Brüggemann-Klein, Anne, Tamer Demirel, Dennis Pagano and Andreas Tai. “Reverse Modeling for Domain-Driven Engineering of Publishing Technology.” Presented at Balisage: The Markup Conference 2010, Montréal, Canada, August 3 - 6, 2010. In Proceedings of Balisage: The Markup Conference 2010. Balisage Series on Markup Technologies, vol. 5 (2010). https://doi.org/10.4242/BalisageVol5.Bruggemann-Klein01.
Balisage: The Markup Conference 2010 August 3 - 6, 2010
Balisage Paper: Reverse Modeling for Domain-Driven Engineering of Publishing Technology
Anne Brüggemann-Klein
Fakultät für Informatik, Technische Universität München
Tamer Demirel
Fakultät für Informatik, Technische Universität Münchenn
Dennis Pagano
Fakultät für Informatik, Technische Universität München
Andreas Tai
Fakultät für Informatik, Technische Universität München
We report in this paper on a technique that we call reverse modeling. Reverse
modeling starts with a conceptual model that is formulated in one or more generic
modeling technologies such as UML or XML Schema. It abstracts from that model a custom,
domain-specific meta-model and re-formulates the original model as an instance of
the
new meta-model. We demonstrate the value of reverse modeling with two case studies:
One
domain-specific meta-model facilitates design and user interface of a so-called instance
generator for broadcasting productions metadata. Another one structures the translation
of XML-encoded printer data for invoices into semantic XML. In a further section of
this
paper, we take a more general view and survey patterns that have evolved in the
conceptual modeling of documents and data and that implicitly suggest sound
meta-modeling constructs.
Taken together, the two case studies and the survey of patterns in conceptual models
bring us one step closer to our superior goal of developing a meta-meta-modeling
facility whose instances are custom meta-models for conceptual document and data models.
The research that is presented in this paper brings forward a core set of elementary
constructors that a meta-meta-modeling facility should provide.
Modeling is a pivotal activity in the engineering of software systems; it is the key
method to deal with complexity, adaptivity requirements and change. Models support
communication and drive software development processes.
In the Engineering Publishing Technology Group, we aim to leverage modeling and other
proven methods of software engineering for document engineering and electronic publishing.
One focus has been on the modeling of persistent data [BST07,ES08,PB09]. In a 2009 Balisage paper [PB09], we have discussed the relationships between conceptual
data models and their implementations in an XML schema language; furthermore, we have,
following current thinking in the field, posed three requirements for the modeling
of
persistent data:
Modeling of persistent data must be integrated into system modeling.
Modeling of persistent data must be independent of data implementation
technology.
Modeling of persistent data should be amenable to forward engineering.
Our previous work and the three requirements cited above have been inspired by a
long-standing vision of software engineering, namely to drive the development process
by
models that are systematically transformed into lower-level models and software artifacts,
that has found its expression in the approach of model-driven
architecture [MSUW04]. Recently, the role of
modeling in software engineering has been even further emphasized: The emerging software
engineering discipline of domain-driven design [E04] puts
domain models at the heart of software development, letting them delineate so-called
ubiquiteous languages that are used by domain experts and software engineers alike
and that
are embodied both in the code and in the user interface of systems. Hence, we should
like
to replace the last requirement in the list above by the following item:
Models of persistent data should be amenable to being embodied in every aspect of
the system.
Over the last two years, in two projects we have deviated from the much-travelled
road
of modeling to support forward engineering. In fact, in both projects, we apply a
technique
that we call reverse modeling. Starting with a pre-existing conceptual model that
is
formulated in one or more generic modeling technologies such as UML or XML Schema,
we
abstract from that model a custom, domain-specific meta-model and re-formulate the
original
model as an instance of the new meta-model. In both cases, the new domain-specific
meta-model explicitly captures salient points of the model that come to bear on system
and
interface design. We are convinced that in both cases reverse modeling leads to a
better
understanding of the domain and to a more flexible system that is resilient against
future
changes in the model.
