DE102017217663A1 - Analysis of a data structure - Google Patents

Abstract

A data structure comprises a plurality of objects that can represent or model, for example, functional components of a control device. A method includes steps of determining a comparison key for at least one of the objects; and assigning the determined comparison key to the object such that the objects are assigned different comparison keys. In this case, the comparison key of the at least one object is determined on the basis of a structure definition assigned to the object.

Description

The invention relates to a method and a device for analyzing a data structure. The data structure may in particular represent or model functional components of a control device.

A motor vehicle includes a controller that includes a plurality of components that are interconnected and that can exchange messages with each other. The control unit can influence a physical aspect of the motor vehicle by, for example, influencing a longitudinal or transverse movement of the motor vehicle or driving a physical device on board the motor vehicle, such as a heater, an adjustable exterior mirror or an adjustable seat. A malfunction of the control device can cause damage to property or personal injury.

If a component of the controller is changed, for example, by one of its electronic components is replaced by another, then a change to another component may be required to ensure a desired functionality of the controller.

The way in which the components work together may be indicated as a data structure that includes objects that represent the objects. A change of the control device can correspond to a transformation of the data structure. In order to understand each change individually, differences between the data structures have to be determined.

One way to do this is to serialize and then compare the data structures. This requires that the objects of the data structure are brought into a predetermined sequence during serialization. However, some objects may not include a comparison key that defines an order.

An object underlying the invention is to provide an improved technique for determining comparison keys for objects of a data structure. The invention solves this problem by means of the subjects of the independent claims. Subclaims give preferred embodiments again.

A data structure comprises several objects. A method includes steps of determining a comparison key for at least one of the objects; and assigning the determined comparison key to the object such that the objects are assigned different comparison keys. In this case, the comparison key of the at least one object is determined on the basis of a structure definition assigned to the object.

The structure definition indicates how the object is constructed so that the comparison key for each object can be determined in an appropriate manner. In particular, the comparison key can take into account a characteristic of the object, so that the order can not only be reproducible but also meaningful with respect to the object. For example, a comparison key for an object associated with a controller may be determined based on a designation of the controller, wherein different portions of the label may be treated differently.

Preferably, at least two objects of the data structure are assigned different structure definitions, and comparison keys for the two objects are determined in different ways. Objects with the same or similar structures can thus be compared, while objects with different structures do not have to be comparable. For example, comparison keys of different objects may have different lengths to reflect possible object varieties and to reduce storage space for the comparison key. For an object consisting of only one digit, a short comparison key can be determined, which can take at least 10 different values, while for an object comprising a table with several entries, a longer comparison key can be determined which has more different values can accept.

The structural definition of the at least one object may describe a relationship between two objects of the data structure, the comparison key being determined on the basis of both objects. The relationship may exist between other objects or between the object and one or more other objects. As a result, a meaningful comparison key can also be determined if the object comprises no attributes or only a few of its own, on the basis of which a comparison key is usually determined.

The structure definition may describe a relationship to an optional object, where the comparison key is determined depending on the optional object, if present in the data structure. As a result, the structure definition can be specified flexibly. A determination of which optional objects are actually related to the processed object, how this relationship is designed, and what kind of optional objects may be improved can be determined only at run time.

An object can only be assigned a comparison key if the object does not yet contain a comparison key. As a result, already existing comparison keys can be exploited and only for those objects which do not comprise a comparison key or to which no comparison key is assigned, a new key is determined. A processing effort can thereby be reduced and already certain comparison keys can be utilized in order to enable a meaningful sorting of the objects.

The at least one object may include or reference one or more further objects, and the comparison key for the object may be determined based on the included or referenced objects. Usually, the comparison key of the object is determined on the basis of all included or referenced objects, in particular their comparison keys. In a further embodiment, however, those included or referenced objects that are used to form the comparison key for the parent object may also be actively selected, specifically based on a structural definition of the object or one of the included or referenced objects.

