A few FAQs on LEGEND

[Ajith-K Dharwar]

Hi Pierre & James,

Greetings. First of all I wanted to provide the group a quick update on LEGEND & showcase within Deutsche Bank. I have had several round of demos using the public instance of LEGEND and it has been received with interest. However like others we are also awaiting the DOCKER images to setup & kick-off in-house trials.

 

The following are some FAQs I haven’t been able to answer authoritatively back to the Modelling, Engineering & Governance teams. Hence I look forward to your responses

 

FAQs

1.       Can I create common classes in shared models that can be utilised by many other models? In other words can I setup remote dependencies to other projects/repos and branches?

2.       Can an instance of LEGEND work with multiple GitLab Repos?

3.       Are Tests written in PURE & Model-to-Model mapping scalable for validating payloads of different characteristics (batch snapshots, stream). If YES can you please share any code examples how a MAP Reduce or SPARK job can validate the payload by calling the appropriate services?

4.       Does LEGEND support ability to interact with enumerations curated outside the model & tool? Example: A set of valid PAYMENT PURPOSE CODES from a local/regional regulator provided as a service with an endpoint?

 

 

Kind regards
____________________________________________________

Ajith Dharwar

Deutsche Bank AG, Filiale London
Chief Data Office
10 Upper Bank Street, 9^th floor, Canary Wharf, E14 5GW London, United Kingdom
Tel. +44 207 5417523
Mobile +44 7800826872
Email ajith-k...@db.com

 

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[Nelke, Beeke-Marie [Engineering]]

Hi Ajith,

 

Apologies for the late reply! Please see answers below. We also created GitHub issues for these (and various other questions) and I replied there as well so that it’s easier for everyone to find questions asked and follow the discussion. Feel free to come back to us via email or directly on the issues in GitHub.

 

>> As a general note to the Legend community – we created an initial inventory of FAQs in our Legend GitHub repo. Please feel free to post questions there (using the label “question”) and we encourage everyone to engage in these discussions. Looking forward to seeing more questions coming in! <<

 

Answers to your questions (some are slightly re-worded):

1.      Can I create common classes in shared projects that can be utilized by many other models? In other words can I setup remote dependencies to other projects/repos and branches? (Issue Link)

a.      We do support this feature internally but didn’t push it externally yet. In order for this to work we need to finish the SDLC build pipeline which is currently scheduled for end Q1. We will notify everyone when this feature is supported externally.

2.      Can an instance of LEGEND work with multiple GitLab Repos? (Issue Link)

a.      A Studio project can depend on other Studio projects hosted on the same Gitlab server. However, this feature has not been open sourced as yet. We expect this to be open sourced in 2021 Q2.

3.      Is it possible to test a Model-to-Model service in a dataflow e.g. batch snapshots, stream? (Issue Link)

a.      Model-to-Model services are specified and tested as a unit, they may be used as a node in a dataflow pipeline but the scope of their test is to validate the composed function in terms of input and output.

4.      Does LEGEND allow users to build models which refer to (model) elements outside of the Legend tooling, for example, could a payment model be enriched with a set of payment purpose codes from a service endpoint? (Issue Link)

a.      In the simple case, a model to model mapping can be configured with a HTTP url that serves JSON. The JSON served by the url is used as the source data to drive the model to model mapping. But there are limits to this approach. For e.g HTTP endpoint authentication, pagination etc. Another approach is to use fetch the data outside of Legend and use it to drive the model to model mapping. Expressed in pseudo code, this looks like :

 

String json =  readFromHTTP(…)

MyLegendService service = new MyLegendService()

service.execute(json)

 

The ability to execute model to model mappings and generate code is not available in the latest version of open source Legend. These features will be open sourced soon.

 

Please feel free to reach out with any other questions you may have or if further clarifications are needed!

 

Thanks,

Beeke

 

__________________________________________________

Beeke-Marie Nelke

Tel: (212) 357-5755| E-mail: Beeke-Ma...@ny.email.gs.com

_____________________________________________________________

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