O reilly perl and xml pdf

Given a reference to a hash containing an encoded document, this subroutine generates XML markup and returns it as a string of text. If you like, you can build the document from scratch by simply creating the data structures from hashes, arrays, and strings. Just be careful to avoid using circular references, or the module will not function properly.

Among its features is the ability to import and export XML files representing mailing lists. Your assignment is to write a program that can edit the XML datafiles to convert just the names into all caps. Accepting the challenge, you first examine the XML files to determine the style of markup. Example shows such a document.

Having read the perldoc page describing XML::Simple , you might feel confident enough to craft a little script, shown in Example Running the program a little trepidatious, perhaps, since the data belongs to your boss , you get this output:.

Well, almost perfectly. The output is a little different from what you expected. Also, the spacing between elements may be off.

Could this be a problem? This scenario brings up an important point: there is a trade-off between simplicity and completeness. Sometimes the order of elements is vital, and then you might not be able to use a module like XML::Simple. Or, perhaps you want to be able to access processing instructions and keep them in the file. This is only the beginning of your journey. Most of the book still lies ahead of you, chock full of tips and techniques to wrestle with any kind of XML.

Not every XML problem is as simple as the one we just showed you. You need to consider these quirks when working with XML and Perl. For this reason, a computer program that actually does something cool or useful with XML uses a processor as just one component. It usually reads an XML file and, through the magic of parsing, turns it into in-memory structures that the rest of the program can do whatever it likes with. In the Perl world, this behavior becomes possible through the use of Perl modules: typically, a program that needs to process XML embraces, through a use directive, an existing package that makes a programmer interface available usually an object-oriented one.

When Perl programmers identify a need and write a module to handle it, they are encouraged to distribute it to the world at large via CPAN. Without a governing body, they all coexisted in inconsistent glee, with a variety of structures, interfaces, and goals. Later, the field of basic, low-level parsers started to widen. Of course, the goofy, quick-and-dirty tools are still there if you want to use them, and XML::Simple is among them.

It could have been received over a network, constructed from a database, or read from disk. Mind you, the program as a whole might care a great deal. Structurally, all XML documents are similar. This, in turn, means that all these processors can share a common base.

XML Gotchas 2. An XML Recap 2. Markup, Elements, and Structure 2. Namespaces 2. Spacing 2. Entities 2. Unicode, Character Sets, and Encodings 2. The XML Declaration 2. Processing Instructions and Other Markup 2. Declaring Elements and Attributes 2. Schemas 2. Other Schema Strategies 2.

Transformations 3. XML Parsers 3. XML::Parser 3. Example: Well-Formedness Checker Revisited 3. Parsing Styles 3. Putting Parsers to Work 3. XML::XPath 3. Document Validation 3. DTDs 3. Schemas 3.

XML::Writer 3. Other Methods of Output 3. Character Sets and Encodings 3. Unicode, Perl, and XML 3. Unicode Encodings 3. UTF-8 3. UTF 3. Other Encodings 3. If you run the following code on the previous SVG image, you will notice that it is cropped because ImageMagick does not yet recognize the scaling attribute:.

It is also becoming more accepted on the web, but it is still not as prevalent as the SWF format. An SWF file is a sequence of opcodes that describe single or multi-frame animations called movies. Movies can be embedded within other movies as sprites , and all elements of the document are scriptable with the ActionScript language. SWF is the most powerful and common animation format currently on the Web.

One of the sample Ming applications in Chapter 9 is a program that assembles previously created Flash movies into a new composite movie according to an XML description:. See Chapter 9 for the full example. Skip to main content. The XML parser stitches up all the pieces into one logical document;. In theory, a public identifier will endure any location shuffling.

Of course, for this to work, the XML processor has to know how to use public identifiers,. If the XML processor for some. The only place from which. Comments are notes in the document that are not interpreted by the XML processor. They can be used to identify the purpose of files and sections to help navigate. Figure shows the form of a comment. It starts with the delimiter 3. Between these delimiters goes the comment text 2. Comments can go anywhere in your document except before the XML declaration.

The XML processor removes them completely before parsing begins. The content of the section 2 may contain markup characters.

It is a container for data that is targeted toward a specific XML processor. How the data will help processing. The target is a keyword that an XML processor uses to determine whether the data is. But it still may not be clear to. Visit conferences. Safari Bookshelf safari. Conduct searches across more than 1, books. Subscribers can zero in on answers to time-critical questions in a matter of seconds.

Read the books on your Bookshelf from cover to cover or simply flip to the page you need. Try it today with a free trial. Instead of strutting around, pecking at seed, the chickens are all lying on the ground or draped over fences as if they were made of rubber. You see, it was a boneless chicken ranch. Just as skeletons give us vertebrates shape and structure, markup does the same for text.

Take out the markup and you have a mess of character data without any form. It would be very difficult to write a computer program that did anything useful with that content. Software relies on markup to label and delineate pieces of data, the way suitcases make it easy for you to carry clothes with you on a trip. Here I will describe the fundamental building blocks of all XML -derived languages: elements, attributes, entities, processing instructions, and more. Mastering these concepts is essential to understanding every other topic in the book, so read this chapter carefully.

