Intro to XML in libraries
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This document discusses XML use in libraries. It notes that XML allows for easy information sharing, has a strict yet human-readable syntax, and can create any needed structure. While XML requires an external application and is verbose, it supports schemas and namespaces. The document then summarizes several XML standards used in libraries, including EAD, OAI-PMH, NCIP, MARCXML and Dublin Core. It contrasts the DOM and SAX parsing methods and advises that XML is best for documents, messaging and data transport.
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Intro to XML in libraries
- 1. Intro to XML in libraries Kyle Banerjee banerjek@ohsu.edu
- 2. Why do libraries use XML? • Easy to share information • Strict syntax and human readability make it easy to work with • Create any structure you need • Many tools for all operating systems • Schema support • Namespace support 2
- 3. Disadvantages • Requires an external application • Verbose • Inefficient • Picky – everything stops when data is not well formed • No intrinsic data types 3
- 4. Encoded Archival Description (EAD) 4
- 5. Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) 5
- 6. NISO Circulation Interchange Protocol (NCIP) 6 <!DOCTYPE NCIPMessage PUBLIC "-//NISO//NCIP DTD Version 1.0//EN" "http://www.niso.org/ncip/v1_0/imp1/dtd/ncip_v1_0.dtd"> <NCIPMessage version="http://www.niso.org/ncip/v1_0/imp1/dtd/ncip_v1_0.dtd"> <LookupUserResponse> <ResponseHeader> <FromAgencyId> <UniqueAgencyId> <Scheme>http://136.181.125.166:6601/IRCIRCD? target=get_scheme_values&scheme=UniqueAgencyId</Scheme> <Value>zv229</Value> </UniqueAgencyId> </FromAgencyId> <ToAgencyId> <UniqueAgencyId> <Scheme>http://136.181.125.166:6601/IRCIRCD? target=get_scheme_values&scheme=UniqueAgencyId</Scheme> <Value>melir</Value> </UniqueAgencyId> </ToAgencyId> </ResponseHeader> … [rest of entry deleted]
- 9. Search / Retrieve via URL (SRU) 9
- 10. And enough other stuff to blow your mind • RDF • Darwin Core • VRA Core • MODS 10 • MADS • PBCore • Webapps and other cool stuff
- 11. XML is not a language • It’s a grammar that specifies a structure for exchanging information • XML cannot do anything by itself • When most people talk about XML, they are actually referring to a family of related technologies • Don’t confuse XML (a data structure standard) with content standards such as AACR2R/RDA, DACS, LCNAF, LCSH, MeSH, and AAT 11
- 12. Interpreting XML • Common methods are Document Object Model (DOM) and Simple API for XML (SAX) • DOM is more common and far more powerful. Best for smaller files and documents • SAX is much faster and requires much less memory. Best for large files 12
- 13. XML Document <?xml version = “1.0”?> <inventory> <book> <title>My Dog</title> </book> <book> <title>My Cat</title> </book> </inventory> DOM (tree structure) SAX (linear events) Start document Start element: inventory Start element: book Start element: title Characters: My Dog End element: title End element: book Start element: book Start element: title Characters: My Cat End element: title End element: book End document DOM vs. SAX 13 inventory book book title title My Dog My Cat
- 14. DOM basics • Platform independent way to represent and interact with XML documents • All nodes and relationships are accessible • Great for generating and displaying documents (e.g. EAD), interpreting messages (e.g. NCIP, OAI-PMH) • Must load entire document into memory – terrible for transferring millions of records 14
- 15. SAX (Simple API for XML) • Not formally defined • Relies on events – detects beginnings/ends of elements, attributes, etc. • Does not require loading file into memory • Great for extracting info from large files but awkward for interpreting documents 15
- 16. XML Document <?xml version = “1.0”?> <inventory> <book> <title>My Dog</title> </book> <book> <title>My Cat</title> </book> </inventory> JSON { “inventory”: { “book”: { “title”: “My Dog” }, “book”: { “title”: “My Cat” } } } Delimited Inventory Common Alternatives to XML 16 Item type Title book My Dog book My Cat
- 17. Why Delimited or JSON? • Delimited – Easiest to parse – Works great with tabular data – Not good for arbitrary and nested structures • JSON – Much simpler and easier to use – Bad for situations where markup languages are appropriate (e.g. documents) 17
- 18. XML = Data Duct Tape • Very useful and is here to stay • Best uses are documents, messaging, and data transport • Can be used for almost anything but sometimes not a good choice 18
- 19. XML and Life after MARC • Use of XML will expand as the role of the traditional catalog wanes • Expect growth as libraries need to provide access to a greater variety of resources • XML will be critical as linked data becomes more common 19
- 20. What You Should Do Now • Be aware of what XML is • Know what it is good for • Learn specifics on an as needed basis 20