An introduction to XML
Overview of HTML, XML, VRML, CSS, browsers, mime, cern, web, web page, http , be able to write pages using graphics, text formatting, tables, frames and links. HTML has its origins in SGML which has spawned many markup languages. HTML and XML are both markup languages (hence the *ML). XML is a generic markup language suitable for representing arbitrary data, while HTML is a. The oth- er markup languages discussed were SGML, VRML, and XML. Partici- These connections not only contain links to other pieces of text, but to other.
Phase 3 Develop a common standard for specifying the layout of documents encoded in these languages. Phase 1 is now completed, since the XML 1. Phase 2 is still under way, although there is a working draft.
What is the relationship between SGML,HTML , XML and XHTML? - pugliablog.info Specialties
Phase 3 has not yet reached that stage, as there only exists a suggestion at this stage. They leave out a lot of the standards and are for reasons of readability a little inaccurate.
If you want more detailed and accurate information you should go on to read the appendices below. Also note that these standards are not finalized yet, so that they may change before they're officially accepted. As a first introduction, however, this document should be useful. However, SGML is quite complex to implement and contains a lot of features that are very rarely used. Its support for different character sets is also a bit weak, which is something that can cause problems on the web where people use many different kinds of computers and languages.
The main point of XML is that you, by defining your own markup language, can encode the information of your documents much more precisely than is possible with HTML. This means that programs processing these documents can "understand" them much better and therefore process the information in ways that are impossible with HTML or ordinary text processor documents.
Imagine that you marked up recipes for, say, soups and sea food dishes etc according to a DTD tailored for recipes where you entered the amounts of each ingredient and alternatives for some ingredients.
You could then easily make a program that, given a list of the contents of your fridge, would go through the entire list of recipes and make a list of the dishes you could make with them. Given nutritional information about the ingredients x calories per ounce of this, y calories per once of that etc the program could sort the suggestions by the amount of calories in each dish.
Or by how long they'd take to prepare, or the price given price information for the ingredientsor The possibilites are almost endless, because the information is encoded in a way that the computer can "understand". Defining your own markup language with XML is actually surprisingly simple. If you wanted to make a markup language for FAQs you might want it to be used like this: A,B means that you must have an A first, followed by a B. This means that a program can read the document without knowing the DTD which is where it says that IMG does not have any contents and still know that IMG does not have an end tag and that what comes after IMG is not inside the element.
It is far more advanced than what's possible with HTML and contains a lot of stuff not useful on the web. To make it possible to use this linking standard in any DTD regardless of which elements the DTD has there aren't defined any particular elements for linking.
Mark up languages - INFO
Instead, linking elements use special attributes that identify them as linking elements. What happens when you follow the link is specified with SHOW, which can take the following values: EMBED This means that the resource the link points to is to be inserted into the document the link comes from. This will happen either during the displaying of the document or during processing of the document. It can also be used to insert footnotes into the text and ACTUATE will then specify if the user has to click on the footnotes to include them or whether all footnotes will be inserted automatically.
If you have two different versions of a paragraph you can link them in such a way that one can see the other version in the same context by following the link.
NEW In this case, following the link will not affect the resource the link came from. XML is even more advanced than this. Links can be between more than one resource, they can be specified outside the actual documents themselves and the linked-to element inside a resource can be specified in very powerful ways. The element can be identified with an ID-attribute, position in the element structure and one can even specify that the link goes to things like "fourth LI inside the first UL inside BODY".
In FAQML this could have been used both for specifying links to relevant information outside the FAQ as well as specifying internal relationships between different answers.
It could also have been used for footnotes etc. So far, not much has been done about this. One proposal see references has been submitted, but it hasn't been accepted yet, and it's uncertain if it will be. It can be used both as a stylesheet specifying fonts and positioning for the different elements and as a transformational language that can be used to transform documents from one DTD to another.
An introduction to XML
Below I try to show how we could make a stylesheet for FAQML, but without explaining very much of what really happens. I've split the DSSSL file into several parts in order to be able to comment it as it's written, but it is meant to be a single file.