This paper is organized into four further main sections. In the next section, we present
our main case study. More precisely, we apply reverse modeling to broadcasting productions
meta data and demonstrate, how the domain-specific meta-model that we develop reduces
complexity when building a so-called instance generator for broadcasting productions
meta
data. In the section after that, we reflect on reverse modeling, arguing for
domain-specific meta-models. The next section applies reverse modeling in the context
of
translating XML-encoded printer data of invoices into semantically meaningful XML.
In this
case study, the meta-model that we develop structures the procedural method of the
translator. In a further section of this paper, we take a more general view and survey
patterns that have evolved in the conceptual modeling of documents and data and that
implicitly suggest sound meta-modeling constructs. Taken together, the two case studies
and
the survey of patterns in conceptual models bring us one step closer to our superior
goal
to develop a meta-meta-modeling facility whose instances are custom meta-models for
domain
document and data models. They bring forward a core set of elementary constructors
that a
meta-meta-modeling facility should provide.
An instance generator for broadcasting productions metadata
In his Master's Thesis [T09] project, Andreas Tai deals
with several incarnations of a huge data model for broadcasting productions metadata,
the
Broadcast Metadata Exchange Format (BMF). The model incarnations are formulated in
a number
of meta-model technologies, among others UML, XML Schema and a domain-specific registry
format; these incarnations are aligned with each other but are not equivalent, and
the
relationship between them is not documented in detail. Project goal is a so-called
BMF
instance generator; that is, editing support for XML instances of metadata that illustrate
sections of the model by example. Intended users are domain experts who explore sections
of
the model by generating XML instances when devising mappings from other metadata models
into BMF. The initial users are XML experts; yet it is considered a valuable asset
if later
users need to be conversant neither in XML nor in XML Schema. Use of typical schema-driven
XML editors has been tried out, but has not been found particularly helpful; hence,
it is
ruled out. The BMF instance generator must be resilient against changes in the model.
A
domain-specific meta-model that is constructed by what we call reverse modeling is
pivotal
to the solution, as explained below.
Broadcasting productions metadata and their use cases
The Broadcast Metadata Exchange Format (BMF) is a data model that has been developed
over nearly a decade by the Institut für Rundfunktechnik (IRT, Institute for
Broadcasting Technology). A universal format, BMF enables the platform independent
exchange of metadata in IT-based TV production, serving as a lingua franca that
intermediates between different metadata formats in the domain of TV production.
Briefly, BMF consists of types of different metadata sets such as Programme that group metadata elements such as MainTitle or Award. Metadata
elements associate with simple data types or with other metadata sets. Figure 1 demonstrates that metadata element MainTitle is associated with simple type String and that metadata element Award
is associated with a metadata set that is also called Award.
BMF is formulated with different modeling technologies. It was first developed as
an
entity-relationship diagram which later has been replaced with a UML class diagram.
To
leverage data exchange by means of XML documents an XML Schema was dynamically generated
from the BMF UML class diagram. Furthermore the data model is currently being registered
at the Society of Motion Picture and Television Engineers (SMPTE), which requires
its
own format for data models [SMPTE03,SMPTE01,SMPTE08].
BMF meets its proclaimed goal of covering every use case of metadata exchange in the
domain of TV production at the price of being large and complex. Yet there are related
use cases that BMF on its own does not support well, due to its complexity. In this
paper, we are concerned with the specific such use case of generating sample XML-encoded
metadata that conform to BMF, e.g. for the purposes of documentation or of
designing mappings between BMF and other metadata formats. Each of the sample documents
provides a keyhole view into a small part of BMF. What is needed tool-wise for
generating such sample documents is a facility to deeply zoom into parts of BMF, to
select a few illustrative building blocks and to instantiate them, the focus being
on
structures that may be filled with ad-hoc or dummy content.
In the experience of the BMF modeling team at IRT, generic schema-aware XML editors
are inadequate tools for the specific task of generating sample metadata. This seems
to
be due to the discrepancy in the sizes of the large BMF model and the relatively tiny
focus that is relevant for the sample, making it quite time-consuming to generate
sample
documents even for XML experts who otherwise routinely use schema-aware editors.
