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Finally, we expressed business logic as scripts in the OFTP monitor's simple Java-like script language, CapreraScript, to direct Caprera's behavior in every possible database update situation. Each script identified the data items to use and the steps to take when replenishing the LPS or updating the central database.
At the client, a Caprera application consists of the Caprera Client module, LPS and data-collection software. Three server-side components--the Caprera Server module, scripts expressing the business logic, and configuration settings declaring connectivity options and user IDs--come to life when clients reconnect to the central database.
In OFTP parlance, a
n activity consists of the data and business logic that together define an operation Caprera should perform when a given event occurs. Part of the activity can execute on the server and part on the client. The event might be the selling of a widget or a certain time of day. For example, when a client reconnected to the central database, each widget sale triggered our script language instructions (parsed and interpreted by Caprera) for detecting and managing depleted stock and out-of-stock situations. To identify and handle Caprera activity, we followed the CAIR (Clients, Actions, Inputs and Results) approach outlined in the Caprera manual (see "Taking a CAIRful Approach" on page 96).
We also set up a Caprera activity that detected central database widget price list changes and updated clients' LPSes with the changes. We appreciated the way the OFTP monitor encouraged us to treat transactions as objects as we instantiated our business rules for handling activities, and we found we had complete control--at a
detailed level--over the conflicts that arose during LPS-to-database replication. For the test in which we oversold our supply of widgets, we scripted an activity that partially filled the order with remaining widgets, then initiated backorder and restocking transactions. Caprera handled the situation gracefully and automatically.
Custom-written client programs that invoke the OFTP monitor ActiveX components are the typical use of Caprera, but we noted that it also offers a scriptable client GUI for applications whose user interface doesn't require the power of tools like VB, PowerBuilder or Delphi. We also successfully tested the use of Microsoft Access as a front-end GUI to a Caprera-based application.
Under Lock and Key
Administering Caprera is as easy as setting up lists of users and passwords, specifying server domains and servers, and describing the communication links to the servers. For security, the OFTP monitor gave us RSA encryption and password protection, plus a special locksmith f
eature for mobile users who forget their passwords. It didn't offer the use of digital certificates.
Tactica offers 24-hour technical support for Caprera, but it's on a "we'll call you back when someone checks the answering machine" basis; Tactica is a very small company. Surprisingly, and reassuringly, a Saturday afternoon question was answered within a half hour when we pretended to be developers needing some clarifications.
Caprera Server runs on Windows NT, OS/2, AIX, HP-UX and Solaris. Client platforms can be Windows95, 3.1 and NT, with applications typically built with VB, PowerBuilder and Visual C++. Browser-based applications can use Java applets and ActiveX controls. It supports ODBC-accessible databases.
Barry Nance, a computer analyst and consultant for 25 years, is the author of Introduction to Networking, 4th Edition (Que, 1997), Using OS/2 Warp (Que, 1994), and Client/Server LAN Programming (Que, 1994). He can be reached at barryn@bix.com.
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