DSSSL consists of several different parts, and the most basic one is the expression language which is quite simply a subset of Scheme. Another important part which is built on the expression language is the style language, which I've used almost exclusively in this example. A third part is the query language, which can be used to find any element you want in your document. Then style rules for Y and then the contents of Y are specified. The next two lines are comments after ; the rest of the line is ignored.
What is the relationship between SGML,HTML , XML and XHTML?
Then I define two constants that I use below in the styles themselves. This is done to make it easy to change the font size of the entire document without having to adjust sizes for all kinds of headers etc. The flow object is "simple-page-sequence", which I assume is meant for small articles. I then specify what font to use, font size, that whitespace is to be considered insignificant like in HTML and then I give the line height. The line height is set to be 1.
I insert one containing the text "Version: This means that the text "Version: DATE is similar, so I skip that. We've already seen how to do this with sequence, but the problem of getting hold of the number and title is new.
They are only given as attributes, and thus will be ignored by process-children. The function attribute-string gives us what we want.
The rest of this style sheet is so simple that I'll just skip it without comments. This should make no difference, though. What will XML be used for? Please note that what follows is only my personal views on the future of the web and should as such be regarded with a pinch of salt. The layout problem The first thing I hope XML can put right is the problem of making web pages with decent layout that are still accessible to anyone, regardless of browser.
Considering that XSL will be a complete standard to be supported one should, after a while, expect a stable standard to write against. XSL also lets you check whether optional features are present or not and if not you can supply alternative code to take care of those cases.
Just like I produced. PS files for my FAQ above. My hope is that they'll decide they have to make a real effort and do it properly and that if they don't somebody who does will take over the market. They've now promised to support XML, so there's room for hope, but no more See references 5 and 6. This happens a little on the side of the XWGs work, but is still well under way. The members of XWG like to call this "giving Java something to work with. You can also make things like tables that can be sorted by any column by clicking on it.
The possibilities are nearly unlimited, and this is only the tip of the iceberg. This can be made significantly much more advanced.
If you think this is science fiction take a look at reference 8. Well, there would be the applets, but they both install and remove themselves. Jon Bosak describes an even more advanced possibility in reference 4.
The major vendors of electronic components so-called chips have joined forces to make a DTD that can be used to describe components. Together with the right Java applets this could be used to download any descriptions of chips and then model how these work together. Searching and agents The applications described here are currently not feasible, but I hope that in time they may be.
That the information in XML documents is so precisely described by the markup means that one can search them in much better ways than the primitive text searches currently available from search engines like Excite and Altavista today. See references 9 and With standardized DTDs for different applications one could retrieve information much more accurately than today.
One could envision things like a central search engine for chip vendors where you could do very precise searches for components by specification, almost as if they were in an ordinary relational database. Similar services would be possible for all documents with a common DTD. Exploiting this for global search engines like Excite and Altavista is going to be a lot more difficult becaouse of the number of different DTDs.
With an overview of the most important ones and a little artificial intelligence in the search engines this could perhaps be handled, but for now this is pure science fiction. Bob Bemer's home page ASCII is a seven-bit code that consists of decimal numbers ranging from zero through assigned to letters, numbers, punctuation marks, and the most common special characters.
The Extended ASCII Character Set also consists of decimal numbers and ranges from through representing additional special, mathematical, graphic, and foreign characters. The Unicode Standard provides the capacity to encode all of the characters used for the written languages of the world. To keep character coding simple and efficient, the Unicode Standard assigns each character a unique numeric value and name.
The original goal was to use a single bit encoding that provides code points for more than 65, characters. This is sufficient for all known character encoding requirements, including full coverage of all historic scripts of the world, as well as common notational systems.
Introduced new concept of structural markup: Five years later, Bob decided to break with Microsoft which by then had grown to company of over employees and establish his own company: Alt F6, F8 assists you in preparing dot lines.