Functional Component Descriptions for Electrical Circuits based on

Semantic Technology Reasoning

Johannes Bayer

, Mina Karami Zadeh

, Markus Schr

oder

and Andreas Dengel

Deutsches Forschungszentrum f

ur K

unstliche Intelligenz, Trippstadter Str. 122, Kaiserslautern, Germany

Keywords:

RDF, Forward Chaining, Electrical Network, Circuit Diagram.

Abstract:

Circuit diagrams have been used in electrical engineering for decades to describe the wiring of devices and

facilities. They depict electrical components in a symbolic and graph-based manner. While the circuit design

is usually performed electronically, there are still legacy paper-based diagrams that require digitization in

order to be used in CAE systems. Generally, knowledge on speciﬁc circuits may be lost between engineering

projects, making it hard for domain novices to understand a given circuit design. The graph-based nature

of these documents can be exploited by semantic technology-based reasoning in order to generate human-

understandable descriptions of their functional principles. More precisely, each electrical component (e.g. a

diode) of a circuit may be assigned a high-level function label which describes its purpose within the device

(e.g. flyback diode for reverse voltage protection). In this paper, forward chaining rules are used

for such a generation. The described approach is applicable for both CAE-based circuits as well as raw circuits

yielded by an image understanding pipeline. The viability of the approach is demonstrated by application to

an existing set of circuits.

1 INTRODUCTION

Graphs are a traditional mean to describe electrical

circuits (R

ucker, 2012). Computer-aided engineering

(CAE) systems are already used to capture, maintain,

simulate and verify these circuits by exploiting their

underlying graph structure. However, circuits also in-

corporate engineering knowledge. During the migra-

tion of circuits between CAE systems or during the

digitization of circuits from paper sources, maintain-

ing the plain syntactic features of the graph structure

is often focused while high-level functional principles

are not properly processed. Likewise, errors in the mi-

gration process often need to be traced manually.

In order to help developers (and other agents)

understand circuit functionality and to automatically

search for engineering concepts, additional means

are required. This can also be achieved by exploit-

ing graph structures: For example, a diode which

has its anode connected to a terminal of an induc-

tor and its cathode connected to the opposite termi-

https://orcid.org/0000-0002-0728-8735

https://orcid.org/0000-0002-6965-5190

https://orcid.org/0000-0001-8416-0535

https://orcid.org/0000-0002-6100-8255

nal of the same inductor can be considered a ﬂy-

back diode (functional description of the diode com-

ponent). Likewise, a direct electrical connection be-

tween the two terminals of a voltage source can be

considered a shortcut (fault description). Modeling

these engineering concepts by the semantic technolo-

gies in order to reason about their presence in arbi-

trary circuits is the objective of the paper at hand.

2 RELATED WORK

Electrical Rule checker are already existing for CAE

software (e.g. (Beard, 2021)).

Efforts have already been made to model electri-

cal power systems for the purpose of interoperability

(Gaha et al., 2013) as well as fault diagnosis (Bernaras

et al., 1996). In contrast, the paper at hand focuses on

electronic circuits.

(Liu and Farley, 1990) describe a system that inte-

grates physical aspects and statements about circuits,

hence allow to question about the low-level behavior

of the system. Conversely, (Kitamura and Mizoguchi,

1998) describe an approach for assigning functions to

components of technical systems. However, the ap-

proach is rather generic way and demonstrated by the

528

Bayer, J., Zadeh, M., Schröder, M. and Dengel, A.

Functional Component Descriptions for Electrical Circuits based on Semantic Technology Reasoning.

DOI: 10.5220/0011322000003269

In Proceedings of the 11th International Conference on Data Science, Technology and Applications (DATA 2022), pages 528-532

ISBN: 978-989-758-583-8; ISSN: 2184-285X

example of a power plant.

(Kleer, 1979) (De Kleer, 1984) describes a com-

prehensive system for automatically deriving high-

level insights on electronic circuits. Due to the time of

their implementation, the described systems lack sup-

port of modern semantic technologies like RDF (rdf,

2014).

(Kunal et al., 2020) describe an approach for sub-

circuit annotation to based on graph neural networks.

While this approach is powerful, it comes with the

typical limitation of ANNs like a ﬁxed class set the re-

quirement for a (large and usually non-public) dataset

as well as a lack of perfect accuracy and explainabil-

ity.