The comparison key for the object can in particular be determined recursively on the basis of one or more included or referenced objects. In particular, a comparison key of a covered or referenced object can be used to form the comparison key for the higher-level object. An encompassed object that is not characteristic of the parent object, for example, because it is encompassed by a large variety of other objects, can not be taken into account in forming the compare key.

For recursive treatment, a depth of work may be predetermined until the included or referenced objects are followed. This can prevent excessively long or even infinite recursion. In one embodiment, the comparison key is first determined with a predetermined recursion depth. If there is a collision between comparison keys, ie if the same comparison keys have been determined for different objects, then the determination can be repeated with an increased recursion depth until no more collision occurs. The repeated determination can relate to one or more of the objects whose comparison keys conflict with one another, or also to further or all objects of the data structure.

Alternatively, the recursion can be aborted even if a cycle has been detected in a chain of dependencies of the objects. For example, if a first object includes a second, and this the first, then there is a cycle that can not be resolved by recursion. In a further embodiment, objects already visited within the scope of a recursion (or references to the objects) are stored and a renewed processing of these objects is skipped in the following.

The data structure can be serialized in monotonic order of the comparison keys. The objects covered by the data structure can be concatenated in ascending or descending order of their comparison key. The order of the serialized objects in the concatenation is preferably as invariant as possible to a change of one of the objects of the data structure.

The serialized data structure can be compared to another serialized data structure. For example, a data structure that reflects, for example, an architecture of a controller may easily comprise several 10 MB in a serialized form. By the described determination of compare keys for objects comprised by the data structure, the comparison with the other serialized data structure can be made more easily since sequences of serialized objects belonging to portions of the data structures that are equal to each other or the same can also be the same. Differences between the serialized data structures can therefore be found improved and, for example, issued or highlighted in the serialization. A person who checks changes and differences between the data structures and, if necessary, is responsible, can thus be made aware of deviations. As a result, it is possible in particular to better control logic-related changes which are automatically carried out in response to a first change.

The further serialized data structure may be determined based on a transformation of the other data structure. In particular, one of the data structures may have been created by a transformation from the other. The method may include the transformation. The transformation may reflect a change in the matter reflected by the data structures. For example, if the data structure relates to a controller or its architecture, then the transformation may reflect a change to the controller or to the architecture. The control unit can be set up in particular for use on board a motor vehicle. For example, for a design ECU control or scheduling a mass production of ECUs, monitoring of changes can support quality assurance. In a further embodiment, the data structure may also reflect a system of a plurality of control devices, in particular on board a motor vehicle.

The data structure may include a tree-like structure of the objects. As a result, many practical structures, for example linear or hierarchical, can be improved.

An apparatus comprises a memory device for storing a data structure with a plurality of objects; and a processing device. In this case, the processing device is set up to determine a comparison key for at least one of the objects on the basis of a structure definition assigned to the object; and associate the particular comparison key with the object so that the objects are assigned different comparison keys.

The processing device is preferably set up to carry out a method described here in whole or in part and may in particular comprise a programmable microcomputer or microcontroller. The method may be wholly or partially in the form of a computer program product with program code means and run on the processing device or stored on a computer-readable medium. Features or advantages of the method may be related to the device and vice versa.

• 1 ein beispielhaftes Kraftfahrzeug mit einem Steuergerät;
• 2 exemplarische, schematische Repräsentationen eines Steuergeräts und eines geänderten Steuergeräts; und
• 3 ein Ablaufdiagramm eines Verfahrens

illustriert.The invention will now be described in more detail with reference to the accompanying drawings, in which:

• 1 an exemplary motor vehicle with a control unit;
• 2 exemplary, schematic representations of a controller and a modified controller; and
• 3 a flowchart of a method

illustrated.

