🗄️🗒️Data Management: Master Data Management [MDM] [Notes]

Disclaimer: This is work in progress intended to consolidate information from various sources. 
Last updated: 28-Mar-2024

Master Data Management (MDM)

• {definition} the technologies, processes, policies, standards and guiding principles that enable the management of master data values to enable consistent, shared, contextual use across systems, of the most accurate, timely, and relevant version of truth about essential business entities [2],[3]
• {goal} enable sharing of information assets across business domains and applications within an organization [4]
• {goal} provide authoritative source of reconciled and quality-assessed master (and reference) data [4]
• {goal} lower cost and complexity through use of standards, common data models, and integration patterns [4]
• {driver} meeting organizational data requirements
• {driver} improving data quality
• {driver} reducing the costs for data integration
• {driver} reducing risks 
• {type} operational MDM 
• involves solutions for managing transactional data in operational applications [1]
• rely heavily on data integration technologies
• {type} analytical MDM
• involves solutions for managing analytical master data
• centered on providing high quality dimensions with multiple hierarchies [1]
• cannot influence operational systems
• any data cleansing made within operational application isn’t recognized by transactional applications [1]
• ⇒ inconsistencies to the main operational data [1]
• transactional application knowledge isn’t available to the cleansing process
• {type} enterprise MDM
• involves solutions for managing both transactional and analytical master data 
• manages all master data entities
• deliver maximum business value
• operational data cleansing
• improves the operational efficiencies of the applications and the business processes that use the applications
• cross-application data need
• consolidation
• standardization
• cleansing
• distribution
• needs to support high volume of transactions
• ⇒ master data must be contained in data models designed for OLTP
• ⇐ ODS don’t fulfill this requirement 
• {enabler} high-quality data
• {enabler} data governance
• {benefit} single source of truth
• used to support both operational and analytical applications in a consistent manner [1]
• {benefit} consistent reporting
• reduces the inconsistencies experienced previously
• influenced by complex transformations
• {benefit} improved competitiveness
• MDM reduces the complexity of integrating new data and systems into the organization
• ⇒ increased flexibility and improves competitiveness
• ability to react to new business opportunities quickly with limited resources
• {benefit} improved risk management
• more reliable and consistent data improves the business’s ability to manage enterprise risk [1]
• {benefit} improved operational efficiency and reduced costs
• helps identify business’ pain point
• by developing a strategy for managing master data
• {benefit} improved decision making
• reducing data inconsistency diminishes organizational data mistrust and facilitates clearer (and faster) business decisions [1]
• {benefit} more reliable spend analysis and planning
• better data integration helps planners come up with better decisions
• improves the ability to 
• aggregate purchasing activities
• coordinate competitive sourcing
• be more predictable about future spending
• generally improve vendor and supplier management
• {benefit} regulatory compliance
• allows to reduce compliance risk
• helps satisfy governance, regulatory and compliance requirements
• simplifies compliance auditing
• enables more effective information controls that facilitate compliance with regulations
• {benefit} increased information quality
• enables organizations to monitor conformance more effectively
• via metadata collection
• it can track whether data meets information quality expectations across vertical applications, which reduces information scrap and rework
• {benefit} quicker results
• reduces the delays associated with extraction and transformation of data [1]
• ⇒ it speeds up the implementation of application migrations, modernization projects, and data warehouse/data mart construction [1]
• {benefit} improved business productivity
• gives enterprise architects the chance to explore how effective the organization is in automating its business processes by exploiting the information asset [1]
• ⇐ master data helps organizations realize how the same data entities are represented, manipulated, or exchanged across applications within the enterprise and how those objects relate to business process workflows [1]
• {benefit} simplified application development
• provides the opportunity to consolidate the application functionality associated with the data lifecycle [1]
• ⇐ consolidation in MDM is not limited to the data
• ⇒ provides a single functional to which different applications can subscribe
• ⇐ introducing a technical service layer for data lifecycle functionality provides the type of abstraction needed for deploying SOA or similar architectures
• factors to consider for implementing an MDM:
• effective technical infrastructure for collaboration [1]
• organizational preparedness
• for making a quick transition from a loosely combined confederation of vertical silos to a more tightly coupled collaborative framework
• {recommendation} evaluate the kinds of training sessions and individual incentives required to create a smooth transition [1]
• metadata management
• via a metadata registry 
• {recommendation} sets up a mechanism for unifying a master data view when possible [1]
• determines when that unification should be carried out [1]
• technology integration
• {recommendation} diagnose what technology needs to be integrated to support the process instead of developing the process around the technology [1]
• anticipating/managing change
• proper preparation and organization will subtly introduce change to the way people think and act as shown in any shift in pattern [1]
• changes in reporting structures and needs are unavoidable
• creating a partnership between Business and IT
• IT roles
• plays a major role in executing the MDM program[1]
• business roles
• identifying and standardizing master data [1]
• facilitating change management within the MDM program [1]
• establishing data ownership
• measurably high data quality
• overseeing processes via policies and procedures for data governance [1]
• {challenge} establishing enterprise-wide data governance
• {recommendation} define and distribute the policies and procedures governing the oversight of master data
• seeking feedback from across the different application teams provides a chance to develop the stewardship framework agreed upon by the majority while preparing the organization for the transition [1]
• {challenge} isolated islands of information
• caused by vertical alignment of IT
• makes it difficult to fix the dissimilarities in roles and responsibilities in relation to the isolated data sets because they are integrated into a master view [1]
• caused by data ownership
• the politics of information ownership and management have created artificial exclusive domains supervised by individuals who have no desire to centralize information [1]
• {challenge} consolidating master data into a centrally managed data asset [1]
• transfers the responsibility and accountability for information management from the lines of business to the organization [1]
• {challenge} managing MDM
• MDM should be considered a program and not a project or an application [1]
• {challenge} achieving timely and accurate synchronization across disparate systems [1]
• {challenge} different definitions of master metadata 
  • different coding schemes, data types, collations, and more
  • ⇐ data definitions must be unified
• {challenge} data conflicts 
• {recommendation} resolve data conflicts during the project [5]
• {recommendation} replicate the resolved data issues back to the source systems [5]
• {challenge} domain knowledge 
• {recommendation} involve domain experts in an MDM project [5]
• {challenge} documentation
• {recommendation} properly document your master data and metadata [5]
• approaches
• {architecture} no central MDM 
• isn’t a real MDM approach
• used when any kind of cross-system interaction is required [5]
• e.g. performing analysis on data from multiple systems, ad-hoc merging and cleansing
• {drawback} very inexpensive at the beginning; however, it turns out to be the most expensive over time [5]
• {architecture} central metadata storage 
• provides unified, centrally maintained definitions for master data [5]
• followed and implemented by all systems
• ad-hoc merging and cleansing becomes somewhat simpler [5]
• does not use a specialized solution for the central metadata storage [5]
• ⇐ the central storage of metadata is probably in an unstructured form 
• e.g. documents, worksheets, paper
• {architecture} central metadata storage with identity mapping 
• stores keys that map tables in the MDM solution
• only has keys from the systems in the MDM database; it does not have any other attributes [5]
• {benefit} data integration applications can be developed much more quickly and easily [5]
• {drawback} raises problems in regard to maintaining master data over time [5]
• there is no versioning or auditing in place to follow the changes [5]
• ⇒ viable for a limited time only
• e.g. during upgrading, testing, and the initial usage of a new ERP system to provide mapping back to the old ERP system
• {architecture} central metadata storage and central data that is continuously merged 
• stores metadata as well as master data in a dedicated MDM system
• master data is not inserted or updated in the MDM system [5]
• the merging (and cleansing) of master data from source systems occurs continuously, regularly [5]
• {drawback} continuous merging can become expensive [5]
• the only viable use for this approach is for finding out what has changed in source systems from the last merge [5]
• enables merging only the delta (new and updated data)
• frequently used for analytical systems
• {architecture} central MDM, single copy 
• involves a specialized MDM application
• master data, together with its metadata, is maintained in a central location [5]
• ⇒ all existing applications are consumers of the master data
• {drawback} upgrade all existing applications to consume master data from central storage instead of maintaining their own copies [5]
• ⇒ can be expensive
• ⇒ can be impossible (e.g. for older systems)
• {drawback} needs to consolidate all metadata from all source systems [5]
• {drawback} the process of creating and updating master data could simply be too slow [5]
• because of the processes in place
• {architecture} central MDM, multiple copies 
• uses central storage of master data and its metadata
• ⇐ the metadata here includes only an intersection of common metadata from source systems [5]
• each source system maintains its own copy of master data, with additional attributes that pertain to that system only [5]
• after master data is inserted into the central MDM system, it is replicated (preferably automatically) to source systems, where the source-specific attributes are updated [5]
• {benefit} good compromise between cost, data quality, and the effectiveness of the CRUD process [5]
• {drawback} update conflicts
• different systems can also update the common data [5]
• ⇒ involves continuous merges as well [5]
• {drawback} uses a special MDM application

