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simple software solutions to big business problems
Making Software. Better.
Digital By DefaultBuilding APIs for the Government
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I believe the creation of the Government Digital Service is one of the great unsung triumphs of the last Parliament.
Prime Minister David Cameron
A barrier to innovation
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SOAP-based proprietary webservices, which software vendors currently integrate with, are
cumbersome, poorly documented and a disservice to us, the taxpayer
Brave New World
By creating a new API platform built upon user needs, based on RESTFul principles, we have reduced the barrier to entry and innovation.
10 Years of AWS - APIs are forever
“.......Once customers started building their applications and systems using our APIs, changing those APIs becomes impossible, as we would be impacting our customer’s business operations if we would do so. We knew that designing APIs was a very important task as we’d only have one chance to get it right.”http://www.allthingsdistributed.com/2016/03/10-lessons-from-10-years-of-aws.html
5 Golden RulesOf Building APIs at HMRC Digital
Golden Rule 1
Make it Work
Secure, performant and easy
An API platform is not fit for purpose unless it is secure, handles appropriate throughput accurately, is easy to integrate with and is easy to publish and
document
Protect your platform
Throttling is an important part of any API platform but shouldn’t be seen as a backup option for a
poorly performing API, but as protection against poorly written/abusive 3rd party software.
Plan for change
Define a versioning strategy early, one that fits your architecture, organisation and clients. Make
backward compatibility a key goal.
Golden Rule 2
If you can’t make it good, at least make it look good - Bill Gates
Make it Beautiful
Importance of beautiful APIs
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APIs are the public face of your IT. They are part of your brand, reputation and an insight into
your quality. You wouldn’t deliver an ugly website.
Golden Rule 3
Focus your APIs on your domain, not your offline processes
Change your perspective
Why not business processes?
Business processes were not created for the digital world. They were created for cryptic commands into mainframe terminals, paper forms and human (intelligent) intervention.
Reflect these digitally and you limit APIs
Domain not processes
Create APIs that reflect your domain, using Domain Driven Design concepts. You will not limit yourselves to existing processes, you’ll
hide the implementation and you’ll use industry language. In so doing, complexity is removed.
How have we changed our focus?
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HMRC is traditionally siloed along the lines of tax regimes. Code, systems, people, databases. Tax regimes are the processes, not the domain.
The digital world reflected the offline. We’ve changed our focus. Our APIs will be domain
centric and not regime centric.
Golden Rule 4
REST only has one level; Anything else is not REST
Use Hypermedia
Richardsons Maturity Model
Courtesy of www.martinfowler.com
Why we should stop talking about it
Richardson’s Maturity Model has become a justification to not use Hypermedia. It is not meant to be a model for levels of valid REST
development. Just an observation of an organisation’s proximity to REST
No Hypermedia, No REST
“If the engine of application state (and hence the API) is not being driven by hypertext, then
it cannot be RESTful and cannot be a REST API. Period.” - Roy Fielding
What is Hypermedia (HATEOAS){
self: {url: “http://api.reda.com/users/reda”
},data: {
name: “Reda Hmeid”,age: “23”,height: “6ft 2in”,address_url: “http://api.reda.com/users/reda/addresses”,messages_url: “http://api.reda.com/users/reda/messages”
},links:[
{url: “http://api.reda.com/users/reda/messages”,rel: “Send a new message”,method: “Post”
},{
url: “http://api.reda.com/users/reda”,rel: “Update details”,method: “Put”
}]
}
What does Hypermedia provide
By controlling flow and business logic within the API, thereby hiding implementation, you
ensure loose coupling between the client and the API. This allows for more frequent
impactless changes and added functionality.
But also
Hypermedia reduces latency and reduces load on the server. Clients can be much dumber,
needing less business code, making it cheaper to produce software.
Golden Rule 5
Your organisation is mature enough to build RESTFul APIs today
You’re Ready
You can maintain the status quo
Or you can make things better. Maturity of an organisation is where it is now. Not where it can be
and what it can do.
Examples of the GoodProof that beautiful APIs are “pragmatic” APIs
● Github.comhttps://developer.github.com/v3/pulls/
● Stormpath.comhttps://docs.stormpath.com/rest/product-guide/latest/reference.html#application
● Paypal.comhttps://developer.paypal.com/docs/rest/api/
● Visahttps://developer.visa.com
Examples
ReferencesWant to learn more; try these
1. Rest in Practice - Jim Webber2. Domain Driven Design - Eric Evans3. RESTFul Web Services Cookbook - Subbu Allamajru4. http://martinfowler.com/articles/richardsonMaturityModel.html
Thank You
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