1 shows exemplary system 100 , which is realized as a motor vehicle, and at least one control unit 105 includes. The control unit 105 In particular, it can control a physical function of the system 100 be set up, in the present example as a brake system for influencing a longitudinal movement or an electronic stability program (ESP) for influencing a transverse movement of the motor vehicle 100 ,

The control unit 105 usually includes several components 110 of which in the exemplary illustration of 1 exemplarily several input components 115 , a processing component 120 and an output component 125 are shown. Other or further components 110 - 120 may also be included. The control unit 105 can in particular by means of an input component 115 and / or an output component 125 be connected to another controller, a sensor or an actuator. Communication between the controller and other devices on board the motor vehicle 100 can be done by means of a control bus (not shown).

A function, structure or architecture of the controller 105 based on the components 110 can be rendered in the form of a data structure. To analyze or manipulate such a data structure, with reference to below 2 will be described in more detail, a device 130 be provided, which preferably has an input device 135 for acquiring the data structure and a processing device 140 includes. A storage device is also preferred 145 is provided, which is adapted to include the data structure in whole or in part and optionally further information such as a structure definition of an object that is encompassed by the data structure.

2 shows a first data structure 205 , for example, a control unit 105 reflected, and a second data structure 210 that the control unit 105 after a change 215 reflected. Related to the data structures 205 . 210 can the change 215 also be referred to as transformation. In the presentation of 2 If the change exists as an example in the addition of an input component 115 , resulting in a change of part of the second data structure 210 opposite the first data structure 205 is reflected. The added input component 115 in 1 and the corresponding object in 2 are darkened for clarity.

The first data structure 205 exemplifies the basic shape of a tree and includes several objects 220 , Between objects 220 can relationships 225 consist. An object 220 can have one or more attributes 230 include, where an attribute 230 For example, it may include a value or a tuple or a collection of multiple values. Other embodiments are also possible and an attribute 230 can also be very complex, for example in the form of a data object. The exact structure of an attribute 230 can be unknown (BLOB = "binary large object").

An object 220 can be a comparison key 235 be assigned, which allows objects 220 to bring a common level of organization into a clear order, by bringing the objects 220 in ascending or descending order of their assigned comparison key 235 to be brought. For example, all objects 220 that is a common object 220 are subordinate to be sorted in this way.

Some objects 220 can already compare key 235 include or you can compare key 235 already assigned. The presence of a comparison key 235 may depend on the type of each object 220 and their concrete implementation. As comparison key 235 in particular, a unique identification of the object 220 which is also known as a UID ("unique identifier"). It may be unknown how the UID was determined, as long as it is unique, so it is not two objects 220 with the same UIDs. The order thus declared between two objects 220 but can be arbitrary.

However, it is assumed that at least one of the objects 220 initially no comparison key 235 assigned. A structure of this object 220 is in the form of a structural definition 240 specified. The structure definition 240 Specify in particular which attributes 230 the object 220 and with which objects 220 it in what relationship 225 stands. It is suggested that a comparison key 235 for such an object based on its structure definition 240 is determined. Optionally, also the actual structure of the object 220 be considered, for example, if the structure definition 240 Alternatives or an optional element includes. In addition, elements of the object 220 and / or elements of one with the object 220 in relationship 225 standing object 220 for the determination of the comparison key 235 be used.

The comparison key 205 . 210 For example, they can be used to structure the data 205 . 210 to serialize. Serialized versions of the data structures 205 . 210 are in the lower range of 2 shown schematically. The serialized data structures in this way 205 . 210 In particular, a comparison or a determination of differences in the data structures 205 . 210 facilitate.

