interface.

Task 10. Read the texts and match them with the headings below.

1.XML is text, but isn’t meant to be read

2.XML is for structuring data

3.XML is verbose by design

4.XML looks a bit like HTML

a)_______________

Structured data includes things like spreadsheets, address books, configuration parameters, financial transactions, and technical drawings. XML is a set of rules (you may also think of them as guidelines or conventions) for designing text formats that let you structure your data.

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XML is not a programming language, and you don't have to be a programmer to use it or learn it. XML makes it easy for a computer to generate data, read data, and ensure that the data structure is unambiguous. XML avoids common pitfalls in language design: it is extensible, platformindependent, and it supports internationalization and localization. XML is fully Unicode-compliant.

b) _______________

Like HTML, XML makes use of tags (words bracketed by '<' and '>') and attributes (of the form name="value"). While HTML specifies what each tag and attribute means, and often how the text between them will look in a browser, XML uses the tags only to delimit pieces of data, and leaves the interpretation of the data completely to the application that reads it. In other words, if you see "<p>" in an XML file, do not assume it is a paragraph. Depending on the context, it may be a price, a parameter, a person, a p... (and who says it has to be a word with a "p"?).

c) _______________

Programs that produce spreadsheets, address books, and other structured data often store that data on disk, using either a binary or text format. One advantage of a text format is that it allows people, if necessary, to look at the data without the program that produced it; in a pinch, you can read a text format with your favorite text editor. Text formats also allow developers to more easily debug applications. Like HTML, XML files are text files that people shouldn't have to read, but may when the need arises. Compared to HTML, the rules for XML files allow fewer variations. A forgotten tag, or an attribute without quotes makes an XML file unusable, while in HTML such practice is often explicitly allowed. The official XML specification forbids applications from trying to second-guess the creator of a broken XML file; if the file is broken, an application has to stop right there and report an error.

d) _______________

Since XML is a text format and it uses tags to delimit the data, XML files are nearly always larger than comparable binary formats. That was a conscious decision by the designers of XML. The advantages of a text format are evident, and the disadvantages can usually be compensated at a different level. Disk space is less expensive than it used to be, and compression programs like zip and gzip can compress files very well and very fast. In addition, communication protocols such as modem protocols and HTTP/1.1, the core protocol of the Web, can compress data on the fly, saving bandwidth as effectively as a binary format.

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Task 11. Read the text again and find answers to these questions:

1.What is structured data?

2.Do you need to be a programmer to use XML? Why?

3.What are the basic character features of XML?

4.What are the similarities and differences between XML and HTML?

5.What are pros and cons of using text format?

Task 12. Look back in the text and find words or phrases which mean the following:

1.to put sth together in an organized way (§A)

2.clear in meaning; that can only be understood in one way (§A)

3.a danger or difficulty, especially one that is hidden or not obvious at first (§A)

4.to decide what the limits of sth are (§B)

5.the particular way in which sth is understood or explained (§B)

6.to think or accept that sth is true but without having proof of it (§B)

7.used to say that sth could be done or used in a particular situation if it is really necessary (§C)

8.clearly and exactly (§C)

9.similar to sb/sth else and able to be compared (§C)

10.using or containing more words than are needed (§D)

11.deliberate or controlled (§D)

12.to provide sth good to balance/reduce the bad effects of damage, loss, etc. (§D)

Task 13. Read the text below. Use the words in the box to the right of the text, listed 1-12, to form a word that fits in the same numbered space in the text. There is an example (0).

XML is a family of technologies

XML 1.0 is the 0) …… that defines what "tags" and "attributes" are. Beyond XML 1.0, "the XML family" is a 1) …… set of modules that offer 2) …… services to accomplish important and 3) …… demanded tasks. XLink 4) …… a standard way to add hyperlinks to an

e.g. 0) specification

0)SPECIFIC

1)GROWTH

2)USE

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XML file. XPointer is a syntax in 5) …… for pointing to parts of an XML document.An XPointer is a bit like a URL, but instead of pointing to documents on the Web, it points to pieces of data inside an XML file. CSS, the style sheet language, is 6) …… to XML as it is to HTML. XSL is the advanced language for 7) …… style sheets. It is based on XSLT, a 8)

……language used for rearranging, adding and deleting tags and attributes. The DOM is a standard set of function calls for 9) …… XML (and HTML) files from a 10) …… language. XML Schemas 1 and 2 help developers to 11)

……define the structures of their own XMLbased formats. There are several more modules and tools 12) …… or under development. Keep an eye on W3C's technical reports page.

Speaking

3)FREQUENT

4)DESCRIPTIVE

5)DEVELOPER

6)APPLY

7)EXPRESSIVE

8)TRANSFORM

9)MANIPULATION

10)PROGRAMMER

11)PRECISE

12)AVAILABILITY

Task 14. Work in pairs and both look at the pictures on pages 109 and 110.

1.Student A: You should talk about the pictures on page 109. They show different types of user interface. You should

a)describe common features of user interfaces, and

b)comment on the basic principles to design a user interface. You

have about one minute.

Student B: When Student A has finished, comment on what he/she has said. Say if you agree or disagree.

2.Student B: You should talk about the pictures on page 110. They show different websites.

a)compare and contrast them, and

b)comment on the basic principles to design a website. What features make a good website? Talk about features that annoy users. You

have about one minute.

Student A: When Student B has finished, comment on what he/she has said. Say if you agree or disagree.

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Unit 12. Extensible Markup Language

Warm-up

Task 1. Read the explanations and write the term from the text below in the crossword puzzle.

1.a set of unambiguous rules to solve a problem in a definite number of steps

2.scientific knowledge used in practical ways in industry, for example in designing new machines

3.a unit of measurement that is officially used; an official rule used when producing sth

4.a person whose job is to decide how things such as tools, machines, etc. will look or work by making drawings, plans or patterns

5.the rules that state how words and phrases must be used in a computer language

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