Denodo Data Consolidation & Denormalization

As the data modeling process in denodo moves through the conceptual layers of the data warehouse, there is an evolution of the data structure and their associated metadata.

The Base Layer

As the modeling process begins the base layer is the ingestion layer, where the source system data structures are recreated in denodo and field are transformed in denodo Virtual Query Language (VQL) data types. the Business layer is what folks with a traditional data warehousing background would think of as Staging or landing. These base layer views should most closely mirror the technical structure and data characteristics of the input data source and will be the least business friend in their organization, naming, and metadata.

The Semantics layer

The semantics layer is where the major data reorganization, data transformation, and the application of business friend field names and metadata begins. The semantics layer is what folks with a traditional data warehousing background would think of as the Data Warehouse (DW) or Enterprise Data Warehouse (EDW). The semantics layer of the logical data warehouse (LDW) performs serval tasks:

  • Data from multiple input sources are consolidated
  • The model becomes multi-dimensional (Fact and Dimension oriented)
  • Field names and descriptive metadata are changed to meaningful, domain normalized, business-friendly names and descriptions.
  • Domain normalizing business rules and transformations are applied.
  • Serves as a data source for the business layer and reporting layer.

The Business Layer

The business layer, which is considered optional by denodo, is modeled along a more narrow business subject orientation and more specialized business rules are applied. This is what folks with a traditional data warehousing background would think of as a Datamart (DM).

The business layer of the logical data warehouse (LDW) performs serval tasks:

  • Limits and optimizes the data to facilitate business intelligence and report activities concerning a specific line of business or business topic (e.g. Financials, Human Resources, Inventory, Asset management, etc. )
  • Business-specific/customized rules and metadata are applied
  • Supplements the semantic layer and serves as a data source for the reporting layer.
  • Additional data consolidation and data structure denormalization (flattening) may occur in the business layer

The Reporting Layer

The reporting layer, which is considered optional by denodo, is the most customized layer and sees the most reporting topic specialization and specific need transformation. The reporting layer is where a traditional data warehousing may provide customized reporting, or system interface views, interface ETL’s to produce interface files, and reporting team do more of their own development.

The reporting layer of the logical data warehouse (LDW) performs serval tasks:

  • Provides consumer-specific customized rules and metadata
  • Provides consumer-specific data organization/layouts
  • Data is optimized for consumer purposes and may be highly or entirely denormalized to meet consumer needs.

Denodo Best Practices For Base Views

The denodo “Base Layer” in the Logical Data Warehouse (LDW) can be thought of as the Data Staging local layer in a more traditional data warehouse (DW) development pattern.  The Base layer is the level at which the source system data structures are transformed into denodo field types and the source data structures are rendered as created in base views (bv).

Base views (bv), the first step in virtualizing data, are the denodo structures reflecting the source system structure and the second step behind the data source connection and, therefore, are essential elements for the other layers of the Logical Data Warehouse (LDW).  To provide some guidance to facilitate the usefulness and performance of base views here are some best practices:

  • Use consistent Object Naming conventions.  It is strongly recommended that the denodo standard naming conventions be used.
  • Import and or create the Primary Keys (PK), Foreign Keys (FK), and Associations.
  • Have Statistics Collection been set and include all critical fields?
  • Base views, as a rule, should not be cached unless absolutely necessary for reasons of performance.
  • Create indexes on Primary Keys (PK), Surrogate keys, and Foreign Keys (FK)
  • Create performance Indexes to mirror sources system to improve performance.
  • Populate view Metadata properties describing the type and the nature of the data which the view contains. Note:  if you have a governance team, they may want to manage the metadata in the denodo data catalog.
  • Retain the original table name (applying naming convention prefix and field names to facilitate data Lineage traceability.?
  • Use denodo tools against tables, where possible, rather than (Manual) SQL views, Database views, or Stored Procedure.  Denodo cannot rewrite or optimize these objects.
  • Field metadata should be annotated with “Not Used” if the field is always null, blank, or empty.  This saves time and labor when working with levels and researching data issues

Related Reference

Denodo Model Best Practices For Creation of Associations

What Are Denodo Associations?

In denodo associations follow the same concept as modeling tools, which can be described as an ‘on-demand join.’

Where Should Associations Be Created In the Denodo Model?

You don’t necessarily need to define an Association at every level; usually, the best practice is to apply associations at the following points:

  • On final views published for data consumers, indicating relationships between related views; Especially, on published web services.
  • On the component views below, any derived view that brings together disparate (dissimilar) data sources.  The associations should be defined as Referential Constraints whenever appropriate to aid the optimization engine.
  • On the component views below, any derived view that joins a “Base View from Query” with standard views, since Base Views from Query cannot be rewritten by the denodo optimization engine.  Often Base Views from Query create performance bottlenecks.