• - Der Vergleichsschlüssel 235 eines Objekts 220 kann mittels einer Funktion f oder einer Kombination von Funktionen f1 ... fn bestimmt werden
• - Die Funktionen können Werte von Attributen 230, Vergleichsschlüsseln 235 eines in Beziehung 225 stehenden weiteren Objekts 220 oder des weiteren Objekts 220 selbst, insbesondere in dessen Repräsentation in einem Speicher eines Verarbeitungssystems, bestimmt werden
• - Eine Funktion f1 kann beispielsweise auf einem spezifischen Attribut 230 oder einer Referenz oder Beziehung 225 basieren, die einen einzigartigen Identifikator („unique identifier“) repräsentiert, wobei die Funktion den Identifikator als Vergleichsschlüssel 235 bestimmen kann
• - Eine typspezifische Funktion f2(t) kann beispielsweise auf einer Kombination von Attributen 230 und/oder Beziehungen 225 basieren, die zusammen einen einzigartigen Identifikator repräsentieren, wobei die Funktion f2 den Identifikator als Vergleichsschlüssel 235 bestimmen kann
• - Eine Funktion f3 kann auf den Werten von Attributen 230 und/oder den Vergleichsschlüsseln von in Beziehung 225 stehenden Objekten 220 basieren und beispielsweise eine Aneinanderreihung (Konkatenation) dieser Werte als Vergleichsschlüssel 235 bestimmen
• - Eine Ausweichfunktion f4 kann beispielsweise derart definiert sein, dass stets ein nicht-leerer Wert als Vergleichsschlüssel 235 bestimmt wird; dies kann beispielsweise durch eine Funktion realisiert werden, welche eine Repräsentation des Objekts in einem Speicher einem Verarbeitungssystem zurückliefert
• - Mehrere Funktionen können in einer vorbestimmten Reihenfolge ausgeführt werden, beispielsweise zuerst f1, dann f2, dann f3 usw. Dabei kann der erste Rückgabewert einer Funktion f als Vergleichsschlüssel 235 bestimmt werden, der nicht leer ist
• - Der Vergleichsschlüssel 235 eines Objekts 220 kann insbesondere dann rekursiv bestimmt werden, wenn er auf dem Vergleichsschlüssel 235 eines in Beziehung 225 stehenden Objekts 220 basiert

For the concrete determination of a comparison key 235 Many variants are conceivable.

• - The comparison key 235 an object 220 can be determined by means of a function f or a combination of functions f1 ... fn
• - The functions can be values of attributes 230 , Comparison keys 235 one in relationship 225 standing further object 220 or the other object 220 itself, in particular in its representation in a memory of a processing system
• For example, a function f1 may be based on a specific attribute 230 or a reference or relationship 225 which represents a unique identifier, the function being the identifier as a comparison key 235 can determine
• For example, a type-specific function f2 (t) can be based on a combination of attributes 230 and / or relationships 225 which together represent a unique identifier, where function f2 uses the identifier as the comparison key 235 can determine
• - A function f3 can be based on the values of attributes 230 and / or the comparison keys of 225 standing objects 220 based and, for example, a concatenation (concatenation) of these values as a comparison key 235 determine
• An alternative function f4 can for example be defined such that always a non-empty value is used as the comparison key 235 is determined; this can be realized, for example, by a function which returns a representation of the object in a memory to a processing system
• Several functions can be executed in a predetermined order, for example first f1, then f2, then f3, etc. Here, the first return value of a function f can be used as a comparison key 235 be determined that is not empty
• - The comparison key 235 an object 220 In particular, it can be determined recursively if it is on the comparison key 235 one in relationship 225 standing object 220 is based

