BlogJava-gembin-随笔分类-XML

XML Naming Conventions

gembin — Sat, 25 Aug 2012 08:43:00 GMT

Names can start with letters including non-Latin characters.
Names can start with dash (-) character.
Names cannot start with numbers or other punctuation characters.
After the first character, numbers, hyphens, and periods are allowed.
Names can't contain spaces.
Names can't contain the colon (:) character.
Names can't start with the letters xml, in uppercase, lowercase, or mixed.
There can't be a space after the opening <
There can be space before the closing > character.

Here are some examples of valid names:

Following are some examples of invalid names:

which starts with xml,

<123> which starts with a number,

because the equals sign (=)sign is illegal, and

which contains a space.

Case Sensitivity

Most XML standards originating from the W3C tend to use lower case with hyphens.

 is different from , which is different from . 

It's a good idea to pick a naming style and stick to it. 
Some examples of common styles are as follows:

gembin 2012-08-25 16:43 发表评论

SAX vs. DOM

gembin — Sun, 01 Apr 2012 08:32:00 GMT

While comparing two entities, we tend to see both of them as competitors and consequently comparing them to find a winner. This of course is not applicable in every case - not at least in the case of SAX and DOM. Both have their own pros and cons and they are certainly not in direct competition with each other.

SAX vs. DOM

Main differences between SAX and DOM, which are the two most popular APIs for processing XML documents in Java, are:-

Read v/s Read/Write: SAX can be used only for reading XML documents and not for the manipulation of the underlying XML data whereas DOM can be used for both read and write of the data in an XML document.
Sequential Access v/s Random Access: SAX can be used only for a sequential processing of an XML document whereas DOM can be used for a random processing of XML docs. So what to do if you want a random access to the underlying XML data while using SAX? You got to store and manage that information so that you can retrieve it when you need.
Call back v/s Tree: SAX uses call back mechanism and uses event-streams to read chunks of XML data into the memory in a sequential manner whereas DOM uses a tree representation of the underlying XML document and facilitates random access/manipulation of the underlying XML data.
XML-Dev mailing list v/s W3C: SAX was developed by the XML-Dev mailing list whereas DOM was developed by W3C (World Wide Web Consortium).
Information Set: SAX doesn't retain all the info of the underlying XML document such as comments whereas DOM retains almost all the info. New versions of SAX are trying to extend their coverage of information.

Usual Misconceptions

SAX is always faster: this is a very common misunderstanding and one should be aware that SAX may not always be faster because it might not enjoy the storage-size advantage in every case due to the cost of call backs depending upon the particular situation, SAX is being used in.
DOM always keeps the whole XML doc in memory: it's not always true. DOM implementations not only vary in their code size and performance, but also in their memory requirements and few of them don't keep the entire XML doc in memory all the time. Otherwise, processing/manipulation of very large XML docs may virtually become impossible using DOM, which is of course not the case.

How to choose one between the two?

It primarily depends upon the requirement. If the underlying XML data requires manipulation then almost always DOM will be used as SAX doesn't allow that. Similarly if the nature of access is random (for example, if you need contextual info at every stage) then DOM will be the way to go in most of the cases. But, if the XML document is only required to be read and that too sequentially, then SAX will probably be a better alternative in most of the cases. SAX was developed mainly for pasring XML documents and it's certainly good at it. SO, if you need to process an XML document maybe to update a datasource, SAX will probably make a alternative.

Requirements may certainly fall between the two extremes discussed above and for any such situation you should weight both the alternatives before picking any of the two. There are applications where a combination of both SAX and DOM are used for XML processing so that might also be an alternative in your case. But, basically it would be a design decision and evidently it would require a thorough analysis of the pros and cons of all possible approaches in that situation.

gembin 2012-04-01 16:32 发表评论

Eclipse Plugin for eXist (COOL)

gembin — Thu, 11 Sep 2008 05:44:00 GMT

摘要: Eclipse Plugin eXist 阅读全文

gembin 2008-09-11 13:44 发表评论

Why And How To Use PDOM: A Persistent W3C DOM API

gembin — Tue, 29 Jul 2008 09:18:00 GMT

摘要: PDOM stands for Persistent Document Object Model. 阅读全文

gembin 2008-07-29 17:18 发表评论

XQuery Search and Update

gembin — Tue, 29 Jul 2008 09:15:00 GMT

摘要: The XQuery 1.0 specification describes a powerful language for accessing and manipulating XML. In its initial form XQuery lacks two interesting features: fast token-based text search and node-level update. Specifications for these features are under development at the W3C with release dates after XQuery 1.0. This paper looks at the mechanisms by which XQuery can support search and update based on our experience at Mark Logic implementing these features. 阅读全文

gembin 2008-07-29 17:15 发表评论

Native XML Databases

gembin — Tue, 29 Jul 2008 05:50:00 GMT

摘要: Defines a (logical) model for an XML document -- as opposed to the data in that document -- and stores and retrieves documents according to that model. At a minimum, the model must include elements, attributes, PCDATA, and document order. Examples of such models are the XPath data model, the XML Infoset, and the models implied by the DOM and the events in SAX 1.0. 阅读全文

gembin 2008-07-29 13:50 发表评论

SoftwareAG的Tamino Server

gembin — Tue, 29 Jul 2008 05:37:00 GMT

摘要: Software AG是德国的一家多年从事系统软件、ERP、电子商务产品和应用解决方案的软件厂商。阅读全文

gembin 2008-07-29 13:37 发表评论