=Paper=
{{Paper
|id=Vol-1674/iStar16_pp37-42
|storemode=property
|title=iStarJSON: A Lightweight Data-Format for i* Models
|pdfUrl=https://ceur-ws.org/Vol-1674/iStar16_pp37-42.pdf
|volume=Vol-1674
|authors=Oscar Franco-Bedoya,David Ameller,Dolors Costal,Lidia López
|dblpUrl=https://dblp.org/rec/conf/istar/Franco-BedoyaAC16
}}
==iStarJSON: A Lightweight Data-Format for i* Models==
https://ceur-ws.org/Vol-1674/iStar16_pp37-42.pdf
iStarJSON: A Lightweight Data-Format for i* Models
Oscar Franco-Bedoya1,2,3 , David Ameller1 , Dolors Costal1 , and Lidia López1
1Group of Software and Service Engineering (GESSI)
Universitat Politècnica de Catalunya, Barcelona, Spain
2 Universidad de Caldas, Manizales, Colombia
3 Universidad Nacional de Colombia, Manizales
{ohernan,dameller,dolors,llopez}@essi.upc.edu
http://www.essi.upc.edu/˜gessi/
Abstract. JSON is one of the most widely used data-interchange format. There
is a large number of tools open for modelling with i*. However, none of them
provides supporting for JSON. In this paper we propose iStarJSON language,
a JSON-based proposal for interchanging i* models. We also, present an open
source software that transforms XML-based format models to JSON models that
expose a set of web services for mining iStarJSON models.
Keywords: iStarML, JSON, iStar, i-star, i* modelling, REST
1 Introduction
i* is a well-known framework for goal and agent-oriented modelling and reasoning [1].
Throughout the years, different research groups have proposed i* language variations
and several tools for the i* framework [2]. iStarML is an XML-based format for en-
abling interoperability among i* tools [3]. In order to keep i* up-to-date with new trends
in software development (e.g., apps, JavaScript, REST, NoSQL ), we proposed the basic
structure of iStarJSON, a JSON-based model interchange language for i* models. In the
last years, JSON has emerged as the new standard format for exchanging data in both
academy and industy. Additionally, there is a large numbers of tools openly available in
the web that provide transformations between different data representation formats and
JSON. However, most of these approaches only provide a single mapping in the data
structure through individual schemas. In addition, we have developed an open source
software set of RESTful services that exposes the functionality needed to transform iS-
tarML, a XML-based format, models to JSON models. Furthermore, this tool not only
allows mapping from XML to JSON but also change the hierarchy structure of iStarML
schema for a lightweight graph structure. This transformation does not affect the i*
syntax and semantics. However, it allows to use a variety of tools and algorithms for
graph manipulation (e.g., graph layouts, node centrality, shortest path). As a particular
use case we have developed a web service for i* model visualization using different
layouts. Using JSON to represent i* models as a graph enables the i* researchers and
practitioners communities to develop new tools based on graph theory and the simplic-
ity of the JSON-based programing. This tool has been carried out in the context of a
general framework for supporting the open source software ecosystems (OSSECOs)
modelling process.
Copyright © 2016 for this paper by its authors. Copying permitted for private and academic purposes.
Proceedings of the Ninth International i* Workshop (iStar 2016), CEUR Vol-1674
This paper presents JSON-based iStarJSON model interchange proposal is pre-
sented. The objectives of this proposal are: (1) to keep i* up-to-date with new trends in
software development and (2) to present an easy programming, flexible and lightweight
data format for i* models.
2 Background on iStarML and JSON
iStarML is a XML-based interchange format for i* diagrams. It includes six basic cat-
egories to represent the i* abstract concepts: actor, intentional element, dependency,
boundary, intentional element link and actor association [3], [4]. iStarML is also a pow-
erful vehicle that enables interoperability inside the i* community [5]. The iStarML
proposal has been widely discussed in several papers: [2], [6], [5] and [3].
JavaScript Object Notation (JSON) is a lightweight data-interchange format that is
less verbose and more readable than XML [7]. It has become predominant in the mobile
and browser domain in the last few years. JSON and XML are conceptually similar [8],
however XML leads to problems with large models in terms of scaling. On the other
hand, JSON data format supports high scalability [9].