These best practices should cover the majority scenarios; beyond these guidelines, it is best to take an ad-hoc approach to create Associations when you see a specific performance/optimization.

Why Are Associations important in Denodo?

In a nutshell, associations performance and the efficiency of the denodo execution optimizer along with other model metadata, such as:  

  • The SQL of the view(s)
  • Table metadata (Table Keys {PK, FK), Virtual Partitions…etc.)
  • Data statistics, which are used by the Cost Based Optimizer (CBO)

Related References

Associations in Denodo

Importing Associations And Joins From A Database Schema in Denodo

A coworker recently asked a question as to whether denodo generated joins automatically from source RDBMS database schema.  After searching, a few snippets of information became obvious.  First, that the subject of inheriting join properties was broader than joins and needed to in modeling associations (joins on demand). Second, that there were some denodo design best practices to be considered to optimize associations.

Does Denodo Automatically Generate Joins From the Source System?

After some research, the short answer is no.

Can Denodo Inherit Accusations From A Logical Model?

The short answer is yes. 

Denodo bridges allow models to be passed to and from other modeling tools, it is possible to have the association build automatically, using the top-down approach design approach and importing a model, at the Interface View level, which is the topmost level of the top-down design process. 

However, below the Interface view level, associations and or joins are created manually by the developer.

Where Should Associations Be Created?

You don’t necessarily need to define an Association at every level, usually, the best practice is to apply associations at following points:

These best practices should cover the majority scenarios, beyond these guidelines it is best to take an ad-hoc approach to create Associations when you see a specific performance/optimization.

Related References

Associations in Denodo

Which Version Control Systems Are supported by denodo Virtualization 7.0?

Using Version Control is a denodo Virtual DataPort (VDP) recommended best practice. Version 7.0 of denodo virtualization supports three Version Control Systems (VCS):

  • Microsoft Team Foundation Server (TFS) 2010 or later
  • Apache Subversion (1.7), and
  • Git

Related References:

Denodo Virtual Dataport (VDP) naming Convention Guidance

Denodo provides some general Virtual Dataport naming convention recommendations and guidance.  First, there is the general guidance for basic Virtual Dataport object types and, secondly, more detail naming guidance recommends.      

Denodo Basic Virtual Dataport (VDP) Object Prefix Recommendations

  • Associations Prefix: a_{name}
  • Base Views Prefix: bv_{SystemName}_{TableName}
  • Data Sources Prefix: ds_{name}
  • Integration View Prefix: iv_{name}
  • JMS Listeners Prefix: jms_{name}
  • Interfaces Prefix: i_{name}
  • Web Service Prefix: ws_{name}

Virtual Dataport (VDP) High-Level Project Structure

Different layers are identified when creating logical folders hierarchies within each Data Virtualization project.  The recommended high-Level project folders are:

Connectivity

  • Connectivity, where related physical systems, data sources, and base views are part of this folder.

Integration

  • Integration views include the combinations and transformations views for the next layers. Not directly consumed views at this level.

Business Entities

  • Business Entities include Canonical business entities exposed to all users.

Report Views

  • Report Views include Pre-built reports and analysis frequently consumed by users.

Data Services

  • Data Services include web services for publishing views from other levels. It can contain views need for data formatting and manipulation.

Associations

  • This folder stores associations.

JMS listeners

  • This folder stores JMS listeners

Stored procedures

  • This folder stores custom stored procedures developed using the VDP API.

Denodo Knowledge Base VDP Naming Conventions

Additional more detailed naming convention and Virtual Dataport organization guidance are available in the denodo Community Knowledge Base, under Operations

Denodo Knowledge Base Virtual Dataport (VDP) Naming Conventions Online Page

Denodo Virtual Dataport (VDP) Naming Conventions Downloadable PDF

Denodo Scheduler Naming Conventions

denodo Virtualization – Useful Links

Here are some denodo Virtualization references, which may be useful.

Reference Name Link
denodo Home Page https://www.denodo.com/en/about-us/our-company
denodo Platform 7.0 Documentation https://community.denodo.com/docs/html/browse/7.0/
denodo Knowledge Base and Best Practices https://community.denodo.com/kb/
denodo Tutorials https://community.denodo.com/tutorials/
denodo Express 7.0 Download https://community.denodo.com/express/download
Denodo Virtual Data Port (VDP) https://community.denodo.com/kb/download/pdf/VDP%20Naming%20Conventions?category=Operation
JDBC / ODBC drivers for Denodo https://community.denodo.com/drivers/
Denodo Governance Bridge – User Manual https://community.denodo.com/docs/html/document/denodoconnects/7.0/Denodo%20Governance%20Bridge%20-%20User%20Manual

Related References