#Object Data Model

InterSystems FAQ rubric

Class definitions created by users are stored in class definition classes. They can be used to obtain a list of class definitions from a program.

Note: Class definition classes refer to all classes contained in the %Dictionary package.

InterSystems FAQ rubric

You can avoid the error by specifying a stream object as the argument of %ToJSON() used when generating a JSON string from a dynamic object.

A code example is below.

Before we start talking about databases and different data models that exist, first we'd better talk about what a database is and how to use it.

A database is an organized collection of data stored and accessed electronically. It is used to store and retrieve structured, semi-structured, or raw data which is often related to a theme or activity.

At the heart of every database lies at least one model used to describe its data. And depending on the model it is based on, a database may have slightly different characteristics and store different types of data.

To write, retrieve, modify, sort, transform or print the information from the database, a software called Database Management System (DBMS) is used.

The size, capacity, and performance of databases and their respective DBMS have increased by several orders of magnitude. It has been made possible by technological advances in various areas, such as processors, computer memory, computer storage, and computer networks. In general, the development of database technology can be divided into four generations based on the data models or structure: navigational, relational, object and post-relational.

Setting the Scene

I was editing the properties of a persistent ObjectScript class the other day and noticed that the storage definition wasn't updating to reflect my latest changes.

In this case, I deleted a property that was no longer needed from the class definition, saved, recompiled, and still saw it in the storage definition.

I'm participating in the Developing with InterSystems Objects and SQL with Joel Solon. The course is very nice and I will share with you some tips I got during the training. Tips presented in the day 3:

I'm participating in the Developing with InterSystems Objects and SQL with Joel Solon. The course is very nice and I will share with you some tips I got during the training. Tips presented in the day 1:

InterSystems IRIS currently limits classes to 999 properties.

But what to do if you need to store more data per object?

This article would answer this question (with the additional cameo of Community Python Gateway and how you can transfer wide datasets into Python).

The answer is very simple actually - InterSystems IRIS currently limits classes to 999 properties, but not to 999 primitives. The property in InterSystems IRIS can be an object with 999 properties and so on - the limit can be easily disregarded.

In this article I'd like to share with you a phenomena that is best you avoid - something you should be aware of when designing your data model (or building your Business Processes) in Caché or in Ensemble (or older HealthShare Health Connect Ensemble-based versions).

Some time ago, InterSystems introduced the concept of %DynamicObjects.
This feature is a powerful tool that makes it very easy to convert any string of JSON text to objects and vice versa.
However, in the work that J2 Interactive is doing for our customers, there are a couple of things that "need some tweaking".

When I describe InterSystems IRIS to more technically-minded people, I always start with how it is a multimodel DBMS at its core.

In my opinion that is its main advantage (on the DBMS side). And the data is stored only once. You just choose the access API you want to use.

Headache-free stored objects: a simple example of working with InterSystems Caché objects in ObjectScript and Python

Neuschwanstein Castle

Tabular data storages based on what is formally known as the relational data model will be celebrating their 50th anniversary in June 2020. Here is an official document – that very famous article. Many thanks for it to Doctor Edgar Frank Codd. By the way, the relational data model is on the list of the most important global innovations of the past 100 years published by Forbes.

On the other hand, oddly enough, Codd viewed relational databases and SQL as a distorted implementation of his theory. For general guidance, he created 12 rules that any relational database management system must comply with (there are actually 13 rules). Honestly speaking, there is zero DBMS's on the market that observes at least Rule 0. Therefore, no one can call their DBMS 100% relational :) If you know any exceptions, please let me know.

The source class of a DeepSee cube has a property referencing a different class:

Class ClassA Extends %Persistent {
     Property P1 As ClassB;
}

When records in class B change, the ^OBJ.DSTIME global for Class A will not be automatically updated. This means that synchronization of cubes based on source class A will not reflect the changes occurred to property P1.
This post will help you determine the best way to achieve synchronization of properties referencing a different class

What if you could serialize/deserialize objects in whatever format: JSON, XML, CSV,...; attending different criteria: export/import some properties and not others, transform values in this or that way before exporting/importing,...; and all of this without having to change the class definition? Wouldn't that be great??

Well, perhaps it's a goal too ambitious to reach 100% but, exploring this idea, I've developed a bunch of classes that I thought it was good to share. If you want to test, change, modify or improve the code, or just take a look at it, you can do it here. There you'll find a more detailed explanation (see Readme.md)

First-class function^wiki

In computer science, a programming language is said to have first-class functions if it treats functions as first-class citizens. This means the language supports passing functions as arguments to other functions, returning them as the values from other functions, and assigning them to variables or storing them in data structures. Some programming language theorists require support for anonymous functions (function literals) as well. In languages with first-class functions, the names of functions do not have any special status; they are treated like ordinary variables with a function type.

This post continues the article “Declarative development in Caché”.

[2, 3, 5, 7, 11, 13, 17].forEach(function(i) {
  console.log(i);
});

How to do something like this in Caché using COS?

Below are some exercises on this topic.