• - Die Funktionen sollten eine niedrige Kollisionswahrscheinlichkeit aufweisen, das heißt, dass verschiedene Argumente möglichst zu verschiedenen Ausgaben führen sollen
• - Eine Anzahl von Argumenten für eine Funktion ist vorzugsweise irrelevant
• - Ist die Reihenfolge der Argumente relevant, so können sie in einer vorbestimmten Reihenfolge verwendet werden, beispielsweise alphabetisch
• - Ist die Reihenfolge der Argumente relevant, so können Beziehungen 225 mit mehreren Objekten 220 ausgelassen oder vorverarbeitet werden, beispielsweise mittels Sortieren
• - Eine der Funktionen kann eine Hashfunktion (Streuwertfunktion) oder eine Kombination mit einer Hashfunktion umfassen
• - Eine beispielhafte Funktion f bestimmt einen vorhandenen einzigartigen Identifikator eines Objekts 220 kann als Vergleichsschlüssel 235
• - Eine beispielhafte Funktion f2(t1) konkateniert einen Pfad, einen Namen und einen Typ eines Objekts 220 als Vergleichsschlüssel 235, vorausgesetzt die Kombination innerhalb der Datenstruktur 205 ist einzigartig
• - Eine beispielhafte Funktion f3 bestimmt eine Konkatenation von Zeichenketten von Attributen 230 des Objekts 220 und Vergleichsschlüsseln 235 von in Beziehung 225 stehenden Objekten 220 als Vergleichsschlüssel 235; dabei kann können die Bestandteile beispielsweise bezüglich der Namen der Attribute 230 bzw. der Namen der Beziehungen 225 sortiert werden
• - Eine beispielhafte Funktion f3 umfasst eine vorbestimmte Hashfunktion einer zur Implementation verwendeten Programmiersprache, beispielsweise C++ oder C#. Dabei kann der bestimmte Hashwert in eine Zeichenkette umgewandelt werden
• - Im Fall schleifenförmiger Beziehungen 225 können bereits bearbeitete Teile eines Speichers, in welchem Objekte 220 abgelegt sind, markiert werden, um eine erneute Bearbeitung anschließend auszulassen
• - Attribute 230, die nicht kennzeichnend für ein Objekt 220 sind, können bei der Bestimmung eines Vergleichsschlüssels 235 ausgelassen werden. Dies kann beispielsweise Attribute 230 eines der Typen „not changeable“, „transient“, „volatile“ oder „derived“ betreffen
• - Beziehungen 225, die nicht kennzeichnend für ein Objekt 220 sind, können bei der Bestimmung eines Vergleichsschlüssels 235 ausgelassen werden. Dies kann beispielsweise Beziehungen 225 eines der Typen „not changeable“, „transient“, „volatile“, „derived“ oder „container“ betreffen
• - Wird der Vergleichsschlüssel 235 rekursiv über mehrere Objekte 220 bestimmt, so kann eine Bearbeitungstiefe vorbestimmt werden. Es ist möglich, in einem ersten Lauf einen Teilschlüssel zu bestimmen. Sollte dieser Teilschlüssel ungenügend sein, weil es ein anderes Objekte 220 mit dem gleichen Teilschlüssel gibt, so kann die Bearbeitungstiefe schrittweise vergrößert werden, bis alle Objekte 220 in die Bestimmung einbezogen werden
• - Vergleichsschlüssel 235 von Objekten 220 können in einem schnellen Zwischenspeicher (Cache) vorgehalten werden, um weitere Bestimmungen von Vergleichsschlüsseln 235 zu beschleunigen
• - Zusätzliche Funktionen können verwendet werden, um Unterschiede anzugleichen, die nicht berücksichtigt werden sollen, beispielsweise das großschreibungsunabhängige Behandeln von Zeichenketten,

Numerous variants and options are also conceivable for the realization of the function:

• - The functions should have a low collision probability, that is, different arguments should lead to different outputs as possible
• A number of arguments for a function is preferably irrelevant
• If the order of the arguments is relevant, they can be used in a predetermined order, for example alphabetically
• - If the order of the arguments is relevant, then relationships can 225 with multiple objects 220 omitted or preprocessed, for example by means of sorting
• - One of the functions may include a hash function (truncation function) or a combination with a hash function
• An example function f determines an existing unique identifier of an object 220 can as a comparison key 235
• An exemplary function f2 (t1) concatenates a path, a name and a type of an object 220 as a comparison key 235 , provided the combination within the data structure 205 is unique
• An exemplary function f3 determines a concatenation of character strings of attributes 230 of the object 220 and comparison keys 235 in relationship 225 standing objects 220 as a comparison key 235 ; For example, the ingredients may be related to the names of the attributes 230 or the name of the relationship 225 be sorted
• An exemplary function f3 comprises a predetermined hash function of a programming language used for the implementation, for example C ++ or C #. The particular hash value can be converted into a string
• - In the case of loop relationships 225 can already edited parts of a memory in which objects 220 are marked, in order to subsequently omit re-editing
• - Attributes 230 that are not indicative of an object 220 can, when determining a comparison key 235 be left out. This can be attributes, for example 230 one of the types "not changeable", "transient", "volatile" or "derived"
• - Relationships 225 that are not indicative of an object 220 can, when determining a comparison key 235 be left out. This can be relationships, for example 225 one of the types not changeable, transient, volatile, derived or container
• - Will the comparison key 235 recursively over several objects 220 determined, so a processing depth can be predetermined. It is possible to specify a subkey in a first run. This subkey should be insufficient because it is another object 220 with the same subkey, so the processing depth can be gradually increased until all objects 220 be included in the provision
• - Comparison key 235 of objects 220 can be kept in a fast buffer (cache) for further determinations of comparison keys 235 to accelerate
• Additional functions can be used to match differences that should not be taken into account, such as the case-independent handling of strings,

