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#Object Data Model

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An object data model is that data or code is composed of modules that combine data and procedures that work on the data.

Learn more.

Article
· Mar 3, 2016 2m read
Class Projections and Projection Classes

The purpose of this post is to raise the profile of a powerful mechanism that has long been available to us, and to open a discussion about ways in which it can be used or abused.

You can read more detail about the mechanism here. To summarize, your class definition can use the Projection keyword to reference one or more projection classes. A projection class can implement methods that get invoked at key points in the lifecycle of your class.

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Here's one way to determine if a class is mapped (i.e. it is in a package whose definitions come from a database other than the default code database for the current namespace):

SAMPLES>w ##class(%Library.RoutineMgr).IsMapped("Cinema.Film.cls")
0
SAMPLES>w ##class(%Library.RoutineMgr).IsMapped("%iKnow.Objects.Source.cls")
1
SAMPLES>

If you pass a by-ref second argument to IsMapped you can also discover what database the class definition is stored in:

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Article
· Dec 23, 2015 1m read
Caché ObjectScript Quick Reference

In the Caché Foundations course, students are learning about Caché Development and ObjectScript syntax at the same time. To help students complete the exercises, we provide an ObjectScript Quick Reference (aka "the Cheat Sheet").

It is not a reference for all of ObjectScript! It is a list of the ObjectScript commands and functions that students use during the course, along with common syntax for objects, collections, etc. It also contains some useful macros.

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Article
· Jul 7, 2017 19m read
Indexing of non-atomic attributes

Quotes (1NF/2NF/3NF)ru:

Every row-and-column intersection contains exactly one value from the applicable domain (and nothing else).
The same value can be atomic or non-atomic depending on the purpose of this value. For example, “4286” can be
  • atomic, if its denotes “a credit card’s PIN code” (if it’s broken down or reshuffled, it is of no use any longer)
  • non-atomic, if it’s just a “sequence of numbers” (the value still makes sense if broken down into several parts or reshuffled)

This article explores the standard methods of increasing the performance of SQL queries involving the following types of fields: string, date, simple list (in the $LB format), "list of <...>" and "array of <...>".

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Article
· Jul 18, 2016 15m read
Remote proxy objects via dynamic dispatch

This article created as side effect of preparations to the longer set of articles about simple, but still handy MapReduce implementation in Caché. I was looking for relatively easy way to pass arguments to (potentially) multiple targets via remote calling facilities. And after several attempts I have realized that we do have very powerful mechanism in the Caché ObjectScript which might be of particular help here – dynamic dispatch for methods and properties.

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This article was written as an attempt to share the experience of installing the InterSystems Caché DBMS for production environment.
We all know that the development configuration of a DBMS is very different from real-life conditions.
As a rule, development is carried out in “hothouse conditions” with a bare minimum of security measures, but when we publish our project online, we must ensure its reliable and uninterrupted operation in a very aggressive environment.

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This morning on the old Caché Google Group, someone posed the following question, which I've decided to answer here, because it's interesting!

Is there a way to iterate ClassMethod's params, and get param's names and values?

The first answer I can come up with is: it's not easy! In any method, you could try to write code like this (where methodName is the name of your method):

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If you want to dynamically serve images as a property of JSON then there is no perfect encoding solution. One method used frequently is to Base64 encode the image. Whilst there are some negatives to doing this, such as data inflation, there are some positives to working with Base64 images inside the browser.

Let's say you have an image placeholder on a web page...

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Object Synchronization is a feature that has been around for a while, since Caché days, but I wanted to explore a bit more how it works. I've always thought that database automatic synchronization is complex by nature but, for some particular scenarios shouldn't be so hard. So I considered a very simple use case (OK, perhaps the typical one, I'm not discovering anything... but if it's common and it works, it's good wink ).

Open Exchange app
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Here you have an easy way to write and execute COS code from your unix scripts. This way one does not need to write routines or even open Studio or Atelier. It can be an option for simple and small actions for instance things like installation tasks or compiling.

See sample bash script (compile.sh) to compile classes:

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Columnar storage is one of the newer offers provided by InterSystems IRIS. Unlike traditional row-based storage, it optimizes query processing by storing data in columns rather than rows, enabling faster access and retrieval of relevant information.

A couple of articles have been written on when it should be used to give a system the biggest boost, how to create tables like that using SQL

CREATE TABLE table (column1 type1, column2 type2, column3 type3) WITH STORAGETYPE = COLUMNAR  -- ex 1
CREATE TABLE table (column1 type1, column2 type2, column3 type3 WITH STORAGETYPE = COLUMNAR)  -- ex 2

and even the performance tests.

As we all know, InterSystems IRIS is a multi-model DBMS and it gives seamless access to the same data using relational and object access. So the former is covered in other articles, but what about the latter?

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In the previous article, I have demonstrated a simple way to record data changes. At this time I have changed the "Audit Abstract Class" which is responsible for recording audit data and the data structure where the audit log will be recorded.

I have changed the data structure to a parent and child structure where there will be two tables to record the "transaction" and the "fields its values" changed on that transaction.

Take a look at the new data model:

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I'd like to announce the release of something really rather interesting - revolutionary in fact. That may sound like hyperbole, but I don't think you'll have seen anything quite like this, or even thought it possible!

We've pushed out a new JavaScript/Node.js module named glsdb which you can read all about here in detail:

https://github.com/robtweed/glsdb

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The Art of Mapping Globals to Classes (4 of 3)

The forth in the trilogy, anyone a Hitchhikers Guide to the Galaxy fan?

If you are looking to breathe new life into an old MUMPS application follow these steps to map your globals to classes and expose all that beautiful data to Objects and SQL.

If the above does not sound familiar to you please start at the beginning with the following:

The Art of Mapping Globals to Classes (1 of 3)

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Overview

Encryption of sensitive data becomes more and more important for applications. For example patient names, SSN, address-data or credit card-numbers etc..

Cache supports different flavors of encryption. Block-level database encryption and data-element encryption. The block-level database encryption protects an entire database. The decryption/encryption is done when a block is written/read to or from the database and has very little impact on the performance.

With data-element encryption only certain data-fields are encrypted. Fields that contain sensitive data like patient data or credit-card numbers. Data-element encryption is also useful if a re-encryption is required periodically. With data-element encryption it is the responsibility of the application to encrypt/decrypt the data.

Both encryption methods leverage the managed key encryption infrastructure of Caché.

The following article describes a sample use-case where data-element encryption is used to encrypt person data.

But what if you have hundreds of thousands of records with an encrypted datafield and you have the need to search that field? Decryption of the field-values prior to the search is not an option. What about indices?

This article describes a possible solution and develops step-by-step a small example how you can use SQL and indices to search encrypted fields.

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Greetings! This article describes yet another simple way of creating installers for the solutions based on InterSystems Caché. The topic covers applications, which can be installed or completely removed from Caché with one action only. If you are still documenting installation instructions that have more than one step to do to install your application — it’s high time you automated this process.

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Article
· Feb 19, 2016 2m read
Simple $system.Event examples

The attached file contains two $system.Event examples that processes work asynchronously using persistent queues:

Events_Simple

This is a very basic example that creates some worker processes and then enqueue messages to them using $system.Event.

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