Metadata for Dummies

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Metadata for Dummies

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Hello All,

We have all heard a lot about metadata.  I heard this term for the first time on my first day at Sage, during the first day introduction: I was told that Sage CRM is metadata driven.  Huh? I must admit - I didn’t have the faintest idea what it meant.  Fortunately, it didn’t take long to understand it. Over the last few years at Sage, I have noticed that for many people this term is not fully clear – as it wasn’t for me. In this article I will try to explain what metadata is and what are the advantages of applications that are metadata driven.

METADATA
Before going to the definition of metadata itself, I would like to compare a standard application versus a metadata driven one – on the simplistic example of an application that has one button. The following table shows typical actions that are taken when the application starts, and shows the button:

Standard Application Metadata driven application
Start Start

-

Load metadata: load list of buttons;
Prepare main screen: add the button to the screen; Prepare main screen: loop: for each button defined in metadata, add button to the screen
Show the screen Show the screen

 

 

As you can see, the metadata is loaded, and the metadata – in our example application – defines the button(s).  So what is metadata?  Wikipedia says: "Metadata is loosely defined as data about data". Having the previous example in mind, it is not hard to understand this definition: metadata is the information how the application should work, behave, look or feel. In our example metadata stores a list of buttons on the application screen – it stores the information that one button should be there. But what are the advantages? In both applications the result is the same… The answer is: customization. To change the standard application, for example to add a button - the developer must write code, compile it and deploy; to apply the same change in a metadata driven application – the user can change the metadata.

METADATA IN DATABASE APPLICATIONS

Most applications are “database” ones – data (for example customer information) is stored in a database, and an application performs various operations on it: add, modify, delete, search etc. In standard database applications, the only tables in the database are the ones that the system is designed to work with – customer info, company data, invoices – etc. Typically such an application has hardcoded table and column names, as well as most database queries. In a metadata driven application, the database may contain additional tables that store the description of the system – for example the names of data tables and columns, configuration of system menus, content of screens etc. In metadata driven applications, the only hardcoded code is responsible for loading the metadata at the application startup. The rest is generated dynamically at runtime.

METADATA IN SAGE CRM

As I mentioned earlier, Sage CRM is almost completely metadata driven. The metadata in Sage CRM is stored in various tables, most of which have names that start with the word “custom”. A lot of operations performed via the Administration section of Sage CRM alter data stored in those tables. The following table presents some of the Sage CRM metadata tables and their main purpose:

 

Table Name

Description

Custom_Captions

Translations of system captions, definition of items in dropdown fields

Custom_Tables

Definition of entities

Custom_Edits

Definition of fields within entity

Custom_Tabs

Definition of top tabs for entity

Custom_ScreenObjects

Definition of blocks

  Custom_Screens

Definition of screens content

Custom_Lists

Definition of lists

 

As you can see, the whole User Inteface of Sage CRM is auto generated based on metadata tables. What it gives to Sage CRM users is the ability to customize and tailor the system so it fits particular business model much better!