W3C home > Mailing lists > Public > public-credentials@w3.org > April 2021

Re: The ezcap-express library

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Sun, 4 Apr 2021 15:09:21 -0400
To: public-credentials@w3.org
Message-ID: <1416cbe1-864f-667e-9ed3-584c4a3a9319@digitalbazaar.com>
On 4/4/21 2:26 PM, Alan Karp wrote:
> Sounds like a good way to get people to understand the basics, but you 
> might have simplified too much.  Attenuated delegation is key to
> capability systems, but I didn't see that in your write-up.  Maybe you can
> add some examples in your Github repository.

Those exist here:


The docs go into far more detail than is useful for an introductory email to a
mailing list. For folks that know about delegation, attentuation, and caveats;
the link above should prove useful.

> The one thing you know is that any invoker of a resource must understand 
> the API.  In Zebra Copy we took advantage of that fact by representing
> each method of the API being authorized as a string included in the 
> authorization certificate.

ezcap does this by mapping URLs to root capabilities and then delegating from

> I don't think that would be much harder for developers to understand.  In
> the case of RESTful services, you could allow all 4 CRUD methods instead of
> just Read and Update.

The proposal wasn't "Read and Update", it was "read and write", where write
includes CREATE, UPDATE, and DELETE. We may have erred on something too
simple, but also note that it is trivial to add methods to the library... and
again, the library is intended to be an easy way to enter the ecosystem -- not
a complete solution for advanced use cases.

We had considered all CRUD operations, but then found it not to be a common
use case where one can UPDATE but not CREATE... or DELETE but not CREATE.
Those ended up being corner cases, as they do in most database systems.

The other challenge was that you don't really CRUD in REST, but rather GET,
POST, PUT, DELETE, and PATCH... which are, again, confusing to most when
designing a system. Easier to look at being able to read/write resources.

In other words, the library is opinionated; we expect other people to have
different opinions, which is fine... opinionated libraries tend to employ
certain philosophies, which doesn't mean that other philosophies aren't as
useful or powerful.

-- manu

Manu Sporny - https://www.linkedin.com/in/manusporny/
Founder/CEO - Digital Bazaar, Inc.
blog: Veres One Decentralized Identifier Blockchain Launches
Received on Sunday, 4 April 2021 19:09:37 UTC

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