ObjectStore Active Toolkit Reference

Chapter 1 ATK and the Inspector

Introduction

ATK uses the data views and instance formats that you define in Inspector and store in the metaknowledge.

In this chapter

This chapter presents the following topics:

ATK Metaknowledge and Inspector

Accessing Data Views and Instance Formats from ATK

What is a data view?

A data view is a tabular representation of a persistent ObjectStore collection that uses a specified instance format to display persistent instances. You can define a data view based on any of the following:

· Filtering options

· Ordering options

· Arrays

· User-defined extent methods

For example, suppose the class Customer has two data members, name and address. You can use Inspector to build a data view based on a collection of customers. A data view's instance format specifies the set of data members that must be displayed for an instance of the class in the data view. If you are displaying a table of instances, the instance format specifies what columns have to be displayed. This simple data view has an instance format of two columns that represent the name and address of each Customer object contained in the persistent collection.

Defining a filter to list only those customers whose names start with the letter J, or defining an order that lists the customers alphabetically, makes this data view more complex.

You can name and save the view, and reload it later. If the collection changes, the data view changes accordingly.

Accessing Data Views from ATK

To access a data view defined in Inspector, use the ATK ActiveX server or ATK OLE DB provider and specify the name of the data view.

For example, to access a data view named my_first_dataview through the ATK ActiveX server, create an IATKDataView object to represent the view:

atkDataView = atkDatabase.GetDataView("my_first_dataview")

Using the ATK OLE DB provider, open a record set representing the same data view:

adoRecordSet.Open("my_first_dataview", adoConnection)

You can also use SQL statements with OLE DB:

adoRecordSet.Open("SELECT * FROM my_first_dataview",      
adoConnection)

Note that if you use SQL statements, the data view name must follow SQL syntax rules.

Accessing Instance Formats from the ATK ActiveX Server

Using the ATK ActiveX server, you can directly access the instance formats defined for the classes contained in the database schema. An instance format can include navigation pointers and collections of other classes, which provide a powerful means of navigating among objects transparently and displaying the equivalent of relational SQL joins faster and more efficiently than SQL syntax.

When you create a data view in Inspector, you can save the data view template with a symbolic name. When you modify an instance format in Inspector, you usually modify the default instance formats associated with each class. However, the Inspector will save any modification to the template instance format using the symbolic name. The ATK ActiveX server accesses this name and displays data according to the specified instance format.

Refer to Chapter 2, Accessing ATK ActiveX Server from ASP Applications, in the ObjectStore Active Toolkit Tutorial, for an example of defining multiple instance formats for a specific class and accessing them from the ATK ActiveX server, and customizing a data view using the ATK ActiveX server or ATK OLE DB provider.

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Updated: 05/11/99 11:33:45

Chapter 1

ATK and the Inspector