Is a piece of software that allows you to locate a particular node in a hypermedia database.

There are four types:

Example: alta vista.

Uses it’s own database of websites. In background robots/crawlers continually search the web for non-indexed sites. When a new site is found, the search engine must determine key words. These key words are then added to a search engine index with relevant URL’s. When searching it searches the index to locate the URL. Key word allocation: looks for words in the title and first few paragraphs in the body of the text OR are specified in metatags (by designer).

Advantages

• Can be quick

Disadvantages

• May not find site you want (not indexed) • Key words may not relevant if defined from the text • May not be able to search properly.

Example: yahoo.

Created manually, where all entries are categorised under headings. An appropriate category is determined when a new site is submitted.

Advantages • Search is narrowed once relevant category is identified • Human centred (people generated categories)

Disadvantages • Website may be in wrong category • Frustrating because user has to go through many layers

Example: metacrawler, mamma. Search engine, which uses other search engines.

Advantages • Larger success rate (multiple indexes)

Disadvantages • Can timeout before finished complete search with individual server

Example: ask.com

Do not need to use syntax, follows natural language such as asking questions.

Advantages • Human centred • No syntax required

Disadvantages • It pulls out what it thinks are the keywords in the users search

If you don’t search correctly you may get irrelevant sites.

And/or/not/near

Finds the set of words in the quotes.

Lower: finds upper/lower. Upper: only finds upper.

(plus symbol) Site contains all specified keywords

(minus symbol) Only finds sites without that word.

(wildcard) Any combination after wildcard. E.g. Cat* finds catastrophe, cathode.

Search specified length with character. E.g. Sh%%% finds shell

Finds keywords in the title

Finds all sites with named picture.