XML (eXtensible Markup Language) is a W3C recommendation for creating special-purpose markup languages. It is a simplified subset of SGML, capable of describing many different kinds of data. Its primary purpose is to facilitate the sharing of structured text and information across the Internet. Languages based on XML (for example, RDF, RSS, MathML, XSIL and SVG) are themselves described in a formal way, allowing programs to modify and validate documents in these languages without prior knowledge of their form.1 Strengths and weaknesses
The features of XML that make it particularly appropriate for data transfer are:
- simultaneously human- and machine-readable format
- support for Unicode representing all current and many historical character sets
- the ability to represent the most general computer science data structures ( records, listIn computer science, a list is an abstract concept denoting an ordered collection of fixed-length entities. In practice, any list is either an array or a linked list of some sort. The use of the concept allows to treat them regardless of implementation.s and treeIn computer science, a tree is a widely-used computer data structure that emulates a tree structure with a set of linked nodes. Each node has zero or more child nodes, which are below it in the tree (in computer science, unlike in nature, trees grow down,s)
- the format is self-documenting in that it describes the structureA structure can be a building or other thing built, such as a bridge, but here the structure of a thing is how the parts of it relate to each other, how it is put together; how it works is process, but process requires a viable structure. Both reality and and field nameField name can mean a number of different things: In computer science, a field name identifies a field in a database record or other data structure. In the United Kingdom, each field has a field name. In any field science, field name refers to the commons as well as specific values
- strict syntaxThe first meaning of the term syntax originating from the Greek words (sun, meaning ‘together’) and (taxis, meaning sequence/order), can be described as the study of the rules, or "patterned relations" that govern the way the words in a sentence come toge makes the necessary parsing algorithmsA parser is a computer program or a component of a program that analyses the grammatical structure of an input, with respect to a given formal grammar, a process known as parsing. Parsers can be made both for natural languages and for programming language simple, fast and efficient.
XML is also heavily used for document storage and processing, both online and offline, and offers several benefits:
- robust, logically-verifiable format based on international standards
- hierarchicalA hierarchy (Greek hieros sacred, arkho rule) is a system of ranking and organizing things. Different fields use the word in slightly different ways, but a particular definition (below) captures the core of almost all uses. Originally, "hierarchy" meant " structure suitable for most (but not all) types of document
- plain text files, unencumbered by licenses or restrictions
- platform-independent, and so relatively immune to changes in technology
- has already been in use (as SGML) for long over a decade, and is very popular by itself, so there is extensive experience and software available.
For certain applications, the format also has the following weaknesses:
- XML syntax is fairly verbose and partially redundant . This can hurt human readability and application efficiency, and yields higher storage costs. It can also make XML difficult to apply in cases where bandwidth is limited, though compression can reduce the problem in some cases.
- XML syntax contains a number of obscure features due to its legacy of SGML compatibility.
- XML still often requires further parsing to extract individual values.
- Modelling overlapping (non-hierarchical) data structures requires extra effort.
- Mapping XML to the object oriented or relational paradigms may be cumbersome.