Hence, the group decided to look into specific editing support for BMF sample
instances, initiating the project “BMF instance generator”, which
became the topic of Andreas Tai's Master's Thesis T09 at
TU München.
There are two main requirements for the instance generator: First, it must be
resilient against changes in the BMF model. More precisely, it must be able to adapt
itself to any new version of the BMF XML Schema. Second, it must cut down time and
effort to generate sample metadata that conform to the BMF model.
In the remainder of this section, we report on design and implementation of the BMF
instance generator before drawing conclusions.
The quest for the domain model
The leitmotiv question that needs to be addressed in the project is: What makes the
generation of BMF instances so difficult? Apparently, problems that arise from the
inherent complexity and sheer size of the BMF model are aggravated by the choice of
technologies that is used to formulate the model, namely UML and XML Schema. These
technologies bring a complexity to the model that is more due to the intrinsic logic
of
these technologies than to the underlying domain model that they express. They obscure
the domain model of BMF. Furthermore, the different technologies that are in use to
represent model information lead to inconsistent conclusions about the BMF domain
model
itself. One point of inconsistency is the order of metadata elements in metadata sets:
In the UML class diagram, metadata elements are designed as class attributes which
in
UML are unordered; in the XML Schema metadata elements are attached to metadata sets
within sequence content models that impose order on them.
From this analysis, there arises naturally the question what the real domain model
of
BMF is. In order to get the domain aspect of the model back into focus, we need to
strip
BMF from the specifics of the modeling technologies that it is formulated in and to
arrive at a more direct formulation of the model than the BMF UML class diagram and
BMF
XML Schema provide. In a process that we call reverse modeling, we first identify
the
building principles that constitute BMF. These building principles must meet the
following requirements:
They apply to every incarnation of BMF.
They represent the concept that the modeling team of BMF has of the
model.
They are expressed as directly as possible, and certainly independently of
implementation technology.
Naturally, there is no magic wand for reverse modeling. We just have to apply sound
software engineering practices. First, we carefully analyze the existing incarnations
of
BMF, namely the BMF UML class diagram and the BMF XML Schema as well as the registration
data for BMF at SMPTE. Second, we conduct extensive interviews with the modeling team
of
BMF on the conceptual ideas behind the model. The result is a small set of rules the
most important of which we describe in natural language:
BMF consists of types of metadata sets that group metadata elements.
The types of metadata sets are partitioned into packages.
Metadata elements are unordered
Metadata elements reference either simple data types or metadata sets.
The existance of a metadata set that is referenced from a metadata element can
be of one of two types: dependent on or independent of the existence of the
referer.
We view the building principles as a model for the domain model and hence as a
domain-specific meta-model. With such a domain-specific meta-model, we restrict the
terminology of the model to the domain. Instead of generic terms such as classes,
attributes or complex type definitions we only use terms of the meta-model such as
metadata set and metadata element.
The meta-model reduces complexity in two ways: First, it facilitates a direct
expression of the model that is independent of implementation technology. Second,
it
explicitly defines and limits the building principles that are used in BMF, thus
imposing structure on the domain model and, hence, raising understanding to an
accidental to a more principled level.
Leveraging the domain-specific meta-model for the instance generator
Our quest for the BMF domain model has led us to discover a domain-specific
meta-model of which the BMF domain model is an instance. We demonstrate in this section
how we can leverage the meta-model for the instance generator, reducing complexity
and
making the instance generator resilient against changes in the BMF model.
We structure the instance generator into the following three components:
Model advisor: a component that provides all
model-related information.
Shopping mall: a component that lets users select
model elements for later use.
Building site: a component that enables users to
build instances of the BMF model.
To illustrate the role of the domain-specific meta-model we look a bit closer at the
implementation details of the three components.
The model advisor is the key component of the instance generator. The component
provides an interface to answer all questions that might be directed at the BMF domain
model, for example:
Which metadata sets are available?
Which metadata elements are required for a metadata sets?
Does a metadata element reference a simple type value or another metadata set?
