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Met Open Edge heeft Progress Software Corporation de Open Edge Reference
Architecture (OERA) gelanceerd.
Met OERA legt Progress een duidelijke en consistentie visie neer op
software architecturen. De scheiding van User Interface, Business Logic,
Data Access en Data Storage staat garant voor ‘Future proof’
applicaties. |
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Since the beginning of Progress it has been possible to get schema
information from the 4GL by accessing tables such as _file and _field.
In the beginning this used to be unsupported but later on PSC published
the structure of these system files in the documentation and on their
web site. Each description, however, contained a warning that accessing
this information was not guaranteed to work in another Progress version. |
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When programming small utilities for a specific task, such an import or
conversion utility, I have often faced the dilemma of how to provide
feedback to the user. |
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Everybody who is getting involved in version 9 will sooner or later ask
himself or herself the following question: what are good uses for the
new publish/subscribe mechanism? There are programmers who tried to
replace virtually all run statements with publish statements where
others are convinced that pub/sub is unreliable and therefore useless. |
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One of the most exciting features of version 9 is no doubt the support
of dynamic queries, buffers and fields.Progress now enables us to create
and execute queries at runtime. No 4GL license is needed. The
advantages of this capability are numerous. |
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Starting with version 6.3F Progress incorporates a powerful feature to
support the deployment of object code: the Cyclic Redundancy Check
(CRC). Each table in a Progress database has it's own CRC number.
The advantage of the CRC is that the same object code can run
against different database tables with identical structures, even when
these were created at different times using different methods. |
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One of the most common CRC questions I receive are about a .r deployment
situation where the developers are really surprised that the CRCs in
the Production database are different from the Development database.
Usually it is Monday morning, the Production database is huge, it is
in a remote location and the developers have just spent the entire
weekend converting it. First I explain how this is possible and then I
inform the developers about the Three Database System as described in
Progressions number 30. Slowly they start to realize this is the way
they should have done it. I pause for effect. |
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Validation in an event-driven environment is not as easy as in a
procedural environment. In version 6 most validation issues could be
resolved by validate phrases since they would always fire upon leave of a
(modified) field as well as on GO of the frame.
This would satisfy most validation needs since there was no way the
user could continue with the application without applying a GO to the
current frame. |
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In "Reading dBASE files directly from Progress" I describe the structure
of the binary header of dBASE files. Using this information it should
not be too difficult to write this header ourselves. However, we need
some special 4GL constructs to do the trick. This part is in the
makebinary procedure. |
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In these times of object-oriented 32-bit GUI applications I still
regularly receive the request to read dBASE files into a Progress
database. It seems that 'the outside world' is still using good old
dBASE for all kinds of applications, often those that have been running
without any trouble for a number of years. |