The LISI Reference Model is oriented by levels that represent increasing degrees of sophistication required to accomplish interactions between information systems. The use of levels provides a discipline for describing the nature of information interaction between operational nodes, translating that nature into the suite of information system capabilities -- the computing environment -- necessary to support the information interaction in context with the operational need (e.g., timeliness, accuracy), and determining the implementation rules for each system capability.
A level in the LISI model is characterized by the most demanding exchanges the level embodies, as well as the enabling capabilities it requires. The LISI Reference Model defines five levels, currently numbered 0, 1, 2, 3, and 4. Figure D-1 depicts these levels.
Figure D-1 LISI Levels and Corresponding Computing Environments
Each level can be generally defined as follows:
Level 0 -- Isolated: Level 0 systems have no direct
electronic connection. Data exchange between these systems typically occurs
via either manual keyboard entry or an extractable common media format (e.g.,
diskette).
Level 1 -- Connected: Level 1 systems are linked
electronically. These systems conduct peer-to-peer exchange of homogeneous
data types, such as simple "text," e-mail, or fixed graphic files (e.g., GIF,
TIFF images). Generally, level 1 systems allow decision makers to simply
exchange files with one another.
Level 2 -- Functional: Level 2 systems are
distributed, i.e., they reside on local networks that allow complex,
heterogeneous data sets (e.g., annotated images, maps with overlays) to be
passed from system to system. Formal data models (logical and physical) are
present; but generally, only the logical data model is agreed to across
programs and each program defines its own physical data model. Generally,
decision makers are able to share fused information between systems or
functions.
Level 3 -- Domain: Level 3 systems are integrated,
i.e., capable of being connected via wide area networks (WAN) that allow
multiple users to access data. Information at this level is shared between
independent applications. A domain-based data model is present (logical and
physical) that is understood, accepted, and implemented across a functional
area or group of organizations that comprises a domain. Systems are capable of
implementing business-rules and processes to facilitate direct
database-to-database interactions, such as those required support database
replication servers. Individual applications at this level may share central
or distributed data repositories. Systems at this level support group
collaboration on fused information products. Generally, decision-making is
supported by fused information from a localized problem domain.
Level 4 -- Enterprise: Level 4 systems are capable
of operating using a distributed global information space across multiple
domains. Multiple users can access and interact with complex data
simultaneously. Data and applications are fully independent and can be
distributed throughout this space to support information fusion. Advanced
forms of collaboration (the virtual office concept) are possible. Data has a
common interpretation regardless of form, and applies across the entire
enterprise. The need for redundant, functionally equivalent applications is
diminished since applications can be shared as readily as data at this level.
Decision-making takes place in the context of, and is facilitated by,
enterprise-wide information found in this global information space.
