Release 10.1A: OpenEdge Development:
ProDataSets

Preface

This Preface contains the following sections:

Purpose
Audience
Organization
Typographical conventions
Examples of syntax descriptions
Example procedures
OpenEdge messages

Purpose

The Progress® ProDataSet™ represents a significant OpenEdge® technology for creating efficient “in-memory databases” from Progress® and non-Progress data sources. ProDataSets use familiar and new 4GL elements, thereby making ProDataSets easy to absorb for experienced 4GL programmers. This manual provides basic information about ProDataSets, expert-level insight into their mechanics, as well as forward-looking application design suggestions.

Audience

This Expert Series manual is full of the technical detail and design advice that experienced Progress 4GLprogrammers and application architects will need to fully exploit ProDataSet technology. For less experienced 4GL programmers, there are many exercises that carefully walk through and develop ProDataSet sample code.

Organization

Chapter 1 "Introducing the Progress DataSet"

Provides a thorough introduction to the fundamental elements of the ProDataSet.

Chapter 2 "ProDataSet Parameters"

Describes the basic parameters used with most ProDataSet applications.

Chapter 3 "ProDataSets Events"

Describes the basic events used with most ProDataSet applications.

Chapter 4 "Dynamic ProDataSet Basics"

Using dynamic ProDataSets presents expanded possibilities. This chapter covers their use in detail.

Chapter 5 "ProDataSet Attributes and Methods"

Introduces more attributes and methods to further develop ProDataSet programming techniques.

Chapter 6 "Updating Data with ProDataSets"

Covers two critical programming skills: tracking changes and processing changes. Together these techniques allow you to update your data sources with data from ProDataSets.

Chapter 7 "Advanced Events and Attributes"

Provides a thorough introduction to the fundamental elements of the ProDataSet.

Chapter 8 "Batching Data with ProDataSets"

Provides a thorough discussion of batching data with ProDataSets.

Chapter 9 "Advanced Read Operations"

Provides some interesting use cases for ProDataSet reads.

Chapter 10 "Advanced Update Operations"

Discusses several kinds of reusable procedures you may want to develop to execute specific ProDataSet tasks in a distributed environment.

Chapter 11 "Data Access and Business Entity Objects"

Discusses a model architecture for the design of enterprise applications that exploit ProDataSets.

Typographical conventions

This manual uses the following typographical conventions:

Convention	Description
Bold	Bold typeface indicates commands or characters the user types, provides emphasis, or the names of user interface elements.
Italic	Italic typeface indicates the title of a document, or signifies new terms.
SMALL, BOLD CAPITAL LETTERS	Small, bold capital letters indicate OpenEdge® key functions and generic keyboard keys; for example, GET and CTRL.
KEY1+KEY2	A plus sign between key names indicates a simultaneous key sequence: you press and hold down the first key while pressing the second key. For example, CTRL+X.
KEY1 KEY2	A space between key names indicates a sequential key sequence: you press and release the first key, then press another key. For example, ESCAPE H.
Syntax:
Fixed width	A fixed-width font is used in syntax statements, code examples, system output, and filenames.
Fixed-width italics	Fixed-width italics indicate variables in syntax statements.
Fixed-width bold	Fixed-width bold indicates variables with special emphasis.
UPPERCASE fixed width	Uppercase words are Progress® 4GL language keywords. Although these are always shown in uppercase, you can type them in either uppercase or lowercase in a procedure.
	This icon (three arrows) introduces a multi-step procedure.
	This icon (one arrow) introduces a single-step procedure.
Period (.) or colon (:)	All statements except DO, FOR, FUNCTION, PROCEDURE, and REPEAT end with a period. DO, FOR, FUNCTION, PROCEDURE, and REPEAT statements can end with either a period or a colon.
[ ]	Large brackets indicate the items within them are optional.
[ ]	Small brackets are part of the Progress 4GL language.
{ }	Large braces indicate the items within them are required. They are used to simplify complex syntax diagrams.
{ }	Small braces are part of the Progress 4GL language. For example, a called external procedure must use braces when referencing arguments passed by a calling procedure.
|	A vertical bar indicates a choice.
...	Ellipses indicate repetition: you can choose one or more of the preceding items.