Systems for the manipulation of piping and instru-

mentation diagrams (which are structurally similar

to circuit diagrams) have been proposed by (Gr

uner

et al., 2014) and (Bayer and Sinha, 2020).

An extended version of a public dataset of hand-

drawn circuit diagrams (Thoma et al., 2021) has been

used to evaluate the approach described in this paper.

Wikidata is an open knowledge database, in which

entities of many domains as well as general-purpose

properties are available(van Veen, 2019). As it con-

tains entries for describing electric and electronic

components, the RDF circuit representations de-

scribed in this paper is linked against this database in

order to allow for later inference of additional knowl-

edge.

3 APPROACH

The complete approach consists of the following steps

(see Figure 1):

• Conversion from CAE ﬁle formats or recognition

results to a uniform raw RDF representation.

• Preprocessing Rules are applied in order to ab-

stract from the circuit’s optical features like junc-

tions and to compensate structural weaknesses

like directed component connections.

• Component Annotation Rules are applied to

generate functional descriptions within the circuit.

• For avoiding redundancies, the resulting RDF rep-

resentation is generated from a uniﬁcation of the

raw RDF and the functional descriptions.

• The enriched RDF is converted back to CAE or

image ﬁles

Both preprocessing rules and component annota-

tion rules are denoted in Apache Jena (Siemer, 2019)

forward chaining syntax.

Conversion

CAD

Digitized

From

Paper

J T

CAD

Rendered

Image

Preprocessing Annotation

J T

Volt. Div.

Component

Annotation

Rules

Pre

Processing

Rules

J T

Volt. Div.

Raw RDF Uniﬁcation

Conversion

Figure 1: System Overview.

3.1 Ontology

In oder to have a common ontology for describing the

circuits, the following terminology is used:

A circuit is described as a graph structure with

components as nodes and electrical connections as

edges. Components can be either connected directly

or via ports which represent the individual terminals

of a component (e.g. the anode of a diode). Addi-

tionally, junctions and crossover symbols are intro-

duced to support the graphical representation of en-

gineering diagrams as well as their digitization from

analogue sources. Junctions are used both to indi-

cate corners in wiring lines and to allow for con-

necting multiple components (to form hyperedges in

Functional Component Descriptions for Electrical Circuits based on Semantic Technology Reasoning

529

Figure 2: Sample Circuit Image.

Component

Port

Connects

Has Part

C/O

Figure 3: Sample Circuit in Proposed Representation. For

visibility reasons, relations to the owing graph resource and

the positioning are omitted; port names as well as compo-

nent types are denoted as abbreviated labels. Note that the

direction of component connections is unordered.

Figure 4: Electrical Symmetry Rule (result in orange).

Figure 5: Junction Resolution Rule (results in orange; after

prior symmetry rule application).

graph logic). Crossover symbols indicate the cross-

ing of lines without a electrical connection between

them. Components annotation rules add functions

to indicate a component’s purpose in the circuit. All

mentioned terms (including the speciﬁc compoment

classes and function classes) are related to Wikidata

(van Veen, 2019) entries in the circuit’s RDF repre-

sentation.

3.2 Preprocessing Rules

The preprocessing rules create a normalized electrical

view by augmenting the raw RDF structure. There-

fore, they allow a simpliﬁed and ﬂexible design of the

annotation rules:

3.2.1 Electrical Symmetry

The RDF triples which express the electrical connec-

tions between the components form a directed graph,

while there is no physical justiﬁcation for the level at

which the annotation rules are applied. In fact, the

position of subject and object resource is considered

not well deﬁned in the respective triples (i.e. up to the

implementation of the graph generation), resulting in

an directed yet unordered relation. In order to imple-

ment an undirected graph structure and consequently

allow for an abstraction before the annotations rule

application, connecting triples of opposite direction

are added (see also Figure 4):

[ electSymm : ( ? a w : c o n n e c t s ? b )

−> ( ? b w : c o n n e c t s ? a ) ]

3.2.2 Junction Resolution

As junctions are both optical features and a mean to

describe hyperedges (which are tedious to encode in

forward chaining rules), they also need to be bro-

ken down to direct connections between components.

DATA 2022 - 11th International Conference on Data Science, Technology and Applications

530

Figure 6: Port Resultion Rule (results in orange; after sym-

metry rule application).

Figure 7: Crossover Resolution Rule (results in orange; af-

ter prior symmetry rule application).