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Acronyms:

MDM - Master Data Management

ODS - Operational Data Store

OLAP - online analytical processing

OLTP - online transactional processing

SOA - Service Oriented Architecture

References:
[1] The Art of Service (2017) Master Data Management Course 
[2] DAMA International (2009) "The DAMA Guide to the Data Management Body of Knowledge" 1st Ed.

[3] Tony Fisher 2009 "The Data Asset"

[4] DAMA International (2017) "The DAMA Guide to the Data Management Body of Knowledge" 2nd Ed.

[5] Dejan Sarka et al (2012) Exam 70-463: Implementing a Data Warehouse with Microsoft SQL Server 2012 (Training Kit)

🗄️Data Management: Master Data Management (Part I: Understanding Integration Challenges) [Answer]

Data Management Series

Answering Piethein Strengholt’s post [1] on Master Data Management’s (MDM) integration challenges, the author of "Data Management at Scale".

Master data can be managed within individual domains though the boundaries must be clearly defined, and some coordination is needed. Attempting to partition the entities based on domains doesn’t always work. The partition needs to be performed at attribute level, though even then might be some exceptions involved (e.g. some Products are only for Finance to use). One can identify then attributes inside of the system to create the boundaries.

MDM is simple if you have the right systems, processes, procedures, roles, and data culture in place. Unfortunately, people make it too complicated – oh, we need a nice shiny system for managing the data before they are entered in ERP or other systems, we need a system for storing and maintaining the metadata, and another system for managing the policies, and the story goes on. The lack of systems is given as reason why people make no progress. Moreover, people will want to integrate the systems, increasing the overall complexity of the ecosystem.

The data should be cleaned in the source systems and assessed against the same. If that's not possible, then you have the wrong system! A set of well-built reports can make data assessment possible. 

The metadata and policies can be maintained in Excel (and stored in SharePoint), SharePoint or a similar system that supports versioning. Also, for other topics can be found pragmatic solutions.

ERP systems allow us to define workflows and enable a master data record to be published only when the information is complete, though there will always be exceptions (e.g., a Purchase Order must be sent today). Such exceptions make people circumvent the MDM systems with all the issues deriving from this.

Adding an MDM system within an architecture tends to increase the complexity of the overall infrastructure and create more bottlenecks. Occasionally, it just replicates the structures existing in the target system(s).

Integrations are supposed to reduce the effort, though in the past 20 years I never saw an integration to work without issues, even in what MDM concerns. One of the main issues is that the solutions just synchronized the data without considering the processual dependencies, and sometimes also the referential dependencies. The time needed for troubleshooting the integrations can easily exceed the time for importing the data manually over an upload mechanism.

To make the integration work the MDM will arrive to duplicate the all the validation available in the target system(s). This can make sense when daily or weekly a considerable volume of master data is created. Native connectors simplify the integrations, especially when it can handle the errors transparently and allow to modify the records manually, though the issues start as soon the target system is extended with more attributes or other structures.

If an organization has an MDM system, then all the master data should come from the MDM. As soon as a bidirectional synchronization is used (and other integrations might require this), Pandora’s box is open. One can define hard rules, though again, there are always exceptions in which manual interference is needed.

Attempting an integration of reference data is not recommended. ERP systems can have hundreds of such entities. Some organizations tend to have a golden system (a copy of production) with all the reference data. It works for some time, until people realize that the solution is expensive and time-consuming.

MDM systems do make sense in certain scenarios, though to get the integrations right can involve a considerable effort and certain assumptions and requirements must be met.

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References:
[1] Piethein Strengholt (2023) Understanding Master Data Management’s Integration Challenges (link)

📦🔖💫Data Migrations (DM): Comments on "Planning for Successful Data Migration" II (Technical Aspects in Dynamics 365 Finance & Operations)

 

Data Migrations Series

Introduction

This weekend I read the chapter 5 on Data Migrations (Planning for Successful Data Migration) from Brent Dawson’s recently released book "Becoming a Dynamics 365 Finance and Supply Chain Solution Architect" (published by Packt Publishing, available on Amazon). The chapter makes a few good points, however there are statements that require further clarifications, while others can be questionable.  

