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Here are some of the topics covered in our FAQ.
How does HostBridge fit in with IBM's
connector "generations"?
IBM has recently republished the document OS/390 Guide
to eBusiness Connectors: Third Edition (October 2000).
In this document, IBM uses a generational paradigm to
classify connectors to applications running in an OS/390
environment. To some IBM customers, this document has
been quite confusing. Here’s the paradigm introduced
by this document (verbatim):
First Generation (API) connectors, which have been available
for some time, are characterized as being very quick
to implement with existing programming skills. These
include the API-based connections using CICS Web Support
(CWS), IMS TCP/IP OTMA Connection (IMS TOC), Net.Data,
and CWS with 3270 Bridge and Templates. API connectors
tend to have less standard tooling, less portability
and typically better performance than server-side Java
connectors. They are less focused on application re-engineering
or technology upgrade and more on optimizing Web enablement
to their existing application and data.
Second Generation (Java) connectors are characterized by
the use of Java and tooling. For relational databases,
JDBC and SQLJ are provided. CICS, IMS and SAP have developed
respectively the CICS Transaction Gateway (CTG), the
IMS Connector for Java and the VisualAge for Java Connector
for SAP R/3 based on the IBM developed Common Connector
Framework (CCF). This framework is supported by the Java
application development tools of WebSphere, specifically
VisualAge for Java. Host-on-Demand is another solution
for 3270-based applications. These connectors are generally
available now. Second Generation connectors are more
focused on standards, tooling, portability and beginning
the process of application re-engineering. Performance/scalability
is currently below that of corresponding First Generation
counterparts (e.g. CTG versus CWS, IMS TOC versus IMS
Connector for Java, JDBC versus Net.Data).
Third Generation Enterprise Java connectors introduces
Enterprise JavaBeans (EJBs) and the “Java 2”
family of protocols (e.g. JDBC 2.0,). The third generation
connectors are an evolution of second generation with
enhanced transactional and security context at the thread
level, and data persistence built into the application
programming model. Even more of the S/390 platform’s
QoS (Qualities of Service) are provided to the application
transparently. Examples of these key QoS advantages are
Workload Management for Address Space management, RRS
(Recoverable Resource Services ) for distributed transactions
and Parallel Sysplex clustering for data sharing.
Since HostBridge does rely upon 3270 Bridge, these definitions
seem to raise numerous questions.
What is an "API-based connection"?
IBM’s definition of a first generation connector has
to do with “API-based connections”. What is
an “API-based connection”? IBM does not
really say. Does “API-based connector” mean
screen scraping? It can’t. IMS TCP/IP OTMA is mentioned
as a first generation connector and it has nothing to
do with screen scraping. Host-On-Demand is mentioned
as a second generation connector, and it does implement
screen scrapping. CICS Transaction Gateway is also mentioned
as a second generation connector, and it also supports
screen scrapping via the CICS EPI interface.
So what is a first generation API-based connector? Given
the definitions used for the second and third generation
connectors, the most apparent definition for a first
generation API-based connector is anything that does not
use Java. This would make sense, as IBM would certainly
like customers to implement Java-based technologies instead
of the competing Microsoft technologies.
What is "CWS with 3270 Bridge and
Templates" and why is it a first generation connector?
3270 Bridge is a feature of CICS that makes it possible
to intercept the flow of data into, and out of, a CICS
transaction before a 3270 data stream is generated as
output or expected as input. 3270 Bridge works by intercepting
the flow of control between the user transaction and
BMS (or Terminal Control), thereby allowing another software
component, such as HostBridge, to handle input/output
operations for the transaction. Thus, 3270 Bridge, in
and of itself, is not a connector – it’s just
a feature of CICS that can be used to create a connector.
That’s why IBM’s definition specifically mentions
“Templates”.
So what are “templates”? Templates are HTML forms
that reside on the host. These templates can be created
manually, or they can automatically generated by a facility
provided with CICS 1.2, and later. An automatically generated
HTML template is generated from an existing BMS form
and is roughly equivalent in layout and content. To complement
these capabilities, IBM also provided a 3270 Bridge application
that allows a web user to interact with a 3270 transaction
using these templates. It is this capability that is
referred to “CWS and 3270 Bridge with Templates.”
Essentially, the use of templates exchanges the use of
3270 data streams for HTML data streams. Nothing else.
Note that it is not the use of 3270 Bridge that makes “CWS
with 3270 Bridge and Templates” a first generation
connector. Rather, it’s the use of templates that
exposes a non-Java interface to the outside world.
Would anything that relies upon 3270
Bridge be considered a first generation connector?
Absolutely not. 3270 Bridge simply creates the possibility
of eliminating the use of 3270 data streams while leveraging
the business logic embodied in the transaction. And,
as mentioned above, 3270 Bridge, in and of itself, is
not a connector – it’s just a feature of CICS
that can be used to create a connector.
Page 232 of CICS Transaction Server for OS/390 Version
1 Release 3: Web Support and 3270 Bridge reinforces this
view: “The purpose of the 3270 Bridge is to allow
you to run CICS transactions written for 3270 terminals
using non-3270 input and output and still use the business
logic embodied in these transactions without having to
rewrite the code to separate out the presentation logic
from the rest, and without having to create the illusion
of the 3270 interface.”
Using IBM's definitions, is HostBridge
a first, second or third generation connector?
Unfortunately, this is a very difficult question because
of the way IBM defines these terms. IBM’s definition
of first, second or third generation connectors is based
on the language used by the connector to expose/invoke
its interface – not the underlying techniques it
uses. To IBM, first generation connectors are non-Java;
second generation are Java-based; third generation are
based on EJB.
HostBridge is language neutral. The only interfaces it
exposes are HTTP and XML. Thus, HostBridge can be invoked
via Java, EJBs, Java Server Pages (JSPs) or Active Server
Pages (ASPs). As a result, with reference to IBM’s
“connector generations”, it is apparent that
HostBridge is “none of the above!” In the future
we will be providing a Java or Java Connector Architecture
(JCA) interface to HostBridge. Once this is released,
we presume that HostBridge would qualify as a “third
generation” connector.
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