Building Tomorrow's Web Services
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This document discusses the evolution of web service APIs from REST in the 1990s to a potential future Activity Oriented Architecture (AOA). It argues that as more non-human users like intelligent agents start accessing APIs, the focus should shift from resources and hypermedia to activities that achieve user goals. The document proposes supporting auto-discovery of relevant activities, activity search, and activity templates to enable intelligent agents to perform useful tasks on behalf of users. Feedback on this vision for a future AOA is welcomed.
![Activity Properties
• [User]
• Verb
https://raw.github.com/activitystreams/activity-streams-verb-definition/master/activity-streams-verb-definition.txt
• Object
• Target
• May be a Few More for Advanced/Complex Activities...
• Location, Duration, Cost, Priority, Date, TimeSpan...
{user} {verb} {object} [{target}]](https://image.slidesharecdn.com/aoa-120916184108-phpapp02/85/Building-Tomorrow-s-Web-Services-8-320.jpg)
Building Tomorrow's Web Services
- 1. Building Tomorrow’s Web Services API Pat Cappelaere REST Fest 2012 The Day After... Sept 16, 2012
- 2. Web Service API Evolution • 1990 HTTP REST Richardson Maturity Level 0/1 • 2000 Service Oriented Architecture (SOAP, WS-*) • 2010 REST Oriented Architecture • Level Richardson Maturity Level 2/3 -> Caching and HyperMedia I Think That We Are Still Heading In Wrong Direction • Next: 2015-2020??? Richardson Maturity Level 4?
- 3. Why? •Users Do Not Care About Your Resource Model Stop CRUD •Users May Not Care About Your Link Relations Between Resources This is Your Own Plumbing It May Still Be Necessary But... •Tomorrow’s Users Of Your API Will Not Be Humans SO LONG REST AND HYPERMEDIA...??
- 4. Tomorrow’s User •Welcome SIRI Your APP there Your User Here
- 5. What’s Different With a User-Agent? • Has Low Bandwidth - Think 3G-4G - 1MB is a big/costly chunk • Acts on Behalf of User • Performs One or More Activities to Achieve a User Goal • Needs to be Able to Find Relevant Activities That Could Be Performed By Nearby Server(s)
- 6. How Does A User-Agent Work? • Goal (/Preferences) Directed • Sensing • Reactive / Effective • Can Be Programmed To Act “Intelligently” • See Constrained Behavior Trees (Game AI) With Blackboard ... Executing A Specific Activity For Current Context and User Goal Goal: Enabling User Agents By Publishing The Possible Activities They Could Perform
- 7. http://activitystrea.ms/specs/json/1.0/ What’s An Activity (Stream)? • Get/Post/Update/Delete A Document • or better... Execute/Halt/Resume/Delete a Local Process or Workflow • Examples: • Facebook Social Activity Stream aka News Feed • OGC • Process Image (WPS) • Task Satellite (SPS) • Get Observation (SOS), a Map (WMS), a Coverage (WCS), a Feature (WFS)... http://www.socialcast.com/activity-streams
- 8. Activity Properties • [User] • Verb https://raw.github.com/activitystreams/activity-streams-verb-definition/master/activity-streams-verb-definition.txt • Object • Target • May be a Few More for Advanced/Complex Activities... • Location, Duration, Cost, Priority, Date, TimeSpan... {user} {verb} {object} [{target}]
- 9. From Activities To Activity Streams • Once Actors Perform Many Activities, Activity Streams Can Be Generated • See: http://activitystrea.ms/specs/json/1.0/ • Our Problem is to Provide an Activity Template for Actors to Perform Activities (on Behalf of Users) • And Make them Discoverable (Activity Discovery Document???) • And Searchable by User Agents To Meet Current Needs (or Goals)
- 10. Activity Discovery Document? User Agents Could Access It and Mine it For Activity Opportunities... Then Follow Links For Particular Activity Template
- 11. So... • Support Auto-Discovery Of Relevant User-Agent Info • Link to Activity Description Document in End Point Page Header <link rel=‘activities’ href=‘http://www.example.com/activities’/> • Link to Activity Search Document in End Point Page Header <link rel="search" href="http://example.com/opensearchdescription.xml" type="application/opensearchdescription+xml" title="Activity Search" /> • Support Activity Search (Described in Url Template of OpenSearch Document) By Generic Search Terms or Specific Object/Verb Search template="http://example.com/?q={searchTerms}& objects={objectTerms}&verbs={verbs?}"/>
- 12. Activity Template?? { "activities": { Could Easily Be Added To API Discovery Document... "process data": { https://developers.google.com/discovery/ "verb": "process", "object": { "objectType": "http://example.com/terms#data", "displayName": "data" }, "target": { "objectType": "http://example.com/terms# floodmap", "displayName": "floodmap" }, "method": { "httpMethod": "POST", "path": "/activities/1", "mediaType": "application/json", "description": "", "parameters": {...}, "response": {...}, "scopes": {...} }, ... },... } }
- 13. So Where Are We Going? • 1990 HTTP REST Richardson Maturity Level 0/1 • 2000 Service Oriented Architecture (SOA) • SOAP, WS-* • 2010 REST Oriented Architecture (ROA) • Level Richardson Maturity Level 2/3 -> Caching and HyperMedia • Activity Oriented Architecture (AOA ?) • Level 4?
- 14. Rationale • Once We Have An Activity-Oriented Architecture, We Ought To Be Able to Link Data and Actions • See Stu Charlton’s REST FEST Presentation • https://github.com/RESTFest/2012-greenville/blob/master/ presentation/linking%20data%20actions.pdf
- 15. Minor Problems • Expressing Domain Specific Object/Verbs Semantics • Users do not like to express semantics • Example: • User wants to get a floodmap of Haiti (Activity) • But what’s a floodmap? • Note: There is also a huge difference between a MODIS floodmap at 250m resolution and Radarsat-2 floodmap at 4m resolution... Does it matter? There is/could be some big differences as well (data size, generation time and $$)... Hummmm! • Need Activity Aggregator ASAP ?? • PubsubHubbub?
- 16. Feedback? • pat@cappelaere.com Major Thanks To: REST FEST 2012 https://github.com/RESTFest/2012-greenville/wiki/People Activity Streams Group https://groups.google.com/forum/?fromgroups#!forum/activity-streams API-Craft Group https://groups.google.com/forum/?fromgroups#!forum/api-craft OGC REST Standards Working Group NASA SensorWeb Group