Concerning the Data Migration (DM), besides several architectural recommendations, the author makes also several technical recommendations that can be summarized as follows:

(10) migrate transactional data manually via direct input or by using the Excel add-in (and it doesn’t recommend migrating transactional data using data packages because data change frequently)
(11) put in place a data outage should be as a part of the cutover timeframe
(12) new transactional data should be migrated after Go-live;
(13) include the effort for data entry in the cutover plan.

General Aspects

In what concerns the data there are 4 important phases during a cutover: configuring the production environment, migrating the master data, migrating the transactional data, respectively importing/creating the new transactional data. After each of these phases a data validation step is required to assure and sign-off on data quality.

Ideally, one can make sure that the production environment is correctly set up by deploying a copy of the database with the gold configuration (e.g. export the database and restore it in the target environment). Otherwise, direct data entry and templates, when available, can help obtain the same result, though the effort and risks for errors are higher.

Moving to next phases, it’s important to understand that a data migration is not a copy paste of some data from one system to another. Often the systems have different schemas, data definitions or granularity of the data entities. Ideally, a DM layer in between should take as input the source data and prepare the load data for the target system. This applies to master as well as to transactional data.

For importing data in D365 FO there are the following main options: 
(a) manual data entry
(b) import via Excel-add in and templates
(c)  manual/automated data packages
(d) batch API

As rule of thumb, if one has no more than 100-200 records for a data entity, it might be Ok to enter the data manually, eventually by splitting the effort between several users. This would allow users to accommodate themselves with the system, even if errors are made in the process. However, giving the importance of having “clean data” and a repeatable process for Go-Live makes this approach less desirable. On the other side, there will be cases when this will be the only available option.

As soon data's volume goes above this threshold, the effort doesn’t make sense. Preparing the data in Excel and importing them via the Excel add-in is in most cases recommended, as long as the volume of data is manageable. Moreover, data can be partitioned and imported in batches of 1000-2000 records. Ideally, the data should be available in the same structure as required by the templates used.

There will be however a second threshold that makes a batch API solution more attractive.  How big is this threshold? It depends. I was able to import 50-100k records via partitioning in Excel add-in, though these values shouldn’t be taken as fix.

The dependencies existing between data will dictate the order in which data must be imported, while the size of each data entity can be used to decide which approach will be used.

Master Data

In theory, the migration of master data can start as soon as the corresponding configuration is available. However, it is recommended to split the two phases and make sure that the environment is fully configured. This helps take a backup of the configuration, when such a snapshot is not available (see golden configuration in previous post).

Before taking a snapshot of the master data from the source system(s) it’s recommended to disable the access for changing the respective data (aka master data freeze). Otherwise, besides the fact that the changes will not appear in the target system(s), changes can make master data’s validation more complex. Sometimes, that's a risk the business is willing to take. 

The master data are typically imported a few days before the transactional data need to be imported to allow the team to validate the master data and if the data don’t have the expected quality, perform at most one more migration. Thus, the migration of master data can start one or two weeks earlier, however the longer the timeframe, the higher the chances that the business will be impacted by this (e.g. new orders with new products are needed urgently).

Transaction Data

Before migrating the transactional data, a few processes must be run (e.g. monthly/yearly closing, inventory counting, receiving goods in transit, etc.). Once this accomplished, the system can be frozen and thus the access to making changes disabled. This can happen in phases, depending on the requirements (e.g. migrating the balance can happen much later, even weeks after Go-Live).

What one can migrate are only open transactions (e.g. open purchase orders, open sales orders, open customer/vendor invoices, active assets) and balances (e.g. inventory, trial balance). Usually migrating historical data is out of the question. A data warehouse or similar data repository is more appropriate for storing historical data. Otherwise, keeping the source system(s) available for some users for regulatory requirements would be a better option, when feasible.

The biggest issue with transactional data is that the referenced values (products, customers, vendors) must be available in the target system(s). Even if names and descriptions are maybe the same, the unique identifiers or the surrogate keys are more likely to change. E.g. a product, vendor or customer will have other product number, vendor number or customer number than in the source system(s). This means that the old values need to be replaced with the new ones and this can become a tedious and error-prone process even for Excel. Unless the number of records is really small and there’s no other solution, I don’t recommend this approach.

The alternative would be to build a data migration layer that can address many of the challenges of data migrations. The effort for building such a layer might be high comparable with a manual transformation of the data, though it increases the chances of success by a considerable factor.

During and Post-Go-Live

After validating and signing off on the DM, and here extracts from source and target systems can help, the Go-Live will depend only on the functional testing’s results (and many things can go wrong in this area).

During the freeze period(s) of the source systems, more likely that new master and transactional data needed to be created. Ideally, these data should be entered after the Go-Live announcement, though it isn’t a must if a backup of the target system was taken before. For this the Excel add-ins can become the tool of choice.

With the Go-Live the DM should be over, though there will always be inquiries from the business. In fact only when the auditor signed off the DM is over. Even when one thinks that everything is over a few more surprises can appear – forgotten data, data enrichment, data for new features, etc.

Wrap Up

These are the most important aspects the reader should be aware of. There is more to say about the DM architecture and process, there are more best practices that need to be considered in areas like planning, conceptualization, quality assurance, principles, etc.

Comming back to the best practices from the book, it's worth to stress out that the frequency with which data changes is not the main driver for what approach to use in the DM. Definitely more important is the volume and complexity of data entities to be migrated, and this applies to master and transactional data altogether. Therefore, the argumentation behind (10) doesn't stand entirely. 

Concerning (11), a multi-level data freeze is more appropriate than an outage, even if the author intended maybe to say the same thing. 

(12) and (13) make sense, though the new data are part of daily business (business as usual) and not of the DM. Moreover, if the data entry or import fails because of whatever reason, it can't be the DM to blame. Even if the lessons learned during DM can be further used for mass data entry and updates, this doesn't mean that the DM project continues to exist. In theory, the DM layer can be used further on, though the respective layer was build on different premises that become obsolete with the Go-Live. One needs to think only from the perspective of the new system. Data Management or more specifically Master Data Management should be responsible for this type of data changes!

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🧊Data Warehousing: Architecture (Part IV: Building a Modern Data Warehouse with Azure Synapse)

Introduction

When building a data warehouse (DWH) several key words or derivatives of them appear in requirements: secure, flexible, simple, scalable, reliable, performant, non-redundant, modern, automated, real-timed, etc. As it proves in practice, all these requirements are sometimes challenging to address with the increased complexity of the architecture chosen. There are so many technologies on the DWH market promising all these at low costs, low effort and high ROI, though DWH projects continue to fail addressing the business and technical requirements.

