1.
Adding Rules on
Existing Hypermedia
APIs
Michael Petychakis, Fenareti Lampathaki, Dimitrios
Askounis
National Technical University of Athens
WS-REST, 18th May 2015, Florence Italy

2.
Who I am
Michael Petychakis
Researcher in DSS lab, National Technical University of
Athens (NTUA)
PhD Candidate in NTUA
Electrical and Computer Engineer, Dipl.-M.Eng., NTUA
Research Interests
APIs/Linked Data/Web 3.0
@mpetyx

3.
Web, APIs, IoT and .. Hypermedia

4.
REST (as was supposed to be)
Level 3:
Hypermedia
Level 2: HTTP
Verbs
Level 1: Resources
Level 0: POX

5.
REST (today)
Level 3:
Hypermedia
Level 2: HTTP
Verbs
Level 1: Resources
Level 0: POX

6.
Hypermedia as FSM
"hydra:member" : [
{
"@type": "schema:Basket",
"schema:contains": [
{
"@id": "/books/1",
"@type": "schema:Book",
"schema:author": "James Joyce",
"schema:title": "Ulysses"
},

7.
Rules are Good for FSM
If This
then That
If
Basket_Contains( ?Book )
loggen_in_validated_user( ?Michael )
paypal_account_integrated( ?Michael )
Then
Checkout( ?Michael, ?Book )

8.
Rules on the Web
dc:description
Rules
SWRL
Ruleml
RIF
Rule
Inference
Producing valid statements
within rule based system

9.
Rules are there for a Loong Time
Not Web Web

10.
Blending Rules and APIs
Hydra/JSON_LD
SWRL
DeepGraphs

11.
DeepGraphs Approach
Goal: Modelling Hypermedia Responses
1 Vocabulary
 Hydra Documents
 SWRL Rules
 JSON-LD Responses
1 Vocabulary

12.
Vocabulary
• Affordances
• Duration(maxAllowedDuration)
• According to latest updates on Http 1.1
• Parallel Processes
• Synchronizing multiple FSM Clients
• Constraints
• The Actual Rules
Schema:activity Hydra:Resource dg:affordances

13.
Similar Approaches/ Media Types
DeepGraphs
Mason
Uber
JSON-LD
JSON API
Siren
HAL
Collection
JSON
JSON
Schema
JSON
Hyper
Schema
XML
Schema

14.
Example: Bookstore
"dg:affordances": [
{
"@type": ["schema:Action","hydra:Operation"],
"@id": "/RemoveBook",
"hydra:method": "DELETE",
"hydra:expects": "schema:Book",
"hydra:title": "Deletes a Book resource.",
"hydra:returns": "owl:Nothing",
"rdfs:label": "Deletes the Book resource."
},

15.
Example in Diagrams

16.
Complexity grows Exponentially
Clients
Bookstore
Paypal
Sms
Agent
Email
Facebook
Twitter
Servers
Bookstore
Paypal
Sms
-
Email
Facebook
Twitter

17.
Complexity grows Exponentially
Clients
Bookstore
Paypal
Sms
Agent
Email
Facebook
Twitter
Servers
Bookstore
Paypal
Sms
-
Email
Facebook
Twitter
Can We Avoid Building one Client per Server and Vice
Versa?

18.
DeepGraphs Generic Server Implementations
• Developer Designs the FSM
• A designer’s console for:
 Designing the API Atlas
 Verification of API FSM
 Validation (Running Example Workflows)
 Adding Integrity Constraints
Defining the Business Logic through Rules

19.
API Designer
http://api-builder.tools.epu.ntua.gr/web/

20.
DeepGraphs Generic AI Clients
SW
Interoperabilty
Reasoning
REST
Multiple
Servers
Multiple
Transactions

21.
In APIs We Trust

22.
Tools Around Spec
● API Builder
● PyAPI
o from [Swagger, API Blueprints, Hydra, WADL, RAML] to
[Swagger, API Blueprints, Hydra, RAML]
● PyRIF
o from [RuleML, RIF, SWRL] to [RuleML, RIF, SWRL]
● DeepGraphs Parser ( Soon )
● DeepGraphs Reasoner ( Soon )
o Datalog Approach
o FSM resolver implemented now
o Fluent Editor has been used for Evaluation

23.
Dereferencable Rules on the Web
SWRL and Rif
Solution:
Declare 1 Rule within a Graph, and
Reference this. Status: Working, But..
dg:constraint
http://deepgraphs.org/repository/rule1

24.
Advances of the Methodology
• DeepGraphs is not only REST
XMPP
MQTT
CoAP, DDS, AMQP (and more!)
• DeepGraphs aims into reusing Existing APIs that
speak Swagger, RAML, etc
• DeepGraphs aims to facilitate:
• Distributed Reasoning over the web with Affordances

25.
Next Steps
1. First Release of the Specification on June
2. Create a public Community Group
3. DeepGraphs Tools
• Parser
• Client
• Reasoner
• Designer
4. More Events
5. Address Rule Dereferencability by open discussion

26.
Thank you
Michael Petychakis
<a
href="mailto:mpetyx@epu.ntua.gr?Subject=
Hello" target="_top">Drop me an e-mail</a>
@mpetyx
This work has been created in the context of the EU-funded
project OPENi (Open-Source, Web-Based, Framework for
Integrating Applications with Social Media Services and Personal
Cloudlets), Contract No: FP7-ICT-317883.