Metamodel FAQs

What is Meta Model?

Meta model is the format that allows capturing detailed information about attributes of data sets that are to be processed.

How do I build the Meta Model?

Use admin UI to create it. Please refer to its documentation.

or

The Meta Model can be built using the Meta Model UI or CSV format. Please consult the product documentation for sequencing.

What type of information can be captured in Meta Model?

The following types of information can be captured in meta model on a per attribute basis for a given entity.

Data set Description - The module, entity, and description of the data set.
Attribute Description - Name, Description, Format, and Length. This can be captured at both the data model and BI model levels.
Attribute Security - Masking requirement and masking information.
Attribute Transforms - Transform rule that needs to be applied at the inbound and outbound. By default, trim is applied to all categorical attributes.
Attribute Filtering - Whether the attribute should be part of the data filtering process and if so what rule.
Attribute IQM - Whether the attribute should be utilized in IQM match. For more information on IQM, please refer to IQM FAQs and BAPCore documentation.
Attribute EDA - Whether the attribute should be utilized in EDA analysis.
Attribute Calendar - Whether the attribute should be utilized in calendar join operations.
Attribute Validation - Whether the attribute should be part of the data validation process and if so what rule.
Attribute Quality - Whether the attribute should be part of the data validation process and if so what rule.

What are the data types supported in meta model?

Currently, character, integer, and numeric are supported.

It should be noted that while creating an attribute in the metamodel using the AdminUI, if the data type is selected as character, default transformation of Trim is applied. This default transformation isn’t applied for integer or numeric data types.

While editing a meta model, if the data type is changed, that the transform rule is required to be updated appropriately for the workload to run successfully.

Should I specify data columns as character data types as well?

Yes.

How do I validate meta model against the data set?

Developers can use the dataops.applymodeldatacompatibility to check the compatibility of the metamodel with the data.

Where are the Meta Models stored?

Meta models are stored within the Meta folder of the core data lake (SPRINGYCORE/Meta/BDL/Fact).

How is the storage and retrieval of Meta Models?

Meta models are stored within the Meta folder of the core data lake using the springycore API. They can be retrieved using the springycore API as well.

How is the life cycle of the Meta Model managed?

The most current version of Meta Model is stored in Current folder (SPRINGYCORE/Meta/BDL/Fact/Current). The archived version is stored in Archive folder (SPRINGYCORE/Meta/BDL/Fact/Archive). When a new version is pushed, the current version is moved to the archive folder.

Can I know what Meta Model was used for a particular batch process?

Every time an metamodel is used for any data movement, the definition of the meta model is stored in the track folder (SPRINGYCORE/Meta/BDL/Fact/Track) along with the batch_id of the data movement process.

Can I define more than one parent entity?

Currently, that is not supported. A child entity can only belong to one parent entity. If you specify more than one parent, workloads will fail on orphan and nested records processors.

How does nesting work if I can define only one parent entity?

When processing child entity, you can pass a coalesced meta model that has all parents to that particular child based on a strict parent-child relationship. For example, X is the child of Y and Z is the child of X, you can pass the coalesced meta model (both X and Y) along with entity model Z while processing the data set for Z.

How are references to parent meta model stored in entity meta model for a particular batch process?

The parent meta model coalesces with the entity meta model. The coalesced (entity meta model and parent entity meta model) are stored in the track folder (SPRINGYCORE/Meta/BDL/Fact/Track) along with the batch_id of the data movement process. None of the attributes of the parent entity model are changed when coalesced with the child entity model meta model. this helps in troubleshooting if all parent entity models are appropriately applied to the child entity model for nesting processes.

What should the format of entity_effective_date_time be?

Entity effective DateTime should be a string else metamodel.read will fail.

What are the best practices for meta model?