On a basic level for building a DWH is needed a data storage layer and an ETL (Extract, Transfer, Load) tool responsible for the data movement between the various source systems and DWH, and eventually within the DWH itself. After that, each technology added to the landscape tends to increase the overall complexity (and should be regarded with a critical eye in what concerns the advantages and disadvantages).

A Reference Architecture

When building a DWH or a data migration solution, which has many of the characteristics of a DWH, from the many designs, I prefer to keep things as simple as possible.  An approach based on a performant database engine like SQL Server as storage layer and SSIS (SQL Server Integration Services) as ETL proved to be the best choice until now, allowing to address most of the technical requirements by design. Then come the choices on how and where to import and transform the data, at what level of granularity, on how the semantic layer is built, how the data are accessed, etc.

Being able to pull (see extract subprocess) the data from the data sources on a need by basis offers the most flexible approach, however there are cases in which the direct access to source data is not possible, having to rely on a push approach, where data are dumped regularly to a given location (e.g. FTP folder structure), following to be picked up as needed. It's actually a hybrid between a push and pull, because a fully push approach would mean pushing the data directly to the DWH, which can be also acceptable, though might offer lower control on data's movement and involve a few other challenges (e.g. permissions, concurrency). 

Data can be prepared for the DWH in the source systems (e.g. exposed via data objects or API calls), anywhere in between via ETL-based transformations (see transform subprocess) or directly in the DWH. I prefer importing the data (see load subprocess) 1:1 without any transformations from the various sources via SSIS (or similar technologies) into a set of tables that designated the staging area. It's true that in this way the ETL technology is used to a minimum, though unless there's a major benefit to use it for data transformations, using DWH's capabilities and SQL for data processing can provide better performance and flexibility. 

Besides the selection of the columns in scope (typically columns with meaningful values), it's important not to do any transformations in the extraction layer because the data is imported faster (eventually using fast load options as in SSIS) and it assures a basis for troubleshooting (as the data don't change between loads). Some filters can be applied only when the volume of data is high, and the subset of the data could be identified clearly (e.g. when data are partitioned based on a key like business unit, legal entity or creation date).

For better traceability, the staging schemas can reflect the systems they come from, the tables and the columns should have the same names, respectively same data types. On such tables no constraints are applied and no indexes are needed. They can be constructed however on the production tables (aka base tables) - copy of the tables from production. 

Some DWH architects try replicating the constraints from the source systems and/or add more constraints on top to define the various business rules. Rigor is good in some scenarios, though it can involve a considerable effort and it might be challenging to keep over time, especially when considering the impact of big data on DWH architectures. Instead of using constraints, building a set of SQL scripts that pinpoint the issues as reports allow more flexibility with the risk of having inconsistencies running wild through the reports. The data should be cleaned in the source system and not possible then properly addressed in the DWH. Applying constraints will make the data unavailable for reporting until data are corrected, while being more permissive would allow dirty data. Thus, either case has advantages or disadvantages, though the latter seems to be more appropriate. 

Indexes on the production schema should reflect the characteristics of the queries run on the data and shouldn't replicate the indexes from the source environments, even if some overlaps might exist. In practice, dropping the non-clustered indexes on the production tables before loading the data from staging, and recreating them afterwards proves to provide faster loading (see load optimization techniques). 

The production tables are used for building a "semantic" data model or something similar. Several levels of views, table-valued functions and/or indexed/materialized views allows building the dimensions and facts tables, the latter incorporating the business logic needed by the reports. Upon case, stored-procedures, physical or temporary tables, table variables can be used to prepare the data, though they tend to break the "free" flow of data as steps in-between need to be run. On the other side, in certain scenarios their use is unavoidable. 

The first level of views (aka base views) is based on the base tables without any joins, though they include only the fields in use (needed by the business) ordered and "grouped" together based on their importance or certain characteristics. The views can include conversions of data types, translations of codes into meaningful values, and quite seldom filters on the data. Based on these "base" views the second level is built, which attempts to define the dimension and fact tables at the lowest granularity. These views include joins between tables coming from the same or different systems, respectively mappings of values defined in tables, and whatever it takes to build such entities. However, transformations on individual fields are pushed, when possible, to the lower level to minimize logic redundancy. From similar reasons, the logic could be broken down over two or more "helper" views when visible benefits could be obtained from it (e.g troubleshooting, reuse, maintenance). It's important to balance between creating too many helper views and encapsulating too much logic in a view. 

One of the design principles used in building the entities is to minimize the redundance of the fields used, ideally without having columns duplicated between entities at this level. This would facilitate the traceability of columns to the source tables within the "semantic" layer (typically in the detriment of a few more joins). In practice, one is forced to replicate some columns to simplify some parts of the logic. 

Further views can be built based on the dimension and fact entities to define the logic needed by the reports. Only these objects are used and no direct reference to the "base" tables or views are made. Moreover, to offer better performance when the views can be materialized or, when there's an important benefit, physically saved as table (e.g. having multiple indexes for different scenarios). It's the case of entities with considerable data volume called over and over. 

This approach of building the entities is usually flexible enough to address most of the reporting requirements, independently whether the technical solution has the characteristics of a DWH, data mart or data migration layer. Moreover, the overall architectural approach can be used on-premise as well in cloud architectures, where Azure SQL Server and ADF (Azure Data Factory) provide similar capabilities. Compared with standard SQL Server, some features might not be available, while other features might bring further benefits, though the gaps should be neglectable.

Data Management topics like Master Data Management (MDM), Data Quality Management (DQM) and/or Metadata Management can be addressed as well by using third-party tools or tools from the Microsoft stack - Master Data Services (MDS) and Data Quality Services (DQS) in combination with SSIS help addressing a wide range of scenarios - however these are optional. 

Moving to the Cloud

Within the context of big data, characterized by (high/variable) volume, value, variety, velocity, veracity, and further less important V's, the before technical requirements still apply, however within a cloud environment the overall architecture becomes more complex. Each component becomes a service. There are thus various services for data ingestion, storage, processing, sharing, collaboration, etc. The way data are processed involves also several important transformations: ETL becomes ELT, FTP and local storage by Data Lakes, data packages by data pipelines, stateful by stateless, SMP (Symmetric Multi-Processing) by MPP (Massive Parallel Processing), and so on.

As file storage is less expensive than database storage, there's an increasing trend of dumping business critical data into the Data Lake via data pipelines or features like Link to Data Lake or Export to Data Lake (*), which synchronize the data between source systems and Data Lake in near real-time at table or entity level. Either saved as csv, parquet, delta lake or any other standard file format, in single files or partitions, the data can be used directly or indirectly for analytics.