This can be achieved by a simple transitive relation

(see Figure 5):

[ by J : ( ? a w : c o n n e c t s ? j u n c t i o n ) ,

( ? j u n c t i o n w : c o n n e c t s ? c ) ,

( ? j u n c t i o n r d f : t y p e w: JUNCTION)

−> ( ? a w: c o n n e c t s ? c ) ]

3.2.3 Port Resolution

As information model allows electrical connections

between either components or ports or a mixture of

them, rules may or may not address them. As cir-

cuits of different granularity should be supported and

some rules don’t make use of the port attributes, it is

crucial to add connections so that components are al-

ways connected directly. Note that this rule is used

in conjunction with the electrical symmetry (see Fig-

ure 6):

[ r e s : ( ? owner w : h a s p a r t ? p o r t ) ,

( ? p o r t r d f : t y p e w : PORT ) ,

( ? a w : c o n n e c t s ? p o r t )

−> ( ? a w : c o n n e c t s ? owner ) ]

3.2.4 Crossover Resolution

Crossover symbols are resolved by connecting the

connection partners of the opposite crossover symbol

ports (the rule below only describes the resolution of

one pair of opposite crossover ports while a crossover

symbol usually has two pairs, see Figure 7):

[ r e s C r o : ( ? a w: c o n n e c t s ? c o

a 1 ) ,

( ? b w: c o n n e c t s ? c o a 2 ) ,

( ? co r d f : t y p e w: CROSSOVER) ,

( ? c o a 1 w: name a 1 ) ,

( ? c o a 2 w: name a 2 ) ,

( ? c o a 1 r d f : t y p e w: PORT) ,

( ? c o a 2 r d f : t y p e w: PORT) ,

( ? co w: h a s p a r t ? c o a1 ) ,

( ? co w: h a s p a r t ? c o a2 ) ,

( ? j u n c t i o n r d f : t y p e w: JUNCTION)

−> ( ? a w: c o n n e c t s ? b ) ]

3.3 Component Annotation Rules

While the preprocessing rules are considered to be a

ﬁxed set, the component annotation rules are an in-

tended to be extensible by domain experts and knowl-

edge workers. The component annotation rules used

in this paper are:

Name Description

Emitter A bipolar transistor ampliﬁer

Common using a voltage divider biasing

Ampliﬁer to keep base bias voltage at a

constant level.

Coupling Connects the AC part of a signal

Capacitor between two parts of the circuit

while blocking DC Parts.

Electronic Component in either open or

Switch closed state.

Flyback A diode that is connected

Diode inversely to an energy storage

component for protecting

against voltage spikes.

Oscillator Provide a constant stable

Crystal frequency and can be used

as clock in digital circuits

PullUp Provides a well-deﬁned voltage

Resistor level in case of absence of other

connections (e.g. open switches).

Voltage provides an intermediate voltage

Divider level between the surrounding

voltage levels.

3.4 Implementation

Complete circuits diagrams are loaded from KiCad

(Kanagachidambaresan, 2021) schematic ﬁles and in-

ternally captured as NetworkX (Hagberg and Con-

way, 2020) graphs before being converted to RDF

Turtle (World Wide Web Consortium, 2014) repre-

sentations. The preprocessing as well as the compo-

nent annotation itself is performed as forward chain-

ing rules in Apache Jena (Siemer, 2019), where the

component annotation rules are implemented as in-

dividual ﬁles for extensibility purposes. The source

code and the circuit dataset is made publicly avail-

able

https://github.com/DFKI/circuitgraph-insights

Functional Component Descriptions for Electrical Circuits based on Semantic Technology Reasoning

531

Figure 8: Component Annotations (Green Hexagons) on a

Sample Circuit.

4 EVALUATION

In order to validate the approach, the results are

demonstrated on a sample circuit (see Figure 8).

5 CONCLUSION

An RDF-based system for automatically deriving

functional annotations of individual components in-

side circuits has been described. By incorporating

support for an openly available CAE system as well

as referencing ressources from the also openly avail-

able wikidata knowledge base, it connects the world

of circuit modeling with the world of image annota-

tion and the world of circuit understanding.

6 OUTLOOK

So far, many of the rules needed to be formulated in

multiple, rather speciﬁc ways in order to deal with all

desired situations. Further preprocessing steps are re-

quired to allow for more general formulations. For

example, voltage sources as well as vcc and gnd sym-

bols need to be resolved to a uniform representation.

ACKNOWLEDGMENT

This work was funded by the BMBF project SensAI

(grant no. 01IW20007).

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