EIDX Glossary of Terms

• Before the days of the Internet and digital communications, a leased line was a private analog telephone circuit that directly connected two points; in the case of data transmission, both end points are computers.  A modem was still needed to translate the computer's digital signals into phone line analog signals and vice-versa.
• Typically, large companies rent leased lines to interconnect different geographic locations in their company. The alternative is to buy and maintain their own private lines or to use the public POTS lines with secure message protocols.
• The advantages are that leased lines provide always-on reliable, high-speed connectivity, whereas dial-up connections are occasional.  The quality of the connection is far superior to what is normally available through dialup, because of the digital signaling, less noise, fewer exchanges etc
• Costs are higher than dial-up,  and if the connection is to the Internet (instead of directly to another computer), the always-on connectivity means always-on exposure to hackers and things like virus and denial of service attacks.  However, using the leased line in Virtual Private Network mode reduces the security risks considerably.

Legacy System - A computer system orapplication which continues to be used because of the cost of replacing or redesigning it and often despite its poor competitiveness and compatibility with modern equivalents. The implication is that the system is large, monolithic and difficult to modify.

• If legacy software only runs on antiquated hardware the cost of maintaining this may eventually outweigh the cost of replacing both the software and hardware unless some form of emulation or backward compatibility allows the software to run on new hardware.
• Sometimes, the legacy system is one that is running perfectly well, and satisfying all business needs, but doesn't have the latest trendy eBusiness technology or business process built-in, and so is perceived as outdated and in need of replacement -- regardless of whether the trendy new eBusiness technology or business process is going to be utilized.

Level - Relative hierarchical position of a data segment within a message, e.g. "header level", "line item level", etc.

Lexical Ambiguity - See Polysemy.

Local Area Network (LAN) - Grouping of computers connected to a main unit called the server.

Log off - Disconnect from a host system.

Log on - Process of connecting to another computer and successfully gaining access by entering the proper identification. Also; (log in) Connect to a host system or public-access site.

Log-in security - Procedure used network systems to gain access to the system by typing in a previously defined password or code word pertaining to a particular account.

Loosely Coupled - Describes system components - software applications or hardware - that work together but have a low dependence on one another.  When components are loosely coupled, changes to one component are unlikely to affect other components. 

• If software components - applications, modules, subprocesses, etc. - are "loosely coupled", there is no assumption (or requirement) that all the components be available at the moment when one component needs to interact with the other component to send or retrieve data, or to execute a process such as a web service.   The component requesting the interaction needs to have some logic built in that tells it what to do if the other component is not available.  For example, the requesting component might have logic to keep retrying the connection over a period of time, and send out an error notification if the retries are still unsuccessful at the end of the specified period of time.

Lurk -Read messages in a Usenet newsgroup without ever saying anything.