## Norsys Netica

** Category** Intelligent Software>Bayesian Network Systems/Tools

** Abstract** Netica is an advanced, easy-to-use, complete program for working with Belief Networks (see below) and influence diagrams. It has an intuitive and smooth user interface for drawing the networks, and the relationships between variables may be entered as individual
probabilities, in the form of equations, or learned from data files (which may be in ordinary tab-delimited form and have "missing data").

Once a belief network is created, the knowledge it contains can be transferred to other networks by cutting and pasting, or saved in modular form by creating a library of nodes with disconnected links. Of course, the networks and libraries may be saved in files or printed out.

Belief Networks and Decision Networks --

Belief networks (also known as Bayesian networks, Bayes networks and causal probabilistic networks), provide a method to represent relationships between propositions or variables, even if the relationships involve uncertainty, unpredictability or imprecision.

They may be learned automatically from data files, created by an expert, or developed by a combination of the two. They capture knowledge in a modular form that can be transported from one situation to another; it is a form people can understand, and which allows a clear visualization of the relationships involved.

By adding decision variables (things that can be controlled), and utility variables (things we want to optimize) to the relationships of a belief network, a decision network (also known as an 'influence diagram') is formed. This can be used to find optimal decisions, control systems, or plans.

Netica features/capabilities include:

1) Generates presentation quality graphics which can be incorporated into other documents.

2) Compiles belief (Bayesian) networks into a junction tree of cliques for fast probabilistic reasoning.

3) Extensive on-screen help.

4) Utility-free sensitivity analysis (Windows version only).

5) Can test the performance of a network using a file of cases. Netica will print out a confusion matrix, error rate, logarithmic and quadratic (Brier) scoring rule results, calibration table and surprise indexes for each node desired.

6) Can find optimal decisions for sequential decision problems (i.e., later decisions are dependent on the results of earlier ones).

7) Can solve influence diagrams efficiently by using clique trees.

8) Can learn probabilistic relations from data.

9) Provides easy graphical editing of belief networks and influence diagrams, including:

- a) Cut / paste / duplicate nodes without loosing their probabilistic relation;
- b) Many ways of displaying the nodes (bar graphs, meters, etc.);
- c) Links with bends to keep complex diagrams orderly;
- d) Allows comments, keeps track of author, when changed, etc. for each node;
- e) Unlimited levels of undo / redo.

10) Allows the entry of probabilistic relations by equation, with an extensive built-in library of probabilistic functions and other mathematical functions.

11) Has facilities for the easy discretization of continuous variables.

12) Can reverse individual links and "sum out" nodes of influence diagrams or belief networks, for model exploration.

13) Supports disconnected links, which makes possible libraries of probabilistic relationships.

14) It is possible to represent networks with nodes whose values change over time (a persistence is defined for such nodes), and to have links with time delays (which allows cycles).

The software can automatically convert these networks into expanded regular networks covering a limited period of time.

15) Accepts likelihood findings (i.e., virtual evidence), and findings of the form that some variable is Not in some state.

16) Can display nodes and inference results in a number of forms, including bar graphs of beliefs and a true/false meter.

17) Can customize the display to be suitable for an end-user.

18) Supports documentation and tracking of every node and network (with comments, titles, author, when last changed, etc.).

19) Has No built in limits on the size or complexity of Belief networks, so they are limited only by available memory.

20) Can work hand-in-hand with the "Netica API" product (for example, sharing the same files) - an additional product from this manufacturer.

*System Requirements*

Contact manufacturer.

*Manufacturer*

- Norsys Software Corp.
- 3512 West 23rd Avenue
- Vancouver, BC
- CANADA
- V6S 1K5
- Tel: +1 604.221.2223
- Fax: +1 604.221.2238
- E-mail: info@norsys.com

** Manufacturer Web Site**
Norsys Netica

** Price** Commercial $585

Educational / Personal $285

Volume or Site license Contact Norsys

** G6G Abstract Number** 20213

** G6G Manufacturer Number** 102001