By the project requirements, the instance generator and, hence, the model advisor
must refer to the BMF XML Schema for model information. Hence, two questions arise:
First, the access question, how do we query XML Schema? Second, the interface question,
how do we relate the BMF domain model to the BMF XML Schema?
As to the access question, one would expect to be able to use XML technology for
that. Indeed, the work of Wilde and Michel on SCX, an alternative XML representation
of
XML Schema [WM07c], and SPATH, an XSLT
library to query XML schema components [WM07a,WM07b], looks promising. Unfortunately, there is no
full implementation yet, and development seems to have been discontinued. Therefore,
we
resort to a programming-language interface to XML Schema, namely the Java framework
Eclipse XSD. Eclipse XSD is part of the Eclipse Modeling Framework (EMF) and closely
mirrors the abstract data model of XML Schema.
As to the interface question, technically, the model advisor exposes a query
interface of Java methods for dynamic access of the BMF XML Schema. The model advisor's
class model defines the interface in terms of the
domain meta-model, with query methods refering to domain concepts such as metadata
sets
and metadata elements, not to XML Schema concepts such as type definitions and content
models; see Figure 2. The implementation is based
on Eclipse XSD.
Hence, the query interface encapsulates the mapping between the BMF domain model and
its XML Schema incarnation, and the model advisor's system of classes acts as an
adaption layer that takes care of changes in the BMF XML Schema. Thus, the model advisor
is resilient against changes in the BMF XML Schema as long as new versions of the
schema
still conform to the domain meta-model.
To illustrate this with examples, the system will adapt if new types of metadata sets
are defined or the selection of metadata elements within a type of metadata set is
modified, because such a change in the domain model only requires Eclipse XSD to refer
to a different schema at startup time or even at run time. The system will, however,
not
be able to adapt if a new kind of metadata element container is introduced that requires
metadata elements to be ordered, because such a change in the domain meta-model demands
an extension of the query interface.
With its stacked architecture of access layer based on Eclipse XSD and adaption layer
implementing a domain-specific query interface, the model advisor dynamically exposes
the BMF domain model in its XML Schema
incarnation — robust in the face of changes in the
domain model that respect the boundaries of the domain meta-model.
The other two components of the instance generator, namely the shopping mall and the
building site, obtain the model information they need through the model advisor.
The shopping mall component of the instance generator offers a graphical user
interface to explore the BMF domain model and to select the metadata sets and metadata
elements of interest; see Figure 3 and Figure 4. The selected model elements are put in a shopping cart for
later use in the instance generation process. The shopping-mall interface is dynamically
created by querying the model advisor. Whereas the model advisor gives the programmer
access to the domain model, the shopping mall visualises the domain model for the
end
user.
Please note how the shopping mall interface integrates domain concepts into the
shopping-mall metaphor.
The shopping-mall interface has been adopted for uses beyond the task of instance
generation. The collecting of metadata sets and metadata elements into a shopping
cart
provides a new way of browsing through the domain model, notably advancing ease of
access to the model even for the modeling experts at IRT.
We are now turning our attention to the third instance generator component, the
building site. This component is able to open a shopping cart that has previously
been
saved in the shopping mall. It tries then to build a BMF instance from the cart's
content, following user hints that might also be stored in the cart (see Figure 5). Afterwards, it offers a graphical user interface that lets
users edit BMF instances with the help of context-sensitive menues that also are created
dynamically and indirectly, by querying the domain model through the model
advisor.
Once more, the objects that the user is dealing with, in this case metadata set and
metadata element instances, are presented directly as domain objects, independently
of
implementation technology. The target representation of an XML instance that conforms
to
the BMF XML Schema is created by an export modul. This divide-and-conquer strategy
pays
itself off when further output formats need to be supported. As a case in point, the
building site component offers alternative export as a GraphML document that can then
be
visualized with the helpf of the prefuse toolkit; see Figure 6. This kind of visualisation proves to be
instrumental in understanding the inter-dependencies of model elements in BMF, again
on
a conceptual domain level.
Conclusion
In this section, we have presented the method of reverse modeling, as summarized in
Figure 7. Working backwards from pre-existing model
incarnations that only implicitly define the domain model, we have identified the
domain-specific building principles of the implied domain model, thus coming up with
a
domain-specific meta-model, from which an explicit domain model can be derived by
instantiation.
