Reusing components is a well-established practice in modern software engineering and brings many advantages, such as a reduction of development costs and time. However, there are still several ...problems when reusing software components, such as the management of the dependencies of a project. Modern build systems provide dependency managers to support developers when dealing with dependencies. But even with this tool support, dependency management is an error-prone task which can lead to dependency hell if it gets out of control.
In this paper, we propose DValidator, an approach that considers dependencies on project level and method call level for validating dependencies in build configurations. First, DValidator encodes a project’s dependency graph as specified in a build configuration and its call graph into a representation using Answer Set Programming (ASP). Then it uses Clingo as a solver to detect problems with the dependencies in that build configuration. In a preliminary evaluation with four open source Maven projects we show that our approach can detect selected dependency smells in less than eight seconds. Next steps concern the investigation of our approach for automatically improving dependency configurations, such as automatically repairing dependency smells and conflicts.
Editor’s note: Open Science material was validated by the Journal of Systems and Software Open Science Board.
•Dependency management improvements by also incorporating method call dependencies.•DValidator detects dependency smells with high precision.•Enables generative approaches that yield high-quality dependency configurations.•Preliminary evaluation showcases the performance of DValidator.
Previous observations have shown that electron density and temperature in the dayside ionosphere of Mars vary between strongly and weakly magnetized regions of the planet. Here we use data from the ...Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft to examine whether dayside ion densities and ionospheric composition also vary. We find that O+, O
2+, and CO
2+ densities above ∼200 km are greater in strongly magnetized regions than in weakly magnetized regions. Fractional abundances of ion species are also affected. The O+/O
2+ ratio at 300‐km altitude increases from ∼0.5 in strongly magnetized regions to ∼0.8 in weakly magnetized regions. Consequently, the plasma reservoir available for escape is fundamentally different between strongly magnetized and weakly magnetized regions.
Key Points
Densities of all ion species are enhanced in strong crustal field regions
Ionospheric composition above 200 km depends on magnetic field conditions
The O+/O
2+ ratio is smaller in strong crustal field regions
We provide an overview of the composition, vertical structure, and variability of the nightside ionosphere of Mars as observed by Mars Atmosphere and Volatile EvolutioN (MAVEN)'s Neutral Gas and Ion ...Mass Spectrometer (NGIMS) through 19 months of the MAVEN mission. We show that O
2+ is the most abundant ion down to ∼130 km at all nightside solar zenith angles (SZA). However, below 130 km NO+ is the most abundant ion, and NO+ densities increase with decreasing altitude down to at least 120 km. We also show how the densities of the major ions decrease with SZA across the terminator. At lower altitudes the O
2+ and CO
2+ densities decrease more rapidly with SZA than the NO+ and HCO+ densities, which changes the composition of the ionosphere from being primarily O
2+ on the dayside to being a mixture of O
2+, NO+, and HCO+ on the nightside. These variations are in accord with the expected ion‐neutral chemistry, because both NO+ and HCO+ have long chemical lifetimes. Additionally, we present median ion density profiles from three different nightside SZA ranges, including deep on the nightside at SZAs greater than 150° and discuss how they compare to particle precipitation models. Finally, we show that nightside ion densities can vary by nearly an order of magnitude over monthlong timescales. The largest nightside densities were observed at high northern latitudes during winter and coincided with a major solar energetic particle event.
Key Points
The composition of the nightside ionosphere of Mars is characterized
O
2+ is the major nightside ion down to 130 km, below which NO+ becomes the major ion
Nightside ion densities can vary by nearly an order of magnitude over monthlong timescales
Wavelike perturbations in the Martian upper thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been ...analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between approx. 100 and approx. 500 km in the Ar density around the exobase show a clear dependence on temperature (T(sub 0)) of the upper thermosphere. The average amplitude of the perturbations is approx. 10% on the dayside and approx. 20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper thermosphere and in the low-latitude region of Earths upper thermosphere, respectively. The amplitudes are inversely proportional to T(sub 0), suggesting saturation due to convective instability in the Martian upper thermosphere. After removing the dependence on T(sub 0), dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking saturation in the upper thermosphere on Mars, unlike those on Venus and Earth.
We report the first observations of Martian thermospheric warming associated with the Planet Encircling Dust Event (PEDE) of 2018. We used dayglow observations made by the Imaging Ultraviolet ...Spectrograph instrument aboard the MAVEN spacecraft to retrieve the upper atmosphere temperature structures. Our analysis shows that the two‐cell meridional circulation pattern may be operating before the PEDE‐2018, which resulted in the cooling of lower/middle latitudes and warming at higher latitudes. However, after the onset, the existing circulation pattern gets dampened, resulted in a weaker latitudinal temperature structure. We saw that mean temperatures rose by about 20 K for the same local time after the onset of the dust storm. Our 3‐D Mars General Ionosphere Thermosphere Model calculations were able to reproduce the temperatures during the predust and early dust storm but failed to fully capture the temperature trend during the growth phase of the PEDE of 2018.