3 iStarJSON Schema
A schema that serves as a means to understand the structure of a document is as relevant
for JSON as it is for XML. But there is little enthusiasm in the JSON community for
schema languages, especially complex schema languages [10] . However, in the last
three years a set of methodological proposals to promote the definition of a standard
JSON schema have emerged4 .
A JSON schema is a JSON-based grammar declaration used to describe the struc-
ture and content of a JSON document. this schema provides a contract specifying which
JSON data is required for a given application and how to interact with it. A JSON
schema is intended to define validation, documentation, hyperlink navigation, and in-
teraction control of JSON data.
In iStarJSON we represent a i* model as a directed graph G = (V, E) where nodes
V correspond to i* intentional elements and actors:
V = {actor, agent, role, position} ∪ {goal,task, resource, softgoal, belie f }
The set of edges E ⊆ E × E represents relationships connecting nodes. The type of re-
lationships that can exist between nodes is determined by the links defined by iStarML:
Atype ∈ {association, dependency, means end, decomposition, contribution}
In contrast to the other types of links, where one link involve two nodes, dependencies
are represented by three nodes (depender, dependee and dependum) and two links, one
from the depender to the dependum and other from the dependum to the dependee.
4 http://json-schema.org/
38
iStarJSON: A Lightweight Data-Format for i* Models
Fig. 1 show a partial view of the iStarJSON schema. 5
{
"$schema": "http://testoneosseco.azurewebsites.net/json/schemas/istar/schema#",
"properties": { "diagram": {"type": "string", "name": "diagram"},
"modelType": {"type": "string","enum": ["rationale","dependence"]
},
"nodes": {"items": {"properties": {"id": {"name": "id"}, name": {"name": "name"},
"elementType": {"enum": ["actor", "goal", "task", "resource", "softgoal",
"belief"],"name": "elementType"},"boundary": {"name": "boundary"}}}
},
"edges": {"items": {"properties": {"source":{"name": "source"},"target": { "name":
"target"}, "linkType": {"enum": ["association", "dependency",
"means_end", "decomposition", "contribution"]}}}}
}
}
Fig. 1: partial view of the iStarJSON schema
3.1 Representing i* Models in iStarJSON
In order to illustrate how the iStarJSON structure deals with i* representations, two ex-
amples are shown inf Fig. 2. The first example, illustrates a basic Strategic Dependency
diagram with 3 actors and 4 intentional elements. All of them are mapped into iStarJ-
SON array property nodes. The property boundary of each node has the default value
”none” indicating that the elements are in the general environment of the ecosystem.
The second example corresponds to an Strategic Rationale diagram, the iStarJSOn file
is similar to that of the first example, but in this case, the property boundary of each
node has as value the name of the actor where the node is inside.
Fig. 2: An example of software ecosystem modeling using i* (excerpted from [11])
3.2 The iStarJSON Tool
iStarJSON exposes two main services. The service textiStarJSONValidator, uses the
iStarJSON schema for the validation of the JSON document with the i* model, other
5 iStarJSON schema can be downloaded from: http://pastebin.com/Z6CTPgMF
39
Proceedings of the Ninth International i* Workshop (iStar 2016), CEUR Vol-1674
"nodes": [ "edges": [ "nodes": [ "edges": [
{ { { {
"boundary": "none", "linktype": "boundary": "none", "linktype":
"elemenType": "resource", "dependency", "elemenType": "dependency",
"name": "License & "source": "04", "softgoal", "source": "02",
Maintenance Fee", "target": "07", "name": "Variety", "target": "01",
"id": "07" "linksubtype": "" "id": "01" "linksubtype": ""
}, }, }, },
{ { { {
"boundary": "none", "linktype": "boundary": "none", "linktype":
"elemenType": "softgoal", "dependency", "elemenType": "dependency",
"name": "Variety", "source": "07", "actor", "source": "01",
"id": "01" "target": "06", "name": "Customer", "target": "09",
}, "linksubtype": "" "id": "02" "linksubtype": ""
{ }, }, },
"boundary": "none", { { {
"elemenType": "softgoal", "linktype": "boundary": "linktype":
"name": "User Satisfaction", "dependency", "Customer", "decomposition",
"id": "02" "source": "06", "elemenType": "source": "04",
}, "target": "01", "goal", "target": "03",
{ "linksubtype": "" "name": "Have "linksubtype": "or"
"boundary": "none", }, software", },
"elemenType": "resource", { "id": "03"
"name": "Market Chanels", "linktype": }, ]
"id": "03"
}, ] ]
]
The iStarJSON code for the i* strategic dependency diagram The iStarJSON code for the i* rationale dependency diagram
Fig. 3: Representing i* Models in iStarJSON
service, creates a valid iStarJSON document from a valid iStarML file. Additionally,
there are a set of specific services that provide functionality for the i* graph-model6 .