Cloud-native warehouses allow addressing topics like scalability, elasticity, fault-tolerance and performance by design, though further challenges appear as compute needs to be decoupled from storage, the workloads need to be estimated for assuring the performance, data may be distributed across data centers spanning geographies, the infrastructure is exposed to attacks, etc. 

Azure Synapse

If one wants to take advantage of the MPP architecture's power, Microsoft provides an analytical architecture based on Azure Synapse, an analytics service that brings together data integration, enterprise DWH, and big data analytics. Besides two types of SQL-based data processing services  (dedicated vs serverless SQL pools) it comes also with a Spark pool for in-memory cluster computing.

A DWH based on Azure Synapse is not that different from the reference architecture described above for an on-premise solution. Actually, a DWH based on a dedicated SQL pool (aka a physical data warehouse) involves the same steps mentioned above. 

The data can be imported via ETL/ELT pipelines in the DWH, though there are also mechanisms for consuming the data directly from the files stored in the Data Lake or Azure storage. CETAS (aka Create External Table as Select) can be defined on top of the data files, the external tables acting as "staging" or "base" tables in the architecture described above. When using a dedicated SQL pool it makes sense to use the CETAS as "staging" tables, the processed data following to be dumped to "optimized" physical tables for consumption and refreshed periodically. However, when this happens the near real-time character of data is lost. Using the CETAs as base tables would keep this characteristic as long the data isn't saved physically in tables or files, maybe in the detriment of performance.

Using a dedicated SQL pool for direct reporting can become expensive as the pool needs to be available at least during business hours for incoming user requests, or at least for importing the data and refreshing the datasets. When using the CETAS as a base table, a serverless (aka on-demand) SQL pool, which uses a per-pay-use billing model could prove to be more cost-effective and flexible in many scenarios. By design, it helps to keep the near real-time character of the data. Moreover, even if the data are actually moved from the source tables into the Data Lake, this architecture has the characteristics of a logical data warehouse:

Unfortunately, unless one uses Spark tables, misuses views or adds an Azure SQL database to the architecture, there are no physical tables or materialized views in a serverless SQL pool. There's still the option to use data pipelines for regullarly exporting intermediary data to files (incl. over partitions or folders), even if this involves more overhead as it's not possible to export data over SQL syntax to files more than once (though this might change in the future). For certain scenario it could be useful to store data in a Azure SQL Server or similar database, including a dedicated SQL pool. 

Choosing between serverless and dedicated SQL pool is not an exclusive choice, both or all 3 types of pools (if we consider also the Spark pool) can be used in the architecture for addressing specific challenges, especially when we consider that there are important differences between the features available in each of the pools. Moreover, one can start the PoC based on the serverless SQL pool and when the solution became mature enough and used in all enterprise, parts of the logic or all of it can be migrated to a dedicated SQL pool. This would allow to save costs at the beginning in the detriment of further effort later. 

Talking about the physical storage, data engineers recommend defining within a Data Lake several layers (aka regions, zones) labeled as bronze, silver and gold (and probably platinum will join the club anytime soon). The bronze layer refers to the raw data available in the Data Lake, including the files on which the initial CETAS are defined upon. The silver refers to transformed, cleaned, enriched and integrated data, data resulting from the second layer of views described above. The gold layer refers to the data to which business logic was applied and prepared for consumption, data resulting from the final layer of views. Of course, data pipelines can be used to prepare the data at these stages, though a view-based approach offers more flexibility, are easier to troubleshoot, manage and reuse than data pipelines.

Ideally the gold data should involve no or minimal further transformation before reaching the users, though that's not realistic. Building a DWH takes a considerable time and the business can't usually wait until everything is in place. Therefore, reports based on DWH will continue to coexist with reports directly accessing the source data, which will lead to controversies. Enforcing a single source of truth will help to minimize the gap, though will not eliminate it completely. 

Closing Notes

These are just outlines of a minimal reference architecture. There's more to consider, as there are several alternatives (see [1] [2] [3] [4]) for each of the steps considered in here, each technology, new features or mechanisms opening new opportunities. The advantages and disadvantages should be always considered against the business needs and requirements. One approach, even if recommended, might not work for all, though unless there's an important requirement or an opportunity associated with an additional technology, deviating from reference architectures might not be such a good idea afterall.

Note:

(*) Existing customers have until 1-Nov-2024 to transition from Export to Data lake to Synapse link. Microsoft advises new customers to use Synapse Link. 

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Resources:

[1] Microsoft Learn (2022) Modern data warehouse for small and medium business (link)

[2] Microsoft Learn (2022) Data warehousing and analytics (link)

[3] Microsoft Learn (2022) Enterprise business intelligence (link)

[4] Microsoft Learn (2022) Serverless Modern Data Warehouse Sample using Azure Synapse Analytics and Power BI (link)

[5] Coursera (2023) Data Warehousing with Microsoft Azure Synapse Analytics (link) [course, free to audit]

[6] SQLBits (2020) Mahesh Balija's Building Modern Data Warehouse with Azure Synapse Analytics (link)

[7] Matt How (2020) The Modern Data Warehouse in Azure: Building with Speed and Agility on Microsoft’s Cloud Platform (Amazon)

[8] James Serra's blog (2022) Data lake architecture (link)

[9] SQL Stijn (2022) SQL Building a Modern Lakehouse Data Warehouse with Azure Synapse Analytics: Moving your Database to the lake (link)

[10] Solliance (2022) Azure Synapse Analytics Workshop 400 (link) [GitHub repository]

🗄️Data Management: Data Literacy (Part I: A Second Language)

At the Gartner Data & Analytics Summit that took place in 2018 in Grapevine, Texas, it was reiterated the importance of data literacy for taking advantage of the emergence of data analytics, artificial intelligence (AI) and machine learning (ML) technologies. Gartner expected then that by 2020, 80% of organizations will initiate deliberate competency development in the field of data literacy [1] – or how they put it – learning to ‘speak data’ as a ‘second language’.

Data literacy is typically defined as the ability to read, work with, analyze, and argue with data. Sure, these form the blocks of data literacy, though what I’m missing from this definition is the ability to understand the data, even if understanding should be the outcome of reading, and the ability to put data into the context of business problems, even if the analyzes of data could involve this later aspect too.

Understanding has several aspects: understanding the data structures available within an organization, understanding the problems with data (including quality, governance, privacy and security), respectively understanding how the data are linked to the business processes. These aspects go beyond the simple ability included in the above definition, which from my perspective doesn’t include the particularities of an organization (data structure, data quality and processes) – the business component. This is reflected in one of the problems often met in the BI/data analytics industry – the solutions developed by the various service providers don’t reflect organizations’ needs, one of the causes being the inability to understand the business on segments or holistically.  