Key Points
The IUVS Observations show potential thermospheric warming associated with a global dust storm
Our analysis shows active two-cell meridional circulation in the Martian thermosphere before the PEDE-2018
Temperature observations show breakdown of nominal circulation during the dust storm
Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on ...the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft. Average scale heights (over 150–180 km for solar zenith angles ≤75°) from several different sampling periods were obtained from each instrument. NGIMS and IUVS scale height trends were found to be in good agreement, with both showing scale heights decreasing after perihelion and reaching a low value near aphelion (13.6 to 9.4 km). Between these two seasonal extremes, the temperature decreased by ∼70 K (from 240 to 170 K). These trends were also analyzed with respect to the changing solar flux reaching the planet, using the Lyman alpha irradiance measured by the Extreme Ultraviolet Monitor (EUVM) on MAVEN. Scale heights responded strongly to the changing solar flux. During this part of the MAVEN mission (October 2014 to May 2016), it was concluded that over longer timescales (at least several months), dayside thermospheric temperatures are chiefly driven by changing solar forcing, although it is the effects of changing heliocentric distance rather than changing solar activity which seem to have the greatest impact. Furthermore, effects of solar forcing were not observed on shorter timescales (less than a month), suggesting local wave effects may dominate solar forcing on these timescales. Finally, temperatures from two NGIMS sampling periods were compared to temperatures from the Mars Global Ionosphere‐Thermosphere Model (M‐GITM) and found to be in good agreement.
Plain Language Summary
The Martian dayside upper atmosphere (above 100 km) has been studied with limited datasets over several decades prior to 2014. Much controversy has resulted from analysis of this limited data such that derived temperatures plus densities and their variations were poorly constrained. In this paper, dayside temperature variations and their correlation with the solar fluxes measured explicitly at Mars are studied in great detail making use of both in‐situ and remote datasets from the recent MAVEN spacecraft mission to Mars. Results show that dayside temperatures (75 degrees solar zenith angle) over the Mars seasonal cycle vary by at least 70 K, and that variations owing to the changing solar output over its 11‐year cycle should enhance these variations further. This result is important because the dayside upper neutral atmospheric structure (temperatures and densities) and its variations control the reservoir of neutral and ion constituents that participate in the loss of the atmosphere to space over time. This loss to space is specifically being investigated by MAVEN in an effort to estimate the loss of water over time and the evolution of the climate of Mars.
Key Points
Seasonal and solar activity trends of Mars dayside upper atmosphere are revealed by MAVEN
MAVEN NGIMS and IUVS dayside thermosphere scale height trends are very similar
Long‐term variability of Mars dayside thermospheric temperatures is tied to solar‐driven thermal balances
Mars is typically regarded as a non‐magnetic planet. Currents in the Martian ionosphere generate a Venus‐like induced magnetosphere which deflects the solar wind flows and piles up the interplanetary ...magnetic fields. However, crustal magnetic fields in the southern hemisphere influence local plasma properties. Using observations from the MAVEN mission, we characterize the distinguishing plasma characteristics of a mini‐magnetosphere that forms on the Martian dayside. We establish three criteria to differentiate this mini‐magnetosphere from the induced magnetosphere. Notably, the mini‐magnetosphere exhibits higher plasma beta (values near 1), with a balance between planetary ions, crustal magnetic fields, and the solar wind at the magnetopause. Observations show that the crustal magnetosphere reaches an altitude of 1,300 km, larger than one‐third of the Martian radius, indicating a dichotomy between the induced northern and the crustal southern magnetospheres. These findings offer novel insights into the distinctive properties of hybrid magnetospheres in the near‐Mars space.
Plain Language Summary
Mars lacks a global intrinsic magnetic field. Currents in the Martian ionosphere generate a Venus‐like induced magnetosphere which deflects the solar wind flow and piles up the interplanetary magnetic field. However, local crustal magnetic fields in Mars' southern hemisphere significantly influence the nearby plasma. With the support of the MAVEN mission, this work analyses observations from passes of the spacecraft through the mini‐magnetosphere during suitable orbits and investigates plasma pressures in both single orbit data and by a 4‐year statistical analysis. We present an observation of a mini‐magnetosphere filled by trapped heavy ions above the crustal magnetic fields on the Martian dayside. Furthermore, we establish three criteria to distinguish this mini‐magnetosphere from the induced magnetosphere. Observations show that the mini‐magnetosphere reaches an altitude of 1,300 km, larger than one‐third of the Martian radius. The observed mini‐magnetosphere and the dichotomy between the crustal southern and induced northern Martian magnetosphere forms a distinct environment that may help us to test the interactions between stellar winds and magnetic or nonmagnetic bodies.
