This document describes a study of the lexicons used in the REST APIs of three cloud computing providers: Google Cloud Platform (GCP), OpenStack, and the Open Cloud Computing Interface (OCCI). The study found strong diversity between providers in terms of the number of services and URIs offered. Each provider's lexicon was unique, with no terms common across all three APIs and only 17 terms shared between two APIs. The study aims to provide the first analysis of lexical heterogeneity across cloud computing REST APIs and identify opportunities to improve semantic interoperability.

1. Towards a
REST Cloud Computing Lexicon
Fabio Petrillo1,3, Philippe Merle2, Naouel Moha1, Yann-Gaël Guéhéneuc3
1 Université du Québec à Montréal, Montréal, Canada
2 Inria Lille - Nord Europe, Villeneuve d’Ascq, France
3 École Polytechnique de Montréal, Montréal, Canada
7th International Conference on Cloud Computing and Services Science (CLOSER 2017)
April 24-26, 2017 – Porto, Portugal
1

2. Context
2
• Cloud computing = most popular model to provide on-
demand computational resources and services
• REST APIs for offering such computational resources
Web Services

3. • Wide variety of Cloud APIs à heterogeneity à no interop.
• Cloud APIs are difficult to design and therefore to
understand and use
Problem
• Well-named REST APIs may
attract client developers
• Quality factors: understandability
and reusability 4

4. • Right choice of the lexicon of cloud computing APIs
• BUT best naming practices scattered in the litterature
• BUT no study on real-world cloud computing APIs
4
Solution

5. Outline
5
• Contributions
• Study design
• Results and analysis
• Conclusion and Future work

6. Outline
6
• Contributions
• Study design
• Results and analysis
• Conclusion and Future work

7. 7
Contributions
Goal: Empirical study of the lexicon of Cloud REST APIs
C1. A tooled approach for extracting and analysing REST cloud
computing lexicons
C2. A dataset of services, resources, and terms used in three
studied REST APIs
C3. An analysis of the dataset

8. Outline
8
• Contributions
• Study design
• Results and analysis
• Conclusion and Future work

9. 9
Study
Objects:
RQ1. Which lexicon is adopted by cloud computing providers?
RQ2. Are there common terms between providers’ lexicons?
RQ3. What is the global lexicon of all cloud providers?
Commercial Open source Standard

10. Conceptual Model for Cloud Computing REST APIs
- Google Cloud Platform, OpenStack, OCCI, …
10
- GCP products: compute, sql, ...
- OS API: orchestration-api, os-compute-2, …
- OCCI Extensions: Infrastructure, Platform, …
- /{project}/zones/{zone_id}/ instances/{instance_id} in GCP compute
- /{tenant_ id}/servers/{server_id} in os-compute-2
- /compute/{compute_id} in OCCI Infrastructure
- generic CRUD operations: DELETE, GET, POST, PUT, …
- resource-specific actions: start, stop, attach, …

11. Our Tooled Approach
11
Step 1 – Collecting
documentation
Step 2 – Parsing
documentation
Step 3 – Extracting
lexicon
Step 4 – Analysing
lexicon

12. Implementation
• Datasets encoded as CSV files to foster reusability
• Parsers, extractors and analyses implemented in Python
to foster readability, comprehension and auditability
• Freely available on https://github.com/Spirals-Team/CloudLexicon
12

13. Outline
13
• Contributions
• Study design
• Results and analysis
• Conclusion and Future work

14. 14
Providers, Services and URIs
Cloud
Provider
# of
services
% of
services
# of
URIs
% of
URIs
Average
URIs/service
GCP 22 15,49% 505 38,94% 23
OpenStack 115 80,99% 588 45,34% 5
OCCI 5 3,52% 204 15,53% 41
Total 142 1.297 9
Finding 1 – Strong diversity between cloud providers
• GCP - medium services
• OpenStack - a lot of very small services
• OCCI - few large services

15. 15
RQ1. Which lexicon is adopted by cloud providers?
Finding 2 – The lexicon contains a majority of nouns, which are
equally singular or plural, and are mainly in lower case, following
REST API best naming practices.
Cloud
Provider
Lexicon
Terms
GCP 185
OpenStack 137
OCCI 47

16. 16
RQ2. Are there common terms between providers’ lexicons?
Finding 3 – The three cloud computing REST APIs do not share a
common lexicon and very few terms are common between two
APIs.
• No common term
in the three APIs!
• Only 17 terms (5%)
common to two APIs!

17. 17
RQ3. What is the global lexicon of all cloud providers?
Finding 4 – There is no consensus currently on which terms to use
on cloud computing systems.
352
different
terms

18. Outline
18
• Contributions
• Study design
• Results and analysis
• Conclusion and Future work

19. 19
Conclusion
• First study evaluating and comparing the lexicon of three
REST APIs
- Strong diversity between cloud providers
- Cloud REST APIs follow best naming practices
- No common term in the three APIs!
- Only 17 terms common to two API!
- No consensus on used terms!
• First measure of the lexical heterogeneity in cloud
computing

20. 20
Future Work
• Extend this study to more cloud APIs
Amazon Web Services, Apache CloudStack, DMTF CIMI, OASIS TOSCA, etc.
• Study in deep the semantics of lexicons, e.g., synonyms
• Build an ontology of cloud computing APIs in order to
deal with semantic interoperability between clouds
.

21. Towards a
REST Cloud Computing Lexicon
Fabio Petrillo1,3, Philippe Merle2, Naouel Moha1, Yann-Gaël Guéhéneuc3
1 Université du Québec à Montréal, Montréal, Canada
2 Inria Lille - Nord Europe, Villeneuve d’Ascq, France
3 École Polytechnique de Montréal, Montréal, Canada
7th International Conference on Cloud Computing and Services Science (CLOSER 2017)
April 24-26, 2017 – Porto, Portugal
21

22. 22
Excerpt of the Cloud Dataset

23. HTTP Methods
23
à Retrieve
à Update
à Delete
à Create