Putting data into context means being able to use the respective data in answering stringent business problems. A business problem needs to be first correctly defined and this requires a deep understanding of the business. Then one needs to identify the data that could help finding the answers to the problem, respectively of building one or more models that would allow elaborating further theories and performing further simulations. This is an ongoing process in which the models built are further enhanced, when possible, or replaced by better ones.

Probably the comparison with a second language is only partially true. One can learn a second language and argue in the respective language, though it doesn’t mean that the argumentations will be correct or constructive as long the person can’t do the same in the native language. Moreover, one can have such abilities in the native or a secondary language, but not be able do the same in what concerns the data, as different skillsets are involved. This aspect can make quite a difference in a business scenario. One must be able also to philosophize, think critically, as well to understand the forms of communication and their rules in respect to data.

To philosophize means being able to understand the causality and further relations existing within the business and think critically about them. Being able to communicate means more than being able to argue – it means being able to use effectively the communication tools – communication channels, as well the methods of representing data, information and knowledge. In extremis one might even go beyond the basic statistical tools, stepping thus in what statistical literacy is about. In fact, the difference between the two types of literacy became thinner, the difference residing in the accent put on their specific aspects.

These are the areas which probably many professionals lack. Data literacy should be the aim, however this takes time and is a continuous iterative process that can take years to reach maturity. It’s important for organizations to start addressing these aspects, progress in small increments and learn from the experience accumulated.

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References:
[1] Gartner (2018) How data and analytics leaders learn to master information as a second language, by Christy Pettey (link) 

📦Data Migrations (DM): Data Quality’s Perspective I (A Bird’s-Eye View)

Data Migrations Series

Imagine you just finished a Data Migration (DM) project, everything went smoothly, the data were loaded into the new system with a minimum amount of issues, inherent sometimes to such complex projects, the users started to use the new system, everybody seemed to be satisfied, and a few weeks later within the company rumors propagate with the speed of light – “the migrated data are wrong”, “the new system can’t be used” , “IT did a bad job”, “we have to get back to the previous system”, and so on. The panic propagates, a few heads fall, the business tries to revert to the old system but there’s lot of new data available in the new system, and it’s not so trivial to move the data back to the old, in the meantime other rumors appear, and… it’s just a scenario but this could happen to any company if not the appropriate measures were taken at the right time. What could help a company when something like this happens?! A good Plan B aka a good Migration Fallback Plan/Policy, but that’s something nobody would like to do except extreme situations.

A common approach to any type of projects as well to a DM project is to identify and mitigate the risks before or during the project. That’s something I started to do a few days ago, to prepare a list with the risks associated with DM projects. For this exercise I tried to remember what things went wrong in previous similar projects I worked on and to figure out what else could go wrong. Some online resources helped me to refresh my memory too, and I think I found also two or three things I haven’t really thought about. My attempt was primarily focused on this type of problem mentioned above – minimizing the risks of not having the right data when the new system goes live. Before jumping into the thematic I would like to sketch the bigger picture, as I perceive it.

Having the right data when a system goes live primarily means having good Data Quality (DQ) in the target system after the data were migrated! As a DM is the best exemplification of the GIGO (Garbage-In Garbage-Out) principle, in order to have good DQ in the target is important to handle DQ latest during the DM project. That’s essential and common sense – you can’t expect to have good data in the new system when there’s lot of garbage in the old. So, a DM and a Risk Management for such a project should be built around this. In fact not having a DQ initiative or project in a DM project is one of the most important risks a company can take. Maybe in small DM, a DQ initiative isn’t necessary, though when the data are important for your company, DQ is a must! In addition DQ assessments have to be performed in alignment with the new system, and not the old. Even if the data have good quality into the old system, the quality of your data after DM will be judged in corroboration with the new system. This is a requirement that can be easily overlooked and its implications misunderstood!

Many think that DQ is one time activity, we do it for a DM project and we’ll have quality data and never have to care about their quality anymore. Totally false! DQ has to be part of a broader strategy, call it Data Governance, Master Data Management, Data Management or any other initiative in which data plays an important role. DQ is an on going, iterative and consolidated effort, it doesn’t end after DM but continues for the whole data life-cycle, as long the data have value for an organization. It doesn’t help if the data have high quality when the data are migrated and a few weeks or months later the overall quality and trust in data decreased considerably.

Keeping an acceptable level of DQ must be an organization’s strategy, and must be built a culture toward DQ. People need to be aware of the importance of having good quality data, and especially the consequences of having bad quality data. DQ doesn’t concern only the owners or stewards of data, or the people working with data, it concerns the whole organization because decisions are made based on those data, processes are changed and improved, an organization’s performance is often judged based on data. The quality of data is a matter of perception, on how users see the quality of data in corroboration with the needs they have, and the needs change over time. Primarily being aware what good DQ means and which are an organization’s needs in respect to data, it’s also a way of minimizing the negative perception of data, of gaining trust in data and some solid basis on which decisions can be made. Secondarily, these organizational data needs need to be addressed in a DM, they are the success factors upon which the success of a DM project is judged.

For sure considerable costs are associated with DQ initiatives and everything related to data which doesn’t always represent a direct cost component in the products or services handled by an organization. Considering that not all data have the same importance for an organization, it makes sense to prioritize the DQ effort as a whole and the data cleaning needs in particular, the focus should be the data with the highest impact and with time to tackle data with lower and lower impact. It must be found equilibrium between the DQ costs and the value of data. Most probably is important to spend resources on raising people’s awareness in respect to DQ early rather than cleaning retroactively data later. It also make sense to invest in tools that help to clean data using automated or semi-automated methods, though some manual/visual control need to be in place too.

DQ and the way the problems associated with it are tackled depends more on an organization’s internal kitchen – people, partners, organization, strategy, maturity, culture, geography, infrastructure, methodologies used, etc. What it matters is how the various negative and important aspects of an organization are aligned in order to take advantage of one of the most important assets an organization has is its data! For this is important to adopt methodologies that support DQ, align them and tweak them as requested, in order to make most of your data! But before or while doing that remember that a DM is an organization’s opportunity to change the quality of its data and its data strategy!

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🗄️Data Management: Data Quality Dimensions (Part V: Consistency)

Data Management Series

IEEE defines consistency in general as "the degree of uniformity, standardization, and freedom from contradiction among the documents or parts of a system or component" [4]. In respect to data, consistency can be defined thus as the degree of uniformity and standardization of data values among systems or data repositories (aka cross-system consistencies), records within the same repository (aka cross-record consistency), or within the same record at different points in time (temporal consistency) (see [2], [3]). 