This is the second edition of the original which first appeared in Tags If XML markup is a structural skeleton for a document, then tags are the bones. They mark the boundaries of elements, allow insertion of comments and special instructions, and declare settings for the parsing environment.

A parser, the front line of any program that processes XML , relies on tags to help it break down documents into discrete XML objects. There are a handful of different XML object types, listed in Table All rights reserved. This is a paragraph. CDATA section Create a section of character data that should not be parsed, preserving any special characters inside it. They break up the document into smaller and smaller cells, nesting inside one another like boxes.

Figure shows the document in Chapter 1 partitioned into separate elements. Each of these pieces has its own properties and role in a document, so we want to divide them up for separate processing. These are attributes. He needs to be recharged twice a day and if he starts to get cranky, give him a quart of oil. I'll be back soon, after I've tracked down that evil mastermind Dr.

Indigo Riceway Figure In the telegram example earlier, look for an attribute in the start tag of the telegram element. Declarations are never seen inside elements, but may appear at the top of the document or in an external document type definition file. They are important in setting parameters for the parsing session.

They define rules for validation or declare special entities to stand in for text. Processing instructions are software-specific directives embedded in the markup for convenience e. Comments are regions of text that the parser should strip out before processing, as they only have meaning to the author. CDATA sections are special regions in which the parser should temporarily suspend its tag recognition.

Rounding out the list are entity references, commands that tell the parser to insert predefined pieces of text in the markup. Instead of angle brackets for delimiters, they use the ampersand and semicolon. Documents An XML document is a special construct designed to archive data in a way that is most convenient for parsers. It has nothing to do with our traditional concept of documents, like the Magna Carta or Time magazine, although those texts could be stored as XML documents.

It simply is a way of describing a piece of XML as being whole and intact for parsing. Quite often, a document may be spread out across many files, and some of these may live on different systems.

All that is required is that the XML parser reading the document has the ability to assemble the pieces into a coherent whole. Later, we will talk about mechanisms used in XML for linking discrete physical entities into a complete logical unit.

First is the document prolog, a special section containing metadata. The second is an element called the document element, also called the root element for reasons you will understand when we talk about trees. The root element contains all the other elements and content in the document. The prolog is optional. If you leave it out, the parser will fall back on its default settings.

The root element is required, because a document without data is just not a document. An XML parser needs to know about these particulars before it can start its work. You communicate these options to the parser through a construct called the document prolog. The document prolog if you use one comes at the top of the document, before the root element.

There are two parts both optional : an XML declaration and a document type declaration. The XML declaration, if used, has to be the first line in the document. Example shows a document containing a full prolog.

This leads to the amusing fact that the following smiley of a perplexed, bearded dunce is a well-formed document:. Example It can always get worse. It is optional, but when used it must always appear in the first line. Figure shows the form it takes. Figure The version parameter must appear if the other parameters are used: version Declares the version of XML used. Character encodings are explained in Chapter 9.

As I explain in the next section, declarations are constructs that contribute information to the parser for assembling and validating a document. It does not, as the name may seem to imply, mean that no other resources need to be loaded. There could well be parts of the document in other files. The Document Prolog 53 Parameter names and values are case-sensitive. The names are always lowercase. Order is important; the version must come before the encoding which must precede the standalone parameter.

Either single or double quotes may be used. The first is to define entities or default attribute values. The second is to support validation, a special mode of parsing that checks grammar and vocabulary of markup. A validating parser needs to read a list of declarations for element rules before it can begin to parse. In both cases, you need to make declarations available, and the place to do that is in the document type declaration section.

Figure shows the basic form of the document type declaration. It begins with the delimiter 7. Inside, the first part is an element name 2 , which identifies the type of the document element. Next is an optional identifier for the document type definition 3 , which may be a path to a file on the system, a URL to a file on the Internet, or some other kind of unique name meaningful to the parser.

The last part, enclosed in brackets 4 and 6 , is an optional list of entity declarations 5 called the internal subset. It complements the external document type definition which is called the external subset. Together, the internal and external subsets form a collection of declarations necessary for parsing and validation. Form of the system identifier Here is an example with a system identifier.

It points to a file called simple. An alternative scheme to system identifiers is the public identifier. Unlike a system path or URI that can change anytime an administrator feels like moving things around, a public identifier is never supposed to change, just as a person may move from one city to another, but her social security number remains the same. The problem is that so far, not many parsers know what to do with public identifiers, and there is no single official registry mapping them to physical locations.

For that reason, public identifiers are not considered reliable on their own, and must include an emergency backup system identifier. Figure shows the form of a public identifier. It starts with the keyword PUBLIC 1 , and follows with a character string 3 in quotes 2 , and the backup system identifier 4 , also in quotes 2. The XML parser first reads declarations from the external subset given by the system or public identifier , then reads declarations from the internal subset the portion in square brackets in the order they appear.

In this chapter, I will only talk about what goes in the internal subset, leaving the external subset for Chapter 3. There are several kinds of declarations. Some have to do with validation, describing what an element may or may not contain again, I will go over these in Chapter 3.

Another kind is the entity declaration, which creates a named piece of XML that can be inserted anywhere in the document. The form of an entity declaration is shown in Figure It begins with the delimiter 4. Form of an entity declaration The value or identifier portion may be a system identifier or public identifier, using the same forms shown in Figure and Figure