We have also demonstrated how we can follow a divide-and-conquer strategy and
leverage the domain-specific meta-model for the BMF instance generator, so that the
two
main project requirements are met. Consistently reflecting the domain-specific
meta-model in the system design and the user interface also leads to the unexpected
but
highly welcome benefit that also domain experts who are not conversant in XML technology
can work easily and productively with the BMF instance generator.
It is also worth mentioning that reverse modeling and the resulting domain-specific
meta-model raised the level of understanding of the BMF data model. They made a very
sophisticated data model more usable and manageable. We wish to emphasise that usability
is not only an important factor in the design of user interfaces. It is also a decisive
condition for the adoption of a new data model. In our experience, the focussing on
the
domain aspect through reverse modeling has made BMF more accessible to domain users,
especially to those who do not have knowledge in modeling technologies such as UML
or
XML.
Reflection: Models, meta-models and domains
As the name suggests, reverse modeling constructs a domain model working backwards
from
one or more legacy incarnations of a pre-existing model, that may be defined only
implicitly through implementation languages such as XML Schema. We have found in the
BMF
instance generator project that the real value of reverse modeling lies not so much
in the
conceptual model itself but in the domain-specific building principles that allow
conceptual entities to be composed into larger entities. Such building principles
are
customarily considered to be part of the meta-model. This raises the question how
domain-specific building principles AKA constructors on the meta-model level are best
handled when modeling a domain.
By way of an example, let us suppose that we wish to model some entity as a rigid
record
structure that calls for a number of named sub-entities, exactly one for each name
from a
pre-defined list, without restricting the order. In the case that the sub-entities
are each
simply typed, such record structures correspond precisely to tables in first normal
form in
the relational data model.
Naturally, such a model can be expressed in most modeling languages or meta-models,
including UML, XML Schema, and Relax NG, and so can a more flexible record structure
that
allows sub-entities to be optional, or an even more rigid record structure that imposes
order on the sub-entities. The point is that generic meta-models such as UML or XML
Schema
differentiate between these variants of record structures only implicitly, for example
by
consistently affixing specific occurence indicators to sub-entity declarations. In
a way,
they simulate a specific variant of record structures with their generic operators
without
making the common building principles behind them explicit by at least naming or ideally
formally defining them.
The common ground between two record structures, one with sub-entities A, B and C
and
the other with sub-entities D an E is the fact that they are record structures. What is missing in meta-models such as UML, XML
Schema or Relax NG for this scenario is the ability to explicitly provide a building
principle for record structures that can be named in a domain-specific way and that
can be
parameterized by sub-entities such as A, B and C in one case and D and E in the other,
similarly to parameterized types or classes in programming languages.
In contrast, in a meta-model that is customized to a domain that exhibits rigid record
structures we envision a custom operator that directly and explicitly constructs such
a
record structure from its ingredients. In another scenario that displays more flexible
record structures, again there would be a custom operator that caters to flexible
record
structures. And in a scenario that exhibits both rigid and flexible record structures,
there would, of course, be two custom operators, one for each type of record structure.
We
require that in the meta-model we can customize operators: We wish to name them and
to
customize their sub-components as fits the domain.
In the BMF meta-model, we make use of a set operator who assembles named members that
each can be either of simple type or of set type. We have customized it by naming
the set
operator “metadata set” and its members “metadata
elements”. The BMF model instantiates the meta-model by recursively giving names
to metadata sets and their members and by also stating members' types.
We argue in this paper that, compared to generic meta-models, domain-specific
meta-models that directly and explicity express domain-specific building rules may
give
rise to more concise and less complex models that better capture the essentials of
a domain
and better support system development.
Translating XML-encoded printer data for invoices into semantically meaningful
XML
In this section, we briefly present a second case study even though it is not as fully
worked as the BMF study. Yet we feel that it helps to prove the point of the paper.