Unfortunately, uniformity, standardization and freedom can be considered as data quality dimensions as well and they might even have broader scope than the one provided by consistency. Moreover, the definition requires further definitions for the concept to be understood, which is not ideal. 

Simply put, consistency refers to the extent (data) values are consistent in notation, respectively the degree to which the data values across different contexts match. For example, one system uses "Free on Board" while another systems uses "FOB" to refer to the point obligations, costs, and risk involved in the delivery of goods shift from the seller to the buyer. The two systems refer to the same value by two different notations. When the two systems are integrated, because of the different values used, the rules defined in the target system might make the record fail because it is expecting another value. Conversely, other systems may import the value as it is, leading thus to two values used in parallel for the same meaning. This can happen not only to reference data, but also to master data, for example when a value deviates slightly from the expected value (e.g. misspelled). A more special case is when one of the systems uses case sensitive values (usually the target system, though there can be also bidirectional data integrations).

One solution for such situations would be to "standardize" the values across systems, though not all systems allow to easily change the values once they have been set. Another solution would be to create a mapping as part the integration, though to maintain such mappings for many cases is suboptimal, but in the end, it might be the only solution. Further systems can be impacted by these issues as well (e.g. data warehouses, data marts).

It's recommended to use a predefined list of values (LOV) - a data dictionary, an ontology or any other type of knowledge representation form that can be used to 'enforce' data consistency. ‘Enforce’ is maybe not the best term because the two data sets could be disconnected from each other, being in Users’ responsibility to ensure the overall consistency, or the two data sets could be integrated using specific techniques. In many cases is checked the consistency of the values taken by one attribute against an existing LOV, though for example for data formed from multiple segments (e.g. accounts) each segment might need to be checked against a specific data set or rule generator, such mechanisms implying multi-attribute mappings or associational rules that specify the possible values.

As highlighted also by [1], there are two aspects of consistency: the structural consistency in which two or more values can be distinct in notation but have the same meaning (e.g. missing vs. n/a), and semantic consistency in which each value has a unique meaning (e.g. only n/a is allowed to highlight missing values). It should be targeted to have the data semantically consistent, to avoid confusion, accidental exclusion of data during filtering or reporting. More and more organizations are investing in ontologies, they allow ensuring the semantic consistency of concepts/entities, though for most of the cases simple single or multi-attribute lists of values are enough.

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Written: Jan-2010, Last Reviewed: Mar-2024

References:
[1] Chapman A.D. (2005) "Principles of Data Quality", version 1.0. Report for the Global Biodiversity Information Facility, Copenhagen
[2] David Loshin (2009) Master Data Management

[3] IEEE (1990) "IEEE Standard Glossary of Software Engineering Terminology"

[4] DAMA International (2010) "The DAMA Dictionary of Data Management" 1st Ed.

🗄️Data Management: Data Quality Dimensions (Part III: Completeness)

Data Management Series

Completeness refers to the extent to which there are missing data in a dataset, fact reflected in the number of the missing values, also referred as empty (when an empty string or default values is used) or 'Nulls' (aka unknown values), and/or in the number of missing records.

The missing values are typically considered in report to mandatory attributes, attributes that need a not-Null value for each record, though after case might be applied to non-mandatory attributes (optional attributes) too, for example when is intended to understand whether the attributes are adequately maintained or not. It’s interesting that [1] considers also the inapplicable attributes referring to the attributes not applicable (relevant) for certain scenarios (e.g. physical dimensions for service-based materials), which together with the applicable attributes (relevant) can be considered as another type of categorization for attributes. Whether an attribute is mandatory is decided upon business context and not necessarily upon the physical structure containing the attribute, in other words an attribute could be optional as per database schema and mandatory per business rules.

'Missing records' can be a misleading term because is used in several contexts, however within data completeness context it refers only to the cases not covered by data integrity. For example in parent-child table relations the header data was entered though the detail data is missing, either not entered or deleted; such a case is not covered by referential integrity because there is no missing reference, but just the parent without child data (1:n cardinality). 

A mixed example occurs when the same entity is split across several tables at the same level of detail. One of the tables must function as a parent, falling in the previous mentioned example (1:1 cardinality). In such a scenario it depends how one reports the nonconformances per record: (1) the error is counted only once, independently on how many dimensions an error was raised; (2) the error is counted for each dimension. For (2) when the referential integrity failed, an error is raised also for each mandatory attribute. 

Both examples are dealing with explicit data referents – the 'parent' data, though there are cases in which the referents are implicit, for example when the data are not available for a certain time interval (e.g. period, day) even if needed, though also for this case the referents could be made explicit, falling in the previous mentioned examples. In such scenarios all the attributes corresponding to the missing records will be null.

Normally the completeness of parent-child relations is enforced with the help of referential integrity and database transactions, a set of actions performed as a single unit of work, they allow saving the parent data only if the child data were saved successfully, though such type of constraints is not always necessary.

Data should be cleaned when feasible in the source system(s) and this applies to incomplete data as well. It might be feasible to clean the values in Excel files or similar tools, by exporting and then reimporting the clean values back into the respective systems.

In data migrations or similar scenarios, the completeness in particular and data quality in general must be judged against the target system(s) and thus the dataset must be enriched in an intermediate layer as needed. Upon case, one can consider using default values, though this sounds like a technical debt, likely improbably to be addressed later. Moreover, one should prioritize the effort and consider first the attributes which are needed for the good functioning of the target system(s).

Ideally, for the mandatory fields should be applied data validation techniques in the source systems, when feasible. 

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Written: Jan-2010, Last Reviewed: Mar-2024 

References:
[1] David Loshin (2009) "Master Data Management"

🗄️Data Management: Data Quality Dimensions (Part II: Conformity)

Data Management Series

Conformity or format compliance, as named by [1], refers to the extent data are in the expected format, each attribute being associated with a set of metadata like type (e.g. text, numeric, alphanumeric, positive), length, precision, scale, or any other formatting patterns (e.g. phone number, decimal and digit grouping symbols).

Because distinct decimal, digit grouping, negative sign and currency symbols can be used to represent numeric values, same as different date formats could be used alternatively (e.g. dd-mm-yyyy vs. mm-dd-yyyy), the numeric and date data types are highly sensitive to local computer and general applications settings because the same attribute could be stored, processed and represented in different formats. Therefore, it’s preferable to minimize the variations in formatting by applying the same format to all attributes having the same data type and, whenever is possible, the format should not be confusing. 

For example all the dates in a data set or in a set of data sets being object of the same global context (e.g. data migration, reporting) should have the same format, being preferred a format of type dd-mon-yyyy which, ignoring the different values the month could have for different language settings, it lets no space for interpretations (e.g. 01-10-2009 vs. 10-01-2009). There are also situations in which the constraints imposed by the various applications used restraints the flexibility of working adequately with the local computer formats.

