Jade's Business Logic Server abstracts business logic from programs and lets users create complete applications declaratively, with little coding. Vision states that 95 percent of the applications written using Jade can be built without extensive coding, and our experience generally bears that out: We created at least 80 percent of our test applications without adding a line of code. One goal here, besides rapid prototyping and development, is to allow business managers to make business rule changes directly to the "business logic" without making programmers recode. With Jade, there's no need for business managers to write code or programmers to learn all of the business processes.

We found Jade's IDE extremely usable, with features and wizards designed to accelerate the development process. For example, the style, interface, and look and feel of an application can be switched quickly and easily with a mouse click. Prebuilt GUI-style templates ("archetypes") are available, but you can create your own, too. The creation of "business objects"--very flexible logical collections of data and rules--is straightforward. These objects can be introspected from CORBA objects, database tables, COM objects, JavaBeans or Java classes, and are separated into "core objects" and "query objects," which correspond to views or joins.

Applications are defined as a collection of forms, created via a property/ event-based Visual Basic-like GUI. One major weakness: Jade produces only Java client applications, so it's suited primarily for intranet-type use.

While development using the Jade Developer Studio must take place under Windows95/98/NT, the 100-percent Java Business Logic Server runs under AIX, HP-UX, Solaris and NT, with NetWare and Linux versions available but not certified. Jade includes database support for Oracle, Informix, Sybase, SQL Server, Access and DB2, with the XDA interface for business components.

The underlying architecture is adequate, but not outstanding. Failover is available, but not at the session level, and the load-balancing control is simplistic. Connection pooling occurs on the server level, and it's possible to dynamically change the number of connections at run time without restarting the server--useful in terms of dynamic scalability. No support exists for SNMP or SCCAPI, and XML is not handled at all. LDAP is supported, and Vision says it will implement JNDI in the next release. The product supports almost any two-phase commit transaction-processing monitor, and includes Visibroker ITS with the Business Logic Server.

Pricing reflects Vision's aim at large enterprise applications. The basic cost is $25,000 per CPU, with developer licenses sold at $3,000 per seat. Vision is on the right track with Jade and Business Logic Server, and its rapid prototyping and development environment are superb.

Pervasive Software Tango Enterprise Version
More well-known as a cross-platform database-to-Web tool, Tango has the most intuitive and easy-to-learn IDE of any Web application servers we tested. Although it's not nearly as full-featured an IDE as WebObjects, Tango proved much quicker to master; many SMEs with less-complex needs may see it as a near-ideal solution.

Like ColdFusion, Tango will appeal most to shops without a large dedicated programming staff, where it's necessary to get data and applications from back-end data sources to thin, browser-based clients with a minimum of coding. And, like ColdFusion, Tango is incorporating more enterprise-level features to expand its market. The product lacks the sophistication of its higher-priced competitors, however, and features that some enterprise users may require are missing.

Tango has support for XML output, but no parser. COM objects can be implemented via an external action mechanism, but you must know the method calls of the object, as there's no COM introspection functionality. Likewise, CORBA objects are accessible only via Java, and Tango is not object-centric. Object caching is not part of the architecture, and ORBs are not included. Tango supports JavaBeans, but not EJB. The built-in introspection functionality, where we could test it, was excellent. For example, it allowed us to successfully query a MAPI datastore. Native database support for Oracle is included, along with support for FileMaker Pro on the Macintosh, with ODBC connectivity to other data sources under NT.

Cross-platform support is good, with Mac OS, Solaris and NT versions available; Tango Application Files created on any available platform should run without modification or recompilation on any other platform.

Architecturally, Tango supports application partitioning across multiple heterogeneous hosts; load balancing (server and application-level, but round-robin only); thread pooling; and basic data-connection caching. Neither LDAP nor SNMP management is supported, and Tango's remote administration module provides limited granularity of administrative control for load-balancing and other essential features. More built-in security and access control would be useful.

If it fits what you need, Tango is a bargain. The development studio, which includes a Lite version of the application server suitable for development use, is $495, though Pervasive is distributing it free. The unlimited-user server is $995 for Mac, $3,495 for Windows 95/98/NT and $6,995 for Solaris.

Send your comments on this article to Richard Hoffman at rhoffman@nwc.com.