• - Objekte 220 zu sortieren,
• - Unterschiede zwischen Objekten 220 zu bestimmen, oder
• - Objekte 220 zusammen zu führen.

The process can work with any type of object 220 such as collections, models (models), or tables (tables), to:

• - objects 220 to sort,
• - differences between objects 220 to determine, or
• - objects 220 to lead together.

• - deren Reihenfolge nicht verändert werden kann (beispielsweise weil ihre derzeitige Reihenfolge wichtig ist);
• - die bereits eine gewünschte Reihenfolge aufweisen; oder
• - deren Ordnung nicht verändert werden muss, beispielsweise Objekte 220 einer der Typen „not changeable“, „transient“, „volatile“ oder „derived“.

Depending on the determination of the comparison key 235 further optimizations can be applied. If, for example, the order of the objects is to be changed, in particular in the case of sorting, then objects can 220 be skipped

• - whose order can not be changed (for example, because their current order is important);
• - which already have a desired order; or
• - whose order does not need to be changed, such as objects 220 one of the types "not changeable", "transient", "volatile" or "derived".

• - „not changeable“: es ist nicht möglich, einem damit ausgezeichneten Element einen Wert zuzuordnen;
• - „transient“: ein damit ausgezeichnetes Element wird nicht serialisiert;
• - „volatile“: ein damit ausgezeichnetes Element hat keinen zugewiesenen Speicherplatz;
• - „derived“: ein damit ausgezeichnetes Element wird auf der Basis anderer Elemente bestimmt;
• - „container“: ein damit ausgezeichnetes Element umfasst eine Rückwärts-Referenz zu einem Element, das ihm übergeordnet ist.

In the context of this invention means:

• - "not changeable": it is not possible to assign a value to a given element;
• - "transient": an element awarded with it is not serialized;
• - "volatile": an element awarded with it has no allocated memory space;
• - "derived": an element thus awarded is determined on the basis of other elements;
• - "container": an element awarded with it contains a backward reference to an element that is superior to it.

3 shows a flowchart of an exemplary method 300 in particular, in whole or in part on the device 130 of the system 100 from 1 can be executed.

In an optional step 305 becomes a data structure 205 captured and may, for example, in the storage device 145 be filed. Subsequently, the objects should 220 that from the data structure 205 are included, with comparison keys 235 be equipped. This can be done by the objects 220 be checked in any order. In one embodiment, a recursive check is carried out, it being possible in particular to start at a root object if the data structure 205 has a hierarchical shape, such as a tree.

In one step 310 can be an object 220 the data structure 205 be determined, which should be checked. It is preferred in one step 315 determines whether an associated or included comparison key 235 is available. If this is the case, then in step 310 with a next object 220 be continued. Otherwise, it is preferred in one step 320 a structure definition 240 of the object 220 certainly. The structure definition 240 explains a structure of the object 220 from elements like attributes 230 or relationships 225 , The comparison key 235 can in one step 325 be determined, preferably the structure definition 240 and / or the object 220 covered elements are taken into account. For the exact determination of the comparison key, above with reference to 2 possible embodiments and variants indicated. The specific comparison key 235 can the object 220 in one step 330 be assigned. Subsequently, in step 310 with a following object 220 be continued. The steps 310 to 330 can be performed recursively when determining a comparison key 235 a comparison key 235 a covered or related object 220 is required.