Key Points
The crustal magnetic fields trap ionospheric plasma to form a mini‐magnetosphere in the near‐Mars plasma environment
The mini‐magnetosphere reaches 1,300 km on the Martian dayside
The mini‐magnetosphere balances the solar wind through contributions from plasma thermal pressure and the crustal magnetic pressure
Software reuse is a common practice in modern software engineering to save time and energy while accelerating software delivery. Dependency managers like MAVEN offer a large ecosystem of reusable ...libraries that build the backbone of software reuse. Breaking changes, i.e., when an update to a library introduces incompatible changes that break existing client programs, are troublesome barriers to this library reuse. Semantic Versioning has been proposed as a practice to make it easier for the users to find safe updates by encoding the change impact in the version number. While this practice is widely studied from the framework perspective, no detailed insights exist yet into the ecosystem perspective. In this work, we study violations of semantic versioning in the MAVEN ecosystem for 13,876 versions of 384 artifacts to better understand the impact these violations have on the 7,190 dependent versioned packages. We found that 67% of the artifacts introduce at least one type of semantic versioning violation, either a breaking change or an illegal API extension in their history. An impact analysis on breaking methods that (direct or transitive) dependents reference, revealed strong centralization: 87% of publicly accessible methods are never used by dependents and among methods with at least one usage, half of the unique calls from dependents concentrate on only 35% of the defined methods. We also studied method popularity and could not find an indication that popularity affects stability: even popular methods break frequently. Overall, we confirm the previous result that Semantic Versioning is violated repeatedly in practice. Our results suggest that the frequency of breaking changes might be a sign of insufficient change-impact awareness on the ecosystem and we believe that developers require more adequate information, like method popularity, to improve their update strategies.
•67% of the artifacts violate semantic versioning at least once in their lifetime.•The majority of public methods are not used by others.•Popularity does not play a role in whether or not a method is involved in breaking changes.
Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) observations, we have analyzed the role of the crustal magnetic field on ion loss driven by the direct interaction of the solar wind with ...the Mars ionosphere. Crustal magnetic fields significantly attenuate the ion ionospheric motions and raise the flux of returning ions. On the other hand, since the ion densities in the ionosphere with strong crustal field are significantly higher than in the ionosphere with a weak crustal magnetic field, the net escape fluxes from the ionosphere with the crustal sources remain vital. The crustal magnetic field also leads to the expansion of the ionosphere and increase of the area exposed to solar wind. As a result, fluxes from higher altitudes essentially contribute to the flow pattern in Martian tail producing an excess of ion loss rate (∼15%) through the southern part of the tail. Thus, effects of inhibition and enhancement of the escape rate by the crustal magnetic field at Mars operate in competition producing a minor influence on the total ion loss.
Key Points
Crustal magnetic field at Mars has a twofold effect on atmospheric erosion
At lower altitudes the crustal fields form a protective shield around the ionized atmosphere
Due to expansion of ionosphere to higher altitudes, a larger cross‐section area is exposed to the solar wind that increases ion losses
Hyrum’s law states a common observation in the software industry: “With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your ...system will be depended on by somebody”. Meanwhile, recent research results seem to contradict this observation when they state that “for most APIs, there is a small number of features that are actually used”. In this work, we perform a large scale empirical study of client–API relationships in the Maven ecosystem, in order to investigate this seeming paradox between the observations in industry and the research literature.
We study the 94 most popular libraries in Maven Central, as well as the 829,410 client artifacts that declare a dependency to these libraries and that are available in Maven Central, summing up to 2.2M dependencies. Our analysis indicates the existence of a wide spectrum of API usages, with enough clients, most API types end up being used at least once. Our second key observation is that, for all libraries, there is a small set of API types that are used by the vast majority of its clients. The practical consequences of this study are two-fold: (i) it is possible for API maintainers to find an essential part of their API on which they can focus their efforts; (ii) API developers should limit the public API elements to the set of features for which they are ready to have users.
•A systematic large-scale analysis of 2,190,525 Maven client–API relations.•Novel empirical evidence about bloat in Maven dependencies.•A novel way to explore trade-off between API size and supported clients.
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