If for decimal and dates there are a limited number of possibilities that can be dealt with, for alphanumeric values things change drastically because excepting the format masks that could be used during data entry, the adherence to a format depends entirely on the Users and whether they applied the formatting standards defined. In the absence of standards, Users might come with their own encoding, and even then, they might change it over time. 

The use of different encodings could be also required by the standards within a specific country, organization, or other type of such entity. All these together makes from alphanumeric attributes the most often candidate for data cleaning, and the business rules used can be quite complex, needing to handle each specific case. For example, the VAT code could have different length from country to country, and more than one encoding could be used reflecting the changes in formatting policy.

In what concerns the format, the alphanumeric attributes offer greater flexibility than the decimal and date attributes, and their formatting could be in theory ignored unless they are further parsed by other applications. However, considering that such needs change over time, it’s advisable to standardize the various formats used within an organization and use 'standard' delimiters for formatting the various chunks of data with a particular meaning within an alphanumeric attribute, fact that could reduce considerably the volume of overwork needed in order to cleanse the data for further processing. An encoding could be done without the use of delimiters, e.g. when the length of each chunk of data is the same, though chunk length-based formatting could prove to be limited when the length of a chunk changes.

Note:
Delimiters should be chosen from the characters that will never be used in the actual chunks of data or in the various applications dealing with the respective data. For example pipe (“|”) or semicolon (“;”) could be good candidates for such a delimiter though they are often used as delimiters when exporting the data to text files, therefore it’s better to use a dash (“-”) or even a combinations of characters (e.g. “.-.”) when a dash is not enough, while in some cases even a space or a dot could be used as delimiter.

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Written: Jan-2010, Last Reviewed: Mar-2024 

References:
[1] David Loshin (2009) "Master Data Management", Morgan Kaufmann OMG Press. ISBN 978-0-12-374225-4.

🗄️Data Management: Data Quality Dimensions (Part I: Uniqueness)

Data Management Series

Uniqueness refers to "requirements that entities modeled within the master environment are captured, represented, and referenced uniquely within the relevant application architectures" [1]. An alternative name is the one of duplicates, which stresses the existence of duplicate records within a dataset, the not-uniqueness, being a better indicator for the nonconformance especially when considering datasets.

Why is required to enforce the uniqueness of entities? An entity is defined using a number of attributes representing entity’s characteristics, in case the attributes of two entities have the same values, then more likely the two representations refer to the same entity. This could happen in most of the cases, though there are situations in which the attribute(s) that make(s) it possible to differentiate between two distinct entities is/are not adequately maintained or not considered at all. The impossibility of identifying uniquely an entity increases the chances of using one of the respective entities wrongly, for example booking the Invoice against the wrong Vendor and all the implications derived from it. 

For each type of entity there can be one or more attributes that allow identifying it uniquely, for example in case of a Vendor could be Vendor’s name and address. The more such attributes then more difficult becomes the identification of a Vendor; therefore even if such a set of attributes exists, like in Vendor’s case, it’s preferable to use instead a unique identifier, a numeric or alphanumeric key that identifies uniquely an entity. 

A Vendor could be uniquely identified by the Vendor ID, though it allows unique identification of a Vendor only in a data repository, the chances being quite high to have another Vendor ID for the same entity in another data repository. Therefore, in order to guarantee the uniqueness of entities is prefer to use instead an attribute that has the same value indifferently from the data repository the entity is stored in (e.g. Vendor Number, Item Number, Customer Number, Asset Number, Sales Order Number, etc.). Such attributes could be enforced to be unique across a set of data repositories, though one of them must function as 'master'.

Multiple identifiers for the same entity may exist, though this can easily create confusion, especially when this happens within the same system and people or machines are not aware that the respective identifiers refer to the same entity, and the more identifiers we have for the same entity the higher the chances of creating confusion. Imagine that in the same system you book some of the Invoices against one of the identifiers, and the remaining Invoices against another identifier of the same entity.

Especially in reports this might be quite a problem as amounts that should appear for the same entity are split against two references, and even if they refer to the same entity report’s users might be not aware of it, the calculations based on such numbers not reflecting the reality. Imagine that you have booked the invoices against two references to the same Vendor, and you want to consider the first 10 Vendors with the highest volume spent; it might happen that the aggregate amounts for each of the respective references didn’t make it in the top 10, though when considered together they can even make it to the first position.

There are even situations in which the use of multiple identifiers for the same entity is inevitable, and important are here the cases in which more than one different system refer to the same entity in their unique way, often being not designed to use a global unique identifier for an entity. Under such circumstances what an organization could do is to either extend the system(s) to store the global identifier or have a mapping in place with the referents used to indicate the same entity. 

The more systems within an enterprise that use/represent the same entity, the more complex is to manage the correct referencing; the logical thing to do is to have in place a master system that stores the global identifier and integrate it with the other systems in place or at least store the global identifier in each of the systems. Such identifiers used for master or even transactional data allow creating consolidated reports based on several systems and mitigating possible issues existing in the data.

Even if such keys are designed to enforce uniqueness this doesn’t mean it necessarily happens; the reason is simple - behind the assignment of a key to an entity there is a process defined, and no matter how robust a process was created if it doesn’t cover all the scenarios that might occur or if it can’t deal (adequately) with various constraints, then in one point in time a flow might lead to a duplicate, a not unique record. Take for example a Product Number's creation - supposing that a Product Number XYZ is created in an ERP system and one or more of the respective Product’s attributes are incorrect. In many cases such errors can be corrected, though each system comes with its own constraints not allowing changing certain attributes (e.g. the Unit of Measure once Inventory was booked). Because an entity with the wrong attributes is inadequate to be used, a new Product Number is created for the same entity, the two identifiers coexisting for some time. (Some systems allow to build a relationship between the Products, showing that one Product replaces another going forward.)

Some systems could allow the deletion of the first entered Product though that’s not always possible. Even if the two Products Numbers are different, they point to the same Product entity, and even if the first entered Product is marked as obsolete, until this happens transactions might be already made with it, and again, it might be possible to revert the transactions back, though that’s not always possible, and that’s not all, once a Product is marked as obsolete, this doesn’t necessarily imply that a User won’t reactivate the Product in the near or far future. As can be seen, the scenarios are quite complex, not all the systems and processes being designed to handle them. If such deviations from uniqueness can’t be corrected in the legacy systems, at least during conversion and migration should be corrected.

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Written: Jan-2010, Last Reviewed: Mar-2024

References:
[1] David Loshin (2009) "Master Data Management"