LIS618 lecture 8

Thomas Krichel

2003-04-02

Lexis/Nexis

• Lexis is a specialized legal research service

• Nexis is primarily a news services

• adds an important temporal component to all its contents

• restricts contents as compared to Dialog

• potentially bad competition from Google

compilation of Nexis

• Uses a number of news sources such as newspapers.

• Uses company reports databases

• Uses web sites, the URLs of which are found in the news sources. Some of the material there can be of low value (remember the comments in the first lecture)

SmartIndexing

• There is a controlled vocabulary of indexing terms

• A document is indexed– In full text view (except web sites)– With automatic addition of index terms that

correspond to the document.• Index terms are added• Weight of index terms is calculated

• http://www.lexis-nexis.com/infopro/products/index/ has more on it.

Six interfaces to Nexis

• Quick search• Subject directory• Power search• Personal news• Search forms• Real time news• In the remainder of the lecture I will go

through these interfaces…

Quick search

• Implicit OR between terms• Use quotes to require adjacency of terms• You can select from a drop-down box of

sources• You can set the date range.• It seems to OR a plural to your search

term.• Sometimes returns documents with none

of the search terms. “she is the one”

Quick search

• It is not clear what parts of documents are being searched

• It does seem to search the full text.

• But it seems to prioritize – TERM, i.e. smart keywords extracted,– HLEAD for news– TITLE for legal documents– WEB-SEARCH-TEXT for web pages

relevance ranking concerns

• where terms appear within the document

• how many occurrences of the terms appear in the document

• how often those search terms appear throughout the document

• apparently not how much they occur, example search for "the"

• seems that they guard algorithm a secret

Subject directory

• you can follow the subject tree but

• there seems to be only a tiny amount of documents

• categories are not particularly deep or developed

• there is a "more like this" feature of limited use, Thomas finds

Power search

• You can first create a customized set of sources to search

• Do this at the start, you browse a menu, then click “done, search now”

• This is a lot more efficient than trying to build a search strategy on a large set.

Power search connectors

• OR• AND• AND NOT • PRE/n, n is a number, ordered proximity• W/n, n is a number, unordered proximity • W/S words in same sentence • W/P words is the some paragraph • Use parentheses!• There is no implicit or as in the simple search,

so forget about the double quotes.

Power search expressions

• Parentheses group terms together• * for one or no letter• ! for any number of letters• ATLEAST n, where n is a minimum number of

occurrences• PLURAL (term) only the plural of term• SINGULAR (term) only the singular of term• ALLCAPS (term) only capitals of term• NOCAPS (term) no capitals of term• CAPS (term) capitalized term only

power search for news

• uses power search expressions, plus• hlead (expression) ?• headline (expression)• company (expression) for a company• byline (expression) for the author• show (expression) for a television show

transcript

expression is a Boolean expression or simple keyword.

power search for legal data

• uses power search expressions, plus

• name (expression) for the name of a party

• cite (expression) for a citation expression for case law

• title (expression) for the title of a law article

expression is a Boolean expression or simple keyword

Search forms

• There are special forms for – News– Company reports– Market indicators– Portfolio– News and quotes about companies

Personal news alert

• do a search

• then click on “track in personal news” to get to a screen where you can enter – periodicity – what documents to be sent– subject

Real time news

• This uses a different query language– terms are implicitly ANDed– explicit AND and OR allowed– phrases have to be put in quotes– * starts for any number of characters, not just

one as in power search– parenthesis can be used

• I have poor experience with this.

Summary

• It has access to sources that are not freely available but

• The search interface is poor when compared to what is offered by Google.

• So you spend a lot of time working with it to get what you want.