In his Diploma Thesis [DemirelDA]
project, Tamer Demirel tackles the problem of up-converting XML-encoded printer data
for
invoices into semantically meaningful XML. The XML-encoded printer data are gathered
from
PDF versions of the invoices with the help of publicly available XML printer drivers,
with
the XML data representing the invoice data at page level, in terms of positions, font
information and text strings. The target XML documents need to conform to an XML Schema
for
invoices.
Related invoice data from a single source share a common layout that facilitates
analysis and offers the opportunity to up-translate the low-level printer data into
higher-level, semantically meaningful XML data. An XSLT transformation program can
be
controlled by configuration data that express the common layout. In his Diploma Thesis
project, Tamer Demirel designs and implements an Excel tool that enables clerical
workers
to capture the common layout of related invoice data. These data are saved in XML
format
and then transformed, via XSLT, into an XSLT program that up-translates any invoice
data
instances that conform to the common layout from the printer data into established
workflows “on the side”, without interfering with non-XML
practices.
How is all this related to the topic of this paper, reverse modeling? The link is
in the
XML Schema for the target invoice data. This schema models a flexible record structure
similarly to the one we have presented in the reflection section of this paper, with
the
twist that some field values are not of primitive but of tabular type. Tables generalize
flexible record structures by allowing for repeated sets of values. This description
gives
rise to a meta-model for invoice data that structurally happens to be quite similiar
to the
meta-model for BMF data that we have introduced earlier. Note, though, that the meta-model
is customized to the business domain in its use of terminology.
In Tamer Demirel's Diploma Thesis project, the meta-model serves a double purpose:
First, it structures system design and algorithms for data analysis by dividing all
tasks
into the two separate concersn of record structures and tables. Second, it makes the
work
resilient against change in the schema, since it can be adapted to any schema that
follows
the meta-model.
Patterns as a source for meta-models
In the previous two sections, we propose two custom meta-models for domain models
and
demonstrate how to leverage them for two specific publishing applications. In this
section,
we take a more general view and survey patterns that have evolved in the conceptual
modeling of documents and data and that implicitly suggest sound meta-modeling constructs.
Taken together, these three sections bring us one step closer to our superior goal
to
develop a meta-meta-modeling facility whose instances are custom meta-models for domain
document and data models. They accomplish that by identifying a core set of elementary
constructors that a meta-meta-modeling facility should provide.
Maler and El Andaloussi in their early seminal work on document
modeling [MA95] propose to classify
document constituents into one of four categories, which we call metadata, organizational
items, information items and information snippets. Document constituents in any of
the four
categories exhibit specific structures which today would be called patterns.
Metadata are commonly blocked together and associated with the document as a whole
or
with its major divisions, but may also be associated with more fine-grained document
constituents. As the name “metadata” implies, they hold information
about a document constituent rather than being part of it. Typical high-level metadata
are
author, publisher, publication date and so on as standardized by the Dublin Core initiative
and others. Examples for low-level metadata are the height, depth or format of a picture.
Metadata are typically structured as the flexible type of records that we have used
above
as an example in the reflection section above.
Organizational items structure a document into high-level units. They typically form
a
hierarchy, of which each level is organized as a sequence of specific and often repeatable
items. Typical organizational items are books with frontmatter, a number of chapters
and
backmatter, of which each chapter is organised into a title, a number of introductory
paragraphs and a number of sections.
Information items are smaller units of discourse that can be semantically understood
out
of context, such as paragraphs, lists, or quotations. Characteristically, an organizational
item of the lowest level will be allowed to contain an arbitrary number of information
items whose type may be freely chosen from a repertoire.
Information items may be shallowly organized into sub-items, as a list is organised
into
list items, but will eventually contain just text, possibly mixed with the smallest
and
lowest type of document constituents, namely information snippets.
Finally, information snippets are small units of information that normally cannot
be
semantically interpreted out of context. Typical information snippets are emphasized
phrases, cross references and technical terms. Characteristically, information snippets
may
contain text and possibly further information snippets that are freely chosen from
some
repertoire.
A custom meta-model could allow modelers to classify document constituents into any
of
the four categories and to further constrain their type in accordance with the typical
structures of their category. This could be another use for HyTime's concept of
architectural forms [DD84].
