Appendix A Software features

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Accessible via web browser	Collections are accessed through a standard web browser (Netscape or Internet Explorer) and combine easy-to-use browsing with powerful search facilities.
Full-text and fielded search	The user can search the full text of the documents, or choose between indexes built from different parts of the documents. For example, some collections have an index of full documents, an index of sections, an index of titles, and an index of authors, each of which can be searched for particular words or phrases. Results can be ranked by relevance or sorted by a metadata element.
Flexible browsing facilities	The user can browse lists of authors, lists of titles, lists of dates, classification structures, and so on. Different collections may offer different browsing facilities and even within a collection, a broad variety of browsing interfaces are available. Browsing and searching interfaces are constructed during the building process, according to collection configuration information.
Creates access structures automatically	The Greenstone software creates information collections that are very easy to maintain. All searching and browsing structures are built directly from the documents themselves. No links are inserted by hand, but existing links in originals are maintained. This means that if new documents in the same format become available, they can be merged into the collection automatically. Indeed, for some collections this is done by processes that wake up regularly, scout for new material, and rebuild the indexes—all without manual intervention.
Makes use of available metadata	Metadata, which is descriptive information such as author, title, date, keywords, and so on, may be associated with each document, or with individual sections within documents. Metadata is used as the raw material for browsing indexes. It must be either provided explicitly or derivable automatically from the source documents. The Dublin Core metadata scheme is used for most electronic documents, however, provision is made for other schemes.
Plugins extend the system's capabilities	In order to accommodate different kinds of source documents, the software is organized in such a way that “plugins” can be written for new document types. Plugins currently exist for plain text, html, Word, PDF, PostScript, E-mail, some proprietary formats, and for recursively traversing directory structures and compressed archives containing such documents. A collection may have source documents in different forms. In order to build browsing indexes from metadata, an analogous scheme of “classifiers” is used: classifiers create browsing indexes of various kinds based on metadata.
Designed for multi-gigabyte collections	Collections can contain millions of documents, making the Greenstone system suitable for collections up to several gigabytes.
Documents can be in any language	Unicode is used throughout the software, allowing any language to be processed in a consistent manner. To date, collections have been built containing French, Spanish, Maori, Chinese, Arabic and English. On-the-fly conversion is used to convert from Unicode to an alphabet supported by the user's web browser.
User interface available in multiple languages	The interface can be presented in multiple languages. Currently, the interface is available in Arabic, Chinese, Dutch, English, French, German, Maori, Portuguese, and Spanish. New languages can be added easily.
Collections can contain text, pictures, audio, and video	Greenstone collections can contain text, pictures, audio and video clips. Most non-textual material is either linked in to the textual documents or accompanied by textual descriptions (such as figure captions) to allow full-text searching and browsing. However, the architecture permits implementation of plugins and classifiers even for non-textual data.
Uses advanced compression techniques	Compression techniques are used to reduce the size of the indexes and text. Reducing the size of the indexes via compression has the added advantage of increasing the speed of text retrieval.
Administrative function provided	An “administrative” function enables specified users to authorize new users to build collections, protect documents so that they can only be accessed by registered users on presentation of a password, examine the composition of all collections, and so on. Logs of user activity can record all queries made to every Greenstone collection.
New collections appear dynamically	Collections can be updated and new ones brought on-line at any time, without bringing the system down; the process responsible for the user interface will notice (through periodic polling) when new collections appear and add them to the list presented to the user.
Collections can be published on the Internet or on CD-ROM	The software can be used to serve collections over the World-Wide Web. Greenstone collections can be made available, in precisely the same form, on CD-ROM. The user interface is through a standard web browser (Netscape is provided on each disk), and the interaction is identical to accessing the collection on the web—except that response times are more predictable. The CD-ROMs run under all versions of the Windows operating system.
Collections can be distributed amongst different computers	A flexible process structure allows different collections to be served by different computers, yet be presented to the user in the same way, on the same web page, as part of the same digital library.
Operates on both Windows and Unix	Greenstone runs under both Windows (3.1/3.11, 95/98/Me, NT/2000) and Unix (Linux and SunOS). Any of these systems can be used as a webserver. Collections cannot be built on low-end Windows systems (3.1/3.11), but pre-built collections can be transferred to them.
What you get with Greenstone	The Greenstone Digital Library is open-source software, available from the New Zealand Digital Library ( nzdl.org ) under the terms of the Gnu General Public License. The software includes everything described above: web serving, CD-ROM creation, collection building, multi-lingual capability, plugins and classifiers for a variety of different source document types. It includes an autoinstall feature to allow easy installation on both Windows and Unix. In the spirit of open-source software, users are encouraged to contribute modifications and enhancements.