Basic Concepts and Terminology

Objectives
After completing this lesson, you will be able to:

After completing this lesson, you will be able to:

  • Understand modeling terminology of SAP HANA Cloud so that you are ready to begin modeling

Key Concepts of Data Modeling

Before introducing calculation views in SAP HANA Cloud, you should become familiar with some key modeling concepts that are frequently used when creating calculation views.

Measure and Attribute

A data model is usually based on measures and attributes.

Measure Versus Attribute

 MeasureAttribute
What is it?Always a numeric value, such as a price or quantity, on which you can process arithmetic or statistics operations, such as sum, average, top N values, and calculations.A descriptive element that is used with measures to provide meaningful information. For example 'Sales Revenue by <attribute>'.
Examples
  • Quantity

  • Sales Revenue

  • Product

  • Customer

  • Country

  • Year

Attributes are used to filter or aggregate the measures, in order to answer questions such as the following:

  • What are the total sales originating from Hamburg?

  • What is the sales revenue for Cars by Month?

Dimension

A dimension is a group of related attributes. In the example below, we have defined a dimension called Product. The dimension includes various attributes including product name, category, supplier.

Dimensions are re-useable objects and appear in star schemas.

Star Schema

A star schema is a very powerful type of data model that we can create in SAP HANA Cloud.

Watch this video to learn about the Star Schema.

Note
A fact table is often defined from a combination of tables to produce a view of a transaction, such as a sales order. Dimensions are then connected to the fact table to provide additional, descriptive information about the transaction, such as, the country of the customer.

Hierarchy

A hierarchy is a structured representation of an organization, a list of products, the time dimension, and so on, using levels.

It is often used to provide easy navigation of a large data set in a drill-down.

Watch this video to learn about the hierarchy concept.

Semantics

The term semantics is used to describe the meaning of an attribute or a measure. For example:

  • A monetary value

    For example, the total amount sold would need to indicate the currency (for example USD, EUR, or GBP). Amount without a currency is meaningless.

  • A quantity, weight, volume, or distance

    For example, the quantity would need to specify the unit of measurement in which the data is expressed. Again, a quantity without a unit of measurement is meaningless.

Calculation Views in SAP HANA

A calculation view is the key modeling object of SAP HANA Cloud.

The purpose of calculation views is to project data from the individual database tables, and to perform a variety of data calculations in order to generate a meaningful result set to answer a specific business question.

Benefits of Calculation Views

Design-Time Versus Runtime Calculation Views

Deploying Calculation Views

When you deploy a design-time file with the Business Application Studio, SAP HANA Cloud generates the corresponding runtime object in a database container. A container is where all related run-time objects are stored in the database. An SAP HANA Cloud database can have many containers. We will cover containers later.

Analytical Versus Transactional Requirements

In transactional applications, such as SAP ERP, the underlying data (stored in physical tables) is generally handled by the application server. This layer is necessary to handle the business process logic. The application usually reads and writes directly to the database tables. Calculation views are not usually needed, however it is technically possible for the application to read a calculation view if this benefits the application. For example, it is possible to consume a calculation view from ABAP.

Calculation views are read only, and cannot change data in the SAP HANA Cloud database.

Analytical applications that do not usually need to write to the database so they can bypass the application server and directly query the calculation views, where data is calculated on-the-fly, in the SAP HANA Cloud in-memory database.

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