After the comparison key 235 of all objects 220 are determined, the data structure 205 in one step 335 be serialized by the objects it encompasses 220 in an order and preferably expressed as strings. Here is the order of the objects 220 through the comparison key 235 certainly. Alternatively, the objects can 220 also within the data structure, for example 205 sorted or otherwise with respect to their comparison key 235 be manipulated.

In its serialized form, the data structure 205 with a serialized second data structure 210 be compared. Differences between the data structures 205 . 210 can in one step 345 determined and highlighted in one of the representations or output separately.

LIST OF REFERENCE NUMBERS

100

System (motor vehicle)

105

control unit

110

component

115

input component

120

processing component

125

output component

130

contraption

135

input device

140

processing device

145

storage device

205

first data structure

210

second data structure

215

Change / transformation

220

object

225

relationship

230

attribute

235

Compare key

240

structure definition

205

first data structure

210

second data structure

215

modification

300

method

305

Capture data structure

310

Determine object

315

Key available?

320

Determine structure definition

325

Determine comparison key

330

Assign Comparison Key

335

Serialize data structure

340

Compare with another serialized data structure

345

Determine differences

Claims (14)

A method (300), comprising the steps of: - detecting (305) a data structure (205) having a plurality of objects (220); - determining (325) a comparison key (235) for at least one of the objects (220); Assigning (330) the determined comparison key (235) to the object (220), so that the objects (220) are assigned different comparison keys (235); characterized in that - the comparison key (235) of the at least one object (220) is determined (325) on the basis of a structure definition (240) associated with the object (220). Method (300) according to Claim 1 wherein at least two objects (220) of the data structure (205) are assigned different structure definitions (240) and comparison keys (235) for the two objects (220) are determined in different ways. Method (300) according to Claim 1 or 2 wherein the structure definition (240) of the at least one object (220) describes a relationship between two objects (220) of the data structure (205) and the comparison key (235) is determined based on both objects (220). Method (300) according to Claim 3 wherein the structure definition (240) describes a relationship with an optional object (220), and the comparison key (235) is determined depending on the optional object (220) only if present in the data structure (205). Method (300) according to one of the preceding claims, wherein an object (220) of the data structure (205) is assigned a comparison key (235) only if the object (220) does not yet comprise a comparison key (235). The method (300) of any one of the preceding claims, wherein the at least one object (220) comprises one or more further objects (220) and the comparison key (235) is determined based on the included objects (220). The method (300) of any one of the preceding claims, wherein the at least one object (220) comprises one or more further objects (220) and the comparison key (235) is determined based on comparison keys (235) of the included objects (220). Method (300) according to Claim 7 wherein the comparison key (235) for the object (220) is determined recursively. The method (300) of any one of the preceding claims, further comprising serializing the data structure (205) in monotonic order of the compare keys (235). Method (300) according to Claim 9 further comprising comparing the serialized data structure (205) with another serialized data structure (205). Method (300) according to Claim 9 wherein the further serialized data structure (205) has been determined based on a transformation of the other data structure (205). The method (300) according to one of the preceding claims, wherein the data structure (205) comprises a tree-like structure of the objects (220). Method (300) according to one of the preceding claims, wherein the data structure (205) describes a control device. Apparatus (130) comprising: - a storage device (145) for storing a data structure (205) having a plurality of objects (220); - processing means (140) arranged to: - determine a comparison key (235) for at least one of the objects (220); and - assign the determined comparison key (235) to the object (220), - so that the objects (220) are assigned different comparison keys (235); characterized in that - the processing means (140) is arranged to determine the comparison key (235) of the at least one object (220) on the basis of a structure definition (240) associated with the object (220).

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