Fig. 4 shows the architecture of iStarJSON
Client Application iStarJSON Application
Client Applications ccistarml graphConstructor
iStarJSOnConverter
HTTP/REST
JSON REST JSON REST iStarJSON
Client Server Converter
HTTP/REST iStarJSON
iStarJSONValidator Validator
Fig. 4: Overview of the iStarJSON architecture.
We have implemented a simple program to transform a iStarJSON document to
DOT-code7 . This allows to draw directed graphs as hierarchies (see Fig. 5). iStarJSON
is composed by the following components:
– JSON REST server component: handles REST request from the client application
and calls internal services.
– ccistarml package: [6] allows creating, reading and modifying iStarML files.
– graph construct package: creates a dynamic graph structure from the iStarML file.
– iStarJSON converter package: transforms the dynamic graph structure into a valid
JSON file.
– iStarJSON validator package: validates the JSON input document using the iStar-
JSON schema.
6 availables in http://testoneosseco.azurewebsites.net/iStarJSONServiceREST/
istar/
7 DOT is a plain text graph description language. It is a simple way of describing graphs that
both humans and computer programs can use
40
iStarJSON: A Lightweight Data-Format for i* Models
iSarJSON is an open source software project and its source code is freely available
as a GitHub repository8 .
4 Proof of Concept: Graph Visualization
In this section we show a proof of concept of the iStarJSON tool. We have developed
a REST web service that creates a visual representation of i* models by transforming
iStarJSON files into a variety of output formats (e.g., PostScript, PDF, SVG, PNG, GIF)
and using different types of layouts (i.e., dot, neato, sfdp,fdp, twopi and circo). To do
that, we have created a DOT program from the iStarJSON document. For drawing the
models we have used GraphViz an open source graph visualization software with a
heterogeneous collection of graph drawing tools 9 .
Fig. 5 shows the DOT programs and the graphics representation of the iStarJSON
example 2.
Fig. 5: Representing i* Models in DOT
5 Conclusions and Future Work
In this paper we present iStarJSON a light-weight technical contribution supporting
i*models in JSON. Our proposal, allows to represent iStarML models into JSON, also
we have provided a set of RESTful services for transforming iStarJSON files into a
variety of output formats (e.g., PDF, SVG, PNG). The iStarJSON approach supports
interoperability and flexibility of i* models, similar to iStarML, but with the advantages
of JSON. Table 1 shows a comparison of XML and JSON.
Table 1: Comparison of XML & JSON
Criteria XML JSON
Undestandability Machine readable Machine & human readable
File size Min. number of lines for object=3 Min number of lines for object:1
Mapping Tree structure Graph structure
JavaScript Not subset subset of JS
8 https://github.com/UPC-gessi-oscar-franco/iStarJson
9 http://www.graphviz.org/
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Proceedings of the Ninth International i* Workshop (iStar 2016), CEUR Vol-1674
Next steps on iStarJSON include extending the functionality to support PLATEOSS
a framework for OSS ecosystems (OSSECOs) analysis. We plan to use i* for modelling
OSSECOs and iStarJSON graph representation for enabling the power of network anal-
ysis statistics and reasoning tools of visual analytics (e.g., identify main business goals
automatically, analyze quality of dependences between actors, calculate goals centrality
measures).
ACKNOWLEDGMENTS
This work is a result of the EOSSAC project, founded by the Ministry of Economy and
Competitiveness of the Spanish government (TIN2013-44641-P).
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