Speaking of information snippets, their characteristic recursive structure of stretches
of text interspersed with lower-level information snippets are aptly described by
the data
modeling pattern [GHJV95] called
Composite, as has been pointed out in a 2007 Extreme Markup
Languages Paper [BST07]. A Composite constructor would
be a valuable tool in a meta-meta-model facility.
Some work has been done on implementational patterns that are applicable to models
written in XML Schema [KS06,L10,S04]. Examples
are the patterns Russion Doll, Venetian Blind, Salami Slice and Garden of Eden, the
four
possibilities that arise when combining local or global element declarations with
local or
global type definitions, respectively. In further studies, we are going to discuss,
if any
of these patterns can be usefully “lifted” from the implementational
to a conceptual level. We will also mine the literature on data modeling, particularly
the
foundational book by Simsion [S07] for
patterns in data modeling that also apply to document modeling.
Conclusion and further work
A number of modeling languages or meta-models have been used in the XML context, mostly
with the goal of integrating XML Schema as an implementation technology into the
development of XML-based systems. Nečaský [N06] surveys conceptual modeling languages that extend
the entity-relationship model. Bernauer et al. [BKK04] survey methods of integrating XML Schema into modeling
with UML. The conference series Extreme Markup Languages and Balisage offer a number
of
papers in the area [KH00,PB09,B09], the latter introducing a subset of
Guizzardi's [G05] Unified Foundational Ontology as
a conceptual modeling language on a layer of abstraction above UML. All these languages
are
of a generic nature; that is, their meta-models only offer generic constructors that
cannot
be customized to the domain.
We find it beneficial to put modeling into a larger context, taking up ideas from
domain-driven design. We put forward the notion of domain-specific meta-models that
capture
building principles of domains. This raises the larger research question of a
meta-meta-modeling facility, instances of which are domain-specific meta-models. We
have
identified potential constructors of a meta-meta-modeling facility by doing reverse
modeling in two case studies and by studying patterns in conceptual models that can
be
abstracted into constructors.
Benefits of domain-specific meta-models are: Clarity of unterstanding, reduction of
complexity, support of system design and guidance for user interfaces.
In our work at EPT, we will futher explore customized meta-models. We intend to build
(or even generate) editors for domain-specific meta-models, for example for forms
documents. And we will formalize meta-models (that is, define a meta-meta-model),
probably
using abstract state machines [BS03] as a
technology-neutral specification language.
Acknowledgments
We extend our heartfelt thanks to BMF project leader Andreas Ebner as well as to Rico
Zimmermann und Christoph Nufer at Institut für Rundfunktechnik for expertise, commitment
and support.
We also gladly acknowledge the long-standing collaboration with Werner Simon and
Thorsten Reinheimer of ExxTainer AG, who suggested and sponsored Tamer Demirel's Diploma
Thesis project. We appreciate their vision regarding XML technology in business and
their
competent and engaged supervision of students.
Dedication
The first author of this paper, Anne Brüggemann-Klein, dedicates the paper to colleague
and friend Professor Derick Wood, PhD, on occasion of his 70th birthday this year.
Derick
has been a most influentical scientific mentor to me. I have learned from him much
that I
know about the English language and scientific writing, and I enjoyed our long-standing
and
quite successful research collaboration. I also appreciate that through Derick and
his
wife, Mary Chen, I got a bit of an inside view of Canada and Hongkong. Thank you!
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Universität München, 2010.
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SPath: a path language for XML schema. In: WWW ’07:
Proceedings of the 16th international conference on World Wide Web, S. 1343–1344.
ACM,
2007. doi:https://doi.org/10.1145/1242572.1242842.
E. Wilde und F. Michel:
SPath: A Path Language for XML Schema. In: Paper
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http://dret.net/netdret/docs/wilde-irep07-001-spath.pdf.
E. Wilde und F.
Michel: XML-based XML schema access. In: WWW ’07:
Proceedings of the 16th international conference on World Wide Web, S. 1351–1352.
ACM,
2007. doi:https://doi.org/10.1145/1242572.1242846.