Examples of syntax descriptions

In this example, ACCUM is a keyword, and aggregate and expression are variables:

Syntax

ACCUM aggregate expression

FOR is one of the statements that can end with either a period or a colon, as in this example:

FOR EACH Customer:   DISPLAY Name. END.

In this example, STREAM stream, UNLESS-HIDDEN, and NO-ERROR are optional:

Syntax

DISPLAY [ STREAM stream ] [ UNLESS-HIDDEN ] [ NO-ERROR ]

In this example, the outer (small) brackets are part of the language, and the inner (large) brackets denote an optional item:

Syntax

INITIAL [ constant [ , constant ] ]

A called external procedure must use braces when referencing compile-time arguments passed by a calling procedure, as shown in this example:

Syntax

{ &argument-name }

In this example, EACH, FIRST, and LAST are optional, but you can choose only one of them:

Syntax

PRESELECT [ EACH | FIRST | LAST ] record-phrase

In this example, you must include two expressions, and optionally you can include more. Multiple expressions are separated by commas:

Syntax

MAXIMUM ( expression , expression [ , expression ] ... )

In this example, you must specify MESSAGE and at least one expression or SKIP [ (n) ], and any number of additional expression or SKIP [ ( n ) ] is allowed:

Syntax

MESSAGE { expression | SKIP [ ( n ) ] } ...

In this example, you must specify {include-file, then optionally any number of argument or &argument-name = "argument-value", and then terminate with }:

Syntax

{ include-file     [ argument | &argument-name = "argument-value" ] ... }

Long syntax descriptions split across lines

Some syntax descriptions are too long to fit on one line. When syntax descriptions are split across multiple lines, groups of optional and groups of required items are kept together in the required order.

In this example, WITH is followed by six optional items:

Syntax

WITH [ ACCUM max-length ] [ expression DOWN ]   [ CENTERED ] [ n COLUMNS ] [ SIDE-LABELS ]   [ STREAM-IO ]

Complex syntax descriptions with both required and optional elements

Some syntax descriptions are too complex to distinguish required and optional elements by bracketing only the optional elements. For such syntax, the descriptions include both braces (for required elements) and brackets (for optional elements).

In this example, ASSIGN requires either one or more field entries or one record. Options available with field or record are grouped with braces and brackets:

Syntax

ASSIGN   { [ FRAME frame ] { field [ = expression ] }             [ WHEN expression ] } ...        | { record [ EXCEPT field ... ] }

Example procedures

This manual provides numerous example procedures that illustrate syntax and concepts. You can access the example files and details for installing the examples from the following locations:

The Documentation and Samples CD that you received with your product.
The Progress Documentation Web site:

http://www.progress.com/products/documentation

OpenEdge messages

OpenEdge displays several types of messages to inform you of routine and unusual occurrences:

Execution messages inform you of errors encountered while OpenEdge is running a procedure; for example, if OpenEdge cannot find a record with a specified index field value.
Compile messages inform you of errors found while OpenEdge is reading and analyzing a procedure before running it; for example, if a procedure references a table name that is not defined in the database.
Startup messages inform you of unusual conditions detected while OpenEdge is getting ready to execute; for example, if you entered an invalid startup parameter.

After displaying a message, OpenEdge proceeds in one of several ways:

Continues execution, subject to the error-processing actions that you specify or that are assumed as part of the procedure. This is the most common action taken after execution messages.
Returns to the Progress Procedure Editor, so you can correct an error in a procedure. This is the usual action taken after compiler messages.
Halts processing of a procedure and returns immediately to the Progress Procedure Editor. This does not happen often.
Terminates the current session.

OpenEdge messages end with a message number in parentheses. In this example, the message number is 200:

** Unknown table name table. (200)

If you encounter an error that terminates OpenEdge, note the message number before restarting.

Obtaining more information about OpenEdge messages

In Windows platforms, use OpenEdge online help to obtain more information about OpenEdge messages. Many OpenEdge tools include the following Help menu options to provide information about messages:

Choose Help Recent Messages to display detailed descriptions of the most recent OpenEdge message and all other messages returned in the current session.
Choose Help Messages and then type the message number to display a description of a specific OpenEdge message.
In the Progress Procedure Editor, press the HELP key or F1.