Special character issue in filter and validation rules - filter records process would fail. The error log will indicate a ‘special character error’. Avoid special characters while defining filter and validation rules. If you are defining meta-model in excel or CSV, export that to an R file using dput function and search for any special characters and if there are any special characters, remove those before saving the metamodel to the core data lake.
No parent is defined in meta model - If no parent information is defined in the meta model i.e parent location and parent attributes, no nested data would be created.
For integers, the default should be ‘0' and for numeric, it should be ‘0.01’. For characters, the default value should be ‘NOT AVAILABLE’
Impute method for numeric and integer should be mean and for characters, it should be DEFAULT.
meta model column names should be all lower case.
IQM metric match should be ‘YES’ only for integer and numeric columns. This should be set to YES only for integer or numerical columns that are meaningful to data analysis.
IQM codes should be ‘YES' for characters columns. This should be set to YES only for categorical columns that are meaningful to data analysis.
Entity Name should be exactly as defined in the HDFS folder structure. The entity name is used to dynamically lookup data lake paths.
EDA Dimensions should be ‘YES’ for character columns. This should be set to YES only for categorical columns that are meaningful to data analysis.
EDA Metrics should be ‘YES’ for integer and numeric columns. This should be set to YES only for integer or numerical columns that are meaningful to data analysis.
EDA iterate by should be the as of the date and only the as of date. This would allow for creating EDA analytics on daily basis.
entity_attribute_nested_key_role should always be set to YES when it is a parent lookup key and it is in use indicator is also set to YES
Entity Attribute Calendar Join Key should only be specified as of the date and no other key.
Each record in meta-model needs to be unique (entity names, object/BI names all need to be unique).
Parent Lookup location should have a relative path instead of an absolute path
IQM Processor should be run with the nesting records processor ON, otherwise, turn IQM off if not Nesting.
Regarding nested attributes
- We recommend to keep entity_attribute_compare_key_role, entity_attribute_parent_lookup_key_role as NO for as_of_date if the dates are not matching between two entities. If you keep YES then it would introduce NULLS in nesting for those rows where as_of_date is not matchig between the two entity data sets and replace it with impute method defined in the meta model for the given attribute.
- Moreover, entity_attribute_nested_key_role should be NO for the parent entity and it’s YES for the child entity. If the child entity has another child entity then it should be NO for that as well. The reason is if as_of_date values are different then it would introduce as_of_date_x and as_of_date_y in the data after nesting.
- For other matching ID columns between two entities, entity_attribute_compare_key_role, entity_attribute_parent_lookup_key_role should be YES, with entity_attribute_parent_lookup_location defined to the FDL/Stage of the parent entity. This will nest the column between two entities based on the defined common attribute.
Regarding entity_attibute_calendar_join_key_role
- If the data size is small, then don’t set entity_attibute_calendar_join_key_role to YES to any of the attributes. (NOTE: In spark, partitioning is an expensive operation when we try to partition too small or too big dataset)
- If the data size is too big (greater than 100GB or something), then the best practice is, don’t try to partition the dataset i.e. don’t set entity_attibute_calendar_join_key_role to YES to any of the attributes.
- If the data size is big and If you are setting entity_attibute_calendar_join_key_role to YES to any of the attributes then make sure that column is a date column and the actual data for the date column should be in the format of 'YYYY-MM-DD'. (NOTE: General thumb rule is that there should be one column called as_of_date which would serve all the purposes.). The value of as_of_date should not be ‘NOT AVAILABLE’ when calendar_join_key_role is YES for it.

I have a large number of small files in Meta folder that may impede read performance?

You can consolidate multiple Meta files into one using consolidate functionality. This is assuming that the schema of all files in the meta-model folder is the same.

Can I consolidate Meta files?

You can consolidate multiple Meta files into one using consolidate functionality. This is assuming that the schema of all files in the meta-model folder is the same.

What if there is Parent-child relationship in your data module?

You need to update the field (through which you are planning to make a join with the parent entity) of your child entity in meta model by updating the “Entity Attribute Compare Key Role“ to “Yes”, “Entity Attribute Parent Lookup Key Role“ to “Yes” and in “Entity Attribute Parent Lookup Location“ you need to give the FDL/Stage location of your parent entity. Please refer above screenshot, where “movies” is the parent entity and “roles” is the child entity.

How can I create custom transform rules in the Meta Model?

Transform rules are SQL queries you can write in order to filter data by a variable, change certain values in a column, and apply the other functions that are in the Spark SQL library. We can write the transform rules in the meta model by clicking the edit icon next to the column name and going to the Rules page.

Here are a couple things to keep in mind when writing your transform rules:

Do not put ‘Select’ at the beginning of the query, as it is appended automatically to the front when the backend processor runs
The SQL query should end in “as <column_name>”

The transform rules that you define will be executed in the SDL-FDL workload when you define the TRANSFORM_RECORDS_PROCESSOR in the Ingest Model